Corrections for frequency response differences in multiple receiver arrays

In interference-cancelling antenna array systems where the signals are combined after passing through receivers, the differential frequency responses of the receivers act to limit the null depth and therefore the degree of interference rejection attainable for finite-bandwidth interference. An experimental four-element HF antenna array is used as an illustration; the measured differential frequency dependent phase and amplitude responses of the receivers are presented and the corresponding limits to null-depth derived, for a 3 KHz bandwidth. Correction techniques, including an exact software procedure and a hardware-implementable approach to linear phase correction are presented, and their requirements and anticipated performance considered.