  Frequency diverse array (FDA) differs from conventional array techniques in
that it imposes an additional frequency offset (FO) across the array elements.
The use of FO provides the FDA with the controllable degree of freedom in range
dimension, offering preferable performance in joint angle and range
localization, range-ambiguous clutter suppression, and low probability of
intercept, as compared to its phased-array or multiple-input multiple-output
(MIMO) counterparts. In particular, the FO of the coherent FDA is much smaller
than the bandwidth of the baseband waveform, capable of obtaining higher
transmit gain and output signal-to-interference-plus-noise ratio (SINR). In
this paper, we investigate the problem of joint design of the transmit and
receive weights for coherent FDA radar systems. The design problem is
formulated as the maximization of the ratio of the power in the desired
two-dimensional range-angle space to the power in the entire area, subject to
an energy constraint that limits the emitted energy of each transmit antenna
and a similarity constraint such that a good transmit beampattern can be
guaranteed. Due to the resultant problem is NP-hard, therefore, a sequential
optimization method based on semidefinite relaxation (SDR) technique is
developed. Numerical simulations are provided to demonstrate the effectiveness
of the proposed scheme.
