An Adaptive Antenna for Rejection of Wideband Interference

Imposing pattern nulls on broadband array responses

“…(h n k] sinc(k ; n (u 0 ))) = 0 8k (13) where denotes convolution in the k index and sinc(x) = sin( x)=( x).…”

“…Equation (14) yields (12) and the inverse discrete-time Fourier transform of (15) yields (13). ./ It is not immediately clear how (12) and (13) may be easily enforced.…”

“…Proof: If n (u 0 ) i s a n i n teger for all n, then (13) The null constraint (16) is illustrated in Figure 2. Speci cally, when n (u 0 ) i s a n i n teger for all n, the sum of the delayed lter impulse responses can be made exactly zero.…”

“…7{9 In phased arrays, where the beamformer weights are xed as a function of frequency, broadband pattern nulling is e ected by imposing a null over a wide spatial region centred on the required broadband null direction. Methods of producing such a n ull trough include imposing multiple pattern nulls, 10{12 imposing derivative constraints at the desired direction, 10,13,14 and constraining the average power over an angular region, 15,16 in the vicinity of the required broadband null direction.…”

Eigen-approach for wide-band interference suppression

“…The problem of designing a class of linear antenna arrays with broad nulls to suppress interfering signals of arbitrary arrival direction has been extensively studied in the literature (Prasad 1979, Takao and Komiyama 1980, Steyskal 1982, 1983. The need for a broad null to suppress a prescribed interference arises when the interfering signal varies with time or when the direction of a narrow band signal is not known exactly.…”