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A Harmonic-Free Wilkinson Power Divider Using Lowpass Resonators

Authors:
Gholamhosein Moloudian at Tyndall National Institute
Gholamhosein Moloudian
Ali Lalbakhsh
Ali Lalbakhsh
Ali Lalbakhsh
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Sirous Bahrami at Pohang University of Science and Technology
Sirous Bahrami
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A Harmonic-Free Wilkinson Power Divider Using
Lowpass Resonators
Gholamhosein Moloudian
Wireless Sensor Network Group,
Tyndall National Institute,
University College Cork, Ireland.
ORCID: https://orcid.org/0000-
0001-7825-9408
Ali Lalbakhsh*
School of Engineering, Macquarie
University, Sydney, NSW 2109,
Australia
ORCID: https://orcid.org/0000-0003-
2033-0333
*Email:ali.lalbakhsh@mq.edu.au
Sirous Bahrami
Electrical Engineering
Department, Pohang University
of Science and Technology, South
Korea
ORCID: https://orcid.org/0000-
0002-4217-1006
Abstract—This paper presents a Wilkinson power divider
(WPD) capable of suppressing unwanted bands up to 16th
harmonic with high isolation. In this WPD, a lowpass filter
composed of a main resonator and three bended stubs are used to
guarantee a wide stopband. The presented WPD illustrates suitable
performance at 0.85 GHz for GSM applications. Isolation between
of output ports, input return loss and insertion loss are better than
24 dB, 20 dB and 3.4 dB, respectively.
Keywords—Wilkinson power divider, isolation, lowpass filter,
microtrip.
I. INTRODUCTION
In recent years, in line with the modern applications of
telecommunication systems, demand for microstrip devices with
compact size, low insertion loss (IL), wide stopband, high
isolation, and low cost has been rapidly increased. Filters [1-6],
diplexers [7-9], and power dividers [10-16] play a key role in
cutting-edge communication circuits. Over the recent years,
several resonators and methods such as hexagonal [1], artificial
periodic transmission lines [2], defected ground structure (DGS)
[4], and stepped impedance resonator [5-6] have been used for
designing lowpass filters (LPFs). In [1], a compact LPF with
sharp response and a harmonic suppression was presented for
application in envelop detector structures. In [3, 4], compact
LPFs with a wide stopband by using DGS are presented. A
compact LPF with high selectivity and ultra-wide stopband is
presented in [5]. In [6], a LPF with simple structure and sharp
response by using stepped impedance resonator and some open
stubs was reported. A compact diplexer with high isolation, low
insertion loss (IL) and tunable frequency response was presented
[7-9]. In recent years, several methods and techniques such as
high-low impedance resonator [10], radial and rectangular
resonator as a LPF structure [11], open stubs [12-14],
electromagnetic bandgap resonator [15] and T-shaped resonators
based on an artificial neural network [16] were reported for the
out-of-band improvement.
In this paper, a WPD with good performance at 0.85 GHz
utilizing radial resonator and three bended open stubs is
presented. The paper is organized as follows: designing LPF
structure is presented in Section II, the proposed WPD
(conventional and modified) is designed and simulated in Section
III and finally conclusion and discussion of proposed WPD are
reported in Section IV.
II. LPF STRUCTURE
A. Designing of Main Resonator
Fig. 1 depicts the topology, analysis of a presented radial stub
resonator (main resonator) and third-order LPF circuit. The
coefficients for this filter f=1.2 GHz, IL (dB)=0.1, N=3,
g0=g4=1, gL1=1.202, gL2=0.1614, gC2=1.255, gL3=1.604. To
calculate of the LC circuit (values of the inductors and
capacitors) and layout of the main resonator, relationships in eq.
(1 to 6) have been used [6, 17].
Fig. 1. Proposed resonators, (a). Third-order circuit, (b). Layout,
(c). Main resonator, (d). LC circuit, and (e). Frequency response.
