Proposed Feed Network Research Articles

An efficient feed network for small multibeam secondary surveillance radars

ABSTRACT In this paper, an efficient feed network for small secondary surveillance radar (SSR) antennas is introduced. It integrates all three required beams (SUM, DIFF, and CTRL) into a single-sheet design. The architecture employs a side element to generate the control (CTRL) beam for a 7-element 1.5-meter SSR antenna array. The target performance includes keeping the gain above 15 dBi and a side lobe level exceeding 20 dB at 1030 MHz and 1090 MHz for the SUM port while reducing the loss of the CTRL beam. In this work, a modified Gyzel unequal power combiner replaced the conventional Wilkinson power combiner to adjust the feed network’s power-sharing. Also, a practical method for implementing a high coupling value of 7 dB in a directional coupler is presented as one of the key steps to achieve a very low loss of 2.9 dB in the CTRL path (2.4 dB improvement). Simulation and measurement results validate the proposed feed network’s performance.

A ±45°-Polarized Antenna System With Four Isolated Channels for In-Band Full-Duplex (IBFD)

An in-band full-duplex (IBFD) antenna system having four ports with good self-interference cancellation (SIC) is presented in this article. Two of the four ports provide +45°-polarized radiation and the other two generate − 45°-polarized radiation. Every port of the proposed antenna is well isolated from the other three ports, enabling simultaneous transmitting (TX) and receiving (RX) with both two polarizations. To achieve this goal, three different types of couplings need to be addressed simultaneously. In this work, a novel isolation feed network is proposed, which is the first of its kind that can achieve three targets at the same time, i.e., feeding the antenna differentially, forming the original horizontal and vertical polarizations into ± 45° polarizations, and canceling out the reflected and coupled signals between the TX and RX ports. Then, a double-antenna IBFD system with four isolated channels is attained by combining the proposed feed network, defected ground structure (DGS), cross-shaped walls, and metal baffles, which effectively mitigated all the three types of couplings at the same time. The double-antenna system has high isolations of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt;$ </tex-math></inline-formula> 39 dB between any two of the four ports from 3.3 to 3.9 GHz. The four radiation patterns obtained by exciting the four ports are very similar to each other and are stable with frequency, which makes it an excellent candidate for 5G sub-6 GHz IBFD applications.

W-Band Beam-Tilted H-Plane Horn Array Antenna with Wideband Integrated Waveguide Feed Network Based on MMPTE

A W-band H-plane horn array antenna with tilted radiation beam based on waveguide structure is proposed in this paper. The designed antenna array consists of four H-plane antenna elements and a broadband feed network. The distribution of excitations is determined by the theory of maximum power transmission efficiency (MMPTE). A multiple branch coupler, two T-junctions and three fixed phase shifters are employed to construct the feed network, which can generate the required amplitude and phase in broadband frequency range from 80 GHz to 100 GHz. The computer numerical control (CNC) milling machines technology is employed to machine the feed network and antenna. All measured and simulated results are in good agreement, which verify the feasibility of the theory of MMPTE to generate a radiation beam directed to any angle from -35° to 35° with suitable excitation provided by the proposed feed network in this paper.

A Wideband Feed Network for Vivaldi Antenna Arrays

A wideband feed network for a Vivaldi antenna array is presented. A limitation of current wideband antenna arrays is the bandwidth of either the feed network or the antenna element. The proposed antenna array consists of four wideband Vivaldi antennas fed with an improved wideband feed network to extend the useable bandwidth of the array. The proposed feed network consists of coplanar waveguide-to-slotline-to-microstrip line transitions. The feed network has a single coplanar waveguide input and four microstrip line output ports. The feed network achieved uniform amplitude and phase balance and an impedance bandwidth of 160% from 1 GHz to 9 GHz. The feed network was used in a uniform linear antenna array to feed four Vivaldi antenna elements. The Vivaldi antenna array achieved stable radiation patterns from 1.3 GHz to 8 GHz, resulting in a useable bandwidth of 144%. The antenna array has a minimum gain of 8 dBi and a maximum of 13.8 dBi within the frequency band. Results for a prototype Vivaldi antenna array, measured in a compact antenna test range, are presented and compared to simulated results from CST Studio Suite.

Wideband circularly polarized array antenna based on weakly coupled sequential phase feed network

AbstractThis letter introduces a wideband circularly polarized (CP) array antenna for wireless communication application. The array consists of 2 × 2 sequentially rotated symmetric antenna elements and a wideband weakly coupled feed network providing stable 90° phase difference. By using the proposed feed network and introducing the slot coupling feed, the CP array antenna can achieve a wideband CP performance with a low profile of 0.03 λ0 (at 5.0 GHz). The proposed antenna exhibits the impedance bandwidth (IMBW) of 73.9%, axial ratio bandwidth (ARBW) of 53.6%, and 3‐dB gain bandwidth (GBW) of 60% with the peak gain of 10.4 dBi and the maximum efficiency of 82%. The measured results are in good agreement with the simulated results, indicating that a promising application in compact wideband C‐band wireless systems.

