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Bioinspired planar switched beam network using Butler matrix on a flexible substrate targeting multifaceted millimeter-wave applications
Abstract
This paper details the design and development of a planar switched beam network using 4 × 4 Butler matrix (BM) over a thin and flexible type biocompatible substrate. Four mils thick liquid crystal polymer (LCP) is used as a substrate here ( ϵ r = 2.92, tan δ = 0.002). The proposed design is centered at 28 GHz, targeting commercial millimeter-wave applications. Floral-shaped antenna with defective ground structures has been implemented as basic radiating elements. The whole structure is based on microstrip line configuration. The architecture occupies an area of 23.85 × 19.20 mm ² over the LCP substrate. Individual components of the BM are detailed here, followed by a system analysis of the whole integrated structure. The present work also covers the electrical equivalent circuit modeling of the whole beam-forming network. The fabricated prototype offers better than 18 dB return losses at each input port for the desired frequency band with 6 dBi (max.) peak gain and 500 MHz bandwidth around the center frequency. Port-to-port isolation of better than 15 dB is achieved with this topology. Experimental and simulated results are in good agreement in all aspects. A comparative study is also chalked out to highlight the significance of the current research work with respect to alike earlier reported structures.
This paper presents a detailed design and realization of a switched‐beam network. The concept is verified using planar microstrip technology. Beam forming network is constructed by a 4 × 4 Butler matrix on a single‐layer substrate. The proposed design is centered at 5.5 GHz (C‐band) for commercial WLAN applications. Individual components of the Butler matrix are discussed here and further integrated system analysis is outlined in this article. The whole architecture is realized on low‐loss FR4 substrate. Design aspects, measured results and comparative study are summarized here.
This work describes the capability of Liquid Crystal
Polymer (LCP) as an attractive choice for antenna usages
targeting several bio-medical applications. One lower frequency
application details about the development of a conformal,
wideband, fractal implemented miniaturized antenna for
wireless capsule endoscopy purpose over 2450 MHz Industrial,
Scientific and Medical (ISM: 2400-2480 MHz) band. Whereas,
another application outlines the developmental activity targeting
high gain 100 GHz planar antenna array for medical imaging
with appreciable resolution. Both of the works have been
explained in detail with design, modeling, and fabrication issues.
Substrate has also been modelled for high-frequency application.
This work presents a 28-GHz Butler matrix based switched-beam antenna for fifth-generation (5G) wireless applications. It integrates a 1 × 4 microstrip antenna, a 4 × 4 Butler matrix, and a single-pole four-throw (SP4T) absorptive switch in a single planar printed circuit board and is housed in a metal enclosure. Co-integration of a packaged switch chip with the Butler matrix based switched-beam antenna greatly enhances the form factor and integration level of the entire system. A wideband two-section branch line coupler is employed to minimize the phase and magnitude errors and variations of the Butler matrix. The aluminum metal enclosure stabilizes the electrical performances, reduces the sidelobes, and improves the structural stability. The fabricated antenna with the metal enclosure assembled has a dimension of 37 × 50 × 6.2 mm3. With an RF input signal fed to the antenna’s input port through a single Ka-band connector, and the switching states chosen by 2-bit dc control voltages, the antenna successfully demonstrates four directional switched beams. The beam switching operations are verified through the over-the-air far-field measurements. The measured results show that the four beam steering directions are −43°, −17°, +10°, +34° with side lobe levels < −5.3 dB at 28 GHz. The antenna also shows reasonably wideband radiation patterns over 27–29 GHz band. The 10-dB impedance bandwidth is 25.4–27.6 GHz, while a slightly relaxed 8-dB bandwidth is 25.2–29.6 GHz. Compared to previous works, this four-directional switched-beam antenna successfully exhibits the advantages of high integration level and satisfactory performances for the 28-GHz 5G wireless applications.
