Advanced microwave circuit for novel beamforming phased arrays

Peizhao Li

doi:10.7273/000004241

Beamforming is a powerful technique which has been commonly used in signal processing, radar and sonar, biomedical, and particularly in communications. In applications of beamforming in communications systems, the basic concept is to optimally process signals received from or transmitted to different antennas simultaneously by changing the signal amplitudes and phases, to form a strong beam toward the direction of interest. Nowadays, both receive beamforming and transmit beamforming were extensively studied in the literature leading to numerous innovative and interesting beamforming schemes. In the thesis, a novel microstrip line symmetric ports 180° coupler is presented to feature arbitrary coupling ratio, transparent termination impedance and second harmonic frequency separation. The proposed coupler is composed of two quadrature hybrid couplers and two phase shifters. The analytical design equations are derived to determine the electrical length of two delay lines which control the coupling ratio and absolute phase delay of proposed coupler. With the novel 180° coupler, a new microstrip line 3 × 3 Nolen matrix phased array with three inputs and three output ports is proposed. For each input port excitation, the signal is divided into three equal magnitudes and unique progressive phase shifts at its output ports. This phased array feeding network is composed of three 180° couplers with two of them having identical coupling factor and two microstrip line phase shifters. To expand the operating bandwidth of proposed phased array, a group delay compensation approach is proposed for uniplanar 3×3 Nolen matrix to reduce the progressive phase delay variation across the frequency band, which improves the beam squinting problem for wideband multiple input multiple output wireless communication, radar, remote sensing and autonomous driving applications. Additionally, a 24GHz continuous tunable beamforming network is presented in this paper by merging three tunable phase shifters with tuning range 0~120° into 3×3 Nolen matrix. For each input port excitation of the proposed network, the 120° progressive phase tuning is obtained at the output ports, and the full 360° tunable phase progression is realized by switching the three input ports.

Advanced microwave circuit for novel beamforming phased arrays

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