Development of a low cost 94ghz imaging receiver using multilayer Liquid Crystal Polymer technology

The W-band remains the most suitable band for high resolution near-real-time imaging in security, airborne and defence applications. The benefits of higher frequencies are counteracted by reduced penetration and also by very high component costs, due to the need for precision machining of metal, assembly of semiconductors, supporting circuit boards and manual tuning to achieve the required performance. Novel multi-layer circuit technologies are now achieving excellent performance at 94GHz, allowing the integration of high frequency components and supporting DC circuitry, along with automated assembly which delivers substantially lower manufacturing costs. Liquid Crystal Polymer (LCP) has excellent electrical properties: a dielectric constant of 3.16±0.05 and a dielectric loss tangent of 0.0049 to 100GHz, as well as good repeatability. These properties result in the simulated insertion loss of 0.04dB/mm in stripline waveguides. This paper describes the design and measurement of direct detection receiver modules based on LCP substrates for imaging applications in the W-band. The measured substrate loss at 94GHz is believed to be the lowest reported in the literature, and contributes to achieving receiver sensitivities of <0.8°K NETD required for imaging applications. Use of this approach for high capacity point-to-point communications links is also discussed.