PULSE FILTER FILTER [c(1)] [A*(T-t)] DEMOD SOURCE (c) Matched Filter Reference System Figure 1.2. Simple SS system configurations. (The notation z(t) is used to denote an estimate of z(t).) Spread-Spectrum System Configurations and Components 2. Stored reference (SR) systems require independent generation at trans- mitter and receiver of pseudorandom wideband waveforms which are identical in their essential characteristics (Figure 1.2(b)). The receiver's SS waveform generator is adjusted automatically to keep its output in close synchronism with the arriving SS waveform. Data detection, then, is accomplished by cross-correlation. The waveform generators are ini- tialized prior to use by setting certain parameters in the generating algo- rithm, thereby denying the jammer knowledge of the waveform set being used (even if the jammer has succeeded in determining the generator's structure). 3. Matched filter (MF) systems generate a wideband transmitted signal by pulsing a filter having a long, wideband, pseudorandomly controlled impulse response (Figure 1.2(c)). Signal detection at the receiver employs an identically pseudorandom, synchronously controlled, matched filter which performs the correlation computation. Matched fil- ter systems differ from SR systems primarily in the manner in which the inner-product detection process is mechanized, and hence, have exter- nally observed properties similar to those of SR systems. Certainly, a pure TR system has several fundamental weaknesses including: (1) The system is easily spoofed since a jammer can in principle transmit a pair of waveforms which are accepted by the receiver, (2) relatively poor per- formance occurs at low signal levels because noise and interference are pre- sent on both signals which are cross-correlated in the receiver, (3) the data is easily determined by any listener who has access to both transmitted sig- nals, and (4) the TR system's two channels may require extra bandwidth and may be difficult to match. Some of the problems associated with TR sys