Ku-band microstrip diplexer based on dual behavior resonator filter

This report describes the design of original planar filters and of a diplexer based on dual behavior resonator (DBR) filter, and introduces measurement data. The specifications dealt with a limited frequency band in Ku-band where a high isolation is needed between Rx and Tx frequency bands. This study evidences the benefits of oversized DBR in particular for getting a high rejection level. Moreover, folding the oversized resonators allows one to keep constant the filter overall size. The first DBR filter for the Ku-band receiver is of 3rd-order with a central, folded, oversized and low-frequency stub; the second DBR filter for the Ku-band transmitter is also of 3rd-order with three folded, oversized and high-frequency stubs. Then, a diplexer as presented in Rhodes and Ievy (1979) and Matthanei et al. (1980) was realized from both filters as stated in Goron et al. (2003) and Tudosie and Vahlieck (2004).