  Digital phased arrays have often been disregarded for millimeter-wave
communications since the analog-to-digital converters (ADCs) are power-hungry.
In this paper, we provide a different perspective on this matter by
demonstrating analytically and numerically how the ADC resolution can be
reduced when using digital phased arrays. We perform a theoretical analysis of
the quantization noise characteristics for an OFDM signal received and
processed by a digital phased array, using Gaussian approximation of the OFDM
signal. In particular, we quantify the quantization noise suppression factor
analytically and numerically. This factor describes how much the coherent
combining reduces the quantization noise as a function of the number of
antennas, which allows for reducing the ADC bit resolution. For instance in a
8-16 antenna digital phased array the ADC resolution can be reduced with 1-2
bits compared to the ADC required for an analog phased array.
