| 摘要 |
<p>The traditional minimum antenna area limit for synthetic aperture radar (SAR 204), imposed by ambiguity considerations, is eliminated by using a transmitter format providing distinguishable sub-pulses (256). Signal formats which are feasible for implementing such sub-pulses include frequency-division (i.e., a distinct frequency band is used for each sub-pulse), and code-division (i.e., sub-pulses occupying the same frequency band are grouped in distinguishable combinations). The nominal pulse period is divided into N sub-pulses (252), and the sub-pulse group is transmitted with the nominal pulse repetition frequency (f) (256). The range ambiguities are determined by the repetition rate of the sub-pulse group (f) and the azimuth ambiguities are determined by the repetition rate of the sub-pulses (N f). The antenna is capable of sampling a Doppler bandwidth that is a factor of N times the traditional value and the antenna (22) area can be reduced by a factor N from the limiting value presently used in SAR antenna design. A reduction in antenna length by a factor of N, for example, can be obtained at the expense of a signal-to-noise decrease of N and an increase in signal bandwidth by the same factor. Alternatively, the same antenna length reduction of N and an increase in signal-to-noise by a factor N can be obtained using the original bandwidth if the resolution is degraded by N.</p> |
