The authors have demonstrated a fully integrated receive frontend addressing the ISM-Band at 24GHz utilizing a standard SiGe HBT MMIC process with a relaxed emitter scaling of 1.2 pm, for the first time. Extremely compact circuit design and layout techniques are applied to a mature Si/SiGe technology, resulting in a low-cost integrated circuit enabling consumer-oriented systems at Ka band. The integrated components are a preamplifier, a mixer with an IF buffer and a local oscillator. The conversion gain is determined to be 16.3 dB for an intermediate frequency of 100 MHz.

This paper describes a compact Doppler sensor consisting of a SiGe MMIC and patch antennas for transmitting and receiving. The MMIC has a differential oscillator operating at 31-32 GHz and a single balanced Gilbert cell mixer. For the differential oscillator lumped elements are used and the Gilbert cell mixer serves two purposes. First it generates the difference frequency of the transmitted and received signal, secondly it lets the rf-signal pass. This results in a total chip size of only 380x770µm 2 .On the microwave laminate substrate TMM3 patch antennas are realized, one for receiving and two for transmitting. The pads for the MMIC are prepared with solder bumps. This way the MMIC can be flip-chip mounted to the substrate of the patch antennas resulting in low losses at the interconnects.