In this research paper, work relating to microstrip monopole antenna is carried out. The objective is to aim for the ultra-wideband range which is 3.1 to 10.6 GHz. For this, a bio-inspired novel Korean striped maple leaf structure; under the binomial name, Acer Tegmentosum is considered. The design is carried out on a ground plane with dimensions 60 x 60 mm (W x L). The substrate used is FR4 epoxy with dielectric constant 4.4. The overall leaf dimension was taken to be 43.48 mm in terms of width with two adjacent petals of length 25.12 mm each and a center petal of length 16.42 mm. The maple leaf patch is supported by a partial ground of dimension 60 x 13.5 mm (W x L). Simulations were done and bandwidth achieved was 9.62 GHz (152.98%) from 1.47 GHz to 11.1 GHz with a peak gain of 6.53 dB. Comparisons are drawn for different antenna parameters. The proposed monopole structure is also fabricated and tested where a good agreement between simulated and measured results was seen.
This paper presents electrical equivalent circuit modelling of various fractal-based UWB antennas. Three different designs have been discussed here as case studies, whose characteristics are diversified in nature. Even the implemented fractal geometries are also unique in nature for these antenna problems. An easy circuit model for each antenna structure is proposed which deciphers the insight device physics of the structure. Without applying much more complicated mathematical jugglery, the models have been presented here. Finally, a comparison of FEM simulated data and the result obtained from circuit modelling is concluded, which establishes the validity of the proposed models.
Millimeter wave (mm-Wave) technology is likely the key enabler of 5G and early 6G wireless systems. The high throughput, high capacity, and low latency that can be achieved, when mm-Waves are utilized, makes them the most promising backhaul as well as fronthaul solutions for the communication between small cells and base stations or between base stations and the gateway. Depending on the channel properties different communication systems (e.g., beamforming and MIMO) can accordingly offer the best solution. In this work, our goal is to design millimeter wave beamformers for switched beam phased arrays as hybrid beamforming stages. Specifically, three different analog beamforming techniques for the frequency range of 27–33 GHz are presented. First, a novel compact multilayer Blass matrix is proposed. Second, a modified dummy-ports free, highly efficient Rotman lens is introduced. Finally, a three-layer true-time-delay tree topology inspired by microwave photonics is presented.
Millimeter-wave (mmWave) networks with the frequency spectrum ranging from 30 GHz (with wavelength 10 mm) to 300 GHz (with wavelength 1 mm), can support massive wireless data in fifth-generation (5G) systems. Importantly, large colocated antenna elements can be exploited at the base station (BS) to facilitate beam-steering synthesis along the users’ directions. This paper proposes the Butler matrix (BM) frequency diverse retrodirective array (BM-FDRA) beamforming network at the BS for multiuser communications in mmWave networks. We utilize the orthogonal feature of the M×M BM with M elements of the FDRA to create directional beams for concurrent transmission towards different users in range-angle locations. The proposed scheme has the following merits: (a) there is beam-steering orthogonality without beam interferences and (b) there is automatic tracking functionality, i.e., the prior knowledge on the user location is not required by the proposed BM-FDRA at the BS. The proposed method can serve multiple users concurrently using the beam-steering orthogonality property. Furthermore, performance metrics such as the multiaccess secrecy sum rate (SSR) model, bit error rate (BER), system capacity, and energy efficiency are examined. The proposed BM-FDRA scheme achievements are highlighted via simulation results.
This paper proposes a novel compact 4x4 butler matrix (BM) with improved bandwidth based on open-circuit coupled-lines and interdigital capacitor unit-cell to develop composite right/left handed (CRLH) transmission-line (TL) metamaterial structure. The BM is implemented by the combination of compact 3dB quadrature hybrid couplers, 0dB crossover and 45° phase shifter on a single FR4 substrate (εr = 4.3 and h = 1.66 mm). The simulated and measured result shows that the return loss and isolation loss are better than 14 dB at all the ports, good insertion loss of -7 ± 2dB, which cover the frequency range of 3.2 GHz to 3.75 GHz. The phase difference of -45°,135°, -135° and +45° are achieved with a maximum average phase tolerance of 5°. The overall dimension of the BM is 70mm x 73.7mm, which shows the compactness of the proposed design that is 75% size reduction and 8.2 times improvement in the bandwidth (550MHz) as compared to conventional BM. The CST microwave studio is used to design and perform the simulations. Additionally, the simulated and measured scattering parameters and phase differences show that they are in good agreement. This compact and improved bandwidth of the proposed BM is suitable for 5G beamforming network.
