On-Chip RF Phased Array Characterization with DC-Only Measurements for In-Field Calibration

This paper presents a low-cost, on-chip built-in self-test (BIST) measurement for calibration solution of RF phased arrays. Mathematical modeling of the circuit impairments and phased array behavior indicate that by using two distinct input amplitudes, both of which can remain unknown, it is possible to measure gain and phase mismatch of the phased array using the proposed BIST solution. In addition, a test signal steering circuit is designed in order to ensure that test signal amplitudes are identical through different phases of testing. The proposed BIST measurement circuit is designed and fabricated using 0.18μm IBM_7RF process. A prototype four-element phased array PCB operating at 1 GHz is also designed and fabricated for verifying the proposed method. With the proposed method, the phase difference between elements can be measured with less than 1. error, which would allow for self-monitoring in 6-bit phased array applications.