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New Miniature Narrow Band Microstrip Diplexer for Recent Wireless Communications

Authors:
Kadhum Al-Majdi at Ashur University college
Kadhum Al-Majdi
  • Ashur University college
Yaqeen Sabah Mezaal at University of Information Technology and Communications
Yaqeen Sabah Mezaal
  • University of Information Technology and Communications
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Abstract and Figures

Using Kappa substrate material, a compact microstrip diplexer is developed in this research with two separate channels based on the coupled junction and two bandpass filters functioning in independent frequency bands. Each filter comprises an input/output feed line and a number of resonators with different impedances. The diplexer’s frequency response was modeled and optimized using the Sonnet EM solver. At 2.84 and 4.08 GHz for TX/RX channels, the insertion loss is better than 1 dB for both channels, while the return loss values are 21.2 and 17 dB for transmit and receive filters, respectively. The microstrip diplexer has miniature dimensions of 24 mm × 18 mm with highly narrow bands and band isolation of more than 35 dB. The simulated scattering parameters are in agreement with the measured ones.
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Citation: Al-Majdi, K.; Mezaal, Y.S.
New Miniature Narrow Band
Microstrip Diplexer for Recent
Wireless Communications. Electronics
2023,12, 716. https://doi.org/
10.3390/electronics12030716
Academic Editor: Reza K. Amineh
Received: 26 December 2022
Revised: 21 January 2023
Accepted: 27 January 2023
Published: 1 February 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
electronics
Article
New Miniature Narrow Band Microstrip Diplexer for Recent
Wireless Communications
Kadhum Al-Majdi 1and Yaqeen Sabah Mezaal 2,*
1Medical Instrumentation Engineering Department, Ashur University College, Baghdad 10071, Iraq
2Medical Instrumentation Engineering Department, Al-Esraa University College, Baghdad 10071, Iraq
*Correspondence: yaqeen@esraa.edu.iq
Abstract:
Using Kappa substrate material, a compact microstrip diplexer is developed in this research
with two separate channels based on the coupled junction and two bandpass filters functioning in
independent frequency bands. Each filter comprises an input/output feed line and a number of
resonators with different impedances. The diplexer’s frequency response was modeled and optimized
using the Sonnet EM solver. At 2.84 and 4.08 GHz for TX/RX channels, the insertion loss is better
than 1 dB for both channels, while the return loss values are 21.2 and 17 dB for transmit and receive
filters, respectively. The microstrip diplexer has miniature dimensions of 24 mm
×
18 mm with highly
narrow bands and band isolation of more than 35 dB. The simulated scattering parameters are in
agreement with the measured ones.
Keywords: microstrip; diplexer; UIR; SIR; Kappa substrate; negative group delay; narrow bands
1. Introduction
Over the past few years, numerous ground-breaking advancements have been made
in wireless communication systems. These include introducing ultra-wideband systems,
the rapid development of wireless internet technologies like Wi-Fi and WiMAX, and mo-
bile wireless communication systems that employ 3G and 4G innovations. More robust
radio frequency components are required to keep up with the pace of development. Satel-
lites have shifted their focus from strictly stationary communications to dynamic fields,
including remote sensing, maritime applications, and mobile [1].
Various communication systems rely heavily on multiplexers. Broadband wireless
communications, radio transmission, satellite communication, and so on are all examples.
The most elementary multiplexer design is called a diplexer. It enables the use of a single
antenna by two transmitters operating on separate channels. For various cellular radio
system standards, diplexer technology is employed in both the base station and the radio
handset. The diplexer features a power divider and two filters with defined frequency
responses, physical dimensions, and bandwidths, as seen in Figure 1. The transmit filter
must withstand the rather powerful signals generated by the transmitter. However, the
receiver must be sensitive enough to notice weak signals. In addition, diplexers are
commonly employed in the transceivers of broadband wireless access communication
systems. Increased demand for these broadband access systems has increased the need for
tiny, low-cost diplexers. These diplexers separate incoming and outgoing signals in the
front end [2].
The negative group delay (NGO) has recently garnered a lot of attention, particularly in
the realm of RF and microwave devices. The NGD idea is a relatively new field of electrical
and electronic engineering study. It is predicated on an uncommon function: producing an
output signal that appears to be generated in advance of the input signal. Due to the long
delays and signal distortion that arise with positive group delay (PGD), achieving a certain
quality of signal transmissions needs attention to signal phase characteristics in addition
to signal amplitude characteristics. The NGD function has been used to create innovative
Electronics 2023,12, 716. https://doi.org/10.3390/electronics12030716 https://www.mdpi.com/journal/electronics
Electronics 2023,12, 716 2 of 13
design features of RF and microwave electronic devices, such as power dividers, filters,
antennas, and amplifiers, as well as to produce experimental high-performance electronic
devices [3,4].
Electronics 2023, 12, x FOR PEER REVIEW 2 of 13
.
Figure 1. TX/RX diplexer.
The negative group delay (NGO) has recently garnered a lot of attention, particularly
in the realm of RF and microwave devices. The NGD idea is a relatively new field of elec-
trical and electronic engineering study. It is predicated on an uncommon function: pro-
ducing an output signal that appears to be generated in advance of the input signal. Due
to the long delays and signal distortion that arise with positive group delay (PGD), achiev-
ing a certain quality of signal transmissions needs attention to signal phase characteristics
in addition to signal amplitude characteristics. The NGD function has been used to create
innovative design features of RF and microwave electronic devices, such as power divid-
ers, filters, antennas, and amplifiers, as well as to produce experimental high-performance
electronic devices [3,4].
This work shows a new small microstrip diplexer built on a Kappa substrate. This
diplexer uses a variety of step impedance resonators and uniform impedance resonators
along with input and output ports. As can be seen in its frequency responses, the projected
diplexer exhibits effective band isolation of greater than 35 dB. It also exhibits very narrow
bands at each channel, with negative group delays at several frequency values.
2. Related Work
Salah I. Yahya and Abbas Rezaei presented a new structure for a flat dual-channel
microstrip diplexer. It was built at the height of 0.787 mm on a dielectric substrate and has
a tiny surface area of 95.7 mm2. The fractional bandwidth of the first channel is 34.3%,
while the second is 38.6%. Modifying the suggested diplexer allows for the second channel
to be used for broadband purposes. The value of f1 = 1.6 GHz is where the L-resonance
band’s frequencies can be found. WiMAX uses a frequency of f2 = 3 GHz [5]. Patch and
thin cells tailored for 0.78 GHz and 1.85 GHz for GSM requirements are the primary em-
phases of the structural design, as indicated in [6]. Given the symmetrical nature of the
suggested resonator, it is possible to learn more about its behavior by doing investigations
in both the odd and even modes. In addition to its small size, sound isolation, and return
loss performance, this diplexer also offers low insertion and return loss. Compact sub-
strate integrated waveguide (SIW) diplexers with square cavities for C-band applications
are shown in a new design [7]. This diplexer functions at frequencies below the cut-off
frequency of the concavity, taking advantage of the propagation of evanescent modes. The
computed insertion losses for the lower and higher passbands, with their centers at 6.16
GHz and 7.72 GHz are 0.83 dB and 0.77 dB, respectively. For each high insulation pass-
band greater than 22 dB, the suggested diplexer offers a fractional bandwidth of more
than 5.1%. Due to these characteristics, the suggested diplexer is a viable option for the C-
band requirement. In [8], two microstrip multiband diplexers are described. The diplexers
Figure 1. TX/RX diplexer.
