Patent GB-934750-A (GB)
Title: Electric signal channel switching arrangements
Inventor: CLARE JOHN DICKENS
IPC: H04B1/74
Filed: 1954-07-07
Abstract: 934,750. Waveguide switches. MINISTER OF AVIATION. June 16, 1955 [July 7, 1954], No. 19868/54. Class 40 (8). A double pole change-over switching arrangement for electric signal channels comprises a first hybrid and a second hybrid, the output branches of the first hybrid being connected one to each input branch of the second hybrid so that input signals at each of the two input branches of the first hybrid correspond one to each signal at the output branches of the second hybrid, and phase change means for introducing a change of 180 degrees or an odd multiple thereof in the relative phase of signals transmitted from the output branches of the first hybrid to the input branches of the second hybrid whereby its correspondence between the input signals to the first hybrid and the output signals from the second hybrid is interchanged when the phase change means, is operated. Referring to Fig. 1, if signals A and B are supplied to terminals 2 and 4 of the first hybrid, the outputs at 3 and 5 will be A+B/#2 and A-B/#2; if these are transmitted in phase to the second hybrid the outputs at terminals 11 and 12 will be A and B respectively. If a 180 degrees phase change is introduced in one of the paths between the two hybrids, the outputs at terminals 11 and 12 will be B and A respectively. Fig. 2 shows a cross-section of a waveguide hybrid, a five-slot binominal type: that is to say the widths of the slots, which are spaced apart by a quarter wavelength, are so chosen as to give each slot a coupling coefficient of the corresponding term in a binominal expansion. Thus in the present case the coupling coefficients are in the ratio 1: 4: 6: 4:1. Fig. 3 shows a schematic diagram of a twin double-pole changeover switch. Signals A, B are fed to a hybrid 15 and signals C, D to a hybrid 20, the signals being such that A+B is approximately equal to C+D. The difference outputs of hybrids 15, 20 are fed direct to hybrids 30, 31. The sum outputs are added in a hybrid 23, passed through a phase changer 26, and split into two parts by hybrid 27. The two outputs of hybrid 27 may be regarded as A+B/#2 and C+D/#2 since A+B is nearly equal to C+D. Thus the outputs of hybrids 30 and 31 are A, B and C, D, and operation of the single phase-shifter 26 interchanges the A and B outputs of the hybrid 30, and simultaneously interchanges the C and D outputs of the hybrid 31. Fig. 4 shows a thermionic valve circuit corresponding to units 26, 27, 30 and 31 of Fig. 3. Unit 32 corresponds to units 26 and 27 and comprises a centre-tapped transformer 35 to which the input is fed; the output from one half of the transformer is fed to the valve 37, which half depending on the polarity of the centre-tap which is controlled by a square-wave generator 41. The output of valve 37 is fed to the centre tap of a transformer 53 in each of the units 30, 31, and the other inputs to these units are fed to the primaries of transformers 53. Thus one input to each of units 30, 31 is fed in push-pull to valves 51, 52 whereas the output from unit 32 is fed in push-push to valves 51, 52, so that the outputs of these valves are the sum and the difference of the two inputs.