GB1418851A - Coupling arrangement for multiplexing and demultiplexing purposes - Google Patents

Abstract

1418851 Filters, signal separation; multiplex systems THOMSON-CSF 14 Feb 1974 [16 Feb 1973] 6874/74 Headings H3V and H4L A multiplexer-demultiplexer coupling arrangement, Fig. 3, comprises a first port S which is coupled to three or more further ports A-D, each corresponding to a respective frequency band, and networks 10, 20, 30 each comprising the circuitry shown in Fig. 2. Thus each network comprises two four-port hybrid transformers T 1 , T 2 interconnected by two complementary filters F 1 , F 2 Ports 111, 112 of transformer T 1 are conjugate, as are ports 121, 122 of transformer T 2 . When inputs at ports A-D are being multiplexed to port S, inputs are applied on a coaxial cable 133 and a twin-wire line 144 of each network and an output appears on a respective coaxial cable 143. Cables 133, 143 are respectively connected to ports 113, 123 of T 1 , T 2 and line 144 is connected across port 124, 125 of T 2 , the remaining port 114, 115 of T 1 being terminated by a dissipative resistor 134. The transformer-filter arrangement is similar to that disclosed in Specification 1,370,511 except that F 1 , F 2 are preferably low-pass filters. They may however be bandpass filters and may be symmetrical or non- symmetrical and dissipative or non-dissipative. In addition the windings of the transformers may be consituted by the conductors of a coaxial cable wound on a magnetic circuit. During multiplexing operation a signal applied at A within the pass-band of the filters F 1 , F 2 of network 10 is substantially fully transmitted to output port 12 and a signal applied at B, outside the pass-band of the said filters, is substantially fully reflected to port 12. The signals, both of which lie within the pass-band of the filters in network 30, are then transmitted through this network to port S. In a similar fashion signals from all the "further" ports are multiplexed to port S. The pyramidal arrangement of Fig. 3 may be extended to include further networks. The networks 10-30 may alternatively be connected in cascade (Fig. 4, not shown). The invention permits the addition of further transmission channels to a multiplexer-demultiplexer without the necessity of modifying the existing channels by the addition thereto of band-stop filters.