Strip Line-Type Microwave Modulator Using Photoconductivity.

When the strip line containing a semiconductor material is illuminated by light with an energy larger than the band gap, the resistivity of the semiconductor changes and the control of the microwave propagation in the line cab be realized. For high-speed control it is necessary to use the semiconductor with short lifetime and to increase the intensity of illuminating light. In this paper, a fundamental study has been performed for the microwave modulator using photoconductivity. Strip lines suitable for this modulator are a coplanar waveguide and a slot line. This paper investigates the coplanar waveguide. An optimum structure is found the provides the strongest microwave attenuation for a given light intensity. The dependence on the frequency of the attenuation constant is also found. The analysis is based on the frequency of the attenuation constant is also found. The analysis is based on the spectral domain method. To confirm the usefulness of the modulator proposed here, the modulator has been made of Si and tested at 10 GHz is possible even with a light source such as a light emitting diode. [ABSTRACT FROM AUTHOR]