Low Profile Dielectric Rod Tuned Reconfigurable Band Pass Filters

A novel low profile mechanical tuning technique is introduced in this paper to change the center frequency of substrate integrated waveguide (SIW) based reconfigurable bandpass filters (BPF), by loading dielectric rods of different permittivity in resonant cavities and coupling apertures. The technique is simple, cost-effective (rods are machined from conventional substrates), and the same physical structure provides a wide frequency tuning. First, the tunability of center frequency of the SIW cavity resonator is theoretically explained and then estimated with the help of full-wave 3D EM simulator and electrical equivalent circuit. This concept is extended to the tuning of coupled resonator BPF loaded with dielectric rods followed by the analysis of maintaining constant bandwidth. Following the analysis technique, the tunability concept is studied for different arrangements of dielectric rods inside the SIW BPFs. The characteristics of the fabricated filters are experimentally validated. It is shown that center frequency tunability can be achieved by simply varying the permittivity of all the dielectric rods simultaneously. The proposed technique is further extended for obtaining wider tunability and constant bandwidth by using dielectric rods of dissimilar permittivities from a look up table. These designs demonstrate a simple and cost-effective passive tuning technique achieving high Q-factors in the range of 102–210.5, lowest insertion loss