AbstractA transmission system suitable for a small Hi‐Vision wireless camera is proposed and a small transmitter and receiver for the 42‐GHz band is developed. In the present system, no signal processing is performed on the camera output which is directly frequency modulated. Orthogonal circular polarizations are co‐used for transmission.By means of this system, miniaturization and weight reduction of the equipment (with a transmitter of 5 kg) are attained. At the same time, the transmission bandwidth is reduced to 80 MHz. Also, as the key 42‐GHz devices for realization of the present equipment, a direct FM modulator (modulation sensitivity of 20 MHz/ V), an HEMT power amplifier, an orthogonal circular polarization feed system (with a cross‐polarization discrimination ratio of more than 23 dB), a low‐noise down‐converter (with a noise figure of less than 5 dB) and a simple IF cross‐polarization interference equalizer are developed.The antenna for the transmitter automatically adjusts its direction by means of the signal returned from the receiver at 10 GHz. The present equipment has a transmission distance of about 250 m with a transmitter output of 25 mW and the signal‐to‐noise (SN) ratio is 48 dB (Y signal). Also, the equipment can be unified with the Hi‐Vision two‐thirds inch small CCD camera developed in our laboratory and can be operated for close to one hour with one battery.