TABLE OF CONTENTS After the detection of targets in the search mode there follows target location with range and direction estimation which is as precise as possible. This procedure may in principle be performed with the same receiving data as that already used for detection. Multifunction radar systems with phased arrays may apply an additional acquisition mode after target detection to confirm the first target detection and thereby cancel to a large extent false alarms produced by noise and interference. This radar task may be performed with increased transmit energy compared to that used for the search mode, because there are relatively fewer acquisition orders. Because of the higher SNR for the acquisition mode the location accuracy will be improved. The waveform will be chosen for improved range resolution, as discussed in chapter 7. After target acquisition the location function will also be applied to the target tracking process.
The parameter estimation may be implemented according to chapter 3 as a maximum-likelihood estimation. The assumed probability density distribution for the received signal depends on the unknown parameter direction, which has to be estimated.
A planar array with antenna element positions r n = ( x n, y n) with n = 1, , N receives from a target with the unknown direction ? = ( u, v) and complex amplitude b the signal vector and the unavoidable noise vector n, the vector z given by:
with:
Vector a