This work shows a new small microstrip diplexer built on a Kappa substrate. This
diplexer uses a variety of step impedance resonators and uniform impedance resonators
along with input and output ports. As can be seen in its frequency responses, the projected
diplexer exhibits effective band isolation of greater than 35 dB. It also exhibits very narrow
bands at each channel, with negative group delays at several frequency values.
2. Related Work
Salah I. Yahya and Abbas Rezaei presented a new structure for a flat dual-channel
microstrip diplexer. It was built at the height of 0.787 mm on a dielectric substrate and
has a tiny surface area of 95.7 mm
2
. The fractional bandwidth of the first channel is
34.3%, while the second is 38.6%. Modifying the suggested diplexer allows for the second
channel to be used for broadband purposes. The value of f1 = 1.6 GHz is where the L-
resonance band’s frequencies can be found. WiMAX uses a frequency of f2 = 3 GHz [
5
].
Patch and thin cells tailored for 0.78 GHz and 1.85 GHz for GSM requirements are the
primary emphases of the structural design, as indicated in [
6
]. Given the symmetrical
nature of the suggested resonator, it is possible to learn more about its behavior by doing
investigations in both the odd and even modes. In addition to its small size, sound
isolation, and return loss performance, this diplexer also offers low insertion and return
loss. Compact substrate integrated waveguide (SIW) diplexers with square cavities for
C-band applications are shown in a new design [
7
]. This diplexer functions at frequencies
below the cut-off frequency of the concavity, taking advantage of the propagation of
evanescent modes. The computed insertion losses for the lower and higher passbands, with
their centers at 6.16 GHz and 7.72 GHz are 0.83 dB and 0.77 dB, respectively. For each high
insulation passband greater than 22 dB, the suggested diplexer offers a fractional bandwidth
of more than 5.1%. Due to these characteristics, the suggested diplexer is a viable option
for the C-band requirement. In [
8
], two microstrip multiband diplexers are described.
The diplexers have long feed lines and bandpass filters (BPFs) for each channel. One BPF
controls all the individual channel parameters, allowing for greater freedom in the layout.
Long, high-isolating microstrip feeding lines support the channel filters. A microwave
diplexer was built by exchanging a dual-band BPF for two single-band BPFs [
9
]. In contrast
to the traditional diplexer, which uses many junctions to split up the energy, this design
reduces the requirement for external connectors. In [
10
], a high-efficiency and commercial
Ku-band diplexer made up of fourth-order TX and RX Chebyshev filters is introduced
Electronics 2023,12, 716 3 of 13
along with a design and realization of a microwave diplexer using groove gap waveguide
resonators. The interesting consistency between the simulation and measurement data
validates the design process. In [
11
], the authors presented a microstrip diplexer that uses
modernized H-shaped resonators to achieve small size and sound band isolation. This
layout is compatible with the ISM (2.4 GHz) band and the GPS (1.575 GHz) frequencies.
The diplexer was created by attaching two BPFs designed with the modified H-shaped
resonator and tapped microstrip input/output lines. The paper introduces a new H-
shaped BPF and provides an analytic theory for its H-shaped resonator and a model of
its equivalent LC circuit. The electrical capabilities of the presented microstrip diplexer
are enhanced by etching two cross-slots in the ground plane to create the passbands at
low frequencies. Unfortunately, the circuit’s poor grounding means it cannot function
properly on the GPS L1 or L2 frequencies. An ADS simulator has been used to analyze
the diplexer’s performance, and CST microwave studio has been used to verify those
results. In [
12
], the authors developed a microwave diplexer using substrate-integrated
waveguide (SIW) technology. For simplicity and compactness, the diplexer was made
using a common junction rather than the traditionally used external connection for energy
distribution. The use of microstrip structures with a huge relative dielectric constant of
80 and no short-circuited elements [
13
] allows for the development of diplexers using
two- and three-resonator microstrip structures. With frequency-contiguous channels for
the differential mode and strong common-mode rejection, a new type of balanced dual-
band planar diplexer was projected in [
14
]. It uses a diplexer ’s symmetry plane, which
contains filtering cells loaded with two stubs and coupled to one another through resistors.
Each diplexer channel can operate as a differential-mode dual-passband filter with severe
rejection at both passbands. Low common-mode in-band input power reflection and
improved common-mode suppression are further benefits. Using microstrip open-loop
coupled resonators, a dual-channel diplexer with two operational bands per channel
was presented using a first channel of (1.424/1.732 GHz) in transmit and receive ends of
(2.014/2.318 GHz) for a second channel [
15
]. When using load 1, the insertion loss is 1 dB,
whereas when using load 2, it drops to 1.5 dB. The effective isolation of 35 dB between
channels generates return loss magnitudes greater than 10 dB. The presented design is very
good for wireless applications due to its straightforward topology, compact circuit size,
and narrowband frequency responses.
3. Design Concept
A transmission line resonator with stepped impedances consists of two or more
lines with a varied characteristic impedance that operates in TEM or quasi-TEM mode.
Figure 2depicts the two most common types of SIR, a short-circuited
λ
g/4 resonator and
an open-circuited
λ
g/2 resonator. According to Figure 2, the quarter wavelength SIR
comprises a short-ended line with characteristic impedance Z
1
and electrical length
θ1
coupled to an open-ended line with characteristic impedance Z
2
and electrical length
θ2
.
Two such elements connected through short-circuited ends, with this connection in place
of grounding, might be thought of as the essential constituent of SIR and half-wavelength
resonators [16,17].
The definition of this element allows us to see
λ
g/4- and
λ
g/2-type SIR as composed of
one and two elements, respectively. The SIR is defined in terms of electrical parameters by
the ratio of the impedances Z
1
and Z
2
of the transmission lines, as shown in the following
equation [17]:
Rz=Z2
Z1
(1)
The input admittance of λg/4 SIR is equal to:
Yin =jY2
Y2tan θ1. tan θ2−Y1
Y2tan θ1+Y1tan θ2
(2)
Electronics 2023,12, 716 4 of 13
The
λ
g/4 resonator with a short circuit behaves like a parallel resonant circuit. For a
quarter-wavelength SIR, the parallel resonance under condition Yin = 0 is:
tan θ1. tan θ2=Y1/Y2=Z2/Z1=Rz(3)
As shown in Equation (3), the resonant state of SIR can be determined by λg/2 trans-
mission line and the impedance ratio R
z
relative to typical uniform-impedance resonators
(UIR). The electrical length is 2
θ
, and the characteristic impedance is Z
1
. This is depicted
for approximately UIR in Figure 3. Half-wavelength UIR is used to determine the angular
resonance frequency for this resonator [17].
