Digital linear chirp receiver for high chirp rates with high resolution time-of-arrival and time-of-departure estimation

Abstract

The use of chirp signals in modern radar and ranging systems have numerous benefits. They are extensively used to improve signal-to-noise ratio and range resolution. The performance capabilities of these signals are directly related to their time-bandwidth product, i.e., the duration and bandwidth of the pulse. Ultra-wideband chirp signals are further desirable because they span a large bandwidth, making them resistant to narrowband environmental interference. The accurate detection and measurement of high chirp signals is difficult due to the necessity of a high-sampling analog-digital converter, a target measurement platform with high computational power, and a time-of-arrival (TOA) estimator with high temporal resolution. The difficulty of the problem is further compounded with the requirement that no a priori knowledge of the signal, noise, or operating environment is known. This paper presents a practical approach and implementation of a high linear chirp rate receiver and TOA estimator pair capable of detecting and measuring stationary radio frequency pulses as well as linear chirp rates up to 1.18 GHz in 400 ns. The high-resolution TOA algorithm and linear chirp receiver have been prototyped, synthesized, and placed and routed for a Virtex 6 SX475 FPGA.