Патент USA US2263902код для вставки
Patented Nov. 25, 1941 " ST? .S FAT 2,263,902 DELAY'DEVECE FOR USE IN'TRANSM‘KSSION 0F OSCILLATION S William- Spencer Percival, Ealing, London, England, assignor to Electric &, Musical Industries Limited, Hayes, Middlesex, Engi‘and‘, a company of GreatBritain. Application February 2, 1939,.Serial.No'..254>,l_71 In Great-Britain February 8, 1-938 5 Claims. ((31; 178-44) mission of high; frequency signals and according This inventionv relates to delay devices and to the‘ invention an. electric time delay device is of general application: in obtaining delay in the transmission of electric oscillations repre senting signal or controlling voltages. High frequency signalling transmitting and receiving systems sometimes include delay net works which are required for example when the comprises a: quartz crystal. for generating super sonic waves in aliquid through which saidwaves are transmitted and then' detected‘ by another quartz crystal, the delay in transmissionv being determined by the. distance. through the. liquid between the crystals. Water or kerosene have been found to be suitable liquids for‘ the. purpose of the invention. The crystalsshould; have the same or substantially. the: same resonant fre quency and provision may‘ be made. to» ensure order that the transmission times of the separate an‘ unimpeded path through the liquid. between channels shall be equal, a delay network is placed the‘ crystals in order to-reduce or avoid. reflec ‘in the channel having the shorter transmission 15 tion of the supersonic waves. time. Again, in the interference.- suppression system The liquid container may be tubular: in shape described in the speci?cation of British Patent or narrow in one dimension and wide in another signals are passed through separate channels, the outputs of which are subsequently com bined and the time of transmission through one channel is different from that in the other. In #468,994, for “Improvements in. and relating. to or wide in both dimensions. The effective length of’ the liquid container will, of‘ course, depend transmission systems,” accepted July- 8, 1937, an 20 upon the amount of‘ delay required. If any of auxiliary channel supplied with interfering sig the dimensions other than those of the length nals provides a controling voltage which serves are notv small compared with the length it‘ is to switch off the main signal channel and in desirable- to take steps to reduce re?ection of order that the controlling voltage shall be ap the waves passing through the-liquid. Such re the reduction of interference in electrical signal plied to the main channel at the desired in? 25 ?ection can be reduced» or- eliminated by cov stant, the delay in the auxiliary‘ channel due ering the walls of'the liquid container with a to the selective and voltage generating circuits, suitable absorbent material such as wool or' cork is compensated in the main channel by the pro or alternatively the inside- of’ the‘ liquid‘ container vision of a delay network capable of passing a may‘ have a number of narrow" slots or holes 30 formed therein- so that the- waves passing into band of signal frequencies. In low frequency volume compression or ex the slots or holes are rapidly absorbed; Again pansion systems, it is necessary to generate a a number of sheets of" absorbent material may controlling voltage proportional to the compres be hung in the liquid so as to leave clear a sion effect introduced and in such systems delay straight line between the quartz crystals. in the auxiliary circuits provided, again has to be 35 In order to obtain a large delay in a com compensated. paratively small volume of liquid the container In the speci?cation of U. S. Patent application may be divided into a number of compartments, Serial No. 223,911, ?led Sept. 8, 1938, for “Sig space being left alternatively at each end of naling system,” by William S. Percival, now U. S. Pat. #2219936, patented Oct. 29, 1949, there 40 the container so as to provide re?ecting surfaces is described a wave ?lter system in which pro vision is made for selecting from a range of signal frequencies a frequency band of given width and subsequently including said selected for the supersonic waves which are thus re?ected into the adjacent compartments. Such a con struction is shown diagrammatically in the ac companying drawing in which I represents a band within said range, the output from a ?lter 45 liquid container, 2 a tortuous space in the con employed to elfect the selection of the smaller band being subtracted from said range. The whole of the frequencies in the range are in cer tain cases delayed before the subtraction is ef tainer in which kerosene or water is placed, quartz crystals 3 and 5 being arranged at 0p posite ends of the space 2. The approximate path of travel of the supersonic waves gener fected by a period equal to the time delay of the ated by the quartz crystal 3 to the crystal 4 is ?lter, shown by the dotted line 5. Assuming a velocity of the supersonic waves of 105 ems/sec. a distance through the liquid of 10 cms. will give a delay of 100 micro seconds. The delay may, of course, be varied by adjusting The delay networks employed may con sist of ?lter sections including inductance and capacity in known combinations. The object of the present invention is to pro vide apparatus for producing delay in the trans- . 