Electronics 2023, 12, x FOR PEER REVIEW 4 of 13
.
Figure 2. SIR varieties: (a) quarter-wavelength type; (b) half-wavelength type.
The definition of this element allows us to see λg/4- and λg/2-type SIR as composed
of one and two elements, respectively. The SIR is defined in terms of electrical parameters
by the ratio of the impedances Z1 and Z2 of the transmission lines, as shown in the follow-
ing equation [17]:
=2
1 (1
)
The input admittance of λg/4 SIR is equal to:
=22tan 1.tan 2−1
2tan 1+1tan 2 (2
)
The λg/4 resonator with a short circuit behaves like a parallel resonant circuit. For a
quarter-wavelength SIR, the parallel resonance under condition Yin=0 is:
tan 1. tan 2=12=21=
⁄⁄ (3
)
As shown in Equation (3), the resonant state of SIR can be determined by λg/2 trans-
mission line and the impedance ratio Rz relative to typical uniform-impedance resonators
(UIR). The electrical length is 2θ, and the characteristic impedance is Z1. This is depicted
for approximately UIR in Figure 3. Half-wavelength UIR is used to determine the angular
resonance frequency for this resonator [17].
.
Figure 3. Half-wavelength UIR.
Figure 2. SIR varieties: (a) quarter-wavelength type; (b) half-wavelength type.
Electronics 2023, 12, x FOR PEER REVIEW 4 of 13
.
Figure 2. SIR varieties: (a) quarter-wavelength type; (b) half-wavelength type.
The definition of this element allows us to see λg/4- and λg/2-type SIR as composed
of one and two elements, respectively. The SIR is defined in terms of electrical parameters
by the ratio of the impedances Z1 and Z2 of the transmission lines, as shown in the follow-
ing equation [17]:
=2
1 (1
)
The input admittance of λg/4 SIR is equal to:
=22tan 1.tan 2−1
2tan 1+1tan 2 (2
)
The λg/4 resonator with a short circuit behaves like a parallel resonant circuit. For a
quarter-wavelength SIR, the parallel resonance under condition Yin=0 is:
tan 1. tan 2=12=21=
⁄⁄ (3
)
As shown in Equation (3), the resonant state of SIR can be determined by λg/2 trans-
mission line and the impedance ratio Rz relative to typical uniform-impedance resonators
(UIR). The electrical length is 2θ, and the characteristic impedance is Z1. This is depicted
for approximately UIR in Figure 3. Half-wavelength UIR is used to determine the angular
resonance frequency for this resonator [17].
.
Figure 3. Half-wavelength UIR.
Figure 3. Half-wavelength UIR.
As a rule, dielectric substrate materials for UIR applications should have a small
loss-tangent, a high permittivity, and a stable temperature. Comparing the two types of
resonators again, we can conclude that the electrical length is the primary determinant of
the resonance condition for UIR. SIR has additional flexibility that can be employed in new
designs. Referring to Figure 4, where
θT
represents the resonant electrical length of the
resonator, we have [17]:
θT=θ1+θ2=θ1+tan−1Rz
tan θ1(4)
Electronics 2023,12, 716 5 of 13
Electronics 2023, 12, x FOR PEER REVIEW 5 of 13
As a rule, dielectric substrate materials for UIR applications should have a small loss-
tangent, a high permittivity, and a stable temperature. Comparing the two types of reso-
nators again, we can conclude that the electrical length is the primary determinant of the
resonance condition for UIR. SIR has additional flexibility that can be employed in new
designs. Referring to Figure 4, where represents the resonant electrical length of the
resonator, we have [17]:
=+=+tan
tan (4
)
For various values of the impedance ratio Rz, the overall electrical length for SIR is
depicted based on , as illustrated in Figure 4.
Figure 4. For various impedance ratios, a depiction between a total electrical length and Ɵ1 for the
resonant.
As it can be comprehended, the resonator’s overall electrical length has the highest
magnitude at 1 and the lowest magnitude when 1.
The condition for these highest and lowest values can be derived as:
==tan (5
)
The condition = stands for a specific condition that provides the highest and
lowest lengths for SIR, as expressed below:
 =tan󰇧2
1󰇨 (6
)
Equation (6) has a minimum value for when 0 < < 1 and 0 < <2
.
When comparing SIR to UIR, the critical difference is that the length of the resonators can
be tuned by altering the impedance ratio Rz. This can be utilized for the same fundamental
resonance frequency to design SIRs that are physically smaller than their UIR equivalents.
Figure 4.
For various impedance ratios, a depiction between a total electrical length and
θ1
for
the resonant.
For various values of the impedance ratio R
z
, the overall electrical length for SIR is
depicted based on θT, as illustrated in Figure 4.
As it can be comprehended, the resonator’s overall electrical length has the highest
magnitude at Rz≥1 and the lowest magnitude when Rz≤1.
The condition for these highest and lowest values can be derived as:
θ1=θ2=tan−1√Rz(5)
The condition
θ1=θ2
stands for a specific condition that provides the highest and
lowest lengths for SIR, as expressed below:
θT min =tan−12√Rz
1−Rz(6)
Equation (6) has a minimum value for
θT
when 0
<Rz<
1 and 0
<θT<π/
2. When
comparing SIR to UIR, the critical difference is that the length of the resonators can be tuned
by altering the impedance ratio R
z
. This can be utilized for the same fundamental resonance
frequency to design SIRs that are physically smaller than their UIR equivalents. SIRs
regulate the passband of a bandpass filter’s first spurious mode, which can be employed in
developing dual-band BPFs. The relationship between the frequency of the first spurious
resonance and the frequency of SIR’s fundamental resonance is as follows:
fs
f0
=
π
tan−1√Rz−1 (7)
fs
f0
=
π
2 tan−1√Rz
(8)
Equation (7) stands for the quarter-wavelength SIR ratio in the case of
fs
f0=
3 and
Rz=
1. Equation (8) represents a ratio of the half-wavelength SIR when
fs
f0=
2 and
Electronics 2023,12, 716 6 of 13
Rz=
1. Both categories of resonators have their normalized spurious resonance frequencies
illustrated in Figure 5.
)
)
Figure 5. Normalized spurious resonance frequency concerning impedance ratio.
Step impedance filters are a great choice if you are looking for an alternative to stub-
based filters. They are the least performing type of filter because they have the highest and
lowest practicable impedance transmission lines. They are an excellent option for tasks that
do not require precise cutting. Increased isolation and a broad and deep stopband can be
achieved with microstrip filters and diplexers based on varying SIRs [15].
