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Phased-Arrays and Adaptive Arrays
 

This TUTORIAL course is based on the FOUR books 1) Introduction to Airborne Radar by G. W. Stimson, 2) Fundamentals of Radar Signal Processing, by Dr. M. A. Richards, 3) Practical Phased Array Antenna Systems by Dr. Eli Brookner  and 4) Tracking and Kalman Filtering Made Easy by Dr. Eli Brookner.  The course, the books, and the course notes will provide an ideal introduction to: airborne radars; pulse Doppler radars, range and Doppler ambiguity removal; clutter and jammer rejection using DPCA, Anomalous Nulling, adaptive arrays and Space-Time Adaptive Processing (STAP); radar antenna stealthing, Low Probability of Intercept (LPI) radars; jamming (ECM) and counter jamming techniques (ECCM), Electronic Warfare Intelligence Functions (ELINT, ESM, RWR); the principles of phased array antennas – phase and time delay steering, linear and planar arrays, avoiding grating lobes, effects of amplitude and phase errors and element failure on array performance, radiating elements, phase shifters (including MEMS), limited scan systems, feed systems, digital beam forming (DBF), sequential detection, optimal scanning.

This TUTORIAL course offers a concise, introductory-level survey of the fundamentals without dwelling on extensive mathematical derivations or abstruse theory. The material on airborne radars is very useful and informative to the engineer designing ground and space-based radars. It is very useful to see the ingenious way the airborne radars handle the clutter rejection and range-doppler ambiguity problems.

The 3rd book is derived from a set of twelve detailed lecture notes that originally accompanied a series of intensive short courses presented in the mid-seventies on phased-array fundamentals. The course lectures, notes and reprints update technology and techniques to 2006 and give future trends.

This course is intended for the engineer or scientist not familiar with airborne-radars and phased-arrays  as well as the specialist who wants to learn about other aspects of these systems.  It is not necessary to have taken the Radar Part 1 course before taking this course.

Day 1 February 27

Lecture #1 – Airborne Radar Basics:  Pulse and Pulse Doppler Radar Fundamentals; Example Airborne Radar Applications; Selection of Carrier Frequency; Range-Doppler Ambiguity Problem.

Days 2 and 3, March 6 and 13:

Lecture #2 – Review of  Basics: Radar Equation and Pulse Compression; Sources of Clutter and its Spectrum; Techniques for Eliminating Clutter  — Airborne Moving Target Indicator (AMTI), TACCAR, DPCA (Array and Monopulse), Notching Technique, Anomalous Nulling; Combining These Techniques, 3-Phase Center Clutter Cancellation to Estimate Target Angle; Performance of AMTI and DPCA processors.

Days  4 and 5, March 20 and 27

Lecture #3 – Choice of  PRF: 1) Low, Medium and High;  Pros and Cons of Each; Methods for Eliminating range and Doppler Ambiguities (Chinese Remainder Theorem); Range and Doppler Eclipsing; Signal Processing Architectures for Each; Sidelobe Blanker to Eliminate Large Discrete Clutter Scatterers coming in through the sidelobes; Use of FM Ranging to Determine Range with very high PRF.

Day 6  April 3

Lecture #4 ­– Example  Airborne Systems: F-15, APS-134, ASTOR, AWACS, E-2C, JSTARS, F-22, F-16 C/D, F-18 C/D,B-2, B-1 B,AH-64D Apache Helicopter radar, commercial radars.

Lecture #5 - Phased Array Fundamentals, Part 1: Example system: COBRA DANE and PAVE PAWS.

Lecture #6 – Phased Array Fundamentals, Part 2: Phase and time-delay steering; grating lobes for 1- and 2-dimensional arrays; array factor; sine space.

Day 7 April 10

Lecture #7 – Phased Array Fundamentals, Part 3: Effects of errors and failures on gain, sidelobes and angle accuacy; array weighting; thinning; blindness, elements (waveguide, dipole, patch, notch), phase-shifters (diode, ferrite, MEMS) and feeds (constrained, space, ROTMAN).

Day  8 April 17

Lecture #8 – Phased Array Fundamentals, Part 4: Limited field-of-view (LFOV) arrays.

Minimum number of phase shifters needed and how to achieve it (HIPSAF and MLS array). Example systems; sequential detection.

Lecture #9 – Phased Arrays – Past and Present; Future Trends: Digital beam forming; $10 T/R module; Future planned production of  100’s of F-15, F-22, F-18 MMIC arrays for airborne systems: ASTOR; MP-RTIP; AMSAR; THAAD; SBR.

Day 9 April 24

Lecture #10 – Sidelobe Canceling: Single-loop and multi-loop feed-forward and feedback canceller (with and without hard limiting) is introduced in easy terms.  Multiple-loop sidelobe canceller (MSLC). 

Day 10 May 1

Lecture #11 – Adaptive Arrays: Simple derivation of optimum fully adaptive array (Weiner filter) given.  Calculating of optimum weight using Sample Matrix Inversion (SMI), Applebaum-Howells and recursive methods.  Use of eigenvector beams and a whitening filter. Obtaining the benefits of a fully adaptive array without its disadvantages given through use of adaptive-adaptive array processing of eigenbeams. Performance of STAP in presence of real world errors. 

Lecture #12 - Least-Squares Estimation (LSE): Simple 3-D geometric derivation given. Covered are Gram-Schmidt, Givens and Householder voltage methods (square-root) and power methods. Use for sidelobe cancelling, adaptive array processing and SAR speckle reduction. Systolic array implementations.