  Direct blast is a strong interference in bistatic sonar and difficult to
suppress due to multipath propagation for blasts and signals. A generalized
likelihood ratio test (GLRT) based detection scheme in the frequency domain of
the received signals is proposed in this study, and the unknown parameters are
estimated using Maximum Likelihood Estimates and Weighted Fourier Transform and
Relaxation in a multipath environment. The distributions of the test statistic
of detectors for known and unknown noise power are given in theory, and the
detection probability is determined. The performance of the detector decreases
by 4 dB when the noise power is evaluated with maximum likelihood estimates.
Simulations show the effectiveness of the detector under a forward scattering
detection configuration with a low signal-to-direct blast ratio. The
sensitivity of many factors is discussed, and robustness is achieved.
