Miniaturized 4 x 4 switched-beam butler matrix with bandwidth enhancement for 5G communication system
A 4 x 4 Butler Matrix (BM) without phase shifter is proposed to provide bandwidth enhancement and size reduction by removing a conventional 0 dB/90⁰ crossover, two 0⁰ phase shifters and two 45 phase shifters. Two proposed 3 dB/45⁰ patch couplers replace the combination of two conventional 3 dB/90⁰ b...
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| Summary: | A 4 x 4 Butler Matrix (BM) without phase shifter is proposed to provide bandwidth enhancement and size reduction by removing a conventional 0 dB/90⁰ crossover, two 0⁰ phase shifters and two 45 phase shifters. Two proposed 3 dB/45⁰ patch couplers replace the combination of two conventional 3 dB/90⁰ branch-line couplers and two 45⁰ phase shifters, whilst a modified0 dB/0⁰ crossover removes two 0⁰ phase shifters from the conventional BM. The -10 dB fractional
bandwidths of reflection coefficients and isolations for the proposed BM are 18.46% in simulation and measurement. The -6 dB ± 1.5 dB average transmission coefficient and +45⁰, �135�, +135⁰and +45⁰ of output phase differences with 1.8� average phase imbalance are accomplished at 6.5 GHz. The simulated and measured scattering parameters (S parameters) and phase differences are in close compliance with each other. Four switched-beams pointed at +15⁰, -50⁰, +50⁰ and +15⁰ are developed by integrating the proposed BM with inset feeding patch antennas. The proposed BM is miniaturized by 51.56%, whilst the bandwidth performance is enhanced by 9.7% compared to the conventional BM. Hence, this compact BM is a promising candidate for the fifth generation (5G) communication system. |
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