This work presents a Butler matrix based four-directional switched beamforming antenna system realized in a two-layer hybrid stackup substrate for 28-GHz mm-Wave 5G wireless applications. The hybrid stackup substrate is composed of two layers with different electrical and thermal properties. It is formed by attaching two layers by using prepreg, in which the circuit components are placed in both outer planes and the ground layers are placed in the middle. The upper layer that is used as antenna substrate has εr = 2.17, tanδ = 0.0009 and h = 0.254 mm. The lower layer that is used as a Butler matrix substrate has εr = 6.15, tanδ = 0.0028 and h = 0.254 mm. By realizing the antenna array on the lower-εr layer while the Butler matrix on the higher-εr layer, the Butler matrix dimension is significantly reduced without sacrificing the array antenna performance, leading to significant overall antenna system size reduction. The two-layer substrate approach also significantly suppresses parasitic radiation leaking from the Butler matrix toward the antenna side, allowing overall radiation pattern improvement. The fabricated beamforming antenna is composed of 1 × 4 patch antenna array and a 4 × 4 Butler matrix. The measured return loss is lower than −8 dB at all ports in 28-GHz. It demonstrates the switched beam steering toward four distinct angles of—16°, +36°, −39°, and +7°, with the sidelobe levels of −12, −11.7, −6, and −13.8 dB, respectively. Antenna gain is found to be about 10 dBi. Due to the two-layer hybrid stackup substrate, the total antenna system is realized only in 1.7λ × 2.1λ, which shows the smallest form factor compared to similar other works.
There are three mathematical conditions that must be solved simultaneously for the analysis of a fully-symmetric radio-frequency (RF) crossover. When additional reciprocal two-port networks - which might be of an arbitrarily high complexity - are appended at each port of a crossover, analysis of the modified crossover becomes very tedious. Therefore, this paper examines the requirement of the three conditions in such scenario. We show that two of the three conditions can be invoked without considering the additional two-port networks altogether. This is a remarkable simplification considering that the additional two-port networks, in general, would necessitate dealing with more involved algebraic calculations. To demonstrate the usefulness of the presented theory, for the first time, analysis and design of a dual-frequency port-extended crossover is included. A prototype of the dual-frequency crossover operating concurrently at 1 GHz and 2 GHz is manufactured on a Rogers RO4350B laminate having 30 mil substrate height and 3.66 dielectric constant. The close resemblance between the EM simulated and measured results validates the analytical equations.
This letter presents acompact dual-layer 4 $\times$ 8 Butler matrix (BM) with sidelobe level (SLL) suppression in substrate integrated waveguide (SIW) technology. Addressing the excessive crossovers in the classic 4 $\times$ 8 BM, a novel dual-layer configuration is proposed here.Such a configuration can help reduce the required crossovers from original five sets to merely one set. Therefore, the 4 $\times$ 8 BM can be significantly simplified to achieve better compactness. Based on this configuration, a SIW dual-layer 4 $\times$ 8 BM is designed with a dimension of 6.1λ $\times$ 4.1λ. To evaluate its SLL suppression effect, a multibeam array fed by the proposed BM is designed, simulated and measured.
In this work, an H-plane and an E-plane single-ridge waveguide T-junction exhibiting compact size and broadband performance are presented. Thanks to these features the proposed devices turn out to be key components for the implementation of high-performance multilayer antenna beam-forming networks. Effectiveness and suitability of such T-junctions are demonstrated through the design of a broadband array antenna feeding network. The presented components operate at Ku band, nevertheless the adopted architectures are fully scalable to other frequency band of interest.
