Millimeter wave systems based on SIMMWICs

The use of active integrated antennas (AIAs) as a promising measure of the reduction of millimeter wave systems´ costs has been proposed by several authors. Minimization of costs demands integration of the complete millimeter wave front-end on one single chip of minimum dimensions. The demand of minimum dimensions is best met by the active antenna concept, where the generation and/or detection coincides with the transmission and/or reception of a millimeter wave signal. Up to now, millimeter wave systems based on Silicon Monolithic Millimeter Wave Integrated Circuits (SIMMWICs) for the interesting frequency bands above 60 GHz have to employ AIAs due to the behavior of the active elements. In these SIMMWICs an IMPATT diode or a Schottky diode is integrated in the antenna structure. Many sophisticated active antenna designs (based on SIMMWICs and GaAs devices) have been published in recent years. But only a few fully functional demonstration systems were actually built. This is due to some serious design restrictions of AIAs: short-term and long-term stability is supposed to be not sufficient for many system applications; interfacing additional millimeter wave components like mixers is very difficult; and direct modulation is restricted to relatively slow on-off-keying. This paper investigates these problems and develops solutions compatible with the AIA concept. Based on these enhanced front-ends several systems were built. As active devices for signal generation, silicon IMPATT diodes have been employed. For detectors and mixers, silicon Schottky diodes were used.