A 28-GHz CMOS 2×4 Phased Array Chip with High-Precision Phase-Adjusting Function Between Subarrays for Beam Multiplexing

We propose a transmitter configuration with a phase-adjusting function between subarrays for beam multiplexing. We demonstrate a 28-GHz CMOS phased array chip with a phase-adjusting function for a beam-multiplexing transmitter. The phased array chip has two subarrays, each having four transmit channels to accurately set output phases and amplitudes via a multi-channel 10-bit-resolution digital-to-analog converter. The phase-setting resolution of the chip is less than 1.0°. The phase array chip also has nine mixers for detecting the phase difference between subarrays in the chip, between channels in the subarray, and between the chip and another chip. The measured root-mean-square (RMS) output phase error and the measured RMS phase-difference detection error of the chip are both 0.7°. Using this chip with a high-precision phase-adjusting function, it is possible to realize a transmitter with a signal-to-interference ratio of over 25 dB for beam multiplexing. We also propose an antenna configuration for two-dimensional beam scanning and horizontal beam multiplexing using the phased array chips.