Synthetic-Aperture Radar Based on Nonsinusoidal Functions: III-Beam- Forming by Means of the Doppler Effect

Synthetic-aperture radar based on nonsinusoidal functions was discussed in two previous papers [1]. The Doppler effect was not used to produce the synthetic aperture, even though the conventional synthetic-aperture radar would not work without it. This paper shows how the Doppler effect of a nonsinusoidal wave can be used to produce a synthetic aperture. The main result is that the range resolution is about two orders of magnitude better than with a sinusoidal carrier, under the constrint that the highest significant frequency used is the same in both cases. A limit on the highest frequency is necessary, since the absorption due to rain and fog, as well as noise, increase rapidly above about 10 GHz. The paper shows that for the best use of nonsinusoidal carriers, one has to develop a theory of carrier coding, which is considerably more complex than the theory of coding for baseband signals.