Analog Signal Processing for Pulse Compression Radar in 90-nm CMOS

This paper presents a pulse-compression radar baseband analog signal processing integrated in a silicon process for low cost and power dissipation. The analog signal-processing circuitry exhibits the autocorrelation properties of the polyphase codes, maximizes the sensitivity and resolution of a pulse radar system, and alleviates speed and resolution requirements of the analog-to-digital converter (ADC) via an analog correlator. The circuitry includes a two-stage variable gain amplifier (VGA) for high dynamic range, a correlator/integrator circuit, a comparator, and offset calibration circuits. The differential 6-bit VGA is designed to adaptively track the Friis path loss through rapid change of the VGA gain and offset calibration, relaxing the dynamic range requirements of the correlator. The measured performance shows a VGA gain variation of 52 dB and a VGA group-delay imbalance of 50 ps over 64 states. The high-speed pulse compression/correlation is performed in analog current domain and the speed requirement on the ADC is reduced by a factor equal to the duty cycle lowering the ADC power consumption. The chip is fabricated in a 90-nm process, wire bonded on the FR4 printed circuit board, and tested with a Stratix IV field-programmable gate-array board to evaluate the system performance for different radar polyphase codes.