A 16-Element 4-Beam 1 GHz IF 100 MHz Bandwidth Interleaved Bit Stream Digital Beamformer in 40 nm CMOS

Abstract

A 1 GHz intermediate frequency, 16-element, 4-beam digital beamformer facilitates multi-in multi-out, 5G mobile, and other emerging communication standards. Digital beamforming has been limited by high power consumption, large die area, and the need for a large number of analog-to-digital converters (ADCs). The proposed digital beamformer addresses these issues by combining interleaved bit stream processing (IL-BSP) with power- and area-efficient continuous-time bandpass delta-sigma modulators (CTBPDSMs). Compared to conventional DSP, IL-BSP reduces both power and area by 80%. The new CTBPDSM architecture reduces ADC area by 67% and the energy per conversion by 43% with a power- and area-efficient three-stage nested $G_{m} - {C}$ op-amp and a passive summer. With an 11.2 dB array gain, the digital beamformer achieves a 58.5 dB signal to noise and distortion ratio and a 59.6 dB SNR over a 100 MHz bandwidth. Thanks to the accurate digitization and digital processing, the measured beam patterns of the four simultaneous beams are near ideal.