Traditional high resolution Synthetic Aperture Radar (SAR) systems
operate by placing a narrow transmit beam on a given ground patch
for an extended time period. An alternate method of achieving high
resolution is to increase the beamwidth. This approach allows both
high resolution and large coverage areas, but increases the Doppler
spread of the clutter echoes and therefore the required Pulse
Repetition Frequency (PRF). Unfortunately, the required PRF for
avoiding Doppler aliasing can become impractical rather quickly.
This paper begins by introducing a recently proposed technique for
mitigating these Doppler aliasing artifacts using continuous
transmission of Stepped-Frequency (SF) waveforms. By randomizing
the subpulse frequency order on a waveform-to-waveform basis,
matched filter processing has been shown to build a composite
ambiguity function which places Doppler filter nulls on top of
Doppler aliasing artifacts, effectively removing them from the
Using Xpatch radar scattering data of a backhoe, this technique is
demonstrated for the first time using a non-point scatterer target.
The 2-D spatial frequency data is used to produce uncompressed
target echoes of randomized SF waveforms. A Doppler mismatch is
applied to simulate the return from an aliased target. By applying
the appropriate filter to the SF echoes, the aliased target is
eliminated, dropping the peak of the aliased energy by nearly 40 dB.