GB1373736A - Short-range transceiver - Google Patents

Abstract

1373736 Radio signalling; aerials; radar THOMSON-CSF 12 Dec 1972 [28 Dec 1971] 57355/72 Headings H4L H4A and H4D A transmitter-receiver comprises a millimetric wave oscillator connected as a superregenerative amplifier relaxed by a relaxation oscillator and forming the final stage of the transmitting channel and the first stage of the receiving channel. As shown in Fig. 2, the transceiver comprises a millimetric wave oscillator connected as a super-regenerative amplifier 4 which is coupled to an antenna 5 and controlled by a relaxation oscillator 3 frequency modulated by the output of microphone 1 via amplifier 2. The amplifier 4 delivers R.F. pulses of variable recurrence frequency. At the remote station the relaxation oscillator operates at a frequency differeing from that of oscillator 3. During reception the oscillator 3 provides a fixed frequency for application to amplifier 4 the output of the amplifier being detected at 6 and supplied to a filter 7. For simpler operation the output of the filter may be amplified and frequency demodulated, Fig. 1 (not shown). For duplex operation, the output of filter 7 is supplied to a mixer 12 together with the output of oscillator 3 and the difference signal is amplified at 8, frequency demodulated at 19 and supplied via amplifier 10 to earphones 11. Doppler radar.-A millimetric wave oscillator connected as a super-regenerative amplifier 54, Fig. 3, is relaxed at a frequency of, for example, 300 MHz by a relaxation oscillator 53. Amplifier 54 is coupled to an antenna 55 and to a receiver comprising detector 56, filter 57 covering from 10 to 100 Hz, amplifier 58, L.F. detector 59 and a display instrument 60. The pulses reflected by a moving target produce at the output of detector 56 the Doppler frequency component which provides a measure of the speed of the target. Circuit and antenna details.-A cavity 70, Fig. 4, having a resonant frequency in the E.H.F. band contains an avalanche diode 61 a passage being provided to a horn antenna 5. One terminal of the diode is connected to an adjustable plunger 62 and a lead passing through a decoupling capactor 64 connects the other terminal to a filter 81, 82 (filter 7) and to a circuit comprising transistor 65 and resonant circuit 66, 67, the base of the transistor receiving negative pulses from the relaxation oscillator 3. The diode 61 oscillates for the duration of these pulses and effects detection by virtue of its negative resistance characteristic. Where the detected frequencies are very low, as in Fig. 3, circuit 66, 67, may be replaced by a resistor and circuit 81, 82, by a choke coil.