Focusing Bistatic FMCW SAR Signal by Range Migration Algorithm Based on Fresnel Approximation.

Yake Li,Siu O’Young

doi:10.3390/s151229910

Abstract

Frequency modulated continuous wave (FMCW) technique has recently been employed by synthetic aperture radar (SAR) to decrease the radar cost and volume. However, the operation range is limited by the direct energy leakage from the transmitting channel to receiving channel due to the operation principle of FMCW technique. Bistatic configuration is an efficient way to increase the isolation between the transmitter and receiver, which could significantly increase the radar standoff range. A bistatic FMCW SAR spectrum model is proposed by using the Fresnel approximation in this paper. This model is similar to that of a monostatic FMCW SAR spectrum, which allows the existing imaging algorithms to be used on bistatic image processing. Based on the new model and the characteristics of FMCW signal, a modified range migration algorithm (RMA) for FMCW SAR is proposed to focus the image, which requires less memory and computational load than the traditional RMA. Point-target simulation is used to verify the proposed spectral model and real data processing verified the effectiveness of the proposed RMA.

Highlights

A Frequency modulated continuous wave (FMCW) radar constantly transmits and receives signals and is capable of maintaining a high signal to noise ratio with much less peak power than a corresponding pulse radar system
This paper first proposed a two-dimensional spectrum model for bistatic FMCW synthetic aperture radar (SAR) based on Fresnel approximation and proposed a modified range migration algorithm (RMA) for processing the FMCW SAR data
The given spectrum model is accurate under small squint and long range SAR working conditions

Summary

Introduction

A Frequency modulated continuous wave (FMCW) radar constantly transmits and receives signals and is capable of maintaining a high signal to noise ratio with much less peak power than a corresponding pulse radar system. The operation range of FMCW SAR is still limited to several kilometers because the compact size of a monostatic FMCW SAR does not allow much space separation between the transmitting and receiving antennas. The other contribution of this paper is a modified range migration algorithm (RMA) for FMCW SAR signal processing. The modified RMA is proposed based on the novel monostatic-like spectrum obtained by using Fresnel approximation. It reduces the data size needed in the traditional RMA, which improves the processing speed and reduces the memory needed. Real data are used to verify the proposed RMA on monostatic FMCW SAR signal processing.

FMCW Principle

BistatiTc

Modified RMA Based on the Bistatic Equivalent Spectrum

Results 9

Simulation

Real Data Results

Conclusions