A 0.9-THz Integrally Manufactured High-Precision Waveguide Cavity Filter Using Electrochemical Micromachining Technology

Terahertz (THz) systems are in urgent need of the reliable and flexible implementation of high-precision metallic waveguide microdevices, particularly in the challenging waveguide rectangular 1.0 (WR-1.0) band. To this end, a 0.9-THz integrally manufactured sixth-order bandpass waveguide filter with high-dimensional accuracy, low surface roughness, and perfect verticality of sidewalls is proposed by using electrochemical micromachining (ECMM) technology in this article. This hybrid micromachining process contains three key steps, namely, wire ECMM, gold microelectroplating, and selective chemical dissolution (SCD). The maximum manufacturing tolerance for the fabricated filter prototype is well controlled within
$1.5~\mu \text{m}$
. After meticulous alignment between test flanges and the device under test, the measured 3-dB bandwidth of the filter prototype is 8.56% with respect to 0.9 THz, from 0.862 to 0.939 THz, and the minimum passband insertion loss (IL) is 5.219 dB at 0.9025 THz. Considering such high THz frequencies up to the WR-1.0 band, the good measured electromagnetic responses indicate that high-performance THz metallic waveguide components can be constructed with the aid of the proposed ECMM technology.