A very compact 26-GHz transmitter/receiver for high-speed digital radio subscriber systems has been developed. The transmitter/receiver makes extensive use of MIC technology in the RF sections. Transmitting power of 18 dBm and a receiving noise figure of less than 12 dB is obtained. The freqnency of the local oscillator is stabilized to within +-100 ppm by means of a high-Q dielectric resonator. The bit error rate is measured in order to evaluate the overall system, and good performance of the equipment is obtained. A field test rising this equipment is now under way. The technique described in the text can be extended to transmitter/receiver for terrestrial radio relay systems and satellite communication systems. In addition, the various MIC components developed here can be scaled to the millimeter-wave region.