2 2,263,902 the position of one or other of the quartz crystals 3 and 4 along the length of the path 2. 2. The method of obtaining a large time delay in the transmission of electric oscillations cover The delay obtained by the use of the device described can be advantageously utilised for most purposes by employing a carrier wave of, for eX transmitting said oscillations through a liquid ample, 10 megacycles per second which carrier wave can be modulated by the signal it is desired to delay. The use of a modulated carrier wave is desirable owing to the relatively rapid change of attenuation with frequency and owing to the resonant character of the quartz crystals. If a wider frequency band is desired than can be obtained by means of the natural damping of the quartz crystals by the liquid then the natural frequency of the two crystals can be “staggered” ing a wide band of frequencies which consists in indirect path between a transmitting and a re ceiving quartz crystal source, the ?uid volume of said path being small as compared with the length of the time delay path which is determ ined by the distance through the liquid between the transmitting source and the receiving source. 3. An electric time delay device comprising a casing member, a liquid within said casing, a pair of quartz crystals located within said casing member, one of said crystals arranged for gen erating supersonic waves in said liquid through to obtain a relatively ?at response over a wide which said waves are transmitted and subse pass-band. The device described enables delays quently detected by the other quartz crystal, a labyrinth having slanting side walls creating a to be obtained of the order of several hundred micro seconds with a pass-band of one mega cycle or more. A particular application of the invention lies in the system described in the speci?cation of co-pending U. S. Patent application Serial No. 228,911, now Patent No. 2,235,018, March 18, 1941, the device taking the place of the delay net- works consisting of ?lter sections including in ductance and capacity as indicated in that speci ?cation. The device can, however, replace any delay network when a long time delay covering a wide pass-band is required. In such cases it will generally be desirable to include either a modu lating and demodulating device respectively be fore and after the delay in order to change the frequency band to within a region of the order of, for example, 10 magacycles. Alternatively, ' an oscillator may be used to heterodyne the signal to be delayed to the required frequency. ' I claim: 1. An electric time delay device comprising a ?rst piezo-electric crystal for generating super- sonic Waves in a liquid, a second piezo-electric crystal for detecting said waves, a structure for increasing the length of time delay path, a liquid within said structure through which said waves are transmitted, said ?rst crystal located at one end of said delay path, said second crystal 10 liquid relatively long indirect path of varying volume and located within said casing, the time delay in transmission being determined by the distance through said liquid path, labyrinth and between the crystals. 4. An electric time delay device comprising a casing member, a liquid within said casing, a labyrinth having slanting side walls creating a liquid relatively long path of varying volume and located within said casing, a pair of quartz crystals located within said casing, said crystals having substantially the same resonant fre quency as the waves which are to be transmitted, one of said crystals arranged for generating the frequency to be transmitted through said liquid path contained Within said labyrinth, the other crystal being arranged to receive said waves, the time delay being determined by the distance through said liquid path within the labyrinth and between the crystals. 5. An electric time delay device comprising a ?rst piezo-electric crystal for generating Waves in a liquid, a second piezo-electric crystal for detecting said Waves, a casing member, a plu rality of partitions within said casing which form a tortuous space to provide a relatively long in direct liquid path, the opposed surfaces of said partitions being shaped to act as re?ectors to ensure unimpeded re?ection of the transmitted waves from said ?rst and second piezo-electric cated at the other end of said delay path, a plu rality of partitions and re?ecting surfaces with crystals. in said structure to form an indirect time delay path, and means within the Walls of said struc 50 ture for absorbing undesired re?ection of said waves passing through said liquid. WILLIAM SPENCER PERCIVAL.