Патент USA US2124191код для вставки
'July 19, 1938. _ M, GEIGER ' 2,124,191 DEMODULATION SYSTEM IN SURERHETERODYNE RECEIVER Filed Sept. 25, 1936 ’ 129.1 'Ml/L T/PL/CA 7/0”) FACTOR 0F 15' 0.6140001!) 70? 11119.2 STAGE 02 zwosr. 6 7 E QVMPl/IWDE L/M/TEQ , INVENTOR » MAX_ QEIGER BY m ATTORNEY Patented July 19, 1938 1 UNITED STATES PATENT OFFICE. "2,124,191 DEMODULATION SYSTEM IN SUPERHETER ODYNE RECEIVER , Max Geiger, Berlin, Germany, assignor to Tele funken Gesellschaft fiir vDrahtlose Telegraphic m. b. IL, Berlin, Germany, a corporation of Germany Application September 25, 1936, Serial No. 102,475 In Germany“ October 23, 1935 3 Claims. ' This invention discloses a novel method of and means for demodulation which may be usefull particularly for the production of an intermediate or beat frequency in superheterodyne receiver sets. rI‘he method according to the invention con sists in that the frequency to be demodulated (in coming signal frequency) is mixed in a modula tion circuit scheme with an auxiliary oscillation which is obtained from the intermediate fre? 1'19 quency by frequency multiplication. Figures 1 and 2 of the accompanying drawing show diagrammatically two modi?cations accord ing to the invention. ' _ ‘ Referring to Fig. 1' of’ the drawing, the fre l<5i quency to be “demodulated (signal or incoming frequency) E-is impressed in Fig. 1 on the control (01. 250-20) so that the incoming frequency is conve‘rte'd’into an intermediate frequency 16 times lower; " ‘ Inthe case of a heterodyne receiver the ad, vantage of frequency division is that a distinct‘ oscillator is made dispensable. _ This is particu larly desirable Where ultra-short wave'receivers‘ are dealt with, seeing that the local oscillator normally required works With a very high fre-‘ quency ‘the stabilization of which is attended with particularly great difficulties. .A shift in fre 10 quency is transferred to the intermediate "fre quency, and its effect on the latter in terms?of percentage is far greater and moreserious; in‘ fact, there is a risk of the intermediate frequency, in case of'a su?iciently serious drift of the oscill‘ 15 lator Wave-length, falling entirely ‘outside: the‘ range of transmission of the I. F. ampli?er. How hexode, also known as a pentagrid converter. At the plate 3 is made available the intermediate or beat frequency I. F. (which for the time being ever, by resorting to the method here disclosed this risk is wholly precluded seeing that no sep arate oscillator is provided and that the I. F. bears must be imagined to exist) which is then ampli ?ed in the intermediate-frequency ampli?er 4. quency. ?ed and/or demodulated, as Well known in the 25 art, and, on the other hand, is impressed upon the frequency multiplier 5. The frequency from the output of the latter then serves as the hetero dyning frequency 0, instead of an oscillation a ?xed relationship to the incoming signal fre- ' 30 oscillator, and is fed to the other control grid 6 of the mixer tube. The I. F. ampli?er 4 and the frequency multiplier 5 may be of the convential standard receivers comprising a distinct oscil lator. In accordance with the relation 1 I. F. —- Em above laid down, the intermediate frequency I. F. is changed to 1 types as known in the art, and for that reason are E1.——1 +V shown in block form. ' Insuring in the multiplier stage 5 a multiplica tion 1), then the following relations hold good: I. F.=E-O 0:01. F. 40 whence the division ratio between frequencies E and I. F. . Another merit worth mentioning is that fre quency fluctuations of the signal frequency will make themselves less seriously felt than in which would have to be produced in a distinct For instance, if the multiplication is 11:40, it will 35 be noted that the shift of the I. F. will amount only to i 41 40 of the shift in the incoming signal frequency. What may also be mentioned is’that the ar =1. F._ 1 #5 ‘ grid I of. a mixer tube or demodulator 2, say, a This I. F., on the one hand, is then further ampli 5 ‘ Numerical examples are indicated in brackets in Fig. l. The intermediate frequency is here as sumed to be 2.5 megacycle's (120 m.) and the same is raised ?fteen times. The ensuing heterodyne r frequency of 37.5 megacycles forms with the in "0 coming signal frequency of 40 megacycles (7.5 meters) the intermediate or beat frequency of 2.5 megacycles. The dividing ratio is t 1 rangement here disclosed will operate only if the multiplication is so chosen that the heterodyning frequency is lower than the incoming or signal 45 frequency, lest the arrangement becomes un stable. This condition will be understood most clearly by assuming, for instance, that the I. F. grows a little. In that case also the heterodyning frequency increases and as a result by Way of the 50 mixer tube the I. F. becomes smaller again so that a counter-action to the assumed increase takes place. However, this effect will arise only where the incoming frequency is higher than the hetero dyning frequency, otherwise a higher heterodyn 55 2 2,124,191 ing frequency would in turn result in a higher I. F., etc. The building-up of oscillations in the system from its quiescent state to the oscillatory state C21 occurs, in the presence of the incoming frequency E, just as in the case of a regenerative transmit ter tube as a result of and in response to small accidental changes in the tube current which are always present. A system wherein occurs' 10 the building up of oscillations such as here re megacycles, this frequency is chosen in this case as the I. F. Fig. 2 differs from Fig. 1 by the insertion of an amplitude limiter ‘l. The purpose of ‘the same is to prevent frequency 0 from being modulated in case of reception of a modulated oscillation, for a modulation would occasion distortions in the mixing process. It may ?nally be mentioned that the invention is useful not only for receiving sets, but generally 1O ferred to is shown and described in the U. S. for frequency division work. patent to O’Brien No. 2,039,923. What I claim is: 1. In the reception of signals by the super heterodyne principle, the method of demodula tion which consists in collecting the received sig nal frequency, mixing the received signal fre quency with a second frequency which results in an intermediate frequency, and deriving said If the arrangement is to be capable of receiv ing different frequencies E without a change of the I. F., the arrangement may be rendered use ful by that the multiplication u of multiplier stage 5, when tuning to another station, is so altered that always together with the prevailing signal frequency E the same or a ?xed I. F. is pro 20 duced. If the stage 5 consists of a tube with tuned plate circuit (Whose rotary condenser may be coupled with the condenser of the receiving circuit so as to obtain uni-control) and if the same is operated with a markedly negatively biased grid, then the quantity 1? will always be a wholevnumber. In the light of the last equation above indicated, I. F. will then be always an integral fraction of frequency E. This relation prevents any desired signal frequency E from be ing received. However, it is possible to pick up 1 second frequency by frequency multiplication of a portion of said intermediate frequency. 2,. A demodulation circuit arrangement com prising a vacuum tube provided with a cathode, anode, and a plurality of interposed grills, a signal input circuit connected to one of the grids, an intermediate frequency ampli?er having an output circuit fed from the anode circuit of said tube, and a frequency multiplier coupled to the output circuit of the intermediate frequency ampli?er, and a connection from the output cir cuit of the frequency multiplier to one of the 30 those frequencies which are a multiple of the I. F. This fact is particularly valuable and im interposed grids other than the signal grid. portant in connection with television reception. Television stations are to operate with fre amplitude limiter is interposed between the in termediate frequency ampli?er and the frequency quencies of 40, 42.5, 45, etc., megacycles. Inas multiplier. much as these frequencies are multiples of 2.5 3. A circuit according to claim 2 wherein an MAX GEIGER.