Abstract
A microfabricated hollow air-filled waveguide with two back-to-back bends operating in the WR-3 frequency range of 220 to 325 GHz has been successfully fabricated through a multilayered ultrathick SU8 process and has ultralow transmission loss of 0.028 to 0.03 dB/mm in a performance test. This is the first SU8 constructed hollow waveguide operating at WR-3 frequencies having transmission loss comparable with the state-of-the-art computer numerical control (CNC) machined metal circuits. The multilayered SU8 processing technique has a great advantage of reducing the transmission loss by decreasing the probability of air gaps between SU8 layers. The excellent device performance is also attributed to the precisely controlled layer thickness and ultimately low surface roughness of evaporated silver which only contributes a small part of the microwave signal attenuation.
Highlights
Millimeter-wave and terahertz components in the frequency range from 100 GHz to 10 THz have been finding more and more application prospects
The frequency of 300 GHz represents a cusp in the current technology development where industrial development is progressing rapidly at lower frequencies (
We present the first WR-3 (220 to 325 GHz) waveguide with back-to-back right angle bends having ultralow insertion loss (IL) similar to the computer numerical control (CNC) machined metal circuits
Summary
Millimeter-wave and terahertz components in the frequency range from 100 GHz to 10 THz have been finding more and more application prospects. SU8 photolithography process has been successfully used for fabricating low frequency waveguides, filters, and slot antenna.[3,4,5,6] as the frequency increases, there is less space for the manufacturing tolerance and more work is needed to meet the requirements of high-dimensional accuracy, extreme surface smoothness, and low transmission loss. It should be noted that, in order to connect the measurement system, accurate alignment is required between the WR-3 waveguide bends on the upper and lower surfaces of the structure and the measurement port This is extremely accurately achieved in this case by having the waveguide precision alignment pin holes formed in the SU8 itself, making the alignment as accurate as the photolithographic process.
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