3.1 SURVEY OF CURRENT AND FUTURE INTERCEPT RECEIVERS

An LPIS must be designed to counter many different current intercept receivers. Any LPIS design also must anticipate future intercept threat trends. There are several trends in both airborne warning receivers and ground-based receivers that will continue well into the future. First, Chapter 3 provides an overview of the general operating techniques for six separate types of intercept receiver implementations. Second, intercept receiver performance limitations are discussed. Third, possible future threats are analyzed. Finally, two LO/LPI countermeasures for intercept receivers are suggested.

There are six general kinds of intercept receiver implementation (see Table 3.1). The first and simplest class is wideband channelized crystal video receivers (CVRs) with RF preamplifiers. The second class, which is widely used, is instantaneous frequency measuring (IFM), usually employing preamplifiers and wideband channelization. The third class is digitally controlled scanning superheterodyne/homodyne receivers, which are characterized by narrowband filters that are swept over the frequency range of interest. Fourth are completely channelized high-dynamic-range intercept receivers that are characterized by wide frequency coverage but broken into reasonably small filter bins, implemented with multiple discrete filters. These provide very high dynamic range. Fifth are transform receivers (microscan, Bragg cell, or compressive), which in essence form a filter bank from a frequency-dispersive or optical device. Last are hybrids of the above types, which allow cueing of high-resolution, high-dynamic-range analysis receivers. The six types are described in more detail in Section 3.2.