Detection performance is optimized and range and doppler both improved by maximizing the SNR. Since this needs the pulse to have high energy, long pulses are required unless a very high power transmitter is available. Long pulses also permit good doppler accuracy, but, for simple pulses, give poor range accuracy. The system designer can avoid this apparent dilemma by using phase-modulated pulses. These can be constructed to give the large bandwidth that, after pulse compression, leads to good range accuracy. Whatever transmitted waveform is chosen, the resolution constraints imposed by the ambiguity function cannot be escaped. All that the designer can do is to attempt to move the significant areas of ambiguity into regions of the range-doppler plane where targets are unlikely to be present.