Патент USA US2404712код для вставки
July 23, 1946. 2,404,712 R. L. HOLLINGSWORTH ' I 'GAIN CONTROL ‘CIRCUIT FOR RADIO TELEGRAPH Filed Dec. 30, 1943 Aq 26 a ‘ 22 /6 - Oar/J07 /7 INVENTOR BY Mé/ZMW ATTORN E3’ ' Patented July 23,1946 2,404,712 UNITED STATES PATENT OFFICE ' 2,404,712 GAIN CONTROL CIRCUIT FOR RADIOTELEGRAPH R. Lee Hollingsworth, Riverhead, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application December 30, 1943, Serial No. 516,148 7 Claims. ' (01. 250-20) 2 This invention relates to automatic gain con trol systems and is particularly adapted for use with a radio receiver which is intended to receive interrupted carrier wave telegraph signals. winding III, the space path through triode tube l6 and resistance [1. A bias battery furnishes a potential gradient in a potentiometer 26, and adjustable taps 20 and 2| on this potentiometer may be set to maintain suitable threshold biases on the grids of tubes l6 and 22‘ respectively. The It is an object of my invention to ‘provide an automatic gain control system whereby the gain 'of the receiver is adjusted to an optimum value tap 2i. biases the grid in tube 22 more. negatively during each signal impulse, that gain value be than the bias which is applied to the grid of tube ing retained during a space interval until the next succeeding impulse. , It is another object of my invention to pro vide an automatic gain control system which I 6 through tap 20. Resistor 23 and capacitor‘ l0 24 constitute the time constant device for this AVC system. ‘ . Output potentials derived from the recti?er tube 1 I may be taken either from the cathode of produces almost instantaneous adjustment of the gain to a new level in response to a change tube l6 or from a suitable point on the poten in the incoming signal level. It is another object of my invention to con 15 tiometer I‘! in the anode circuit of tube [6. ‘The trol the gain in an interrupted carrier wave re ceiver in such a manner that the tube noise cur the setting of a double pole switch I8. ‘By means of the circuit arrangement shown and described it is, therefore, possible to control any desired 20 translating device such as a_ keyer tube, a bal rents in the receiving circuitswill be substan tially eliminated. ' It is another object of my invention to provide a system comprising a plurality of discharge polarity ofthe output potential depends, upon anced modulator, or a recorder. ‘ ' _ In operation the signal wave energy is ampli tubes operative to so influence an automatic gain control circuit that incoming static impulses are ?ed by vacuum tube ‘5_ and heterodyned with the local oscillations to produce an intermedate‘fre quency, which is further ampli?ed by interme diate frequency ampli?er tube 8, output from which is recti?ed by the recti?er tube H; The prevented from paralyzing the receiver circuit. The invention will now be fully described, ref erence being made to the accompanying drawing, the sole ?gure of which shows a circuit diagram triode tube l6 has applied thereto a low bias . of a preferred embodiment. potential sufficient to render this tube non-con Referring to the drawing, I show an antenna 30 ductive to very. low strength signals and, tube l for collecting electromagnetic wave energy. noise currents. When signal energy passes This antenna is connected through coupling coil through tube l6 and resistance. I l the full 2 and thence to ground. Electromagnetic wave ~voltage across tube 16 and resistance I] is ap-_ energy ?owing through coupling coil 2 induces plied to the AVG circuit. The application of signal currents in the tuned circuit comprising 35 this AVC voltage reduces the gain of the receiver the transformer secondary 3 and the adjustable during a single impulse and the gain remains at capacitor 4 in shunt therewith. Applied to the that particular gain value since the control , grids suppressor grid g3 of converter tube 5 is the of vacuum tubes 5 and 8 are isolated until recti energy from a local oscillator 25. The ‘local ?er tube [6 is again conductive. If the next oscillations beat with the incoming signal to pro 40 succeeding signal impulse be stronger than the duce an intermediate frequency of a desired value. This intermediate frequency energy is preceding impulse, the gain of the receiver will be lowered still further, whereasfif the follow transferred to the control grid of an amplifying ing signal impulse be less in value than the pre tube 8 by way of an intermediate frequency ceding impulse, ‘the gain of the receiver will be transformer which is included in tuned circuits 45 increased and will retain this gain value as here 