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A compact near-field sensor for material characterization is proposed. It is composed of a substrate integrated waveguide resonator with coplanar waveguide interfaces, thus enabling easy integration and advanced multilayer technology. The material under test (MUT) is sensed by a tiny tip protruding from the resonator. If placed near this tip the MUT sensitively detunes the sensor. The response can be translated into precise, local permittivity information. As simulation shows microscopic applications seem possible thanks to the near-field character and the small effective scanning volume of the sensor. Measurements at X- and K-band frequencies confirm the general functioning of the sensor and demonstrate good principal agreement with simulation.

An active 30 GHz transmit antenna array featuring digital beamforming (DBF) and polarization multiplexing is reported. The array elements rely on open substrate-integrated waveguides, as reported previously. The paper discusses the miniaturization and optimization of these radiators. Furthermore, a concept for the integration of the active components is proposed, realized, and tested on a scaled antenna version. Simulation as well as measurement data is presented and discussed.

An efficient design procedure for directional couplers based on the effective even and odd mode characteristic impedances and electrical lengths is presented. These quantities which are extracted from the scattering parameters of the overall coupler structure allow for a systematic optimization. This is useful, for instance, when designing compensated high directivity couplers or when large bandwidth performance is desired. The method is applied to optimize a 2 GHz wiggly line coupler. Measurements yield a directivity of better than 30 dB from DC to 3.5 GHz, confirming the simulation results.