A robust and tuneless micromachined waveguide diplexer operating in the frequency range 71–86 GHz is here presented. The diplexer is based on multiple coupled cavities and it is manufactured using micromachining technology on two staked silicon layers. The diplexer consists of two filters combined to a common waveguide port via an E-plane T-junction. The two eight-order band-pass filters are centered at 73.5 and 83.5 GHz. The fractional bandwidths for two bands are 8.8 and 7.8% at higher- and lower-band, respectively. The measured insertion loss is below 0.7 dB for both the filters and the diplexer isolation is better than 55 dB, as required. The proposed technology allows for a very compact device (<20 × 20 × 1.5 mm) and the first prototypes were proved to be very robust to manufacturing tolerances and environmental tests, thus leading to an excellent tuneless manufacturing yield in future production. The diplexer will be employed in next generation terrestrial radio-link communications front-ends.

E-band cavity diplexer based on micromachined technology

A new concept for compact and low-loss Ka-band micromachined bandpass filters for next generation on-board communications is presented which combines micromachined cavities with multilayer technology on silicon. The resonator consists of a gold-plated micromachined shielding cavity with a longitudinal 20 μm thick gold-plated silicon membrane. The membrane is short-circuited at both anchored ends and it operates as a λ/2 TEM line resonator. The footprint of a single resonator is reduced by more than 50% with respect to conventional micromachined cavities using the TE101 resonant mode. The measurements of single transmission-type resonators are in very good agreement with the full-wave simulations, demonstrating a high filter robustness to process tolerance. The expected unloaded Q of the resonators for 500 μm thick layers is 600, and the measured value is above 500. Qs above 1000 are feasible with the available technology by simply increasing the number and the thickness of the silicon layers. A 4th order pseudo-elliptic filter at 30 GHz (FBW = 1.7%) has been designed and is under fabrication.

Micromachined filters in multilayer technology for on-board communication systems in Ka-band

This paper describes a substrate integrated waveguide (SIW) based filter at K band frequency on silicon substrate. TMAH etching is used to form the via-holes for SIW cavities. Simulations and comparison of TMAH and Deep reactive ion etching (DRIE) etched cavity has been presented. A micro- machined filter is made from rectangular cavities integrated into a silicon substrate and is fed by coplanar waveguide (CPW) transmission-lines through current probes. Simulated filter using TMAH etching shows insertion loss of 0.29dB and return loss of 21.96 dB.

Sumit Kumar Khandelwal

Papers

Silicon micromachined K-band filters