OVERVIEW

As we have seen, the probability of detection of a receiving system depends upon false-alarm rate, type of receiver technique, the antenna system, and factors established by the target such as range, scan, and time modulation factors. Accuracy depends directly on some of these factors; however, we shall study the problem from the viewpoint of how the receiver system designer can optimize the accuracy with respect to those factors under his control. There is also the question of noise and how it affects accuracy since it is obvious that noise will mask variations representing signal changes, degrading accuracy or requiring higher signal-to-noise ratios that reduce operating sensitivity. The antenna choice and placement, the associated system balance and dynamic range, and the assignment of the error budget are crucial considerations. In any DF system design, there are subtle factors: An aircraft system that must fly a great distance along a line of bearing should have a system that is very accurate and able to be updated as the target is approached. If the system overloads or if the detection process deteriorates as the signal becomes stronger, the mission will be in vain. In a corollary sense, a warning receiver should always give warning, even if the DF measurement is inaccurate due to reception of weak signals, since there will be more time available to improve the accuracy, make decisions, or take action.

Much of the accuracy of a system when mounted in an aircraft or on a ship or other...