Mixer-Free Phase and Amplitude Comparison Method for Built-in Self- Test of Multiple Channel Beamforming IC

This paper presents a built-in self-test (BIST) method of a multiple channel beamforming IC, based on successive comparisons of phase and amplitude differences between a pair of signals in beamforming channels. This is implemented with a simple difference detection circuit without a mixer and a reference LO. The phase and gain differences of the channels are obtained independently using the proposed simple detector. The phase difference detection accuracy is improved by removing the DC offset caused by the amplitude difference of the signals. The detection circuit is integrated into a 4-channel beamforming IC and the BIST concept verified for both the transmitter and receiver paths. The errors of phase and gain differences between the pair of channels measured through the proposed circuits are as low as to and -0.29dB to 0.38dB for the transmitter and -8.8°to 15.3°and -0.31dB to 0.41dB for the receiver, respectively.