= 1
2 (1)
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= 1
2
1
(2)
 = λ
2 2
 (3)
= λ
2 (2) (4)
The values for inductors: W=0.1, lL1=13.8, lL3=15.3,
lL2=13.8 and for capacitors: W=4, lC2=9.4 are obtained by
optimization method in ADS software (all in mm). The
dimensions of the proposed main resonator as depicted in Fig. 1
are a=5.4, b=5.4, R=3.7, and p=5.2 (all in mm). The proposed all
structures in this paper have been designed on the Rogers-
RT/Duroid 5880 substrate with a thickness of 10 mil (0.254 mm),
dielectric constant of 2.2 and loss tangent of 0.0009. The values
of LC equivalent circuit for the main resonator have been
obtained by using optimization method in ADS that are La=0.5
nH, Lb=4.66 nH, CR= 1.67 pF, and Lp=4.38 nH.
B. Suppression Cells
To achieve a wider stopband bandwidth for the LPF, we need
to use suppressor cells. In fact, these cells create some
transmission zeros (TZs) in the stopband and it is very useful for
achievement to the wider stopband. The proposed suppressor
cells are illustrated in fig. 2. The proposed suppressor cells
consist of three bended open stubs which create three TZs near
4.2 GHz, 6.1 GHz and 7.8 GHz.
Fig. 2. Proposed suppression cells.
C. LPF Design
The proposed LPF consists of a radial resonator as main
resonator and three bended open-ended stubs as harmonic
suppression cell is depicted in fig. 3. According to the simulation
results, the -3 dB cut-off frequency is 1.6 GHz, IL in the passband
is better than 0.3 dB and stopband is wide from 2.1 GHz to 8.7
GHz with 15 dB attenuation level.
III. DESIGNING OF WILKINSON POWER DIVIDER
A. Designing of Conventional Power Divider
The conventional WPD composed of two quarter-wavelength
transmission line (50√2 Ω ) and a 100 Ω resistor is depicted in
Fig. 4. This structure has been designed at 0.85 GHz.
Fig. 3. Proposed LPF.
Fig. 4. Proposed conventional power divider.
Fig. 5. Simulation results of the proposed conventional power
divider.
B. Designing of Modified Power Divider
To achieve a wider stopband and suppression of unwanted
harmonics, the proposed LPF is fixed in the proposed
conventional WPD. The proposed modified WPD is depicted in
This paper's copyright is held by the author(s). It is published in these proceedings and included in any archive such as IEEE
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Fig. 6. The simulation results of the conventional WPD are
shown in Fig. 5. According to the simulation results, the insertion
loss (S21) or IL, isolation (S32) and input return loss (S11) at 0.85
GHz are better than 3.08 dB, 32 dB and 29 dB, respectively.
According to Table 1, the insertion loss (S21) or IL, isolation (S32)
and input return loss (S11) at 0.85 GHz are better than 3.4 dB, 24
dB and 20 dB, respectively.
Fig. 6. Proposed modified WPD and simulation results.
The suppression levels of the WPD for the second to
sixteenth harmonic frequencies (f2 to f16: 1.7, 2.55, 3.4, 4.25, 5.1,
5.95, 6.8, 7.65, 8.5, 9.35, 10.2, 11.05, 11.9, 12.75 and 13.6
GHz), are better than 8.7, 25, 20.1, 28.8, 23.2, 28.9, 27.3, 53,
18.2, 16, 14.2, 13.8, 12.6, 23.2 and 15.8 dB, respectively.
Table 1. Comparison of the proposed WPD with other works.
Refs. F0
(GHz)
Isolation
S32 (dB)
S11
(dB)
S21
(dB)
Harmonics
suppression
[10] 2.65 22 27 3.3
3
rd
and 5
th
[11] 1.8 34.6 20.4 3.01
2
nd
to 6
th
[12] 1.8 20.1 21.2 3.1 2
nd
to 11
[15] 1.8 20 20 3.2 2
nd
and 3
rd
[16] 1.75 23 20 3.1
2
nd
to 5
th
This
Work 0.85 24 20.8 3.4 2nd to 16th
IV. CONCLUSION
In this paper, a modified WPD with high isolation and harmonic
suppression structure is presented. The proposed LPF is utilized
in the conventional WPD as a harmonic suppresser structure to
achieve a wider stopband and remove unwanted harmonics.
