Patent GB-589153-A (GB)
Title: Angular-velocity-modulated wave-signal receiver
IPC: H03D11/06
Filed: 1945-01-02
Abstract: 589,153. Frequency and phase modulation. HAZELTINE CORPORATION. Jan. 2, 1945, No. 180. Convention date, Feb. 1, 1944. [Class 40 (v)] A demodulator for angular velocity-modulated waves comprises two circuits off-tuned in opposite senses from the carrier mean frequency, and coupled to separate super-regenerative receivers, the outputs of which are combined to develop the modulation components of the carrier. As s own in Fig. 1, the incoming wave is fed from aerial 18 through radiofrequency amplifiers 19 to a pair of tuned circuits 10, 11, 10<1>, 11<1>, one of which is tuned above and the other below the mean frequency of the applied wave. Each tuned circuit is coupled to a valve 12, 12<1> to form a Hartley oscillator and quenching for super-regeneration is effected by supplying the valve anodes from an A.C. source 20 through a transformer 21 and switch 22 which permits quenching of the two tuned circuits simultaneously or alternately. Oppositely poled diodes 24, 24<1> are connected across the respective tuned circuits and the demodulated signal, developed across the differentially connected load resistors 25, 25<1>, is applied through resistors 28, 28<1> to the loudspeaker 27, if necessary through an audioamplifier. In a modification, Fig. 3, a single tuned circuit 30 is coupled to a pair of regenerators 31, 31<1> and its resonant frequency switched from one off-tune frequency f<1> to the other/2, by a reactance tube modulator 32 energized from a pulse-wave source 33. Source 33 also functions to quench alternately the regenerators 31, 31<1>, each regenerator being energized at one particular frequency f<1> or f<2> of the tuned circuit. The detectors 34, 34<1> associated respectively with the regenerators 31, 31<1> are rendered operative only during the required periods by control pulses also derived from the source 33 and delayed in networks 35, 35<1>. The detector outputs are, as for Fig. 1, applied differentially to the loud-speaker 27. Fig. 5 (not shown) shows the arrangement of Fig. 3 in more detail. In another arrangement, Fig. 6, a single tuned circuit 10, 11 is back coupled to two oscillator valves 31<11>, 31<111> arranged to be quenched alternately by a source 20 acting through a transformer 45. A resistor 47<1> in the anode circuit of valve 31<111> produces feed-back through the grid anode tube capacitance, thus shifting the frequency of the tuned circuit to the other off-tune frequency while this valve is functioning. Quench source 20 also supplies a biassing voltage through a coil 49, inductively coupled to the transformer 45, to the opposed detectors 24<1>, 24<11> so that these become conducting only during the appropriate halves of the quench cycle. The appropriate delay or phase displacement between the switching of the detectors and the quenching of the regenerators 31<11>, 31<111> is effected by adjustment of the condensers 46, 46<11> and the inductance of the tapped secondary 45. The arrangement thus functions similarly to that shown in Fig. 3. In all cases an A.V.C. voltage derived in known manner may be applied to bias the regenerators. Specification 571,580 is referred to.