This is the accepted version of a paper published in IEEE Transactions on Terahertz Science and Technology. This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination.
This is the accepted version of a paper published in IEEE Transactions on Terahertz Science and Technology. This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination.
Abstract-In this paper, we present a microfabricated fourthorder sub-THz WR-3.4 bandpass waveguide filter based on TM110 dual-mode circular-shaped cavity resonators. The filter operates at the center frequency of 270 GHz with fractional bandwidth of 1.85% and two transmission zeros are introduced in the upper and in the lower stopband using a virtual negative coupling. The microchip filter is significantly more compact than any previous dual-mode designs at comparable frequencies, occupying less than 1.5 mm 2 . Furthermore, in contrast to any previous micromachined filter work, due to its axially arranged interfaces it can be directly inserted between two standard WR-3.4 rectangular-waveguide flanges, which vastly improves system integration as compared to previous micromachined filters; in particular no custom-made split-block design is required. The cavities are etched in the handle layer of a silicon-on-insulator (SOI) wafer, and coupling is realized through rectangular slots fabricated in the SOI device layer. Couplings of the degenerate modes in one cavity are facilitated by means of small perturbations in the circular cavity shapes. The measured average return loss in the passband is -18 dB and worst-case return loss is -15 dB, and an insertion loss of only 1.5 dB was measured. The excellent agreement between measured and simulated data is facilitated by fabrication accuracy, design robustness and micromachined self-alignment geometries.
A silicon micromachined waveguide hybrid coupler for J-band (220-325 GHz) applications is presented. The coupling and phase shifting functions are realised using a 90° ridged waveguide phase shifter, a joint waveguide section and a port extension. The hybrid coupler is fabricated using a micromachined waveguide technology employing a double Hplane split that results in low losses. For the design band 230-300 GHz, initial VNA measurements indicate coupling coefficients of -3.2±0.4 dB, amplitude imbalance better than -0.5/+0.3 dB, phase imbalance better than -14°/+11° and an input reflection coefficient below -14 dB. To the best of our knowledge, this is the first time a low-loss micromachined hybrid coupler of this type is characterised within this frequency range.
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