A 24-GHz CMOS transmitter front-end for vital signal monitoring radar system

Abstract

In this paper, a 24-GHz CMOS direct-up transmitter front-end is presented for vital signal monitoring radar system in a vehicle. The proposed RF transmitter front-end consists of an I/Q up-conversion mixer, a two-stage power amplifier, and I/Q local oscillator (LO) generator circuit. The I/Q up-conversion mixer adopts transconductance stage composed of nMOS and pMOS and switching stage, and the dc current between nMOS transconductance stage and switching transistors was adjusted in order to obtain the optimum conversion gain of the mixer. Two-stage power amplifier is composed of two cascade differential cascode amplifiers. The I/Q LO generation circuit consists of a single-ended differential output amplifier, 1-stage RC polyphase filter, and two LO buffers. The presented 24-GHz CMOS direct-up transmitter front-end was implemented using a 65nm CMOS process. The S-parameters of all passive devices and routing lines including signal and power supply lines were considered using an electromagnetic simulator. The core chip area is 1500 μm ×670 μm. The fabricated transmitter front-end use supply voltage of 1.2V for an I/Q up-conversion mixer and LO generation circuit and 2.2V for a two-stage power amplifier. The power consumption of the transmitter front-end is approximately 200 mW. LO power of −10 dBm was used for the measurement. The measured return losses of the LO input port and RF output port are less than −10dB from 23.9 GHz to 24.3 GHz. The measured gain of transmitter front-end is 34dB, output power is 9.5 dBm and output 1dB compression point (P1 dB) is 8dBm from 23.9 GHz to 24.3 GHz.