A SMALL 42-GHZ TRANSMITTER AND RECEIVER FOR A WIRELESS HDTV (HI-VISION) CAMERA

A transmission system suitable for a small Hi-Vision wireless camera i s proposed and a small transmitter and receiver for the 42-GHz band is developed. In the present system, no signal processing is performed o n 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 re alization of the present equipment, a direct FM modulator (modulation sensitivity of 20 MHz/V), an HEMT power amplifier, an orthogonal circu lar polarization feed system (with a cross-polarization discrimination ratio of more than 23 dB), a low-noise down-converter (with a noise f igure of less than 5 dB) and a simple IF cross-polarization interferen ce equalizer are developed. The antenna for the transmitter automatica lly adjusts its direction by means of the signal returned from the rec eiver at 10 GHz. The present equipment bias a transmission distance of about 250 m with a transmitter output of 25 mW and the signal-to-nois e (SN) ratio is 48 dB (Y signal). Also, the equipment can be unified w ith the Hi-Vision two-thirds inch small CCD camera developed in our la boratory and can be operated for close to one hour with one battery.