GB452582A - Improvements in or relating to carrier wave transmitters - Google Patents

Abstract

452,582. Modulating systems. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Electra House, Victoria Embankment, London, and DITCHAM, W. T., Tudor House, Broomfield Road, Chelmsford. Feb. 25, 1935, No. 5993. [Class 40 (v)] In a carrierwave transmitting system employing a power amplifier following the modulating stage, distortion is avoided by rectifying the modulated carrier derived from circuits preceding and following the power amplifier, combining the rectified voltages in opposition, and applying the resultant voltage as grid bias to the modulating valve in such a way as to compensate the distortion. As shown, a carrier amplifier Vl is connected in series with a valve V2 to the grid of which modulating-voltage is applied through a transformer M. The modulated output in the circuit LC1 is fed to a power amplifier V3 having an output circuit LC2. Coils MA, PA coupled to the circuits LC1, LC2 feed rectifiers D1, D2, the rectified current being smoothed and passed through load resistances R1, R2. These are connected in series opposition in the grid biassing circuit of the valve V2. Any distortion introduced by the valve V3 causes compensating-voltages to be applied to the valve V2. The voltage across the combined resistances R1, R2 may be amplified by a direct-current amplifier before application to the grid circuit of the valve V2, Fig. 2 (not shown). A single rectifier may be fed jointly by the coils MA, PA, Fig. 3 (not shown). Specification 262,820, [Class 40 (v)], is referred to.