Slit-Loaded Series Feed Network for Millimeter-Wave Array Antenna With a Low Sidelobe Level Over a Wide Bandwidth

A slit-loaded series feed network and its design procedure were proposed for millimeter-wave (mm-wave) array antennas with a low sidelobe level (SLL) over a wide bandwidth. In the proposed feed network, slit structures are used to suppress internal reflections within the array and to control the aperture amplitude in such a way to reduce the SLL. Four types of slit-loaded structure units are investigated to control the coupled power on an antenna element. A $1 {\times }13$ end-fed and $2 {\times }26$ center-fed array antennas were designed and fabricated based on the proposed design procedure, and their performances were measured. The proposed arrays were shown to have impedance bandwidths of 11.3% (75–84 GHz) and 10.2% (77.5–85.8 GHz), respectively. Moreover, they show stable radiation patterns with low SLLs under −17 dB over the frequencies of 75–83 and 78–84 GHz, respectively. The designed arrays were compared with other mm-wave array antennas and shown to have a lower SLL over wide bandwidths.

A New Method for Arbitrary Amplitude Distribution Generation in ${4}\times{8}$ Butler Matrix

We propose a new technique in this letter to design a 4 × 8 Butler matrix (BM) using a four-port network and variable phase shifters. This method helps the proposed BM to produce arbitrary output amplitudes for beam steering applications. It also contributes to reducing the size of its configuration. In addition to the two mentioned advantages, we can develop a 4 × 4 BM, which generates unequal amplitudes. For validation, a single-layer 4 × 8 BM with -21-dB Chebyshev distribution was designed and manufactured. We also used the high-frequency simulation structure (HFSS) software to simulate the proposed feed network and observed a good agreement between the simulation and measurement results.

Tunable wideband frequency and switching polarisation reconfiguration antenna for wireless applications

In this article, a circular microstrip tunable wideband frequency and polarisation reconfigurable antenna are investigated. The wideband tunability is achieved by placing the four varactor diodes between circular microstrip patch and circular ring. The impedance bandwidth of 2.09-2.96 GHz (34.52%) is realised by tuning the capacitance value from 4.15 pF (0 V) to 0.94 pF (6 V). Both frequency tunability and polarisation reconfigurability are controlled in the antenna using the proposed cascaded branch line coupler feed network. The four single pole double throw and two dual in-line package switches are used in the feed network to control the tunable impedance bandwidth of the antenna over a wideband from 1.25 to 2.95 GHz. The vertical linear polarisation and horizontal linear polarisation (H-LP) are achieved by any one of the feed port excited in the antenna. Similarly, the right-hand circular polarisation and left-hand circular polarisation are realised by exciting both the feed ports in the antenna with±90° phase difference. The impedance bandwidth of proposed feed network is well matching with the tunable bandwidth of the patch antenna. Simulated and experimental verification results show good agreement.

Wideband Frequency Tunable Concentric Circular Microstrip Patch Antenna with Simultaneous Polarization Reconfiguration

i»?A wideband frequency tunable concentric circular microstrip patch antenna with simultaneous polarization reconfiguration is demonstrated by using four varactor diodes between a circular patch and a concentric ring patch around it. Both frequency tunability and polarization reconfigurability are controlled by a proposed feed network. Varying the capacitance value of the varactor diodes varies the operating frequency of the antenna from 1.17 to 1.58 GHz (around 30% tunability) with impedance matching better than S11 = S22 = -10 dB. Each set of the two varactor diodes provides vertical and horizontal linear polarizations excited using one of the feed ports at a time. Similarly, the right-handed circular polarization (RHCP) and left handed circular polarization (LHCP) radiation patterns are realized by employing all four varactor diodes and both feed ports with +90 degree time phase difference. The antenna is fabricated on a 120-mil-thick (3.05 mm) Arlon AD450 dielectric substrate (Er = 4.45, tan = 0.0035). The proposed feed network to control the excitation of ports for each of the polarizations is fabricated on 62-mil-thick (1.58 mm) FR-4 substrate material (Er = 4.4, tan = 0:02). A single-pole 4 through radio-frequency switch and two single-pole double through switches are used in this feed network for realizing the control circuitry. Simulated and measured impedance matching and radiation pattern results show good agreement with acceptable gain over the tunable frequency bands.

