Detection of Targets with Small Apparent Doppler Frequencies in LFMCW Radars

Abstract

Linear Frequency Modulated Continuous Wave (LFMCW) radars are widely used in automotive applications or borders protection because of their noticeable performance. These radars should include Moving Target Indicator (MTI) to suppress all fixed targets in urban crowded areas or open borders. MTI attenuates signals with small apparent Doppler frequencies coming from slowly moving targets, high speedy targets, or those moving with an angle near 90 or -90 degrees to the radar radial direction. In this paper, the frequency response of the MTI is modified by adding a Single Delay Line Integrator (SDLI) following it to enhance its gain for small Doppler frequencies with some degradation in detecting middle Doppler targets. A choice between the traditional structure and the proposed one through a maximum-of criterion is proposed to achieve an improved equal detection performance for all Doppler frequencies. The detection superiority of the proposed method for slowly moving or high speed targets detection over the traditional one is validated for different target scenarios through the Receiver Operating Characteristic (ROC). Implementation considerations for single delay line integrator such as complexity and stability are discussed. A suggested scheme is proposed to achieve complexity reduction as well as stable operation.