3.1 Intercept System Characteristics and Functions

The characteristics that are important to intercept system designers reflect the functions which such systems are expected to perform, namely, (1) to intercept signals, (2) to recognize the type of transmitter, and (3) to measure signal parameters. The purposes of making detailed parameter measurements include determining:

• Technical features of the radar s design and construction;

• The radar s performance capabilities;

• The radar s weaknesses for jamming (including deception), or other kinds of attack.

The intercept system characteristics of interest include those shown in Table 3.1. In general, interception requires high sensitivity and dynamic range covering large angular regions and frequency bands, but the only information expected is the existence of the signals. The dynamic range need not be excessively wide, since some saturation can be tolerated. For the recognition function, the receiver demands can be relaxed somewhat if the interception process has allowed reducing the angular sector and frequency coverage. Then only a few signals will be received at once. Usually, recognition requires measuring the basic signal parameters (typically RF, PRI, pulse duration, and scan period) to accuracies on the order of 0.1 to 1%. Naturally, any unusual modulations must be noted to aid in the recognition process.