GB1326564A - Micro-wave transmitter-reiceiver device - Google Patents

Abstract

1326564 Radio transmitter receivers; semiconductor oscillators and mixers SHORROCK DEVELOPMENTS Ltd 28 April 1971 [13 May 1970] 23141/70 Headings H3Q H3T and H4L [Also in Divisions G4 and H1] In a microwave transmitter-receiver device comprising a conductive plate on a dielectric substrate and a printed circuit on the surface of the substrate remote from the conductive plate, the circuit includes a transmitter half-wave resonator 2, a transmitting aerial 12, a transmitter transmission line 11 coupling the resonator and the aerial, a receiving resonator 14, a receiving aerial 16 and a receiving transmission line 11, coupling the receiving aerial to the receiving resonator and the transmission lines 11 are so formed and located as to act as a directional coupler. A microwave oscillator device 1 such as a Gunn Impatt or LSA diode is mounted on the half wave resonator 2. Bias is fed to the device 1 by a low pass filter 6 formed by a line 5 and a #/4 line 4. A f.m. modulation signal or tuning bias is applied at 9, 10 to a varactor diode 8 so as to vary the oscillator frequency. The output from the oscillator 1 is fed via a 1 : 1 impedance transformer 7, a 20 dB backward directional coupler 11 and a double #/4 line 22 having a #/2 delay to a transmitting aerial dipole 12. An opaque window 23 is formed in the substrate and a reflective plate (not shown) is provided so as to enclose the dipole on all sides but one so as to make the aerial directional and provide transmission through the window 23. The receiving dipole 16 has a similar reflective plate and a window 25. The received signal is fed from the dipole 16 via a double #/4 line 24 having a delay, a #/2 impedance transformer 17 and the directional coupler 11 to a Schottky barrier mixer diode 13 of the receiver. The diode 13 is mounted on a tuned resonator 14 and is fed with bias via a low pass filter 20 formed by line 19 and a #/4 line 18. A low frequency output is obtained at 21. A screening cover may be placed over the microwave transmission line circuit and a protective varnish coating may be applied over the circuit. The arrangement may be used as part of a speed or obstacle detecting device such as a Doppler radar intruder detector in which case it may be mounted on a universal joint in a box with a cover which is opaque to light but which is transparent to radio waves. Also the device may be used to determine the distance of stationary targets by frequency modulating the carrier by the varactor diode.