Patent GB-596924-A (GB)
Title: Improvements in wave guide apparatus for ultra high frequency electromagnetic waves
IPC: H03D9/06
Filed: 1945-06-13
Abstract: 596,924. Wave-guides; modulating- apparatus. WESTERN ELECTRIC CO., Inc. June 13, 1945, No. 15051. Convention date, June 16, 1944. [Classes 40 (iii) and 40 (v)] Wave-guide apparatus comprises a pair of polarization selective elements arranged at separated points along a conductively bounded path for the waves and each adapted to reflect selectively a wave of two differently polarized waves, and means coupled to the waves of both polarizations and located intermediate the selective elements for converting the waves from one polarization to the other. Fig. 1 shows a modulating system comprising a rectangular wave-guide 1 in which is arranged a rectifier bridge a, b, c, d having conductors 3, 7 extending in a vertical direction to coaxial tuners 4, 8 and conductors 5, 9 extending horizontally to coaxial tuners 6, 10. A carrier frequency source 13 supplies vertically polarized waves which excite conductors 3, 7 to apply a potential across points a, c of the bridge, while a modulating voltage is applied by means of conductors 5, 9 across points b, d. Modulated signal currents appear in conductors 5, 9 and launch horizontally polarized waves in the guide 1. Gratings 11, 12 are arranged respectively to pass vertically polarized carrier waves and horizontally polarized modulated waves. Grating 12 also serves to reflect any carrier waves back to the bridge, and grating 11 reflects any modulated signal waves in the direction of transmission. The apparatus could also be used for demodulating a signal wave applied from the right, the modulation signal being recovered from conductors 5, 9. The polarity selective gratings may be replaced by rectangular guides 25, 36, Fig. 7, arranged at right angles. In this case vertically polarized carrier waves from guide 25 are reflected back from guide 36 which, however, passes the horizontally polarized modulated waves lauched from conductors 5, 9. Similarly, guide 25 reflects any modulated wave energy. The dimensions of the intermediate chamber 35 allow both waves to exist. Guides 25, 26 are connected to movable pistons 37 which are adjustable for matching and also allow guides 25, 36 to be relatively turned to suppress any carrier wave energy which may appear in guide 36. Alternatively, the guides 25, 36 may be fixedly connected to opposite ends of a rectangular guide section (Fig. 6, not shown). In a further alternative (Fig. 8, not shown), the polarity selective means comprise conducting septa one half-wavelength long arranged horizontally and vertically across a circular guide on either side of the rectifier bridge. Fig. 4 shows an arrangement comprising rectangular guides 25, 26 joined together with their longer dimensions at right angles. A rectifier bridge a, b, c, d is mounted in guide 25 on flat conductors 28 leading through a small aperture 27 to horizontal conductors 5, 9, connected to coaxial tuners 6, 10 in guide 26. Vertically polarized waves fed into guide 25 excite the rectifier bridge by way of conductors 3, 7, and modulating signal voltages are applied to points b, d by way of conductors 5, 9 and 28. The modulation products are led by conductors 28 to conductors 5, 9 which excite a horizontally polarized wave in guide 26. The carrier wave in guide 25 and the modulated wave in guide 26 are each reflected back by aperture 27. In a modification of this arrangement, Fig. 5 (not shown), the guide 25 projects into the guide 26 and is terminated by an adjustable piston. Fig. 9 shows a modification of the Fig. 1 arrangement in which the elements of the rectifier bridge are arranged outside the main guide 1. The rectifiers are mounted in telescopic coaxial tuners 42 ... 45 which are insulated from guide 1, and are interconnected by vertical conductors-40, 41, the mid-points b, d of which are connected by horizontal conductors 5, 9 to insulated coaxial tuners. Tuners 43, 45 and 42, 44 are connected in pairs to provide the bridge corners a, c. Alternatively, the two lower rectifiers and coaxial tuners may be dispensed with (Figs. 10, 11, not shown). In Fig. 12, two rectifiers in telescopic coaxial tuners 42, 44 are connected by vertical wires 40, 41 to similar tuners 43, 45 and to a balanced transformer 50 for the introduction of a modulating voltage. A biassing voltage is supplied by source 21. The conductors 40, 41 are excited by vertically polarized carrier waves, and an alternating signal potential appears between all pairs of opposite points such as b, d to generate horizontally polarized waves corresponding to the modulated carrier wave. The above described methods of modulation produce side bands without carrier, and either side band may be selected by choosing the dimensions of the outgoing guide. Specification 552,394 is referred to. The Specification as open to public inspection under Sect. 91 also describes a signal compressor or expander shown in Fig. 13 (Cancelled). A modulated carrier wave enters a wave-guide 1 from the left and after passing a detector 60 and amplifier 63 is rectified in a crystal detector 65. The audio signal is taken off through a series condenser and impedance matching transformer feeding a coaxial line 70. The D.C. component is taken through a choke 69 and D.C. amplifier 71 and applied as bias to detector 60. This varies the impedance of detector 60 and hence the ratio of power absorbed by detector 60 to that passed to the signal detector 65, and may be used to obtain either compression or expansion of the signal. This subject-matter does not appear in the Specification as accepted.