GB417251A - Improvements in carrier frequency signalling systems - Google Patents

Abstract

417,251. Modulating systems; wireless receiving systems. HALSEY, R. J., Hooksway, Woodmansterne Road, Carshalton, Surrey. Jan. 31, 1933, No. 2968. [Class 40 (v).] A modulating or de-modulating circuit comprises a plurality of impedances including one or more rectifiers arranged to form a balanced bridge, the carrier and /or the signal voltage being applied across one diagonal, and the modulated or demodulated output minus one or both of the applied voltages being taken from the other. As shown in Fig. 4, the signal voltage 1 is applied through a transformer, the divided secondaries of which are respectively in series with pairs of rectifiers 3, 4 and the carrier voltage 2 is applied in the common branch. The rectifiers have their likepoles connected as shown. The output is taken through condensers 5 and transformer 6 connected across one pair of rectifiers 4. In Fig. 5b the input voltages are both applied in the common branch of the two circuits, and a resistance 5 replaces one pair of rectifiers 3, 4, the output being tapped off at an intermediate point of the resistance. In another arrangement the input voltages are both applied in push-pull fashion. Fig. 1 shows the carrier applied through a transformer T3 to a tapped resistance P. The end taps are connected through rectifiers W to the opposite ends of a transformer coil T2, and the centre tap is connected to the centre of the coil T2 through a coupling T1 at which the signal voltage is applied. The output is taken from the secondary of the transformer T2. The circuit may be used in wireless reception, the carrier source being either of the same frequency as the incoming signal or of different frequency. The rectifiers 3, 4 may be of the copper oxide type and are similar, so that the sum of the forward resistance of one and the backward resistance of the other is constant. The Provisional Specification describes simpler circuits in which the two input voltages are applied in series to a single rectifier, with the output impedance arranged in series or in shunt ; or two series connected rectifiers may be employed with the output impedance connected across one of them. In a further arrangement, the signal wave and the carrier are applied to the grid circuit of a valve in series with a condenser-shunted resistance, and the plate circuit includes a transformer with a rectifier connected across its secondary coil.