GB1112857A - Arrangement to receive individual channels out of a multichannel carrier frequency band - Google Patents

Abstract

1,112,857. Carrier transmission systems. INTERNATIONAL STANDARD ELECTRIC CORPORATION. 12 Aug., 1966 [19 Aug., 1965], No. 36149/66. Heading H4R. An apparatus for extracting a desired individual channel from a multiple-channel carrier-frequency system comprises a stage wherein the channel is converted to an intermediate frequency by a carrier selectable from a number of carriers mutually spaced in frequency by an amount corresponding to the spacing of the centre frequencies of a plurality of overlapping partial frequency bands in use within the system, a number of filters from which one may be connected to select the channel in the intermediate frequency position, the filters having unlike frequency characteristics and being connected for use according to the type of signal transmission, e.g. single sideband, double side-band, in the desired channel, and a demodulator for reproducing the information component. Carrier frequencies T1, Fig. 2, of 336, 384, 432, 480 and 528 kc/s. are provided to selectably transpose sub-bands 2-58 kc/s., 50-106 kc/s., 98-154 kc/s., 146-202 kc/s. and 194-250 kc/s. to 278-334 kc/s. in a modulator M1 and this band is brought to 62-118 kc/s. by carriers of 216 or 396 kc/s. in a modulator M2 according to whether the signals are erect or inverted. Sub-bands within this latter band are selectably transposed to a band of 26-46 kc/s. by frequencies of 108, 120, 132 and 144 kc/s. and the information channel is separated by a frequency T4 in a modulator M4 and a filter BP4-BP7 appropriate to the type of transmission in the wanted channel. Frequencies T4 are provided in ¢ kc/s. steps from 41 kc/s. to 58 kc/s. A carrier frequency generating arrangement in which all the frequencies are derived from an 8 kc/s. generator by multiplication and division is described with reference to Fig. 3 (not shown) and a modulating arrangement with a second variable frequency generator for producing the frequencies T4 is described with reference to Fig. 4 (not shown).