The schematic for the designed circuit is shown in Figure 6. The entire circuit, in-
cluding the substrate, takes up only 24
×
18 mm
2
in area, making it incredibly small and
straightforward. Two BPFs operating in separate frequency ranges must be created in
the design method. It should be noted that adjusting the length of the depicted UIR and
SIR elements can change the filter center frequencies and bandwidths. Because of the
coupled junction’s space-saving and diplexer design, it was chosen to connect the two
filters. Because the required frequency response is compromised, combining the two filters
in practice could be better. This necessitates thorough optimization of the entire circuit by
an electromagnetic simulator.
Furthermore, separating the SIR- and UIR-based open-loop resonators from the feed
lines can alter the simulated outcomes. Since the new Rogers Kappa-438 substrate (
εr = 4.38
,
tan
δ
= 0.005) and the FR4 substrate (
ε
r = 4.25, tan
δ
= 0.015) share the same dielectric constant
(
ε
r) and substrate height (h = 1.524 mm), they are envisioned as performance substitutes for
one another. Microstrip devices’ size and scattering parameters are all affected by the loss
tangent and dielectric constant, assuming a constant substrate thickness. Kappa-438 excels
over FR4 with a minor loss tangent. Kappa-438 has a smaller loss tangent (0.005) than FR4
(0.015). I/O feeders are all non-symmetrical SIR varieties, but the upper and lower sections
include clearly symmetrical and non-symmetrical parts of SIR varieties.
Electronics 2023,12, 716 7 of 13
Electronics 2023, 12, x FOR PEER REVIEW 7 of 13
Figure 6. The structure and dimensions of the microstrip diplexer based on Kappa substrate, all
dimensions in mm unit. L1 = 3.5, L2 = 0.8, W1 = 0.2, W2 = 0.2, L3 = 6.6, L4 = 9.9, L5 = 4.9, L6 = 4.2, W3
= 1.1, W4 = 1.1, W4 = 1.1, W5 = 3.9, W6 = 4.3, W7 = 3.3, U = 1, g = 0.1, W8 = 1, W9 = 5.4, W10 = 5.6, W11
= 3.6, W12 = 0.8, L7 = 1, L8 = 2.2, L9 = 6.3.
Furthermore, separating the SIR- and UIR-based open-loop resonators from the feed
lines can alter the simulated outcomes. Since the new Rogers Kappa-438 substrate (εr =
4.38, tanδ = 0.005) and the FR4 substrate (εr = 4.25, tanδ = 0.015) share the same dielectric
constant (εr) and substrate height (h = 1.524 mm), they are envisioned as performance
substitutes for one another. Microstrip devices’ size and scattering parameters are all af-
fected by the loss tangent and dielectric constant, assuming a constant substrate thickness.
Kappa-438 excels over FR4 with a minor loss tangent. Kappa-438 has a smaller loss tan-
gent (0.005) than FR4 (0.015). I/O feeders are all non-symmetrical SIR varieties, but the
upper and lower sections include clearly symmetrical and non-symmetrical parts of SIR
varieties.
4. Results and Discussion
The described microstrip diplexer was designed, optimized, and simulated with the
electromagnetic (EM) Sonnet simulator. Scattering parameters for diplexers with a Kappa-
Rogers substrate, as simulated, are shown in Figures 7 and 8. The transmit (Tx) filter has
an insertion loss of 0.7 dB and a return loss of 21.2 dB at 2.84 GHz. The center frequency
of the receive (Rx) filter is 4.08 GHz, and its insertion loss is 0.9 dB, while its return loss is
roughly 17 dB. Furthermore, over a frequency range of 1 to 6 GHz, there is greater than
35 dB of band isolation between the two channels. The bandwidths ranges are 2.82–2.86
Figure 6.
The structure and dimensions of the microstrip diplexer based on Kappa substrate, all
dimensions in mm unit. L1 = 3.5, L2 = 0.8, W1 = 0.2, W2 = 0.2, L3 = 6.6, L4 = 9.9, L5 = 4.9, L6 = 4.2,
W3 = 1.1, W4 = 1.1, W4 = 1.1, W5 = 3.9, W6 = 4.3, W7 = 3.3, U = 1, g = 0.1, W8 = 1, W9 = 5.4, W10 = 5.6,
W11 = 3.6, W12 = 0.8, L7 = 1, L8 = 2.2, L9 = 6.3.
4. Results and Discussion
The described microstrip diplexer was designed, optimized, and simulated with the
electromagnetic (EM) Sonnet simulator. Scattering parameters for diplexers with a Kappa-
Rogers substrate, as simulated, are shown in Figures 7and 8. The transmit (Tx) filter has
an insertion loss of 0.7 dB and a return loss of 21.2 dB at 2.84 GHz. The center frequency
of the receive (Rx) filter is 4.08 GHz, and its insertion loss is 0.9 dB, while its return loss is
roughly 17 dB. Furthermore, over a frequency range of 1 to 6 GHz, there is greater than
35 dB of band isolation between the two channels. The bandwidths ranges are 2.82–2.86 and
4.02–4.11 GHz for the Tx and Rx filters, respectively, which are highly narrow bandwidths.
S11 response is a union of S22 and S33 responses as explained by Figure 8. Figure 9depicts
S11 responses for projected diplexer based on coupling space (g). As we can observe from
this figure, the S11 response in the second channel becomes more effective as g decreases
due to a tight coupling effect. Most changes are distinguished in the second channel, but
minor S11 variations in the first channel exist, especially in the −3 dB region.
Electronics 2023,12, 716 8 of 13
Electronics 2023, 12, x FOR PEER REVIEW 8 of 13
and 4.02–4.11 GHz for the Tx and Rx filters, respectively, which are highly narrow band-
widths. S11 response is a union of S22 and S33 responses as explained by Figure 8. Figure
9 depicts S11 responses for projected diplexer based on coupling space (g). As we can
observe from this figure, the S11 response in the second channel becomes more effective
as g decreases due to a tight coupling effect. Most changes are distinguished in the second
channel, but minor S11 variations in the first channel exist, especially in the −3 dB region.
Figure 7. Simulated S11, S12, and S13 scattering responses for the diplexer based on the Kappa
substrate.
Figure 8. Simulated S22, S33, and S23 scattering responses for the projected diplexer based on the
Kappa substrate.
Figure 7.
Simulated S11,S12, and S13 scattering responses for the diplexer based on the
Kappa substrate.
Electronics 2023, 12, x FOR PEER REVIEW 8 of 13
and 4.02–4.11 GHz for the Tx and Rx filters, respectively, which are highly narrow band-
widths. S11 response is a union of S22 and S33 responses as explained by Figure 8. Figure
9 depicts S11 responses for projected diplexer based on coupling space (g). As we can
observe from this figure, the S11 response in the second channel becomes more effective
as g decreases due to a tight coupling effect. Most changes are distinguished in the second
channel, but minor S11 variations in the first channel exist, especially in the −3 dB region.
