Measurement Method for Characterizing Nonlinearity Under Near-Field and Far-Field Interferers in 5G mmW Phased Arrays
A single antenna output of a phased array receiver has only the directivity of the single element. The array gain is achieved once the parallel branches are summed together. The far-field distance of a large array can be several meters which means that for an indoor scenario the interferer can be located in the radiating near-field. In this paper, we present a measurement method for characterizing the nonlinearity of common and parallel paths of the phased array receiver by controlling the number of active RF branches and common branch attenuation. As a measurement platform, we used a 16-chain, 64-element phased array receiver operating at 28 GHz center frequency. ACPR is used as a figure of merit of linearity of the receiver and it is measured over-the-air over the azimuth sector by using 100 MHz wide 5GNR CP-OFDM waveform.