According to the obtained results, the WPD has a good
performance at 0.85 GHz, suitable for LTE and GSM
applications.
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Xplore under the license granted by the "Agreement Granting EurAAP Rights Related to Publication of Scholarly Work."
Authorized licensed use limited to: POSTECH Library. Downloaded on August 22,2022 at 03:28:07 UTC from IEEE Xplore. Restrictions apply.
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This paper's copyright is held by the author(s). It is published in these proceedings and included in any archive such as IEEE
Xplore under the license granted by the "Agreement Granting EurAAP Rights Related to Publication of Scholarly Work."
Authorized licensed use limited to: POSTECH Library. Downloaded on August 22,2022 at 03:28:07 UTC from IEEE Xplore. Restrictions apply.
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In this article, a modified microstrip Wilkinson power divider with harmonics suppression for GSM communications applications is presented. For low-pass filter designing, one open stub, one radial resonator, and two rectangular resonators are used. According to results related to insertion losses (|S 21 | and |S 31 |), stopband is wide and equal to 7.5 GHz (3.4-10.9 GHz), under the condition of 20 dB harmonic suppression level. The results show that at the designed frequency of 1.8 GHz, the input return loss (|S 11 |) and output return losses (|S 22 | and |S 33 |) are better than 22 dB, and the isolation between of output ports (| S 32 |) is better than 30 dB. The size of the proposed power divider is compact and equal to 10.6 × 14.6 mm 2. Finally, the proposed power divider was fabricated and the measurement results illustrate a good agreement with simulation results.
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Design and fabrication of a continuous tunable microstrip lowpass filter with wide stopband and sharp response
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Tunable microstrip lowpass filters (LPFs) with a good performance are used in most telecommunication systems. In this article, a third‐order circuit with stepped impedance resonator is used to design LPF, and suppression cells are used to improve the performance of the filter in stopbands up to 20 GHz. The −3 dB cut‐off frequency can be controlled in the range of 0.35 to 1 GHz with the tuning range of 96%. Rejection stopbands of 30 dB (type‐I) and 20 dB (type‐II) can be extended to more than 20 GHz. For the passband, the insertion loss variations are in the range of 0.35 to 2.12 dB. The proposed tunable LPF has a sharp roll‐off rate (42‐96 dB/GHz). The varactor‐tuned microstrip LPF is designed, simulated, fabricated, and measured. The results of simulation and measurement for the proposed LPF are in good agreement. The size of the proposed tunable LPF is small and the filter dimensions are equal to 0.267λg × 0.13λg.
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All-Metal Wideband Frequency-Selective Surface Bandpass Filter for TE and TM Polarizations
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  • Jan 2022
A novel technique to design a low-cost Frequency-Selective Surface (FSS) bandpass filter is presented in this paper. Wideband polarization-independent FSS bandpass filters are predominantly made of multiple microwave dielectric substrates, or non-commercially available composite materials with or without active components, contributing to a very high manufacturing cost. The presented FSS filter has neither microwave substrates, nor any active devices, while it has a large controllable operational frequency band, which can support all polarizations, due to its symmetrical configuration. To the authors’ knowledge, such polarization independent wideband bandpass response has never been achieved by any low-cost fully-metallic FSS filter. The proposed FSS filter is made of three thin metal sheets composed of an Engineered Metallic Substrate (EMS) and metallic Orthogonal Dipole Resonator (ODR). The EMS is responsible for ensuring mechanical integrity of the filter without imposing electromagnetic restrictions throughout the desired frequency band. The integration of EMS and ODRs realizes a fully controllable wideband bandpass verified thorough circuital and modal analyses. According to the predicted and measured results, the FSS filter has a large bandwidth of around 31%, extending from 8.76 GHz to 11.96 GHz with sharp roll-offs for the normal incidence. Simulated and Measured results show a low sensitivity of the FSS filter response to oblique angles of incidence for both TM and TE polarizations.
