70-GHz-band MMIC transceiver with integrated antenna diversity system: application of receiver-module-arrayed self-heterodyne technique

Our proposed millimeter-wave self-heterodyne transmission technique is a simple and cost-effective solution to frequency stability problems in millimeter-wave access systems. In addition, this technique enables integration of a high-sensitivity receiver with a combining antenna diversity system that is approximately as effective as a maximal-ratio-combining antenna diversity system for all directions of signal arrival. We explain how our newly developed 70-GHz-band transceiver using the millimeter-wave self-heterodyne transmission technique with a receiver-module array can greatly improve receiver sensitivity for all directions of signal arrival i.e., without affecting the signal reception beam pattern and how this can solve the signal-fading problem in a multipath signal propagation environment. We also theoretically demonstrate that receiver sensitivity improves in proportion to the number of elements in a receiver-module array, and experimentally confirm this using an experimental 70-GHz-band monolithic microwave integrated circuit transceiver with a 4×2 receiver-module array. We show that millimeter-wave signal propagation can be modeled using a two-path model, and that serious signal fading depends on the transceiver height and transmission distance. Carrier and modulated signal transmission experiments using our developed transceiver have revealed that use of a receiver-module array greatly reduces the signal-fading problem in a multipath signal propagation environment. In the signal transmission experiment, we succeeded in transmitting an orthogonal frequency-division multiplexing signal over a 4-m transmission distance with bit-error-free performance.