  When a target is masked by mainlobe clutter with the same Doppler frequency,
it is difficult for conventional airborne radars to determine whether a target
is present in a given observation using regular space-time adaptive processing
techniques. Different from phased-array and multiple-input multiple-output
(MIMO) arrays, frequency diverse arrays (FDAs) employ frequency offsets across
the array elements, delivering additional range-controllable degrees of
freedom, potentially enabling suppression for this kind of clutter. However,
the reception of coherent FDA systems employing small frequency offsets and
achieving high transmit gain can be further improved. To this end, this work
proposes an coherent airborne FDA radar receiver that explores the
orthogonality of echo signals in the Doppler domain, allowing a joint
space-time processing module to be deployed to separate the aliased returns.
The resulting range-space-time adaptive processing allows for a preferable
detection performance for coherent airborne FDA radars as compared to current
alternative techniques.
