Theory of frequency scanning of antennas

This paper presents the theory of
180\deg
scanning for a linear array and Tchebycheff array by frequency variation and discusses the relationships between the linear array theory and the
\omega-\beta
diagram of periodic structures. Each element is excited by a slow-wave structure which is either nondispersive or dispersive. At a center frequency, the spacing is an integral multiple of guide wavelength
M\lambda_{c}
. It is shown that this is in fact the -
M
th space harmonic in the so-called forbidden region, and all the other harmonics are slow. For a given frequency range, the necessary phase velocity and other parameters are determined in order to obtain
180\deg
scanning without causing other main beams, and the example is carried out for the
X
-band frequency range.