GB1559974A

GB1559974A - Electrical transmission system

Info

Publication number: GB1559974A
Application number: GB4022775A
Authority: GB
Original assignee: Marconi Co Ltd
Current assignee: BAE Systems Electronics Ltd
Priority date: 1976-09-16
Filing date: 1976-09-16
Publication date: 1980-01-30

Description

(54) ELECTRICAL TRANSMISSION SYSTEMS (71) We, THE MARCONI COMPANY LIMITED, a British company, Marconi House, New Street, Chelmsford, Essex CM1 1PL, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to electrical transmission systems, and more particularly to such systems in which electrical signals are passed through a routing matrix with little power loss.

According to this invention an electrical transmission system includes a switching matrix consisting of a plurality of intcrconnected switching arrangements bv means of which an electrical signal can be routed through the system, each switching arrangement comprising two symmetrical 3dB couplers as herein defined, the first and second output terminals of one coupler being connected via respective variable phase shifters to the first and second input terminals respectively of the other coupler.

By the term symmetrical 3dB coupler is meant a coupler having first and second input ports and first and second output ports, the power of a high frequency signal fed into either the first or second input port being divided equally between the first and second output ports such that when the first input port is the fed port the signal obtained at the second output port is delayed by 90" relative to the first output port, and when the second input port is the fed port the signal obtained at the first output port is delayed by 90" relative to the second output port.

Ideally there is no phase shift between a signal fed to the first input port and the resulting signal obtained at the first output port, and similarly there is no phase shift between a signal fed to the second input port and the resulting signal obtained at the second output port. In practice though, a small constant phase shift may be present.

Preferably each variable phase shifter is adjustable in discrete steps, and preferably again in steps of 90 phase shift.

The invention is further described, by way of example, with reference to the drawings accompanying the Provisional specification in which: Figure 1 shows a switching arrangement forming part of an electrical transmission system in accordance with the present invention, and Figure 2 shows the electrical transmission system which consists of a number of the switching arrangements interconnected together.

Referring to Figure 1, two symmetrical 3dB couplers 1 and 2 are connected together via a pair of phase shifters 3 and 4. The first and second output ports 5 and 6 of the coupler 1 the connected respectively to the phase shifters 3 and 4 which in turn are connected to the input ports 7 and 8 respectively of the other coupler 2. The coupler 1 is provided with two input ports 9 and 10 which constitute input 1 and input 2 of the switching arrangement, and coupler 2 is provided with two output ports 11 and 12 which constitute output 1 and output 2 of the switching arrangement.

The svmmetrical 3dB couplers are of the kind which the power of a high frequency signal fed into either the first or second input port is divided equally between the first and second output ports such that when the first input port is the fed port the signal obtained at the second output port is delayed by 90" relative to the first output port; and when the second input port is the fed port the signal obtained at the first output port is delayed by 90" relative to the second output port.

Phase shifters 3 and 4 are adjustable in steps via control terminals 13 and 14. By setting the appropriate phase shifts introduced by the shifters 3 and 4, the switching arrangement shown in Figure 1 can be used in a routing mode or in a broadcast mode. In a routing mode, an input high frequency signal applied at either input 1 or input 2 is obtained at output 1 or output 2 in dependence on the phase shifts introduced by the phase shifters 2 and 4. If phase shifter 3 produces a phase shift +1 and phase shifter 4 produces a phase shift +2, an input signal is routed according to the following table.

phase shifts signal applied to 91 02 input 1 input 2

oc oo 90 90 t output 2 output 1 180 1800 180 1800o} output 1 output 2 In a broadcast mode a signal applied to input 1 or input 2 is obtained at both outputs 1 and 2, the input power being split equally between the two outputs. The circuit operates in the broadcast mode when the phase shifters 3 and 4 are set to produce the following phase shifts: Phase shifts bl 2 0 90" 900 or 90" 1800 1800 900 It is evident from both tables that a high degree of inherent redundancy exists in the switching arrangement, and that a particular routing function or broadcast mode can be achieved even if one of the phase shifters sticks at one of its phase shift values.