A PROPOSED DESIGN OF UWB MONOPOLE ANTENNA AND ITS LINEAR ARRAYS

A proposed design of ultra-wideband (UWB) monopole antenna has been presented to cover frequency range 2.49–14.42 GHz with small size. An equivalent circuit model with the parameter values of the optimized UWB antenna has been modeled. Moreover, a compatible lumped-elements utilized in equivalent circuit modeling for the proposed monopole antenna is established using the Advanced Design System (ADS). An UWB feeding network circuit has been designed in order to be used for exciting 2x1 and 4x1 linear antenna array. The measured and simulated results for the proposed feed network has a good return loss, isolation and power division ratio at all ports within the whole UWB frequency range. Two and four element UWB linear antenna arrays are presented. The average gain for the two-element antenna array is about 5.3 dBi and reaches to7.15 dBi for the four-element antenna array, over the whole UWB frequency range. A good agreement between the measured and the simulated results of all parameters for the antenna element and antenna arrays is appeared.

Novel Feed Network for Circular Polarization Antenna Diversity

In this letter, we propose a novel feed network for circular polarization (CP) diversity antennas to enhance communications performances. The previous CP diversity systems adopted dual polarization diversity using right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) within a small space. However, the same rotational CPs need further antenna distance. To overcome the space limitation for the same CP diversity antenna, we propose a feed network for CP antenna using conventional CP with orthogonal polarization radiation characteristics of a linear polarization (LP) diversity system without additional antennas. The port isolation characteristics and impedance matching conditions are numerically verified for the diversity system and antenna characteristics. The proposed feed network with CP patch antennas is fabricated and measured in a reverberation chamber for diversity performances, and their validity is verified.

Coupled line triangular microstrip loop resonator antenna

An isosceles triangular microstrip loop antenna is presented. The resonator is fed by two quarter wavelengths parallel-coupled sections. The proposed feed arrangement is a parallel-coupled microstrip lines with the coupling taking place over an electrical length. The edge-coupled two quarter wavelengths parallel-coupled microstrip line sections are combined capacitively. Each end of the feed arrangement is terminated in 50 Ω impedance. One 50 Ω end of the proposed feed is connected to the source similar to that of the microstrip feed line, while the second end is connected to the resonator itself. Similar antenna structure was designed and fed, first by a conventional microstrip feed line, inset feed, and inset coupled, and finally with a quarter wavelengths microstrip feed. This is done to further identify the specific advantages of the proposed feed structure. The peculiarities of the antenna with its proposed feed network are discussed as well as a theoretical explanation of the concept of the coupled line feed to wit its gain and bandwidth enhancement. It was observed that the measured gain of the proposed antenna is 8.38 dBi with a side lobe level of –10.8 dB, and an antenna aperture size of 30 mm × 16 mm.

육상 이동 위성 시스템의 통신 성능 향상을 위한 MIMO 원형 편파 급전 네트워크

본 논문은 육상 이동 위성(Land Mobile Satellite: LMS) 시스템의 통신 성능 향상을 위해 기존의 <TEX>$2{\times}2$</TEX> MIMO 채널에서 <TEX>$4{\times}4$</TEX> 채널로 확장할 수 있는 MIMO 원형 편파 급전 네트워크를 제안한다. 기존의 추가적인 통신 채널 확보를 위해서는 위성국에서 안테나 설치 공간상의 제약이 있기 때문에 이격 거리가 충분한 추가 위성국을 필요로 한다. 이로 인한 비용 및 MIMO 통신 채널의 한계 문제를 극복하기 위하여, 동일한 원형 편파 간에 이격 거리가 없이도 높은 격리성을 확보할 수 있는 MIMO 원형 편파 급전 네트워크를 제안하였다. 제안하는 급전 네트워크의 포트간 격리성과 각 포트의 매칭 상태를 수식적으로 증명하였고, <TEX>$4{\times}4$</TEX> MIMO 채널의 통신 성능 향상을 채널 모델 측면에서 제시 및 확인하였다. MIMO 원형 편파 급전 네트워크를 원형 편파 패치 안테나 구조로 실제 제작하고 측정하여 7~10 dB의 다이버시티 이득을 얻었고, 약 1.8배로 채널 용량이 향상되었음을 확인하였다. In this paper, we propose the MIMO circular polarization feed network to enhance the communication performances from the previous <TEX>$2{\times}2$</TEX> MIMO channel to <TEX>$4{\times}4$</TEX> channel for Land Mobile Satellite communication system. The only possibility to extend the communication channel is to use the additional satellite because of the limitation of satellite spaces to install additional antennas. For overcoming this problems, we propose the MIMO circular polarization feed network to secure the isolation characteristics without the distant antenna space. The port isolation characteristics and each port impedance matching conditions are numerically verified and we suggest the <TEX>$4{\times}4$</TEX> MIMO channel model of the proposed system and the performances are verified. The fabricated circular polarization patch antennas with the proposed feed network are measured in the reverberation chamber and 7~10 dB of diversity gain and 80 % increasement of channel capacity are obtained.

