4×4 Butler Matrices Implemented by Trans-directional Couplers

• Main Authors: Peng Hao Juan, 阮鵬豪
• Other Authors: J. C. Cheng
• Format: Others
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/21643199976808477439

碩士 === 長庚大學 === 電子工程學系 === 100 === The purpose of this thesis is to present a beam-switching antenna operating at 2.4 GHz. First, Periodically loaded microstrip couplers are presented to design a 4×4 planar Butler matrix, and the traditional bond-wire and the 0-dB coupler are used for signal crossing. The traditional bond-wire Butler matrix uses metal bond-wire to cross a planar microstrip line for signal exchange, achieving smaller area. However, due to the asymmetric configuration, the phases of the output ports need to be adjusted to achieve the ideal phase difference for the 4×4 Butler matrix. The measured results of the phase errors of the output ports are less than ± 5 °, while the insertion loss is -7 ± 1 dB. A Butler matrix using 0-dB periodically loaded forward coupler as a crossover is presented. Due to the use of this coupler, the circuit can be fabricated by fully planar process and achieve more symmetrical output port phase differences. The measured results of the output port phase errors are less than ± 5 °, while the insertion loss is -8 ± 1 dB. Each of the outputs from the Butler matrix is connected to a 4×1 series-fed slot-coupled patch antenna array. The center frequency of the measured result is 2.53 GHz with a 10-dB bandwidth 0.68 GHz and an antenna gain 12.15 dB. The beam switching antenna is realized by connecting the 4×4 planar Butler matrix to the 4×4 antenna array with the 0-dB coupler and phase delay lines. The main beam can switch to four different angles in space successfully. The angles are 16 °, -43 °, 39 ° and -15 °. The gains of those angles are all above 12 dB. The beam switching antenna operating at 2.4 GHz is successfully designed and fabricated. Measured results are in good agreement with simulated ones, verifying our design concept.