This communication presents a low-cost 77-GHz switched-beam slot antenna array driven by a Butler matrix. In the proposed configuration, four broadband couplers are combined and crossovers are effectively avoided. In this case, the overall circuit and beamforming network losses are considerably reduced. A 4 × 4 planar SIW Butler matrix is designed and demonstrated for integrated beamforming network applications, which exhibits about 7 degrees phase error and ±0.75 dB coupling imbalance over 11% bandwidth. This experimentally prototyped matrix is integrated with a four-array slot antenna on the same substrate. An alternating displacement of the slots in subsequent radiating waveguides is proposed to save the arrangement of the input ports and to achieve broadband performances. Measured radiation patterns are in good agreement with simulated counterparts over the proposed 77-GHz frequency range.
In this paper, solutions for developing low cost electronics for antenna transceivers that take advantage of the stable electrical properties of the organic substrate liquid crystal polymer (LCP) has been presented. Three important ingredients in RF wireless transceivers namely embedded passives, a dual band filter and a RFid antenna have been designed and fabricated on LCP. Test results of all 3 of the structures show good agreement between the simulated and measured results over their respective bandwidths, demonstrating stable performance of the LCP substrate.
Electronic packaging evolution involves systems, technology and material considerations. In this paper, we present a liquid crystal polymer (LCP) based multilayer packaging technology that is rapidly emerging as an ideal platform for low cost, multi-band and reconfigurable RF front-end module integration. LCP's very low water absorption (0.04%), low cost and high electrical performance makes it very appealing for RF applications. Here we describe main characteristics and real performance of LCP substrate, by means of several design examples. A Single-Input-Single-Output (SISO) dual-band filter operating at ISM 2.4-2.5 GHz and UNII 5.15-5.85 GHz frequency bands, a dual polarization, dual frequency 2×1 antenna operating at 14 and 35 GHz, and a WLAN IEEE 802.11a compliant compact module (volume of 75×35×0.2 mm<sup>3</sup>) have been fabricated on LCP substrate, showing the great potential of the System-On-Package approach for 3D compact, multi-band and reconfigurable integrated RF and millimeter waves functions and modules.
This article outlines the various configurations of co-planar waveguide (CPW) structures widely employed in silicon-RF (Si-RF) technology along with its empirical circuit modeling. Design aspects, realization techniques, mitigation strategies of commonly associated spurious modes, and finally various kinds of discontinuities in the CPW structures for Si-RF technology has been detailed in this work. Empirical modeling along with full-wave analysis of all these circuits has been carried out to decipher the actual device physics. Qualitative as well as quantitative ways have been adopted here for expressing various parasitic.
A perfect magnetic conductor (PMC) packaging concept is utilized at 30 GHz, which suppresses the higher order cavity modes, improves insertion losses, and helps in developing packaged microstrip lines (PMSLs) and double-ridge gap waveguide (DRGW) transmission lines. The Quasi-TEM PMSLs are used to design quadratic hybrid, crossover, and phase shifters as components of a wideband 4 x 4 Butler matrix (BM) on a single substrate. Two types of electromagnetic bandgap (EBG) unit cells--full height and half height--are investigated to realize artificial magnetic conductors (AMCs) required for the present design. A parametric study is performed for all components. BM is numerically assembled from these components and analyzed. It achieves a 5-GHz (28-33 GHz) bandwidth with return loss and isolation, both better than 15 dB. At 30 GHz, the insertion loss is 0.8 ± 0.3 dB, and antenna-ports' phase distributions are ±45° and ±135°. E-plane-flared horn antennas terminate the BM antenna ports as a linear array. The DRGW horn antenna is designed to reduce the scan loss within an array environment. The H-plane fan-beam switching covers ±42° with a maximum gain of 11.7 and 11.2 dBi for 1R and 2R beams, respectively. The H-plane element pattern and the half-height EBG AMC at the array aperture help to maintain 0.5 dB of gain loss for the outer beams (2R and 2L) compared to the inner beams (1R and 1L). The multibeam prototype is the right candidate for millimeter-wave 5G base station and can easily be scaled to higher frequency bands.
