Over the air characterization for 5G massive MIMO array transmitters

This paper discusses the implementation of a solution to study over the air 5G Massive MIMO antenna transmitter arrays. The proposal is based on a multi-sine approach similar to what is being done to explore nonlinear devices. The approach followed is supported on a multi-sine waveform where each element on the array is excited by two tones, being one the common local oscillator, and the other a modulation with a single sinusoid (called a tickle tone). Since each element in the antenna is fed by a different modulated waveform, the overall structure can be evaluated remotely using a simple probe followed by a Vector Signal Analyser. By measuring each of the sines in the receiver stage, the change in amplitude and phase can give an initial approach to each of the transmitter element. The implementation of this solution will be discussed throughout this paper.