To conquer troubles such as disruptive effects in mm‐wave frequency, many researches have been challenged. Beam‐steering antennas, especially with Butler matrix feed network, are a good suggestion to solve the aforementioned problem. In this study, an innovative design of the Butler matrix fed network is presented to drive patterns of the antenna. Moreover, a broadband Butler matrix feed network is achieved by a 1 × 4 aperture coupled zeroth‐order resonance elements which increases beam‐width of array pattern to triumph short‐range effect. Also using aperture fed, stable broadside pattern is obtained. The offered Butler matrix composes of four 90° couplers which have a combination of edge and patch techniques in the coupler, and two broadband stepped 45° phase shifters. The proposed compactness beam‐steering antenna covers an impedance bandwidth from 33.20 to 37.15 GHz and scans solid angle about ∼94° with the peak gain of 12 dBi.
The present study proposes a novel broadband circularly polarized (CP) multiple‐input multiple‐output antenna array designed for C‐band applications. The first step was the introduction of a reconfigurable circularly polarized square slot antenna (CPSSA) capable of changing polarization diversity, which could cover impedance bandwidth (BW) from 4.48 to 8.21 GHz with 1.9 GHz of −3 dB axial ratio (AR) BW. Then, a feed network composed of 90° and 180° couplers, a crossover, and delay lines was presented. The CPSSA with two metalized via‐holes adopted with two ports polarization diversity fed the networks. A number of reconfigurable CP array antennas using the polarization diversity technique have been presented so far. However, given that the proposed layout designed in a single layer had advantages of reduced antenna size and increased antenna gain and ARBW, this approach has received due attention over recent years. Another promising feature of this approach is its capability to change the polarization diversity by rotation of phases in the array feed network using PIN diodes.
In this paper, a broadband circularly polarized (CP) antenna array for beam-steering applications is presented. The antenna consists of a 2 × 2 antenna array of substrate integrated waveguide (SIW) CP slot elements fed by a Butler matrix network. Each SIW element is rotated sequentially with respect to each other to improve the array CP purity. To validate the performance of the proposed structure, a prototype is fabricated and measured. The measured results show an impedance bandwidth of 18% (9.15-10.92 GHz) for |S11| ≤ −10 dB and a minimum 3-dB axial ratio bandwidth from 9.4 to 10.1 GHz. The beam-steering antenna has about 25-degree scan angle with the peak gain of 14 dBi at 10 GHz.
In this paper, a new method to facilitate the design of Printed Ridge Gap Waveguide (PRGW) structures is introduced. One of the main difficulties in designing such structures is related to their simulation process which is really time and energy-consuming. Therefore, a suitable boundary condition is considered to bring about the primary structure without involving the bed of nails or mushroom unit cells. Using this technique, a wideband PRGW 3 dB hybrid double-box coupler is designed to serve in mm-wave frequencies at a center frequency of 30 GHz, which can be deployed for the next generation of mobile communication. The designed coupler provides a wide matching and isolation bandwidth with low output amplitude imbalance, which is unique in comparison with current couplers. The prototype of the proposed coupler is fabricated and measured where the simulation and measurement results show a good agreement indicating the strength of the proposed method in PRGW structure design as well. The measured results show the couplers achieve better than 10-dB return loss and isolation over the frequency range from 25 to 40 GHz (46% BW) with the power-split unbalance and phase error within ± 1 dB and ± 5°, respectively. In addition, square mushrooms are chosen here to satisfy the high impedance surface. Not only do they bring about larger stop bandwidth, but also their configuration facilitates the arrangement of them around the coupler. The proposed design has superb characteristics such as low profile, low loss, and easy integration with microwave circuits and systems that can be suitable for designing mm-wave beamforming networks.
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