5 and ‘I. The intermediate frequency energy be tofore mentioned until another impulse causes ing ampli?ed by ampli?er tube 8 is coupled by tube IE to again be conductive to reset the gain tuned transformer windings 9 and Ill to a diode level of the receiver at a new level depending recti?er tube ll. Parts 12 and I3 represent a upon the strength of the incoming signal. bias resistance and a radio frequency bypass 50 The action of the tube 22 in this AVC circuit condenser respectively, as do parts l4 and I5. is as follows: If very strong signal currents, or A triode tube 16 is connected in series with heavy atmospheric impulses are received, tube 22' the output of a recti?er tube II and a resistor becomes conductive since a slightly more negative IT. ‘The output terminating resistance of recti bias is applied thereto, than is applied to the grid ?er tube ll includes the transformer secondary 55 of recti?er tube l6, creating ‘a bypass’ circuit 2,404,712 4. to the input circuits of said stages, a load resistor which prevents the grids of ampli?er tubes 5 and 8 from [becoming blocked. Another e?ect present and electronic switching means in series with said ' rectifying means whereby said gain control circuit is rendered effective to adjust the gain in said is that the AVG‘ circuit is momentarily drained of electrons when tube 22 suddenly becomes con receiver to a desired value in the presence of marking signals and to hold thatgain adjustment ’ during carrier wave interruptions of normal spac ductive, causing the gain of the receiver to slight ly increaseas a result of a strong static impulse, whereas, in normal AVC practice the gain of the receiver would be greatly reduced and the time constant circuit would'be overloaded with voltage ing signal duration, an electronic limiter device connected in shunt with said load resistor and switching means, said limiter device being opera possibly producing dropouts of one or more sub able in the presence of peak impulses due to static sequent signal impulses. and other excessive wave energy, and threshold The time constant circuit 23, 24 is preferably biasing means for so controlling the conductivity small in value in order to provide substantially of said switching means and of said limiter device instantaneous gain compensation. This arrange ment has proven very practical when receiving 15 respectively, that said gain control circuit is ren telegraph signals under conditions such that the , dered relatively insensitive to noise energy of low amplitude and also to static crashes of, relatively strength of the incoming signals varies over a high amplitude. very wide amplitude range. Since the 'rate of 3. Apparatus for automatically controlling the gain compensation canibe extremely fast it nat yurally follows that the recti?ed signal energy 20 gain in the ampli?er stages of an interrupted car rier wave receiver comprising a gain control ,cir ' available at switch laremains relatively constant though theinput signal may befadingover a very cuit having time constant elements ins‘nunt with with adiversity receiving system which is at pres ?er stages to said gain control circuit, means operative in response to the reception of model"? a unilateral impedance of the tri'ode discharge wide range. tube type, means including a recti?er for sup ,It will belappreciated that thismethod of auto .matic gain ‘control may ‘be used in conjunction 25 plying recti?ed output energy‘ from said, ampliw ent in wide ‘usage for short wave, long-distance ate strength static crashes and ‘other interfer ence waves of moderate amplitude for causing .Furthenthis method of automatic volume lcon~ trol may be utilized in a conventional all-wave 30 said recti?ed output energy to automatically con trol the gain of the receiver, and means opera vbroadcast receiver and will be found particularly tive to increase the gain of the receiver when useful in establishing a maximum volume at receiving strong static'or other interfering po which positive llimiting results, there-by prevent tentials, this means comprising an auxiliary dis ing heavy atmospheric noises from exceeding the maximum level of modulated waves as received. 