Theoretical Effects of Array Mutual Coupling on Clutter Cancellation in Displaced Phase Center Antennas

摘要

Large phased array antenna systems are being considered for space- based radar (SBR) applications. One particular moving target indicator (MTI) radar system concept which looks promising uses the displaced phase center antenna (DPCA) implementation to cancel background clutter. Ignoring signal generation/processing issues, the ability to cancel clutter rests primarily on the DPCA array forming two (or more) displaced phase center radiation patterns having identical main beam characteristics. In an ideal array with no mutual coupling and no hardware errors, a DPCA array would have identical main beams. However, in a practical array, mutual coupling between the array elements will cause the displaced phase center antenna main beam shapes to become amplitude and phase mismatched. Thus, clutter can only be partially cancelled. It is desirable to quantify the effects of mutual coupling on DPCA performance. The method of moments is used to model finite arrays of thin-wire antennas over an infinite ground plane. In this way, array mutual coupling and array edge effects are included in a numerical simulation of a DPCA phased array. Both sub-scale and full-scale SBR corporate-fed phased arrays are analyzed. Upper-bound DPCA clutter cancellation capability, in terms of radia- tion pattern match, is presented. The influence of main beam scan angle, array illumination, phase center displacement, array size, array lattice, number of passively terminated element guard bands, and radiating element type on two- phase center DPCA clutter cancellation is investigated. Dipole and monopole arrays having square and hexagonal lattices are analyzed. It is shown quantitatively that variation of the above array parameters can influence substantially the DPCA clutter cancellation.