Monolithically Integrated Dual-Channel Filters Using Nested Waveguide Resonator Arrays

This article reports on a new class of 3-D highly miniaturized dual-channel bandpass filters (BPFs). They are based on a new nested waveguide (WG) resonator approach that allows the excitation of two fully isolated and independently reconfigured fundamental resonances within the volume of a conventional ridge WG (RW). Size compactness is achieved by as follows: 1) re-using traditionally unused areas of an RW resonator and 2) monolithic integration enabled by stereolithography apparatus (SLAs)-based 3-D printing. Two alternative RW-WG and RW/post-loaded WG (RW-PW) resonator concepts are proposed and analyzed in detail for the realization of two-channel BPFs with passbands placed at the same frequency or closely/widely spaced frequency bands. Scalability to high-order transfer functions through volume reuse is also demonstrated. For proof-of-concept validation purposes, dual-channel prototypes were designed, manufactured, and tested at C-band, X-band, and Ku-band. They include as follows: 1) a two-channel BPF having two second-order channels at 6.75 GHz and at 10 GHz, and another two-channel BPF having a second-order channel at 6.75 GHz and at 15.375 GHz; 2) a two-channel BPF having two channels co-located at 6.75 GHz; 3) a two-channel BPF having a third-order channel at 6.75 GHz and a fourth-order channel at 8 GHz and another two-channel BPF with a third-order channel at 6.75 GHz and another at 10 GHz; and 4) a two-channel BPF having a third-order channel at 6.75 GHz and a sixth-order channel at 10 GHz.