Patent GB-1442623-A (GB)
Title: Microwave switching matrix
IPC: H03K17/00
Filed: 1973-08-07
Abstract: 1442623 Microwave switching; component assemblies INTERNATIONAL STANDARD ELECTRIC CORP 7 Aug 1973 [7 Aug 1972] 37338/73 Headings H1R and H1W A microwave switching matrix comprises two arrays of matched lines with electronically switchable crosspoints. As shown in Fig. 3, input lines Il, I2...IN, all terminated in matched resistances, are coupled at intersections C11, C12 ... CNN to output lines O1, O2 ... ON, (similarly terminated by matched resistances) by switching circuits, e.g. C21, comprising PIN diodes. Switching potential is selectively applied to the diodes through LC low-pass circuits and signals applied through LC highpass circuits. The inductive part of these circuits may consist of quarter-wave lines or of printed inductances. The switching signals are generated by a digital programmer comprising flip-flops 12.11, 12.12... 12.1N controlled by circuit 11. The inputs and outputs are associated with circulator-isolators which prevent generation of standing waves. A 2 Î 2 matrix may be realized by means of four approximately U-shaped printed strip lines (Fig. 5) having inputs I1, I2, out puts O1, 02, switching diodes 15, isolating capacitors 14. The manner in which switching potentials are applied to the diodes from switching inputs D11, D12, D21, D22 is apparent from the drawing. A modified type of stripline matrix, which may have an order greater than 2, is shown in Fig. 5. This modification requires cross-overs which are effected by means of wire bridges. In further modifications (Figs. 6, 7, 8) not shown, the switches are situated at the cross-over points and the diodes are connected to the bridges which may consist either of wires or of short lengths of strip line. The switching diodes and the bridging lines may be mounted upon small auxiliary substrates situated at the cross-over points. An N Î M matrix may be realized by feeding each of the N inputs to a respective power divider having M outputs and deriving each of the M outputs from a respective power combiner having N inputs. The N x M intersections are, in this case, realized as two-ports since the lines are not continued beyond the intersections. Impedance matching is effected by the power-dividers which consist of known types of directional coupler networks. In the embodiment of Fig. 13, the N input power dividers are printed as stripline circuits on an array of N substrates arranged in parallel horizontal planes, and the M output power dividers are printed on M substrates arranged in parallel vertical planes. Two-port connections, e.g. 55, are effected at the intersections of the planes and each is associated with a switching diode, e.g. 50. Control circuits for the diodes, including amplifiers, e.g. 54 may be printed on substrates attached to the undersides of the power-combiner substrates. A modification of this matrix using co-axial lines is briefly described (Fig. 12, not shown). The switching diode may be arranged in series with the lines or may be arranged to shunt them to earth. Combinations of two or more diodes may be used. Where necessary, line lengths may be equalized by appropriate loading or by addition of extra sections at inputs and outputs.