Design of MTI Filters with Non-Uniform Sampling

Moving target indication (MTI) filters are generally considered as the primary approach to remove echo caused by fixed unwanted targets as well as clutter, in real-world radar systems. The MTI filter is set up as a linear combination of the echoes received from the range cell under test, when the inter-pulse periods (IPPs) are staggered. Hence, the MTI filter is mainly characterized with the coefficients and the IPPs. The MTI filter design problem is to optimize both these parameters to maximize both the blind speed and the clutter rejection, while providing the required signal gain. In this paper, to calculate the coefficients, the deviation of the designed filter from the ideal one in pass-band is optimized using the least squares criterion. The coefficient optimization is done under the constraint to induce nulls at limited number of frequency spots in the clutter rejection band to increase clutter rejection. As to the IPPs, a random IPP search is done to maximize the minimum SCR in the pass-band. At the analysis stage, the performance of the proposed method is compared with the other existing methods, based on two criteria: Improvement Factor (IF) and the minimum SCR gain in the pass-band. Eventually, it is shown that the proposed method has better results.