Performance Study of Quantized Linear Frequency Modulated signals and its application to CW radars

Direct Digital Synthesizers (DDS) are frequently used to generate wideband CW-FM signals in precise high resolution radars. With respect to a perfect linear FM signal, the stepped version produced by DDS can produce undesirable artifacts after range compression. However selecting carefully the configuration parameters of DDS (clock frequency, number of steps, step size, etc.) it is possible to obtain a virtually free of artifacts operation if the compressed signal does not show noticeable degradation with respect to ideal operation. From a theoretical study a simple design guidelines are proposed for the DDS parameters selection. This study has been validated by simulations and experimentally. An experimental CW-FM Full Polarimetric Interferometric Ground-Based SAR using a DDS as a chirp Generator has been developed according to the design guidelines in the TSC labs. The empirical results and system impulsional response are in agreement with this study.