An Inmarsat BGAN Terminal Patch Antenna Array With Unequal Input Impedance Elements and Conductor-Backed ACPW Series-Feed Network

A novel 2 × 2 sequentially rotated patch antenna array with unequal input impedance elements and a conductor-backed asymmetric coplanar waveguide (ACPW) series-feed network is proposed. The corner truncated patch element is fed by a three-dimensional meander strip, which can easily control the input impedance and has slight effects on the radiation performance. Compared to microstrip-line feed networks, the radiation loss of the proposed feed network is lower. Furthermore, the maximum characteristic impedance of transmission lines in the proposed feed network is 91.2 Ohm. As a result, it can be easily realized with printed circuit board (PCB) techniques. The measured results show that the proposed antenna array has an impedance bandwidth (VSWR <; 1.5) of about 40.5% (1244-1876 MHz), a 3-dB axial ratio (AR) bandwidth of about 25.6% (1412-1826 MHz), and a gain-level larger than 11.6 dBi across the broadband global area network (BGAN) operating bands. Therefore, the proposed antenna array can be a good candidate for Inmarsat BGAN portable terminal applications.

분할된 원추형 빔 형성을 위한 안테나 급전 구조

본 논문에서는 <TEX>$2{\times}2$</TEX> 배열 안테나에 적용하여 분할된 원추형 빔 형성이 가능한 새로운 급전 구조를 제안한다. 제안된 급전 구조에는 네 개의 <TEX>$90^{\circ}$</TEX> 하이브리드, 한 개의 크로스오버, 네 개의 <TEX>$90^{\circ}$</TEX> 지연선을 사용하며, 이들은 서로 대칭적인 구조를 갖는다. 급전 구조의 성능을 검증하기 위하여 중심 주파수 2.57 GHz에서 동작하는 마이크로스트립 형태의 <TEX>$2{\times}2$</TEX> 배열 안테나와 급전 구조를 제작하였고, 방사 패턴을 측정하였다. 측정된 안테나의 주 빔방향은 입력 포트의 선택에 따라 고도 방향으로는 <TEX>$45^{\circ}$</TEX>에서, 방위각 방향으로는 <TEX>$45^{\circ}$</TEX>, <TEX>$135^{\circ}$</TEX>, <TEX>$225^{\circ}$</TEX>, <TEX>$315^{\circ}$</TEX>에서 최대지향성을 갖는 것을 확인하였다. We propose a novel feed network for a <TEX>$2{\times}2$</TEX> array antenna to form a sectoral conical beam. The proposed feed network, which is a symmetrical structure, consists of four <TEX>$90^{\circ}$</TEX> hybrids, a crossover, and four <TEX>$90^{\circ}$</TEX> delay lines. To verify the performance of the feed network a <TEX>$2{\times}2$</TEX> array antenna and the feed network are fabricated on a microstrip structure, and the radiation patterns are measured at the center frequency of 2.57 GHz. The maximum radiation is measured at the <TEX>$45^{\circ}$</TEX> elevation angle and at the <TEX>$45^{\circ}$</TEX>, <TEX>$135^{\circ}$</TEX>, <TEX>$225^{\circ}$</TEX>, and <TEX>$315^{\circ}$</TEX> azimuth angles depending on the choice of the input port of the feed network.

A simple switched beamforming network for four‐beam Butler matrix

AbstractA simple switched beamforming network with one 90° hybrid, two switches, and delay lines is designed. By controlling the switches, the antenna can produce four beams with the phase differences between adjacent radiating elements being ±135° and ±45°. The proposed feed network is simple, provides a tapered amplitude distribution, and has the same phase characteristics as the four‐beam Butler matrix feed network. The measured S11 of the proposed antenna is less than −10 dB at the operating frequency of 11.2 GHz. When switch 1 is in the “on” position and switch 2 is in the “off” position, or when both switches are in the “on” position, the measured radiation pattern shows that the scan angles are −12° and +35°. The proposed array antenna has the advantage of low cost, small volume, and easy fabrication. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1413–1416, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24352

Sectoral Conical Beam Former for a 2 $\times$ 2 Array Antenna

We propose a switched feed network for a 2 times 2 array antenna to form a sectoral conical beam. The proposed feed network, which is a symmetrical structure, consists of four 90deg hybrids, a crossover, and four 90deg delay lines. The prototype feed network and a 2 times 2 array antenna were fabricated on microstrip structures. The performance of the feed network was verified by measuring the radiation patterns at the center frequency of 2.57 GHz. The maximum radiation was measured at the 45deg elevation and at the 45deg, 135deg, 225deg, and 315deg azimuth angles, depending on the choice of the input port of the feed network.