35 charge tube rendered conductive by said strong ,radio telegraph-telephone reception. interfering ‘potentials, thereby to shunt ‘to ground This is-accomplishedbyadjusting recti?er tube 22 a portion .of said recti?ed output energy ,along with ya portion of the charge previously, stored ‘to be ,conductiveat approximately 6 to .10 deci :bels below the . maximum modulation level. in said time constant circuit. , ~ , Various modi?cations and applications will be suggested by this disclosure .to those skilled in 40 4. An automatic gain control circuit for use in airadio telegraph receiver, said circuit having the art. The scope oftheinventio-n is to be under .a recti?er coupled to .a certainstage of the re stood, therefore, as comprehending embodiments ceiver, a load in series with the vrecti?er, said other than that which is herein ‘iliustratively load including two discharge tubes which are shownandidescribed. . ‘ mutually vin parallel, a negative biasing means 101mm: 7 so connected between the cathode and control grid of each one of said'tubes that one tube -1. In an interrupted .carrier wave receiver ,an automatic gain control-circuit comprising means for rectifying the output from said receiver, .a ?rst electron discharge tube the space path of which is inseries withlsaid rectifying ,means, said conducts recti?ed signal .energy‘within a normal range of amplitudes and the other tube conducts only in the presence of peak wave impulses ‘and strong atmospherics, and a time constant device tube ‘having a cathode, an anode .and a control grid,=a load resistor connected between said an ode and ground, a-second electron discharge tube the .space vpath-oi? which is connected in shunt between the cathode of .the ?rst .said tube and 55 ground, 'said‘second tubelhaving a cathode, an composed of resistance and capacity forming part [of said gain control circuit andarranged for co operation with .saidload .to control the gain in .said receiver. 5. Apparatus for-automatically controlling the gain .in the ampli?er stages of an interrupted anode and a ‘control grid, means for maintaining vcarrier wave receiver, said apparatus comprising different threshold biases on the grids ‘of said a recti?er circuit coupled to a particular stage tubes whereby the ?rstsaid tube is rendered non of said receiver, said circuit including the space :conductive ‘)in the presence of signal and noise path of an electron discharge tube having a energy below- a predetermined level, and .the sec cathode, an anode and a control grid, negative ond tubeis :held non-conductive in the presence ‘biasing means connected between the cathode of recti?ed.signalenergywithin a normal volume and control grid of said tube, means including range, and-a time ,constantcircuit comprisingse ries resistance and shunt capacity so connected 65 a time constant circuit in shunt with the ‘space path of said tube, said means havingresistance ‘as tosupplygain control potentials to the ampli and capacitance for prolonging the gain control ?er stages .of said receiver, said potentials being effects through space intervals between the mark subject “to ‘the :limiting action of said discharge ing signal elements, and means responsive to vtubes. _ ' 2. .In.an interrupted carrier wave receiver hav 70 static impulses and high amplitudesignals which circuit “comprising series resistanceand shunt ca tend to paralyze the receiver for reducing the bias that would otherwise be derived from said ;pacityin circuit with rectifying means coupled \toaparticular stage of said receiver, said circuit caused to compensate for excessive gainvcontrol ing ampli?er stages, an automatic gain control being operative to apply gain control potentials 75 negative biasing means, whereby said vtube is , 310131011. ' 2,404,712 6. Apparatus in accordance with claim 5 wherein said bias reducing means includes a sec charge tube type, said circuit being operative to reduce the gain in said ampli?er stages in re ond electron discharge tube the space path of sponse to the reception of moderate strength which is in series with a resistor, this tube and resistor being in shunt with the space path of 5 static crashes and other interference waves of moderate amplitude, means occasionally opera the ?rst said tube and the second tube being tive to increase the gain in said ampli?er stages, operatively biased to supply substantially in this means comprising an electron discharge stantaneous adjustment of the gain control po device the space path of which is connected in tential to a new level in response to a change in shunt with said time constant elements, and the incoming signal level. 10 means operative upon reception of strong static 7. Apparatus for automatically controlling the or other noise energy for reducing the impedance gain in the ampli?er stages of an interrupted of said space path, thereby to effect said gain carrier wave receiver, comprising a gain control increase. circuit having time constant elements ‘in shunt with a unilateral impedance of the triode dis- 16 R. LEE HOLLINGSWORTH.