The near fields of long end-fire dipole arrays

Measured phase and amplitude data on a variety of long (40-wavelength) end-fire arrays of dipoles are presented. Correlation with far-field radiation patterns was good, and experimental agreement with a parallel theoretical program was very satisfactory. Measured local phase velocity agreed well with calculated values, and uniform, tapered, and periodically-modulated arrays with the proper average phase shift all had approximately the theoretical expected gain. It is shown that local variations in the near field caused by the individual elements may distort measurements of the phase velocity based upon standing-wave techniques.