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Design and fabrication of a miniaturized lowpass-bandpass diplexer with wide tuning range and high isolation
Article
  • Jul 2019
In this article, a compact lowpass-bandpass (LP-BP) diplexer with high isolation for wireless telecommunication applications is presented. The −3 dB cut-off frequency of the lowpass filter (LPF) is equal to 1 GHz. The roll-off-rate (ROF or ζ) parameter is sharp and equal to 108.8 dB/GHz, and the rejection level in the stopband is 20 dB. The center frequency of bandpass filter (BPF) is 2.4 GHz. The tuning range of −3 dB cut-off frequency of the LPF is wide and ranges from 0.3 to 0.89 GHz. The tuning range of center frequency of the BPF is wide and ranges from 2.65 to 3.1 GHz. The obtained isolation between the two output ports is better than 30 dB. The proposed tunable LP-BP diplexer is designed, simulated, fabricated and measured. The results of measurement and simulation are in good agreement with each other. The proposed diplexer has a compact size of 64 × 38 mm².
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Design, Simulation and Manufacturing Microstrip Low-pass Filter by Wide Stopband and Changing Fast Situation from Passing State to Stopping
Article
  • May 2018
In this paper, a new microstrip low-pass filter will be presented for achieving high ability to choose wide stopband and suitable operation. This filter is built after design and simulation, and results of measurement will confirm the design accuracy. The results show that the overall performance of the recommended structure is improved in terms of physical dimensions, sharpness of response, and width of stopband, compared to old structures. Cut-off frequency of filter is 1.1 GHz. The stopband is so wide, and the amount of weakness in this band is equal to −20 dB. Roll-off rate parameter of the proposed filter is equal to 240 dB/GHz. This means that changing filter condition moves rapidly from passing to stop state. Size of proposed filter is small and equal to 27 mm × 16 mm. Results of simulation and measurement of the fabricated sample exhibit the same reaction.
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Tunable Bandpass Filter Using Switched Tunable Diplexer Technique
Article
  • Dec 2016
In this paper, a new technique using two p-i-n diodes to switch between two channels of a tunable diplexer with constant return loss is proposed to design tunable bandpass filter (BPF) with wide frequency tuning range (FTR). The used third-order tunable diplexer with two independently tuned channels consists of one common varactor-tuned lumped-element dual-resonance resonator (LE-DRR) and two varactor-tuned LC resonators. The ports of its two channels are connected by a single-pole double-throw (SPDT) switch, so that one port of tunable BPF is constituted. And its common port serves as the other port of tunable BPF. In the switched tunable diplexer design, its direct current (DC) bias voltages are also appropriately selected to improve the in-band and out-of-band performances of tunable BPF. As examples, a third-order tunable diplexer with constant return loss of 15 dB is firstly designed. The measured results show that the 3 dB cutoff frequency of its lower channel can be tuned from 0.5 GHz to 1.02 GHz, while the 3 dB cutoff frequency of its upper channel can be tuned from 1.01 GHz to 1.78 GHz. Then, a tunable BPF is designed, and its 3 dB cutoff frequency covers from 0.485 GHz to 1.82 GHz. The proposed tunable BPF exhibits good return loss, wide FTR, and compact size.
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Tunable Dual-Band Filter and Diplexer Based on Folded Open Loop Ring Resonators
Article
  • Dec 2016
Tunable dual-band filter and diplexer based on folded open loop ring resonators (OLRRs) are proposed in this paper. Two pairs of OLRRs of different center frequencies are utilized to couple with microstrip transmission lines in these two devices, and there is no extra matching network in the diplexer structure. Maximal magnetic coupling and high isolation can be obtained by placing the resonators at proper positions along the feeding lines. The passband/channel frequencies of the dual-band filter/diplexer can be tuned independently by varying DC bias voltages applied to the varactors loaded at one end of the resonators. In addition, a broad harmonic suppression can be obtained by choosing appropriate lumped elements adding to the OLRRs. The performances of the proposed devices can be verified by the simulated and measured results.
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