Fundamentals of Signal Processing for Phased Array Radar

This section gives a short survey of the principles and the terminology of phased array radar. Beamforming, radar detection and parameter estimation are described. The concept of subarrays and monopulse estimation with arbitrary subarrays is developed. As a preparation to adaptive beam forming, which is treated in several other sections, the topic of pattern shaping by deterministic weighting is presented in more detail. 1.0 INTRODUCTION Arrays are today used for many applications and the view and terminology is quite different. We give here an introduction to the specific features of radar phased array antennas and the associated signal processing. First the radar principle and the terminology is explained. Beamforming with a large number of array elements is the typical radar feature and the problems with such antennas are in other applications not known. We discuss therefore the special problems of fully filled arrays, large apertures and bandwidth. To reduce cost and space the antenna outputs are usually summed up into subarrays. Digital processing is done only with the subarray outputs. The problems of such partial analogue and digital beamforming, in particular the grating problems are discussed. This topic will be reconsidered for adaptive beamforming, space-time adaptive processing (STAP), and SAR. Radar detection, range and direction estimation is derived from statistical hypotheses testing and parameter estimation theory. The main application of this theory is the derivation of adaptive beamforming to be considered in the following lectures. In this lecture we present as an application the derivation of the monopulse estimator which is in the following lectures extended to monopulse estimators for adaptive arrays or STAP. As beamforming plays a central role in phased arrays and as a preparation to all kinds of adaptive beamforming, a detailed presentation of deterministic antenna pattern shaping and the associated channel accuracy requirements is given. 2.0 FUNDAMENTALS OF RADAR AND ARRAYS 2.1 Nomenclature The radar principle is sketched in Figure 1. A pulse of length τ is transmitted, is reflected at the target and is received again at time t0 at the radar. From this signal travelling time the range is calculated R0= ct0 /2. The process is repeated at the pulse repetition interval (PRI) T. The maximum unambiguous range is Nickel, U. (2006) Fundamentals of Signal Processing for Phased Array Radar. In Advanced Radar Signal and Data Processing (pp. 1-1 – 1-22). Educational Notes RTO-EN-SET-086, Paper 1. Neuilly-sur-Seine, France: RTO. Available from: http://www.rto.nato.int/abstracts.asp. RTO-EN-SET-086 1 1 Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE 01 SEP 2006 2. REPORT TYPE N/A 3. DATES COVERED 4. TITLE AND SUBTITLE Fundamentals of Signal Processing for Phased Array Radar 5a. CONTRACT NUMBER