Figure 7. Simulated S11, S12, and S13 scattering responses for the diplexer based on the Kappa
substrate.
Figure 8. Simulated S22, S33, and S23 scattering responses for the projected diplexer based on the
Kappa substrate.
Figure 8.
Simulated S22,S33, and S23 scattering responses for the projected diplexer based on the
Kappa substrate.
Figures 10 and 11 depict the current intensity distribution for the projected microstrip
diplexer. The highest values of magnetic strength are 42 and 53 A/M, which appeared in the
corresponding resonators at 2.84 and 4.08 GHz for both cases, respectively. Figure 12 depicts
the group delay for all S parameters for the projected microstrip diplexer. Negative group
delay (GD) values are apparent in Table 1. The NGD does not contradict causality, which
means that the diplexer may foretell the future location of the pulse based on its current
position. PGD can be mitigated and its variability reduced with the use of NGD circuits.
Electronics 2023,12, 716 9 of 13
Electronics 2023, 12, x FOR PEER REVIEW 9 of 13
Figure 9. Simulated S11 responses for the projected diplexer based on the coupling space (g).
Figures 10 and 11 depict the current intensity distribution for the projected microstrip
diplexer. The highest values of magnetic strength are 42 and 53 A/M, which appeared in
the corresponding resonators at 2.84 and 4.08 GHz for both cases, respectively. Figure 12
depicts the group delay for all S parameters for the projected microstrip diplexer. Nega-
tive group delay (GD) values are apparent in Table 1. The NGD does not contradict cau-
sality, which means that the diplexer may foretell the future location of the pulse based
on its current position. PGD can be mitigated and its variability reduced with the use of
NGD circuits.
Figure 10. Current intensity distribution @ 2.84 GHz.
Figure 9. Simulated S11 responses for the projected diplexer based on the coupling space (g).
Electronics 2023, 12, x FOR PEER REVIEW 9 of 13
Figure 9. Simulated S11 responses for the projected diplexer based on the coupling space (g).
Figures 10 and 11 depict the current intensity distribution for the projected microstrip
diplexer. The highest values of magnetic strength are 42 and 53 A/M, which appeared in
the corresponding resonators at 2.84 and 4.08 GHz for both cases, respectively. Figure 12
depicts the group delay for all S parameters for the projected microstrip diplexer. Nega-
tive group delay (GD) values are apparent in Table 1. The NGD does not contradict cau-
sality, which means that the diplexer may foretell the future location of the pulse based
on its current position. PGD can be mitigated and its variability reduced with the use of
NGD circuits.
Figure 10. Current intensity distribution @ 2.84 GHz.
Figure 10. Current intensity distribution @ 2.84 GHz.
Table 1. Negative group delay values.
S Parameter Group Delay (ns) Frequency (GHz)
S11 −3.824 4.08
S21 −8.765 3.5
S31 −6.688, −6.604 2.703, 2.923
S32 −2.263, 0.4766 3.469, 4.508
Electronics 2023,12, 716 10 of 13
Electronics 2023, 12, x FOR PEER REVIEW 10 of 13
Figure 11. Current intensity distribution @ 4.08 GHz.
Figure 12. Group delay response for the designed diplexer.
Table 1. Negative group delay values.
S parameter
Group Delay (ns)
Frequency (GHz)
S11
−3.824
4.08
S21
−8.765
3.5
S31
−6.688, −6.604
2.703, 2.923
S32
−2.263, 0.4766
3.469, 4.508
Figure 11. Current intensity distribution @ 4.08 GHz.
Electronics 2023, 12, x FOR PEER REVIEW 10 of 13
Figure 11. Current intensity distribution @ 4.08 GHz.
Figure 12. Group delay response for the designed diplexer.
Table 1. Negative group delay values.
S parameter
Group Delay (ns)
Frequency (GHz)
S11
−3.824
4.08
S21
−8.765
3.5
S31
−6.688, −6.604
2.703, 2.923
S32
−2.263, 0.4766
3.469, 4.508
Figure 12. Group delay response for the designed diplexer.
The developed microstrip in this paper has the lowest compactness and the greatest
band isolation between Tx and Rx channels as compared with [
18
–
25
], as explained by
Table 2. Additionally, it has the lowest fractional bandwidths as compared with reported
diplexers in [18–25].
Electronics 2023,12, 716 11 of 13
Table 2. Comparing diplexers in this research article with the other reported studies.
Reference
Tx/Rx Center
Frequencies in
(GHz)
Insertion Loss
(dB)
Return Loss
(dB)
Fractional
Bandwidths
(%)
Isolation
(dB) Size (mm2)
[18] 1.7/2.5 2.35/1.96 31/45.8 6.11/7.44 >21 32 ×25
[19] 1.75/2.35 1.34/1.44 20/20 10/7.5 >20
14 ×26
(without
feeders)
[20] 1.5/1.76 2.8/3.2 25/30 3.8/3.3 >30 37.3 ×59.1
[21]
ADS Simulator 2.4/3.2 1.7/1.38 30/30 3.5/4.78 >23 16 ×47
[22] 1.95/2.14 1.22/1.12 15/17 3.08/2.8 37 74 ×40
[23] 2.65/5.4 1.94/2.55 >15 12.5/5.9 >25 35 ×23.16
[24] 1.85/2.5 2.05/2.15 >15 . . . . . . . . . >25 50 ×50
[25] 2.36/5.17 2.3/2.8 >10 7.6/6.4 18 61.8 ×34.7
Proposed 2.84/4.08 0.7/0.9 21.2/17 1.41/2.2 >35 24 ×18
Figure 13 is a photograph of the microstrip diplexer after it was fully fabricated. In
order to confirm the validity of the design simulations and test the operation of the diplexer,
it was run through its paces on a Vector Network Analyzer (VNA). Figure 14 displays the
measured and simulated frequency responses of the proposed diplexer. The simulated and
measured results are consistent with one another. There are small differences because of
VNA setup factors including the size of the diplexer, the quality of the SMA soldering, and
the effect of coaxial cable losses.
Electronics 2023, 12, x FOR PEER REVIEW 11 of 13
The developed microstrip in this paper has the lowest compactness and the greatest
band isolation between Tx and Rx channels as compared with [18–25], as explained by
Table 2. Additionally, it has the lowest fractional bandwidths as compared with reported
diplexers in [18–25].
Table 2. Comparing diplexers in this research article with the other reported studies.
