For radar applications, the W-band frequency range (75 – 110 GHz) is a good candidate for high-resolution distance measurement and remote detection of small or hidden objects in distances of 10 cm to ≫ 20 m. As electromagnetic waves in this frequency range can easily penetrate rough atmosphere like fog, smoke or dust, W-band radars are perfectly suited for automotive, aviation, industrial and security applications. Additional benefit is that atmosphere has an absorption minimum at 94 GHz, so relative small output power is sufficient to achieve long range coverage. By combining and enhancing knowledge from the disciplines of heterogeneous integration technology and compound semiconductor-technology, the Fraunhofer Institutes IAF, IPA and IZM developed a miniaturized and low cost 94 GHz radar module. Result of this approach is a highly miniaturized radar module built using a modular approach. The radar components are mounted on a dedicated RF-NF-hybrid PCB while the signal processing is done on a separate board stacked below. This hybrid RF-module is combined with highly integrated digital processing PCB via micro connectors in a way that the radar system and an adapted conical HDPE-lens fit into an aluminum housing of 42×80×27 mm3 with a weight of only 160 grams for the whole module. The paper will describe the technological basis for such a frequency modulated continuous wave [FMCW] W-band radar module and describe in detail the technological features that enabled the assembly of such a miniaturized but high-performance system. The module yields an evaluated distance measurement accuracy of 5 ppm (5 μm deviation per meter target distance) while its low weight and small dimensions pave the way for a variety of new applications, including mobile operation.
A W band second harmonic gyrotron oscillator