W‐band layered waveguide filters based on CNC‐milling technology

Abstract

The development of multi‐pixel receivers on the millimetre‐wave and terahertz bands demands on the integration of key waveguide devices. In this paper, two waveguide bandpass filters operating at the W‐band are developed based on the layered integration architecture. First, the traditional fourth‐order waveguide filter is perpendicularly folded to realise dual‐layered arrangement, meanwhile a cross‐coupling between layers is introduced to obtain the standard quasi‐elliptical response. Then, two layered approaches including 5‐layer and 3‐layer are proposed to fabricate filter prototypes integrating with 90° curved waveguides based on the computer numerical control (CNC) technology. Finally, the measurement exhibits that both filters have achieved the 3 dB fractional bandwidth of 14.8% from 85 to 98.5 GHz, low insertion loss of 0.6 dB (5‐layer) and 0.4 dB (3‐layer), the return loss with better than 20 dB, as well as two obvious transmission zeros in the out‐of‐band. Besides, the layering error analysis and performance comparison of both filters are discussed, which verify the feasibility of the layered integration for CNC‐machined W‐band waveguide filters.

Terahertz waveguide multiplexers: A review

“…In conclusion, there are many development directions for THz waveguide multiplexers, such as high frequencies, wide bandwidth, low‐loss, high‐isolation between channels, solid‐state connection, system integration and scalable channel numbers, which will promote the improvement of THz receivers and systems. The advanced waveguide hybrids, 13 quasi‐elliptical filters, 11 ridged waveguides 34,39 can be introduced into the multiplexer circuits to improve capabilities. In addition, numerous multiplexers reported in the microwave band would be extended up‐to THz band such as the Y‐junction based waveguide diplexers proposed in Yu et al 58 and Vanin et al 59 …”

“…Both electronic and photonic characteristics are coexisted in this band gap, which has provided rich scientific and technological opportunities in numerous fields, such as radio astronomy, 2 atmospheric science, high‐speed communication, 3 and spectral imaging. In recent years, the urgent requirements of advanced THz instruments have promoted the in‐depth study of abundant key components, such as active devices including sources, 4 detectors, 5 mixers, 6 amplifiers 7 and oscillators, as well as passive components including resonant cavities, 8 electromagnetic fluids, 9 power dividers, 10 filters, 11 multiplexers, 12 couplers, 13 and waveguide metamaterials 14 . Therefore, driving THz key devices forward high performance of broadband, low loss, high isolation and integration is always an important research point in this field.…”

“…Comparing with the on‐chip lines, the metal sealed waveguide can avoid the above weaknesses, while can exhibit low loss, high Q ‐factor, simple assembling and interconnection. As a result, waveguides are preferred for designing THz components 4–14 . For the fabrications, the computer numerical control (CNC) milling technology is still the first choice for producing THz waveguide components to strengthen physical robustness.…”

“…As a result, waveguides are preferred for designing THz components. [4][5][6][7][8][9][10][11][12][13][14] For the fabrications, the computer numerical control (CNC) milling technology is still the first choice for producing THz waveguide components to strengthen physical robustness. The errors of current CNC-milling are less than ±10 μm, 26 and the minimum error is even less than ±2.5 μm, which has successfully fabricated waveguide filters up to 700 GHz.…”

Copper micromachined WR‐2.2 band waveguide and bandpass filter

“…Several high-performance terahertz waveguide filters fabricated by CNC technology have been reported in several studies. [10][11][12][13][14][15] However, the high-precision CNC process cost is too high to be suitable for mass production, thereby limiting its application range. In addition, the components machined by the CNC process require assembly, and any errors in assembly would affect their performance.…”