Millimeter-Wave Single- and Dual-Polarized 2x2 MIMO Phased Arrays and In-Situ Over-the-Air System-Level Self-Calibration Techniques for 5G Applications
This dissertation presents two millimeter-wave phased-antenna arrays at 28 GHz for fifth-generation (5G) mobile communication applications as well as techniques for performing in-situ self-test and self-calibration of single- and dual-polarized 5G phased-arrays. First, a scalable 64-element single-polarized transmit/receive phased array is built with 2x2 beamformer chips on a low-cost printed circuit board (PCB). The design emphasis is placed on minimizing the printed circuit board cost, optimizing the cross-polarization performance, and on-grid scalability. The array is capable of scanning +/-50 deg. in azimuth and +/-45deg. in elevation at 29 GHz with cross-polarization rejection better than 20 dB. It achieves an effective isotropic radiated power (EIRP) >50 dBm over a 4 GHz bandwidth from 27 to 31 GHz. Therefore, it is a suitable candidate for Gbps multi-user multiple-input multiple-output (MU-MIMO) base-station applications.
Second, a 2x64-element dual-polarized dual-beam phased array for 5G polarization MIMO is built. The phased-array has two 1:16 dual Wilkinson networks and microstrip antennas with rotated feeds for cross-polarization cancellation. The array demonstrates a measured effective isotropic radiated power (EIRP) at Psat of 52 dBm for each beam and is capable of scanning +/-50 deg.in azimuth and +/-25 deg. in elevation with >28-dB cross-polarization rejection. Simultaneous dual-beam operation is demonstrated with near-ideal patterns for each beam. The array demonstrates independent simultaneously transmitted 2x16-quadrature amplitude modulation (QAM) and 2x64- QAM data streams delivering an aggregate maximum data rate of 2x20 and 2x30 Gb/s, respectively.
Next, the problem of phased-array calibration is considered. Two calibration techniques
are developed and tested for calibrating single and dual-polarized 5G phased arrays at 28 GHz.The first technique addresses the calibration of single-polarized phased-arrays in a MU-MIMO hybrid beamforming base station system. The procedure, labeled Quad-BIST, enables built-in self-test (BIST) and self-calibration of the arrays in-situ without having to remove the array from the field. Quad-BIST relies on mutual coupling between antennas in neighboring arrays arranged in Quad-fashion to extract the calibration coefficients and perform channel characterization. Quad-BIST was successfully applied to 5G 28 GHz arrays with 4x4 and 8x8 elements in each quadrant. The results show that Quad-BIST predicts the channel states (gain and phase control) with rms errors of 0.2 dB/2 deg. and 0.4 dB/2.5 deg. for the 4x4 and 8x8 quadrants, respectively, as compared to far-field techniques. The relative channel ratios are found to be within rms errors of0.8 dB/7.5deg.. Near-ideal patterns are attained using the quadrant-level calibration for both arrays with side-lobe level’s below -20 dB over scan.
The second technique is for the calibration of dual-polarized dual-beam phased arrays. The procedure, labeled (DP-BIST), exploits the mutual coupling between different antennas of orthogonally polarized beams sharing the same aperture to enable in-situ self-calibration and self-test of the phased array channels of each beam. DP-BIST was applied to a 16-element dual-polarized dual-beam linear phased-array at 29 GHz, and predicted the relative channel states (gain and phase control) with rms errors better than 0.3 dB /3 deg. and the relative channel offsets with rms errors of 0.8 dB /6 deg. over a wide-bandwidth. These results demonstrate its feasibility for
use in 5G polarization MIMO phased arrays.