GB597662A - Improvements in and relating to ultra high frequency coupling devices and systems - Google Patents

Abstract

597,662. Wave-guides. BRITISH THOMSON-HOUSTON CO., Ltd. July 12, 1945, No. 17879. Convention date, July 17, 1944. [Classes 40 (iii) and 40 (v)] A combined transmitting and receiving system comprising a transmitter and a receiver connected to a common wave - guide has means for protecting the receiver from the transmitter and for preventing received signals of low intensity from being dissipated in the transmitter. Fig. 1 shows an arrangement for connecting a transmitter 1 and receiver 5 to a wave-guide 3 terminated by a radiating or receiving horn 4. The receiver 5 is coupled to the guide 3 through a guide 9 having transverse metallic walls 6, 7, 8 and 12, 13 each formed with an aperture or slot resonant at the operating frequency. The slots in walls 12, 13 are closed by glass windows thus enabling guide 9 to be filled with gas, and electrodes 15 are provided to maintain a small discharge across the tuned apertures in walls 6 and 7. With this arrangement, received waves of small intensity are unable to break down the resonant apertures, and so pass freely to the receiver 5. Waves of great intensity from transmitter 1 break down the apertures and are unable to pass to the receiver. To prevent loss of received energy in the transmitter 2, a gas-filled quarter wave stub 16 is placed at one quarter wavelength beyond the receiver branch guide 9. Stub 16 has a glass covered resonant slot in an end wall 19 which is not broken down by the received energy and so presents a short circuit at onehalf wavelength from 9, thus matching the incoming energy into receiver 5. Transmitted energy 7 however, breaks down the slot in wall 19 so that stub 16 does not interfere with the passage of the transmitted energy. The effect of stub 16 over a wide band is increased by placing a second stub 24, Fig. 3, at a quarterwavelength distance. In this case the stub includes dissipative elements (Figs. 4-6 not shown), so that the reactive circuits of the transmitter always have a resistance in series which precludes the building up of strong resonances. Fig. 8 shows a form of resonant gap 32 formed, between two apertures 33, 34 in a metal wall 29. The apertures may be rectangular (Fig. 8 not shown). Specifications 582,760 and 587,812 are referred to.