Patent GB-589093-A (GB)
Title: Wave-signal translating system
IPC: G01S13/76
Filed: 1945-02-07
Abstract: 589,093. Wireless signalling. HAZELTINE CORPORATION. Feb. 7, 1945, No. 3166. Convention date, March 7, 1944.' [Class 40 (v)] The output of a device which transmits related reply signals in answer to a received interrogating signal is controlled in accordance with the strength of the received signal. In a superregenerative receiver-transmitter, Fig. 1, the tuned anode circuit 12, 13 of a valve 11 is inductively coupled to an aerial 22. The quench voltage is fed from oscillator 40, through an amplifier 41, a blocking condenser 56 and an R.F. choke 16 to the mid-point of coil 12, one end of which is connected to the grid valve 11 through a grid-leak 14 and byepass condenser 15. The received pulse signal R, appearing across the load resistance 20 of the diode detector 19, is fed into the control unit 60 and a signal derived therein is fed to unit 57. The amplified signal triggers the unit 58, the output pulse T of which is fed through amplifier 54 and step-up transformer 17 to the anode circuit of valve 11, causing it to act as an oscillator for the transmission of a pulse-modulated signal. This signal is detected by diode 19 and a pulse RT applied to the control unit 60 a predetermined time after the reception of pulse R. The amplitude of pulse RT is reduced by the limiter 61, which passes the weaker signal R unaltered to the differentiating circuit 62, which removes the transmitted pulse RT, the wave front of which is considerably less steep than that of the received pulse. The output of unit 62 is fed to a clipper 69 which passes a unidirectional signal, as shown, to amplifier 63, which also removes the remaining traces of the transmitted pulse. The amplified signal is fed, through blocking condenser 65 to the diode rectifier 64 and through amplifier 57 to the transmitter signal-developing system 58. The negative output voltage of diode 64 is applied through a resistance 43 to grid of the quench frequency amplifier 41, controlling its gain in inverse proportion to the strength of the received signal. The quench voltage is applied to the control grid of valve 41 through a coupling condenser 42, and the amplified quench voltage is fed to the anode circuit of valve 11 from a tapping on the coil 44 of the tuned anode circuit 44, 45. Coil 44 is inductively coupled to the tuned anode-cathode circuit 48, 49 of a diode rectifier 50, the output of which, through a filter network 51, 52, 53 and the primary winding of step-up transformer 17, provides the anode voltage for amplifier 54. This voltage, which controls the amplitude of the pulse applied to the anode of valve 11 and the intensity of the transmitted reply signal varies with the gain of the amplifier 41. The sensitivity of the receiver and the magnitude of the reply signal are thus in inverse proportion to the strength of the received signal. In another embodiment. Fig. 2, the strength of the signal transmitted by a separate unit 72 in answer to an interrogating signal is controlled by a unit 73 in accordance with the strength of the signal picked up by superheterodyne receiver 70, which comprises an R.F. amplifier 74, a frequency changer 75, an I.F. amplifier 76 and detector 77. The output of the detector 77 is fed to the control unit 73, which may be similar to the unit 60 of Fig. 1, and also to transmitter 72 to cause a related reply signal to be transmitted from aerial 78. The control voltage derived in unit 73 is applied to the transmitter 72 to control the intensity of the reply signal in inverse proportion to the strength of the interrogating signal. The control voltage is also applied to the R.F. amplifier 74, frequency changer 75 and the I.F. amplifier 76 to control the sensitivity of the receiver in inverse proportion to the strength of the received signal.