Enhanced Dynamic Range Power Independent Doppler Frequency Estimation System

A Doppler shift estimation system with relatively high dynamic range is conceived and demonstrated. The scheme is based on dual mixing the modulated radar echo and frequency to voltage mapping. Hence, it needs no radio frequency auxiliary part. This makes the system capable of becoming integrated into any photonic radar, which would positively affect the cost and size of such system. Since the mixing procedure is all-optical, the system is able to identify the Doppler frequency of a radar echo with carrier frequency as high as 40 GHz independent of its amplitude. The system dynamic range can be as high as 42 dB at 10-GHz radar carrier with an acceptable error of 5%. This dynamic range was achieved using lock-in amplification technique.

I. Introduction

Multiple radar frequency procedure is used in many types of radars for various purposes such as voiding the enemy’s jamming operation, maximum range increase, equalization of false alarm rate and probability of detection rate, overcoming target size fluctuations, and conquering the frequency dependent channel losses. The frequency changes in a pulsed radar could be performed in two ways. One is sending each pulse with different frequency, which is called frequency agility [1]. The other way is to change the carrier frequency within the duration of a single pulse (frequency diversity) [2].