A 37-40 GHz Dual-Polarized 16-Element Phased-Array Antenna with Near-Field Probes

Abstract

With the development of fifth-generation (5G) communication networks, in order to meet the growing demand for high-speed and low-latency wireless communication services, channel capacity has become the main driving force for choosing millimeter wave (mm-wave) over over-crowded sub-6 GHz frequency bands. Recently, beamforming phased array attracts significant research efforts as it is a promising solution and unique in its ability to overcome the high path-loss at high frequency, provide fast beam steering and deliver better user-ends experience. However, to alleviate the issues that associated with beamforming phased array, such as imbalance between array elements and non-linearity caused by power-amplifiers (PAs) in beamforming channels, far-field (FF) based array calibration and digital pre-distortion (DPD) need to be performed, which is not practical in real world scenario. This thesis presents a low-cost 16-element dual-polarized mm-wave antenna-on-printed circuit board (PCB) transmitter RF beamforming array with embedded near-field probes (NFPs) at 37-40 GHz. The elements are orthogonal, proximity-coupled feed dual-polarized patch antenna with a spacing of 0.5λ within 2x2 subarray and 0.6λ between 2x2 subarray at 38.5 GHz, resulting in maximum 17.7 dB gain with a scan angle of +/-50◦, +/-20◦ in azimuth and +/-20◦, +/-50◦ in elevation for vertical polarization and horizontal polarization, respectively. Without affecting phased array performance, the NFPs achieve flat and comparable coupling magnitude and group delay to the closet RF chain for both polarizations, across operating frequency range. This ensures the quality of received output signal from phased array to implement array calibration and DPD. The configuration of embedded NFPs maintains the scalability of phased array and eliminate the needs of impractical FF reference probe for array calibration and DPD.