mitting a frequency modulated wave upward and listening for the return echo [4]. Applications of this concept to aircraft instrumentation were obvious and FM altimetry became a reality in the 1930s, with all major combatants in World War II making use of this tech- nology [5]. Typically, linear-sawtooth or sinusoidal modulations were used in these early systems. The frequency modulation generally serves two pur- poses: 1) it ameliorates the problem of interference leakage of the trans- mitted signal directly into the receiver, and 2) it makes possible the measurement of propagation delay and, hence, range. Historically, the development of pulsed radars has received more atten- tion than that of continuous wave (CW) radars, since isolation of the trans- mitting and receiving systems is a lesser problem in this case. By the end of World War II, the Germans were developing a linear FM pulse compression (chirp) system called Kugelschale, and a pulse-to-pulse frequency-hopping Emerging Concepts radar called Reisslaus [6]. In the 1940s, Prof. E. Huttman was issued a German patent on a chirp pulse radar, while U.S. patents on this type of sys- tem were first filed by R. H. Dicke in 1945 and by S. Darlington in 1949 [7]. The mid-1940s also saw the formulation of the matched filter concept for maximum signal-to-noise ratio (SNR) pulse detection by North [8] and Van Vleck and Middleton [9]. This development indicated that the performance of optimum signal detection procedures in the presence of white noise depends only on the ratio of signal energy to noise power spectral density, thus, leaving the choice of waveform open to satisfy other design criteria (e.g., LPI or AJ). Resolution, accuracy, and ambiguity properties of pulse waveforms finally were placed on a sound theoretical basis by P. M. Woodward [10] in the early 1950s. Spectrum spreading was a natural result of the Second World War battle for electronic supremacy, a war waged with jamming and anti-jamming tac- tics. On the Allied side by the end of the war, every 