A small 42‐ghz transmitter and receiver for a wireless HDTV (hi‐vision) camera

Abstract

A 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 MHzi 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 downconverter (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 m W and the signal-to-noise (SN) ratio is 48 dB (Y signal). Also, the equipment can be unified with the Hi-Vision two-thuds inch small CCD camera developed in our laboratory and can be operated for close to one hour with one battery.