Fully Digital Beamforming Receiver With a Real-Time Calibration for 5G Mobile Communication

Abstract

This paper presents a fully digital beamforming receiver (FDBR) using a method that calibrates the signals of all chains in real time, and is targeted for 5G mobile communication. In the real-time calibration method, the received signals of all chains are adjusted to correct the errors of phase and amplitude using the in-band signal other than operating frequency for calibration. The proposed FDBR with real-time calibration is designed and fabricated. The FDBR consists of eight chains of the tapered slot antenna (TSA) element, low noise block (LNB), and software defined radios (SDRs). The 1 x 8 array TSA with the directional coupler and the 1:8 divider is designed to send eight uniform calibration signals along with the received signal of all the chains. In SDR, the digital phase shifter and the real-time calibration blocks are implemented to realize digital beamforming. The digital phase shifter has an extremely high resolution of 0.72 degrees. After using the real-time calibration method, the average of measured phase and amplitude error between each chain is less than 0.9 degrees and 0.5 dB, respectively. To verify the beamforming performance of the FDBR, the simulation radiation pattern and the measurement radiation pattern are compared for 0 degrees, +/- 15 degrees, +/- 30 degrees, and +/- 45 degrees beam angles. The simulation results are in good agreement with the measured results. An excellent beamforming performance is achieved in the 1 x 8 array FDBR using the real-time calibration.