Increasing data transfer rates for future millimeter-wave communications requires high capacity radio channels and user-centric communication network environments. Therefore, special requirements, such as wide-angle beam steering, wide operational frequency bandwidth, and simultaneous operation with orthogonal polarizations, are essential for telecommunication antennas. In this communication, we present a compact patch antenna array with a Butler matrix (BM) feed network for the frequency band of 26-31.4 GHz. The 16-element planar array has been designed to operate with the two linear orthogonal polarizations and provide ±42° beam switching. To ensure the wideband operation, a novel combination of planar couplers, crossovers, and phase shifters is designed to form the BM. A new phase-shifter topology is used which is based on a combination of open-short stubs and the Shiffman phase shifter. The design is fabricated on a low-cost multilayer board with a size of 120 × 70 × 1.62 mm
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. The size of the feeding network, which is implemented on a single board, is 76 × 23 × 0.1 mm
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. The experimental measurements of return loss, mutual coupling, and radiation patterns confirm simulated results.
This paper presents the design of a multibeam phased array of microstrip patch antennas at 38 GHz with a parallel-plate beam-forming network (BFN). This antenna set, including the antenna elements and BFN, is equivalently triple-folded into two stacked printed circuit board substrates for a compact design of nearly 60% size reduction in comparison to conventional implementation on a single planar dielectric substrate. In particular, the BFN employs a shaped metal reflecting boundary in the bottom substrate to transform the cylindrical waves of feed excitations into planar ones for a relatively linear phase variation to feed the column subarrays on the top substrate. A slot feeding transition structure is designed to couple the energy from the BFN to feed the microstrip patch antenna ports. These two mechanisms are then used to compensate the phase distortions due to BFN cavity disturbance and mutual coupling from subarrays of antennas at millimeter wave frequencies. Numerical techniques to optimize both the metal reflecting boundary and slot feeding transition structure are introduced to minimize phase distortions. Numerical and experimental results are presented to demonstrate the radiation characteristics of the integrated antenna set.
A compact 38-GHz multi-beam antenna array is presented for 5G applications. A beamforming network featuring a substrate integrated waveguide (SIW) multi-folded 4 × 8 Butler matrix is constructed. Benefiting from multilayer structure, the Butler matrix is highly integrated and assembled underneath the radiators to achieve compactness. The Butler matrix is then combined with an 8 × 10 SIW slot-coupled patch array to establish four steering beams along the H-plane and to accomplish size reduction of 53.5% in its longitudinal direction. For demonstration, one prototype of the proposed antenna array was fabricated. The measured four beams point toward ±36° and ±12° with gains equal to 19.8 and 21 dBi, respectively.
This paper presents a new approach to implement planar Antipodal Vivaldi Antenna (AVA) design. A nature fern inspired fractal leaf structure is implemented here. Impedance bandwidth (-10 dB) of the proposed antenna is around 19.7 GHz starting from 1.3 GHz to 20 GHz. The lower operating frequency of this antenna is reduced by 19% with the 2nd iteration as compared to the 1st iteration of fractal leaf structure. The prototype antenna is fabricated and tested in frequency as well as in time domains to obtain various transfer characteristics along with common antenna parameters. Experimental results show that good wide-band feature, stable radiation pattern and promising group delay of less than 1 ns signatures are obtained, which agree well with the simulated data. The miniaturized proposed antenna structure becomes an attractive choice in microwave imaging applications because of its ultra-wide fractional bandwidth at 175%, high directive gain of 10 dBi and finally appreciably large fidelity factor above (>90%).
The remarkable growth of wireless data traffic in recent times has driven the need to explore suitable regions in the radio spectrum to meet the projected requirements. In pursuance of this, millimeter wave communications have received considerable attention in the research fraternity. Due to the high path and penetration losses at millimeter wavelengths, antenna beamforming assumes a pivotal role in establishing and maintaining a robust communication link. Beamforming for millimeter wave communications poses a multitude of diverse challenges due to the large channel bandwidth, unique channel characteristics, and hardware constraints. In this paper, we track the evolution and advancements in antenna beamforming for millimeter wave communications in the context of the distinct requirements for indoor and outdoor communication scenarios. We expand the scope of discussion by including the developments in radio frequency system design and implementation for millimeter wave beamforming. We explore the suitability of millimeter wave beamforming methods, both, existing and proposed till midyear 2015, and identify the exciting new prospects unfolding in this domain.