If either phase shifter fails and sticks in the 0 or 1800 phase position all output states in the preceding tables can be achieved. If either phase shifter sticks in the 90 , all states can still be achieved if the other phase shifter can be controlled to provide a 270 phase state.

High order switch matrices can be built up using a number of the circuits shown in Figure 1. Such a matrix which uses 20 circuits is shown diagrammatically in Figure 2. Matrices of this kind have high redundancy, and hence high reliability. By using 3dB couplers, very little power is absorbed in the matrix itself.

In Figure 2, each circuit 16 contains two 3dB couplers and two adjustable phase shifters, and serves to interconnect the eight inputs to the eight outputs. In a routing mode, an input signal applied to any one of the eight inputs can be routed to anyone of the eight outputs and in a broadcast mode an input signal applied to any one of the inputs appears at all outputs, one eighth of the power at each output.

WHAT WE CLAIM IS:- 1. An electrical transmission system including a switching matrix consisting of a plurality of interconnected switching arrangements by means of which an electrical signal can be routed through the system, each switch- ing arrangement comprising two symmetrical 3dB couplers as herein defined, the first and second output terminals of one coupler being connected via respective variable phase shifters to the first and second input terminals respectively of the other coupler.

2. An electrical transmission system as claimed in claim 1 and wherein each variable phase shifter is adjustable in discrete steps.

3. An electrical transmission system as claimed in claim 2 and wherein each discrete step is 90" phase shifted.

4. An electrical transmission system substantially as illustrated in and described with reference to Figures 1 and 2 of the drawings accompanying the provisional specification.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

shift +2, an input signal is routed according to the following table.

phase shifts signal applied to 91 02 input 1 input 2

oc oo 90 90 t output 2 output 1 180 1800 180 1800o} output 1 output 2 In a broadcast mode a signal applied to input 1 or input 2 is obtained at both outputs 1 and 2, the input power being split equally between the two outputs. The circuit operates in the broadcast mode when the phase shifters 3 and 4 are set to produce the following phase shifts: Phase shifts bl 2 0 90"

900 or 90" 1800

1800 900 It is evident from both tables that a high degree of inherent redundancy exists in the switching arrangement, and that a particular routing function or broadcast mode can be achieved even if one of the phase shifters sticks at one of its phase shift values.

If either phase shifter fails and sticks in the 0 or 1800 phase position all output states in the preceding tables can be achieved. If either phase shifter sticks in the 90 , all states can still be achieved if the other phase shifter can be controlled to provide a 270 phase state.

High order switch matrices can be built up using a number of the circuits shown in Figure 1. Such a matrix which uses 20 circuits is shown diagrammatically in Figure 2. Matrices of this kind have high redundancy, and hence high reliability. By using 3dB couplers, very little power is absorbed in the matrix itself.

In Figure 2, each circuit 16 contains two 3dB couplers and two adjustable phase shifters, and serves to interconnect the eight inputs to the eight outputs. In a routing mode, an input signal applied to any one of the eight inputs can be routed to anyone of the eight outputs and in a broadcast mode an input signal applied to any one of the inputs appears at all outputs, one eighth of the power at each output.

WHAT WE CLAIM IS:- 1. An electrical transmission system including a switching matrix consisting of a plurality of interconnected switching arrangements by means of which an electrical signal can be routed through the system, each switch- ing arrangement comprising two symmetrical 3dB couplers as herein defined, the first and second output terminals of one coupler being connected via respective variable phase shifters to the first and second input terminals respectively of the other coupler.
2. An electrical transmission system as claimed in claim 1 and wherein each variable phase shifter is adjustable in discrete steps.
3. An electrical transmission system as claimed in claim 2 and wherein each discrete step is 90" phase shifted.
4. An electrical transmission system substantially as illustrated in and described with reference to Figures 1 and 2 of the drawings accompanying the provisional specification.