Quarter-Wavelength Coaxial SIRs for Space Tx Bandpass Filters

This paper focuses on the flexibility in the design of quarter wavelength coaxial stepped impedance resonators (SIRs) for space applications. For such resonators, a coaxial geometry owns one degree of freedom allowing to modulate the transverse dimensions, and the SIR effect allows to adjust the longitudinal dimension. For this later, the number of degrees of freedom depends on the number of coaxial nested sections. For these topologies, the electrical model is a cascade of coaxial sections, where the ground conductor of one section becomes the central core of the next, and vice versa. According to the transverse and longitudinal degrees of freedom, it is possible to propose several sets of dimensions, height and footprint, for the same given fundamental frequency. Obviously, this will have an impact on: the quality factor, the multipactor threshold and also the frequency behavior in the attenuated band. In this paper, on the base of 4th order filters, we illustrate this ability by presenting two sets of 1.5 GHz central frequency filters with a similar bandwidth, and different footprints. Two- and three-section configurations are considered, and for each the multipactor threshold is simulated.