In this work, the design, fabrication, and testing of low sidelobe level (SLL) Butler matrix-based beamformers is presented. The paper is divided in two parts. The first part deals with the conventional technique of simultaneous excitation of input ports. The second part introduces some novel modified low SLL Butler matrices, as an alternative advantageous design choice. Circuit architecture makes use of asymmetric branch line couplers able to provide high values of output power division ratios. Radiation patterns with SLLs far lower than −23 dB are achieved, without the use of any additional circuitry, in opposition to the case of simultaneous port excitation. Apart from SLL reduction, the switched line-phase shifter technique is applied in order to increase the number of radiated beams and improve scanning coverage. The beamformers are suitable for interference suppressing point-to-multipoint ground communications, satellite and radar/EW/SIGINT systems. Several microstrip circuit prototypes are designed, fabricated, and tested, whereas extended simulation and measurements results are adduced.
A biologically inspired antenna system, based on the wasp's curved antennae, is presented. A stepped quarter-wave Chebyshev transformer was calculated to minimize the frequency-domain reflection and to maximize the power-transfer gain. The widths and separations of the coplanar strips were then computed to match the Chebyshev design, and smooth curves were fit to the computed steps. A portable transceiver, powered by batteries, was used, along with visual interface software, to automatically monitor the data transfer. A specific MAC address was assigned to verify the accuracy of the data.
A two-octave 4×4 Butler matrix has been presented, for the first time in multilayer microstrip asymmetric coupledline technology. To achieve two-octave frequency band in terms of amplitude and phase responses a recently developed approach has been used in which multi-section coupled-line directional couplers and Schiffman C-sections are applied. A highperformance three-section coupled-line 3-dB microstrip directional coupler has been utilized as a basic element of the Butler matrix and two compensated microstripline Schiffman C-sections have been designed to provide appropriate differential phase characteristics. A very good performance has been achieved over two-octave frequency band in terms of amplitude and phase responses. The designed network can be easily applied in large microstrip networks as a surface mount element.
Many insects possess acute directional hearing capabilities and are able to localize sound sources of interest with an astonishing degree of precision. An analogy can be drawn between the auditory systems of such insects and electrically small antenna arrays that demonstrate enhanced sensitivity to the direction of arrival of an electromagnetic wave, compared to regular arrays occupying the same aperture. Inspired by this, we discuss the design of biologically inspired electrically small antenna arrays that mimic the hearing mechanism of such insects. A method for designing such antenna arrays is presented, and the tradeoffs involved in achieving this enhanced sensitivity are discussed. Simulation and measurement results of two fabricated prototypes are also presented and discussed in this letter.
A 60-GHz substrate integrated waveguide Butler matrix designed based on a systematic approach is fabricated by a standard single-layer print circuit board process, which is more economical for mass production than are the advanced processes such as low-temperature co-fired ceramic, thick-film process, etc. The systematic approach involves design equations, simulations, and measurements. Starting with a set of explicit design equations for the short-slot couplers, one calculates the structure dimensions. The calculated dimensions are then optimized with full-wave simulation to finalize the design of the key components, including the couplers and phase shifters. With the use of a noncoaxial multiport measurement technique, the characteristics of the components are acquired through a probe station and a two-port vector network analyzer. Measurement technique plays a critical role in the systematic design approach. By measuring at the intrinsic ports or the wave ports defined in the full-wave simulations, the components are unambiguously verified and then integrated to complete the design of the Butler matrix. The resulting Butler matrix is also verified by the measured eight-port S -matrix, which is shown in good agreement with the simulated one. As the measured results of the Butler matrix show, for the operating bandwidth from 58 to 62 GHz, the reflections and isolations are lower than -13.5 dB and the insertion losses are below 2.5 dB. Much like the measured results of the components, the measured eight-port S -matrix not only verifies the design of the Butler matrix, but also will facilitate the follow-on design of a switched-beam antenna array.