Reference
Tx/Rx Center
Frequencies in
(GHz)
Insertion
Loss (dB)
Return
Loss
(dB)
Fractional
Bandwidths
(%)
Isolation (dB)
Size (mm 2)
[18]
1.7/2.5
2.35/1.96
31/45.8
6.11/7.44
>21
32 × 25
[19] 1.75/2.35 1.34/1.44 20/20 10/7.5 >20
14 × 26
(without feeders)
[20]
1.5/1.76
2.8/3.2
25/30
3.8/3.3
>30
37.3 × 59.1
[21]
ADS Simulator
2.4/3.2 1.7/1.38 30/30 3.5/4.78 >23 16 × 47
[22]
1.95/2.14
1.22/1.12
15/17
3.08/2.8
37
74 × 40
[23]
2.65/5.4
1.94/2.55
>15
12.5/5.9
>25
35 × 23.16
[24]
1.85/2.5
2.05/2.15
>15
………
>25
50 × 50
[25]
2.36/5.17
2.3/2.8
>10
7.6/6.4
18
61.8 × 34.7
Proposed
2.84/4.08
0.7/0.9
21.2/17
1.41/2.2
>35
24 × 18
Figure 13 is a photograph of the microstrip diplexer after it was fully fabricated. In
order to confirm the validity of the design simulations and test the operation of the di-
plexer, it was run through its paces on a Vector Network Analyzer (VNA). Figure 14 dis-
plays the measured and simulated frequency responses of the proposed diplexer. The
simulated and measured results are consistent with one another. There are small differ-
ences because of VNA setup factors including the size of the diplexer, the quality of the
SMA soldering, and the effect of coaxial cable losses.
Figure 13. Fabricated diplexer prototype.
Figure 13. Fabricated diplexer prototype.
Electronics 2023,12, 716 12 of 13
Electronics 2023, 12, x FOR PEER REVIEW 12 of 13
Figure 14. Simulated and measured S parameters.
5. Conclusion and Future Work
In this paper, a miniaturized microstrip diplexer with dual channels is developed.
This diplexer is built with a linked junction and two BPFs that operate in different fre-
quency bands. Each filter is made with UIR, SIR, and feed lines. To determine the di-
plexer’s response, a Sonnet EM solver was used. The diplexer’s Tx/Rx channel resonances
are 2.84 and 4.08 GHz, providing at least 35 dB of isolation between the two channels. The
proposed diplexer has excellent electrical characteristics, negative group delay values,
and a small size of 24 × 18 mm2, making it suitable for use in various wireless systems. The
bandwidths magnitudes are 40 and 90 MHz for Tx and Rx bandpass filters, respectively,
which are highly narrow bandwidths. These narrow frequency responses are effective in
preventing interferences in adjacent bands. This research can be extended as future work
to take up one of the following suggestions. One, the diplexer presented in this study
could be upgraded to triplexers in order to support three frequency bands. Two, two extra
channels can be added with dual bands for each channel to get four different frequency
ranges for a wireless system.
Author Contributions: Methodology, Y.S.M.; Software, Y.S.M.; Validation, Y.S.M.; Resources, K.A.-
M.; Writing—original draft, Y.S.M.; Visualization, K.A.-M.; Supervision, K.A.-M.; Project admin-
istration, K.A.-M. All authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Conflicts of Interest: The authors declare no conflict of interest.
References
1. Yaduvanshi, R.S.; Parthasarathy, H. Rectangular Dielectric Resonator Antennas; Springer: Berlin/Heidelberg, Germany, 2016; Vol-
ume 10, pp. 978–981.
2. Noori, L.; Rezaei, A. Design of a microstrip diplexer with a novel structure for WiMAX and wireless applications. AEU—Int. J.
Electron. Commun. 2017, 77, 18–22. https://doi.org/10.1016/j.aeue.2017.04.019.
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6
S-Parameters (dB)
Frequency(GHz)
S11(dB) Simulated S21(dB) Simulated S13(dB) Simulated
S23(dB) Simulated S11(dB) Measured S21(dB) Measured
Figure 14. Simulated and measured S parameters.
5. Conclusions and Future Work
In this paper, a miniaturized microstrip diplexer with dual channels is developed. This
diplexer is built with a linked junction and two BPFs that operate in different frequency
bands. Each filter is made with UIR, SIR, and feed lines. To determine the diplexer ’s
response, a Sonnet EM solver was used. The diplexer ’s Tx/Rx channel resonances are
2.84 and 4.08 GHz, providing at least 35 dB of isolation between the two channels. The
proposed diplexer has excellent electrical characteristics, negative group delay values, and
a small size of 24
×
18 mm
2
, making it suitable for use in various wireless systems. The
bandwidths magnitudes are 40 and 90 MHz for Tx and Rx bandpass filters, respectively,
which are highly narrow bandwidths. These narrow frequency responses are effective in
preventing interferences in adjacent bands. This research can be extended as future work to
take up one of the following suggestions. One, the diplexer presented in this study could be
upgraded to triplexers in order to support three frequency bands. Two, two extra channels
can be added with dual bands for each channel to get four different frequency ranges for a
wireless system.
Author Contributions:
Methodology, Y.S.M.; Software, Y.S.M.; Validation, Y.S.M.; Resources, K.A.-M.;
Writing—original draft, Y.S.M.; Visualization, K.A.-M.; Supervision, K.A.-M.; Project administration,
K.A.-M. All authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Conflicts of Interest: The authors declare no conflict of interest.
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people or property resulting from any ideas, methods, instructions or products referred to in the content.
... Its frequency response is illustrated in (Fig. 7d). As shown, this diplexer can select the desired frequencies better than the proposed design in (Majdi and Mezaal, 2023). ...
... (Bukuru, Song and Xue, 2015), (b) 4-channel diplexer (unit: mm) in , (c) fabricated band-pass filter in (Zakaria, et al., 2013), (d) fabricated BP-BP triplexer in . BP-BP: Band-pass-band-pass. (Alhalabi, et al., 2018) Coupler 2.45 0.6, 0.8 70 --- (Shi, et al., 2016) Coupler 1.87 1.4* 20 0.1386 (Majdi and Mezaal, 2023) BP-BP Diplexer 2.84, 4.08 0.7, 0.9 21.2, 17 --- (Yahya, Rezaei and Nouri, 2021) BP-BP Diplexer 1.4, 3 0.06, 0.07 28.6, 20 0.004 (Rezaei and Nouri, 2020) BP-BP Diplexer 1, 1.3 0.21, 0.21 32, 25 0.018 (Majidifar and Hayati, 2017) Lowpass Filter 1.76 0.42 11 0.0215 (Majidifar, 2016) Lowpass Filter 1.71 0.1 18 0.02 (Khajavi, AL-Din Makki and Majidifar, 2015) Dual-band BPF 2.45, 3.7 0.458, 0.672 23.57, 17.2 --- (Fadaee, et al., 2023) Lowpass Filter 2.42 0.1 22 0.042 (Afzali, et al., 2021) BPF 2.4 1.2 ---0.037 (Heng, et al., 2014) Multiplexer 2. 8, 2.809, 2.81,2.82 ...
