Direct IF sampling receivers for 5G millimeter-wave communications systems

Reducing receiver complexity and power consumption are important design goals in fifth-generation (5G) millimeter-wave (mm-wave) communications systems. One approach for achieving these goals is to employ direct intermediate frequency (IF) sampling at sub-Nyquist rates in a superheterodyne receiver architecture using digital downconversion of the IF signal. This paper presents original measured results characterizing in detail the signal-to-noise-ratio (SNR), error vector magnitude (EVM), and block error rate (BLER) performances of a direct IF subsampling mm-wave receiver with subsampling rate as a parameter. A software-defined radio (SDR) receiver using direct IF subsampling was implemented in a 28GHz, beamforming, over-the-air (OTA), hardware-in-the-loop (HWIL), SDR testbed using a 2.52 GHz IF. For a quadrature phase shift keying (QPSK) modulated long-term evolution (LTE) signal subsampled at 500 MHz, a small SNR penalty of ˜3dB at 5% BLER was obtained over a 10 GHz Nyquist sampling benchmark.