Robust Superdirective Beamforming for Hf Circular Receive Antenna Arrays

Abstract

Abstract-Superdirective beamforming can highly reduce the aperture size of high-frequency receive array. At the same time, the closely spaced elements of a small aperture array can make it low efficiency and sensitivity to the array uncertainty, which limit its application in practice. Using a parameter called sensitivity factor, we found that array efficiency and robustness against array error could be considered simultaneously. On that basis, we derive a novel superdirective beamforming criterion based on a constrained sensitivity factor for the HF circular receive array. New method is analytical and computationally inexpensive. Through making the directive gain with a given sensitivity factor maximum, we calculate the optimal weights of the array elements. To illustrate the proposed method can increase the acceptance of HF superdirective receive arrays in practice, several numerical results are provided.

Superdirective Beamforming With Interferences and Noise Suppression via Second-Order Cone Programming

“…As shown in [9], CODG method can provide a good tradeoff among directive gain, array efficiency and robustness against array uncertainty by adjusting the sensitivity factor K. To control SLL, nulls and robustness to uncertainty simultaneously, we add the constraints (14)- (15) to the CODG method and call this new superdirective beamforming method as the Modified Constrained Optimum Directive Gain (MCODG) method. Assume the maximum K corresponding to MODG method with the prescribed SLL and nulls as K max .…”

“…To present the robustness of an array to array uncertainty, we introduce the sensitivity factor K described in detail in [9]. Generally speaking, the larger K is, the more sensitive the array is to array uncertainty.…”

“…Under the condition that the array is relatively accurately calibrated, Optimum Directive Gain (ODG) method in [7] gets the optimum gain. Shown better robustness to array uncertainty, Constrained Optimum Directive Gain (CODG) method in [9] can provide a good tradeoff among directive gain, array efficiency and robustness against array error by adjusting the sensitivity factor. In spite that both kinds of methods can bring about high gain, the existing methods still need improvement.…”

“…Although the array is hard to be calibrated the same as the ideal array model, the residual error after a series of calibration measures cannot be very large. Except array calibration, another way is to develop superdirective beamforming method with robustness to array uncertainty [5,9].…”

“…In the past decades, the so-called superdirective array [4][5][6][7][8][9] has drawn numerous researchers. It is claimed that a small size array using superdirective beamforming method can perform as high directivity as a large-size array using conventional beamforming, which means that the expensive vast aperture HF receive array can be replaced by a lowcost small array without sacrificing gain.…”