... These components find wide applications in various communication systems, such as radar systems, satellite communication, wireless networks, and cellular base stations. They play a crucial role in managing signal interference, Fig. 7. Frequency responses of the energy harvester microstrip (a) BP-BP diplexer in (Majdi and Mezaal, 2023), (b) lowpass filter in (Majidifar, 2016), (c) lowpass filter in (Fadaee, et al., 2023), (d) BP-BP diplexer in (Rezaei and Nouri, 2020). BP-BP: Band-pass-band-pass. (Majdi and Mezaal, 2023), (b) lowpass filter in (Majidifar, 2016), (c) lowpass filter in (Fadaee, et al., 2023), (d) BP-BP diplexer in (Rezaei and Nouri, 2020). ...
Microstrip Passive Components for Energy Harvesting and 5G Applications: A Comprehensive Review
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This review paper provides a comprehensive overview of microstrip passive components for energy harvesting and 5G applications. The paper covers the structure, fabrication and performance of various microstrip passive components such as filters, couplers, diplexers and triplexers. The size and performance of several 5G and energy harvester microstrip passive devices are compared and discussed. The review highlights the importance of these components in enabling efficient energy harvesting and high-speed communication in 5G networks. Additionally, the paper discusses the latest advancements in microstrip technology and identifies key research challenges and future directions in this field. Overall, this review serves as a valuable resource for researchers and engineers working on microstrip passive components for energy harvesting and 5G applications.
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... There are specific requirements that diplexers must meet to be employed in multi-service and multi-band communications. Conversely, larger and more complex diplexers were produced by the conventional way of fabrication, which required a great number of external connectors [26][27][28][29][30]. This has led to the development of numerous different designs that can guarantee compliance with these regulations. ...
... In Table 3, a comparison is made between the current study and previous studies that are associated with the relevant areas. In comparison to the findings of earlier research, the proposed diplexer demonstrates a significant band isolation level that is noticeably higher, as compared with [28][29][30][31][32][33][34][35][36][37][38]. The proposed diplexer demonstrates competitive frequency response characteristics when compared to designs that have been published in [28][29][30][31][32][33][34][35][36][37][38], as well as a compact size, which measures 32 × 26 mm 2 . ...
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Full-text available
  • Jan 2024
Based on stub loaded meandrous coupled lines, a novel microstrip coupler is designed, fabricated and measured for wireless applications. It is very compact with high performance. The size of this coupler is only 0.0028 λg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , where it operates at 875 MHz. The values of S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> , S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> , S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31</sub> at the operating frequency are -24.97 dB, -3.058 dB and -3.033 dB respectively. Therefore, the insertion losses are very low and the magnitudes of S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> and S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31</sub> are well balanced. The phase imbalance at the operating frequency is 0.5°. From 790 MHz up to 1.18 GHz, S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> is better than -10 dB, the maximum phase imbalance is lower than 4.5° and the maximum magnitude imbalance is lower that ±0.5 dB. Therefore, it has 40% fractional bandwidth (FBW) that covers 0.79 GHz to 1.18 GHz. Its in-band isolation factor is better than -25 dB. The important advantages of this coupler compared to most of the previous designs is having a filtering frequency response and having flat passbands with a maximum group delay of 1 ns.
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... High-performance microstrip filtering devices such as couplers, diplexers and triplexers have been extensively applied in wireless RF communication applications [1][2][3][4][5][6][7][8]. In references [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24], various types of microstrip planar resonators and triplexers are reported and all of them occupy large implementation areas greater than 0.01λg 2 . ...
A High-Performance Microstrip Triplexer With Compact Size, Flat Channels and Low Losses for 5G Applications
Article
Full-text available
  • Jul 2023
A new microstrip triplexer with a compact size of 0.007 λ g 2 is proposed in this work, where designing a microstrip triplexer with a size less than 0.01 λ g 2 is a big challenge. In addition to the compact size, it shows a high performance i.e. its channels are wide with low insertion losses. Moreover, the channels are flat with three low group delays (GDs) of 0.65, 0.95 and 1.17 ns, while most of the previously reported triplexers have not considered this important parameter. The proposed resonator is mathematically analyzed to find a method to get rid of harmonics and tune the resonance frequency. Meanwhile, the 1 st , 2 nd , 3 rd and 4 th harmonics are suppressed above the first channel. The designed triplexer is suitable for 5G mid-band applications. The proposed triplexer is exactly fabricated and then measured to confirm the designing method and simulation results. The obtained results show that all the simulation, mathematical analysis and experimental results are in good agreement. Therefore, the proposed triplexer can be easily used in designing high-performance RF communication systems.
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Novel Ultra-Compact Wide Stopband Microstrip Lowpass-Bandpass Triplexer for 5G Multi-Service Wireless Networks
Article
Full-text available
  • Jan 2024
This work presents a very compact microstrip lowpass-bandpass (LP-BP) triplexer, which is designed and analyzed based on a novel structure. Due to its complex design process, this type of triplexer is rarely designed. Compared to the previous LP-BP triplexers it has the most compact size of 0.006 λ, whereas an LP-BP triplexer with dimensions smaller than 0.01 λ has not been designed yet. This triplexer is designed based on a perfect mathematical method and optimization simultaneously. Its lowpass band has a cut-off frequency of 0.67 GHz, suitable for low-band 5G applications. The resonance frequencies of its bandpass channels are located at 2.15 GHz and 3.19 GHz. These bandpass channels make the proposed triplexer appropriate for 5G mid-band applications. This triplexer can suppress the harmonics from the first up to 8th harmonic. The bandpass channels are flat and wide with two fractional bandwidths (FBW) of 15% and 11.97%. To prove the designing process and its simulation results, the presented novel LP-BP triplexer is fabricated and experimentally measured. The comparison results show that the experimental measurement confirms the simulation results. The close alignment between the measurements and simulation results demonstrates a high level of accuracy of our designing method.
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An ultra-compact diplexer based on simple microstrip coupled lines for GSM and wideband wireless applications
Article
Full-text available
  • Oct 2023
  • WIREL NETW
In this work, a microstrip diplexer with 0.004 λg2 (10.1 × 23 mm) overall size is designed, analyzed and fabricated. The proposed diplexer has the smallest size compared to the previously reported microstrip diplexers. The proposed diplexer has a simple and novel structure, wide flat channels and very low \(\left| {S_{11} } \right|_{dB}\). An innovative microstrip structure based on thin coupled lines is used to design of the proposed diplexer. Since in a simple structure the possibility of manufacturing errors reduces, having a simple structure is one of its advantages. Another advantage of this diplexer is two low \(\left| {S_{11} } \right|_{dB}\) of 0.17 and 0.14 dB at the lower and upper channels. The operational frequencies of our diplexer are tuned to work at 0.9 GHz and 1.8 GHz for GSM application. It has the privileges of very compact size, simple structure, small \(\left| {S_{11} } \right|_{dB}\), two wide fractional bandwidths (FBWs) of 21 and 24.3% and acceptable \(\left| {S_{11} } \right|_{dB}\) and isolation. Due to its two wide FBWs, the presented diplexer is suitable for broadband communication systems. We have fabricated and measured the introduced diplexer to verify the design methodology and simulation results. The obtained results of the diplexer measurement confirm the simulation.
