Mutual impedance effects in large beam scanning arrays

An analysis is presented of the driving point impedance of the elements in a flat array of infinite vertical height but finite horizontal width. It is assumed that each of the elements is fed by a separate amplifier, having infinite internal impedance, and that the amplifiers can be phased to direct the beam at various positions in space. The radiating elements considered are infinitely long wires spaced on half-wavelength centers and half-wave dipoles spaced on half-wavelength centers, each backed by a conducting ground plane spaced one-quarter wavelength from the elements. Values of driving point impedance are computed for the 61 elements in arrays 30 wavelengths wide. Values of the driving point impedance near the center of the array are found to agree closely with the values computed for infinitely wide arrays while the driving-point impedance of elements near the edge of the array are found to deviate considerably from the values at the center.