A 94-GHz 4TX/4RX Phased-array Transceiver for FMCW Radar with 16dBm Output and 8.8 dB NF in 65nm CMOS

This paper presents a 94 GHz 4TX/4RX phased-array transceiver for frequency-modulated continuous wave (FMCW) radar in 65nm CMOS process. The transceiver consists of four transmitters (TXs) and four receivers (RXs) to achieve higher distance and receiver sensitivity. A wideband frequency octupler is employed as the local oscillation (LO) chain to lower the frequency of FMCW signal generator and provide the LO signal with lower phase noise. In order to improve output power, a 4-stage power amplifier (PA) adopts 2-way combining technique. Each transmitter channel achieves above 13 dBm output power from 90-100 GHz and a peak 16.5 dBm output power is obtained at 96 GHz. The gm-boosting technique is used to design the low noise amplifier (LNA) to improve the gain and decrease the noise. Therefore, the receiver has a conversion gain (CG) of 20.7 dB and a noise figure (NF) of 8.8 dB at 20 MHz intermediate frequency (IF). The transceiver also integrates the 6-bit 360° phase shifter (PS) and 3-bit 7dB attenuator (ATT) so that it has the beam-forming capability. The dimension and power consumption of the chip are 7 × 3 mm² and 3.44 W, respectively.

Introduction

FMCW technique is a common technique of millimeter wave radar system. Due to the advantages of simple system architecture, smaller chip size, simple signal processing and low base-band power consumption. It is a common radar system in automotive application. The CMOS process has lower cost and higher capacity than SiGe and compound semiconductor process, which is an ideal processing for millimeter-wave radar chips. With the rapid development of CMOS technology, highly integrated millimeter-wave FMCW radar chips have been realized. However, the performance of the CMOS transceivers is inferior to BiCMOS transceivers’, since the BiCMOS process can use a BJT with stronger driving ability and a higher ft. To compensate for the lack of CMOS transceivers’ performance of the output power and NF, the phased-array technique become a key means. For an N-element phased-array, transmitter’s EIRP is increased by a factor of N², and the receiver SNR is increase of N. However, the phased-array technique brings the suppression of the dimension and power consumption.