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Principles of Modern Radar - Volume 2 1891121537

Principles of Modern Radar - Volume 2 1891121537

Principles of Modern Radar - Volume 2 1891121537

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9.3 Adaptive Jammer Cancellation 431E (SINR Loss)10.90.80.70.60.50.40.3FIGURE 9-30SINR loss as afunction <strong>of</strong> the ratio<strong>of</strong> data samples tochannels.0.20.100 1 2 3 4 5 6 7 8 9 10Snapshots/Channels9.3.4.2 Weight Jitter StabilizationIn addition to SINR loss, errors in estimating the adaptive weights can produce elevatedsidelobes that fluctuate from weight update to weight update. This is known as weightjitter, and it results from poor estimates <strong>of</strong> the noise eigenvalues in the covariance matrixestimate. The weight jitter can be stabilized by loading the diagonal <strong>of</strong> the covariancematrix strictly for the purpose <strong>of</strong> computing the weights [30,31].˜R = ˆR + δI (9.39)Diagonal loading has the effect <strong>of</strong> swamping out the noise eigenvalues with a fixed syntheticnoise level. Figure 9-31 shows the eigenvalue decomposition for a covariance matrixwith two different levels <strong>of</strong> diagonal loading indicated. The desired level would be just high60FIGURE 9-31Diagonal loading.7080Diagonal Loading LevelEigenvalue (dB)90100110Diagonal Loading Level1201301400 10 20 30 40 50 60 70 80

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