Some applications of the principle of variation of wavelength in wave guides by the internal movement of dielectric sections

In many radar applications it is desirable that the phase distribution down a wave guide should be capable of variation by some simple control. There are two main instances of this need. Firstly, to adjust the loading of centimetre-wave magnetrons working into a complex load. Secondly, to swing the beam from highly-directive arrays without moving the array. This paper outlines a method of achieving these results by the movement of lengths of dielectric material across the guide between regions of high and low field intensity. The wavelength in the guide is then dependent on the position of the dielectric. Some applications of this principle at frequencies of about 3 000 Mc/s are described, and experimental figures are given for the wavelength variations obtained in practice with different types and arrangements of dielectric sections. For one particular case, the results of a theoretical calculation of the guide wavelength are given and these show good agreement with those obtained experimentally.