Radiation Efficiency of a Linear Array of Point Sources with Periodic Phase Variation

Abstract

The phase of the sources in the array is considered to vary in a “zig-zag” manner. It is found that the amplitude of the zig-zag must be sufficiently great that the phase varies along the length of the source at the same rate as in the radiated wave, before an appreciable decrease in radiation efficiency occurs. It is thus qualitatively similar to the array with a linear phase variation, which it approaches more closely as the length of the zig-zag approaches the length of the array. However, the periodic phase variations result in properties similar to the ghosts arising from imperfect diffraction gratings. If the sources are excited by means of pulses whose timing varies periodically along the length of the array, then the phase will be a function of frequency. It is then impossible to make the source inefficient for all frequencies. Only bands of frequencies will be suppressed.