A 28 GHz-Band Direct RF Undersampling S/H CMOS IC with 40 dB SNR

Abstract

We have studied direct RF undersampling reception to reduce the size and power consumption. We already developed a series/shunt switching type sample and hold (S/H) integrated circuit (IC) by using 90 nm complementary metal oxide semiconductor (CMOS) process for Ka-band (19.4 - 20.2 GHz) very small aperture terminal (VSAT) application. This IC performed signal-to-noise ratio (SNR) of higher than 27.3 dB. For the higher frequency operation and the reception of multi-level modulated signal, the SNR improvement will be required. In this paper, a 28 GHz-band S/H IC with higher SNR has been developed. In order to improve SNR at higher RF frequency, 65 nm CMOS process is introduced to enhance the switching speed of sampling, the size of hold capacitor is optimized and the two-stage output buffer amplifier is employed. The fabricated S/H IC performs the SNR of higher than 41.2 dB and the error vector magnitude (EVM) of 4.4% (32 Mbaud 64 quadrature amplitude modulation (QAM)) in 28 GHz-band.