ABSTRACT
Any radar signal must carry a transmitter signature that permits to recognize the signal produced by a certain transmitter. This transmitter signature is conventionally the carrier frequency. It is taken for granted that the carrier frequency can be recognized if the returned signal has a small radar signature. Hence, one must find coded sequences of pulses, or radar characters, that produce a transmitter signature that will not be made unrecognizable by a large radar signature or, better, target signature. The primary purpose of theoretical advancement in engineering is to provide guidance for the development of technology, not to solve remaining problems after the technology has been developed. Originally, a radar signal was ideally a rectangular pulse amplitude modulated onto a sinusoidal carrier. Real radar signals were always quite different. The first carrier-free radars were ground-probing radars that used a nominally rectangular pulse for the radiated electric and magnetic field strength.
