GB652872A - Improvements in and relating to the generation of pulse-modulated oscillations - Google Patents

Abstract

652,872. High-frequency electric filters. GENERAL ELECTRIC CO., Ltd., and LEVY, M. M. July 25, 1947, No. 20101. [Class 40 (viii)] [Also in Group XL (c)] Following modulation of a carrier, side-band components are selected extending from the carrier over a desired band, components outside this band being excluded. The selecting means may also exclude or substantially exclude parts of the desired band on either side of and adjacent the carrier frequency. The selecting means may be a band-pass filter which should have a constant input resistance over the frequency band employed to prevent reflection of the unwanted energy back into the carrier generator. The filter may be composed of one band-pass filter feeding the aerial and one bandstop filter terminated in a dummy load. The impedance of the two filters in parallel is constant if the terminating half-sections are m-derived and are so designed that m=0.6, and for the same load resistance and if the usual shunting impedances at the inputs of both filters are omitted. In an arrangement for transmitting a pulse-modulated carrier, a magnetron radio-frequency pulse generator 15 is connected to a hybrid wave-guide junction 16. Energy enters at Y and appears in phase at V and X, no energy passing directly from Y to Z. The energy at V passes to a band-stop filter 17 terminated in a dummy load 18 while the energy at X passes to a second band-stop filter 19 terminated in a dummy load 20. The connection from V to 17 is longer by #/4 than the connection from X to 19 so that energy in the desired band reaches V after reflection at 17 with a phase displacement of its voltage of #/2 relative to that reaching X after reflection from 19. These energies combine with their voltages in phase and pass to the aerial 21.