y. On the other hand, the interceptor does not want his equipment to indi- cate a state of signal detection when no actual signal is present. Such a state of false alarm caused by system noise should have a very low probability PFA of occurrence, perhaps on the order of one false alarm per sortie or per day. Typical values of PD and PFA might be PD = 0.9 and PEA=10-6. 1.2.1.2 Maximum or Bounding Performance of Fundamental Detector Types Extensive literature exists on the subject of interceptor detection tech- niques and performance. All of the various methods for detecting hopped signals fall into two basic types of approach: employing a wideband radiome- ter matched in bandwidth to the transmission (i.e., Wss) and integrating energy over the entire transmission (i.e., TM) or using multiple narrowband radiometers whose filter bandwidths and detector integration times are matched, to the bandwidth (Wh) and duration (Th) of the hop pulse. The sec- ond of these two approaches implies, in its generic form, a requirement for Low Probability of Intercept Communications a filter at each of the possible hop frequencies. Structures which ease this requirement have also been considered. The basic difference between the various structures realizable under the second approach centers on the deci- sion procedure used to convert the hop pulse detection data into decisions about the presence of a transmission. The following is a summary of the applicable detector types and their relative practical value: Detector Type Relative Practical Value Wideband Energy Detector Very functional and in (Wideband Radiometer) general use Optimum Multichannel FH Academic-provides an Pulse-Matched Detector optimum performance bound Maximum Channel Filter Suboptimum version of (2) Bank Combiner (FBC) Optimum Partial-Band FH Realizable but complex Pulse-Matched Detector subconfiguration of (2) [not discussed in this chapter] Partial-Band FBC (PB-FBC) Realizable subconfiguration of (3) As will be seen from the following discussions, detector types