ABSTRACT
Adaptive Radar.................................................................................... 461
(E. C. Barile, R. L. Fante, and J. A. Torres)
10.2.1. Background ........................................................................... 461
10.2.2. Theoretical Introduction ....................................................... 465
10.2.3. Two-Element Displaced Phase Center Antenna .................. 472
10.2.4. Simulation Results ................................................................ 478
10.2.4.1. Internal Clutter Motion ....................................... 478
10.2.4.2. Aircraft Crabbing ................................................ 482
10.2.4.3. Near-Field Obstacles ........................................... 484
10.2.4.4. Antenna Errors (Channel Mismatch) .................. 487
10.2.5. Summary ............................................................................... 490
10.3. Clutter Covariance Smoothing by Subaperture Averaging................ 490
(R. L. Fante, E. C. Barile, and T. P. Guella)
10.3.1. Introduction........................................................................... 490
10.3.2. Analysis for an Airborne Radar ........................................... 492
10.3.3. Summary ............................................................................... 496
10.4. Cancellation of Diffuse Jammer Multipath by an Airborne
Adaptive Radar.................................................................................... 497
(R. L. Fante and J. A. Torres)
10.4.1. Introduction........................................................................... 497
10.4.2. Filtered Received Signals ..................................................... 502
10.4.2.1. Received Jammer and Noise Signals .................. 502
10.4.2.2. Interference Covariance Matrix .......................... 505
10.4.2.3. Steering-Vector and Received Target Signal ..... 508
10.4.3.1. Introduction ......................................................... 509
10.4.3.2. Tap Spacing......................................................... 512
10.4.3.3. Total Extent ......................................................... 513
10.4.3.4. Ground Clutter..................................................... 513
10.4.3.5. Temporal Averaging............................................ 514
10.4.3.6. Beam Space ......................................................... 514
10.4.4. Summary and Discussion ..................................................... 517
10.5. Wideband Cancellation of Multiple Mainbeam Jammers.................. 518
(R. L. Fante, R. M. Davis, and T. P. Guella)
10.5.1. Introduction........................................................................... 518
10.5.2. Calculation of the Array Performance ................................. 520
10.5.3. Simulation Results ................................................................ 523
10.5.3.1. Spatial Span and Location of the Auxiliaries..... 523
10.5.3.2. Required Number of Auxiliaries and Gain
per Auxiliaries ..................................................... 524
10.5.3.3. Signal-to-Interference Ratio after
Cancellation ......................................................... 527
10.5.3.4. Simultaneous Nulling of Mainlobe and
Sidelobe Jammers................................................ 529
10.5.4. Summary and Discussion ..................................................... 530
10.6. Adaptive Space-Time Radar.............................................................. 531
(R. L. Fante)
10.6.1. Introduction........................................................................... 531
10.6.2. Understanding the Results in Equation 10.169 and
Equation 10.170 .................................................................... 533
10.6.3. Sequential Cancellation of Jammers and Clutter ................. 536
10.6.4. Typical Results ..................................................................... 538
10.6.5. Additional Considerations .................................................... 539
10.6.6. Summary ............................................................................... 540
10.7. Synthesis of Adaptive Monopulse Patterns ........................................ 540
(R. L. Fante)
10.7.1. Analysis................................................................................. 540
10.7.2. Summary ............................................................................... 542
10.8. Ground and Airborne Target Detection with Bistatic
Adaptive Space-Based Radar.............................................................. 543
(R. L. Fante)
10.8.1. Introduction........................................................................... 543
10.8.2. Analysis................................................................................. 544
10.8.2.1. Sum Beam ........................................................... 544
10.8.2.2. Difference Beam.................................................. 545
10.8.3. Numerical Studies of Effectiveness...................................... 546
10.8.3.1. Sum Beam ........................................................... 548
10.8.3.2. Difference beam .................................................. 551
Discretes .............................................................................................. 553
(R. L. Fante)
10.9.1. Introduction........................................................................... 553
10.9.2. Fully Adaptive SAR ............................................................. 554
10.9.3. Overlapped-Subarray SAR ................................................... 557
10.9.4. Numerical Results................................................................. 559
10.9.5. Summary ............................................................................... 563
10.10. Wideband Cancellation of Interference in a Global Positioning
System (GPS) Receive Array ............................................................. 563
(R. L. Fante and J. J. Vaccaro)
10.10.1. Introduction........................................................................... 563
10.10.2. Adaptive Filter Weights........................................................ 564
10.10.2.1. Maximum Signal-to-Interference
Ratio..................................................................... 565
10.10.2.2. Minimum Mean Square Error ............................. 566
10.10.2.3. Minimum Output Power ..................................... 567
10.10.3. Signal Distortion Introduced by the Processor .................... 567
10.10.4. Suboptimum Space-Frequency Processing ......................... 570
10.10.5. Numerical Simulations ......................................................... 571
10.10.5.1. Introduction ......................................................... 571
10.10.5.2. Effect of Channel Mismatch ............................... 574
10.10.5.3. Effect of Steering-Vector Mismatch ................... 576
10.10.5.4. Distortion Introduced by the
Adaptive Filter..................................................... 577
10.10.6. Space-Time vs. Suboptimum Space-Frequency
Processing ............................................................................. 580
10.10.7. Summary ............................................................................... 585
10.11. A Maximum-Likelihood Beamspace Processor for Improved
Search and Track................................................................................. 585
(R. M. Davis and R. L. Fante)
10.11.1. Introduction........................................................................... 585
10.11.2. Maximum-Likelihood Beamspace Processor (MLBP) ........ 586
10.11.3. Analysis................................................................................. 589
10.11.3.1. The First Stage .................................................... 589
10.11.3.2. The Second Stage................................................ 590
10.11.3.3. Target Detection.................................................. 592
10.11.4. Numerical Examples............................................................. 593
10.11.4.1. Improved Clear Environment Search
Performance......................................................... 594
10.11.4.2. Improved Clear Environment
Angle Estimation................................................. 595
10.11.4.3. Performance against a Single Mainlobe
Interferer .............................................................. 596
Most analyses
of adaptive cancellation of strong jammers consider only the
direct signal from the jammer, and ignore any multipath components
scattered
from the Earth. For a smooth Earth the multipath consists of only a single time-
delayed, specularly reflected ray, but for a rough Earth the multipath consists
of
many time-delayed, diffusely reflected components. The question then arises as to
how one can cancel both the direct jammer signal and these multiple reflections.
There are a number of choices: one can add more spatial degrees of freedom to the
adaptive array, more temporal degrees of freedom, or a combination of both.
Additional spatial degrees of freedom can be achieved by using additional
auxiliary antenna elements. The additional temporal degrees of freedom can be
achieved by using bandwidth partitioning (with a separate adaptive loop in each
subband), an adaptive finite impulse response (FIR) filter,
