Frequency scanning antennas

This paper presents the theory of 180 degree scanning for a linear array and Tchebyscheff array by frequency variation and discusses the relationships between the linear array theory and the\omega-\betadiagram of periodic structures. Each element is excited by an equivalent slow wave structure which is either non-dispersive or dispersive. At a center frequency, the spacing is an integral multiple of guide wavelengthM\lambda_{c}. It is shown that this is in fact the -Mth 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 degree scanning without causing other main beams, and the example is carried out for the X-band frequency range.