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Substrate Integrated Waveguide (SIW) Diplexer with Novel Input/Output Coupling and no Separate Junction
Article
Full-text available
  • Mar 2018
A microwave diplexer implemented by using the twenty-first century substrate integrated waveguide (SIW) transmission line technology is presented. No separate junction (be it resonant or non-resonant) was used in achieving the diplexer, as the use of an external junction for energy distribution in a diplexer normally increases design complexity and lead to a bulky device. The design also featured a novel input/output coupling technique at the transmit and the receive sides of the diplexer. The proposed SIW diplexer has been simulated using the full-wave finite element method (FEM), Keysight electromagnetic professional (EMPro) 3D simulator. The design has also been validated experimentally and results presented. Simulated and measured results show good agreement. The measured minimum insertion loss achieved on the transmit and the receive channels of the diplexer are 2.86 dB and 2.91 dB, respectively. The measured band isolation between the two channels is better than 50 dB.
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A Novel Design of an H-shaped Microstrip Diplexer
Article
Full-text available
  • Dec 2017
In this paper, a new microstrip diplexer using modified H-shaped resonators with a compact size and high isolation is presented. This circuit is designed for the ISM band at 2.4 GHz and GPS at 1.575 GHz. The proposed diplexer is formed by connecting two band-pass filters designed by using the modified H-shaped resonator and tapped microstrip Input/output (I/O) lines. An analytic study of the H-shaped resonator and an equivalent LC model of the proposed H-shaped band-pass filter were introduced. Two cross-slots are etched in the ground plane of the proposed microstrip diplexer in order to enhance its electrical performances and to set the pass bands at low frequencies. The circuit with defected ground structure is able to operate at the GPS L1 and L2 bands. The electrical performances of the diplexer are investigated numerically by using Momentum integrated in ADS from Agilent technologies and verified with another electromagnetic software CST microwave Studio.
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Negative Group Delay Circuits and Applications: Feedforward Amplifiers, Phased-Array Antennas, Constant Phase Shifters, Non-Foster Elements, Interconnection Equalization, and Power Dividers
Article
  • Feb 2021
With the rapid development of newgeneration communication technology such as multiple-input/multiple-output technology, ultrawideband communication, and 5G technology, communication systems have higher requirements for the quality of signal transmissions. Achieving this quality requires attention not only to signal amplitude characteristics but also to phase characteristics because of the long delays and signal distortion that come with positive group delay (PGD). However, negative group delay (NGD) circuits are an effective way to compensate for PGD and decrease the variability of passband group delay.
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A very compact microstrip diplexer fabrication with superior performance for broadband wireless applications
Article
  • May 2020
This study presents a planar dual‐channel bandpass microstrip diplexer based on a novel structure. It has the very compact size of 0.0081 λ g2 (95.7 mm2) fabricated on 0.787 mm dielectric substrate height. Due to the use of close microstrip sections, several coupling capacitors are created. These capacitors can increase the degree of freedom for controlling the diplexer performance while it is optimized easily. Accordingly, the designed diplexer has a high performance in terms of wide fractional bandwidths, attenuated harmonics, flat channels, high return losses and low insertion losses. The wide fractional bandwidths (FBWs%) of 34.3% at the first channel and 38.6% at the second channel make the proposed diplexer appropriate for the broadband applications. The resonance frequencies are located at f1 = 1.6 GHz for the L‐band and f2 = 3 GHz for WiMAX applications. The maximum harmonic level is less than −20 dB for the frequencies up to 6.5 GHz (4f1). The maximum group delays are <1.26 ns at the first passband and 0.56 ns at the second passband. The proposed diplexer is fabricated and measured for verification. The comparison shows that both measured and simulated results are in a reasonable agreement.
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A Novel Microstrip Diplexer with Compact Size and High Isolation for GSM applications
Article
  • Feb 2020
  • AEU-INT J ELECTRON C
A novel high-performance microstrip diplexer is proposed and designed in this work. The design is based on patch and thin cells to operate at 0.78 GHz and 1.85 GHz for GSM applications. Owing to the symmetrical structure of the proposed resonator, the odd and even modes analyses are performed to get information about the resonator behavior. This information is useful to optimize the performance and miniaturization, simultaneously. The introduced diplexer has several advantages in terms of low insertion losses, low return losses, high isolation and compact size. It is well miniaturized and optimized with low insertion losses of better than 0.30 dB at the both channels. Meanwhile, the isolation between the channels is better than 42 dB. Our designed diplexer is able to attenuate 1st up to 5th harmonics. To validate the simulation results, we have fabricated the presented diplexer. The results show a good agreement between the measurement and simulation results.
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Contiguous-Channel Dual-Band Balanced Diplexer
Article
  • Apr 2019
A class of balanced dual-band planar diplexer with frequency-contiguous channels for the differential mode and high common-mode rejection is presented. It exploits double-stub-loaded filtering cells with resistors connected at the symmetry plane of the overall diplexer. In this manner, a sharp-rejection dual-band operation for each diplexer channel with transmission zeroes (TZs) at both sides of the differential-mode dual passbands is obtained. In addition, broadened common-mode suppression and low common-mode in-band input power reflection can be realized. The theoretical foundations and design guidelines for the devised dual-band differential-mode diplexer are provided. Moreover , for practical-validation purposes, a microstrip prototype with imbricated 1.51-GHz/2.41-GHz and 1.92-GHz/2.85-GHz lower and upper dual-band channels is manufactured and tested. Index Terms-Balanced diplexer, balanced filter, common-mode suppression, differential-mode diplexer, differential-mode filter, dual-band diplexer, microstrip diplexer, planar diplexer.
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New Microstrip Diplexer for Recent Wireless Applications
Article
  • Jun 2018
In this study, dual-channel diplexer using microstrip open loop coupled resonators has been designed and simulated; each channel has two operating band frequencies. This microstrip diplexer is designed for (1.424/1.732GHz) for first channel and (2.014/2.318GHz) for second channel. The simulated results for this device have insertion loss (1.8 and 1 dB) at load 1, and (1.5 and 3 dB) at load 2. Additionally, it has reasonable return loss magnitudes better than 10 dB and effective isolation between channels of35 dB. The proposed design has shown an uncomplicated topology, an effectual design method, small circuit size and narrowband frequency responses that are fitting for multi service wireless schemes.
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