This article presents the design and realization of 8 × 8 and 16 × 16 Butler matrices for 7 T MRI systems. With the focus on low insertion loss and high amplitude/phase accuracy, the microstrip line integration technology (microwave-integrated circuit) was chosen for the realization. Laminate material of high permittivity (ε(r) = 11) and large thickness (h = 3.2 mm) is shown to allow the best trade-off of circuit board size versus insertion loss, saving circuit area by extensive folding of branch-line coupler topology and meandering phase shifter and connecting strip lines and reducing mutual coupling of neighboring strip lines by shield structures between strip lines. With this approach, 8 × 8 Butler matrices were produced in single boards of 310 mm × 530 mm, whereas the 16 × 16 Butler matrices combined two submatrices of 8 × 8 with two smaller boards. Insertion loss was found at 0.73 and 1.1 dB for an 8 × 8 matrix and 16 × 16 matrix, respectively. Measured amplitude and phase errors are shown to represent highly pure mode excitation with unwanted modes suppressed by 40 and 35 dB, respectively. Both types of matrices were implemented with a 7 T MRI system and 8- and 16-element coil arrays for RF mode shimming experiments and operated successfully with 8 kW of RF power.
The multidirectional antenna is a linear array which is connected to a multiplex transmission line network. The schematic of the network and array is shown. The principle of operation of this antenna is then derived from an analysis of the forward scatter of a series-exoited array, the radiating elements of whioh are connected to the feedline by direotional couplers. A travelling wave progresses from the input terminal to the load terminal giving up power at each directional coupler to the corresponding radiating element. Many practical applications or this technique are possible. particularly wherever simultaneous surveillance of a wide angular sector with the resolution of a narrow beam is required.
The "radiansphere" is the boundary between the near field and the far field of a small antenna. Its radius is one radianlength (¿/2¿), at which distance the three terms of the field are equal in magnitude. A "small" antenna is one somewhat smaller than the radiansphere, but it has a "sphere of influence" occupying the radiansphere. The power that theoretically can be intercepted by a hypothetical isotropic antenna is that which flows through the radiansphere or its cross section, the "radiancircle." From a small electric dipole, the far field of radiation is identified as a retarded magnetic field. Between two such dipoles, the far mutual impedance is that of mutual inductance, expressed in terms of space properties and the radiansphere. A small coil wound on a perfect spherical magnetic core is conceived as an ideal small antenna. Its radiation power factor is equal to the ratio of its volume over that of the radiansphere. A fraction of this ratio is obtainable in various forms of small antennas (C or L) occupying a comparable amount of space. A radiation shield, in the form of a conducting shell the size of the radiansphere, enables separate measurement of radiation resistance and loss resistance.
A conventional Butler matrix can be modified to achieve a network which is symmetric about an axis midway between the input and output lines. Such a Butler matrix network can be further modified so that the input and output ports are identical. In this manner the half-matrix appropriately terminated in the plane of symmetry corresponds to a reflection-type system in which the feed positions are in the aperture region. This paper describes the modifications which make the Butler matrix symmetric and the method for terminating the network on the symmetry plane so as to achieve a reflective matrix. A computer program has been written to generate and plot these network configurations.
A novel design method for lossy Blass matrix beam-forming networks
(LBNMFNs) is presented. Compared to those formerly developed, the new
method allows the design of an LBMBFN in order to generate not only two
simultaneous beams but also an arbitrary number of them. This skill is
obtained by means of a new approach to minimize losses that allows one
to transform a nonlinear multivariable programming problem into a linear
one-variable problem. The solution of such a design problem, then, can
be carried out in a very straightforward way by applying Gram-Schmidt
orthogonalization. Such a design method takes into account also the
limited availability of coupling values of directional couplers.
Numerical results obtained through the application of such a design
method are then presented. The ease, accuracy, and efficiency of this
novel method for the design of LBMBFN make it very useful in modern
applications of multibeam antenna arrays
Design of Butler matrix integrated with antenna array for beam forming
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