Lower bounds on multiplesource direction finding in the presence of directiondependent antennaarraycalibration errors
Abstract
We consider the problem of direction finding (DF) of multiple, cofrequency narrowband signals with a phased antenna array when directiondependent arraycalibration errors as well as thermal noise are present. Lower bounds on the variance of unbiased estimators for DF are derived under two different types of signal models: completely unknown (i.e., generic) signals and unknown constantenvelope signals. In both models, the complex amplitudes of the signals are modeled as unknown parameters. We derive and evaluate lower bounds on DF of these signals when complex Gaussian array errors and thermal noise are present. In our numerical examples, the bound for generic signals tended to decrease with increasing interference power and, for closely spaced signals, became more optimistic when small array errors were added. With a sufficiently large signalofinterest (SOI) array signaltonoise power ratio (ASNR) and number of looks, the bound numerically approached the bound on DF of multiple generic signals with array errors but no thermal noise (i.e., the multiplegenericsignal, arrayerrorsonly bound). The results for constantenvelope signals showed that the bound with array errors and thermal noise was more optimistic than the analogous genericsignal bound and had little dependence on signal separation and interference power.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 October 1989
 Bibcode:
 1989STIN...9017979K
 Keywords:

 Antenna Arrays;
 Calibrating;
 Direction Finding;
 Electromagnetic Noise;
 Error Analysis;
 Error Signals;
 Phased Arrays;
 Amplitudes;
 Models;
 Narrowband;
 Signal To Noise Ratios;
 Thermal Resistance;
 Communications and Radar