Патент USA US2412244код для вставки
Dec. 10, 1-946. ' ' H. J. BENNER ' 23126244 SUPERHE'I‘ERODYNE RECEIVER Filed Nov. 10, 1938 7'0 AVG 7b Osc/LM 70B Tums/a ‘ . ‘ INVENTOR wmqead ?av/vse 2,412,244 Patented Dec. 10, _ 1946 UNITED STATES PATENT ‘OFFICE 2,412,244 SUPERHETERODYNE RECEIVER Howard J. Banner, Spring?eld, Mass, assignor of one-half to Colonial Radio Corporation, Buf falo, N. Y., and one-half to The F. W. Sickles .Company, Spring?eld, Mass. Application November 10, 1938, Serial No. 239,788 , 16 Claims. (01. 250-20) 1 , tuning reactance which acts simultaneously as a selector of desired frequencies and as an image suppressor; that is to say, the variation'of the variable reactance causes the circuit to select the! desired signal, at the same time to present an ex-; tremely high impedance to the image signal, and I have found that circuits according to my-'invenl-' band. Incoming radio frequency signals are het tion produce signal to image ratios as high 'as, erodyned or “beat” with an oscillation produced by the local oscillator, vand this gives rise to os 2 a simple tuning circuit with only one variable This invention relates to radio receiving ap paratus, and more particularly to signal selecting circuits for superheterodyne receivers, In such receivers, as is well known, the inter mediate frequency amplifying stage or stages are tuned to a frequency above audibility and usu ally below the lowest frequency of the broadcast 10 and in many cases considerably higher than, the cillations of a frequency which may be either the sum of or the difference between the incoming frequency and that of the local oscillator. Only those oscillations thereby produced which have a frequency enabling them to pass through the in 15 termediate frequency ampli?er are then ampli best signal to image ratios produced ‘by conven-~ tional wave trap circuits. As an example, em ploying the single tuned circuit of my invention, I have been able to obtain signal to image ratios as high as 70,000. ' 7 Among the objects of my invention are: H To provide an image suppression circuit which ?ed. does not require separate wave trap or preselec-_ For example, if the intermediate frequency am tor circuits; ‘ ' ' pli?er is tuned to 400 kilocycles and a 550 kilo cycle signal is being received, and the local oscil 20 To provide a circuit in which the image sup pression is automatically performed by the main lator has, when this particular signal is being re tuning circuit, ceived, a frequency of 950 kilocycles, then there Still another object of my invention is to pro will be produced a f‘beat” frequency of 400 kilo vide a simple signal selecting circuit which will' cycles. However, if there is also an incoming sig nal of 1350 kilocycles at the same time, a new 25 deliver signal to image ratios as high or'higher than those obtained from conventional wave trap oscillation will be produced by the heterodyne ac or preselector image suppressors. ' tion between the local oscillation and the 1350 Still other objects of my invention~ will be ap kilocycle signal, and this new oscillation will like parent from the speci?cation, ’ ' ' wise have a frequency of 400 kilocycles and will In this application I have particularly pointedv accordingly pass through the intermediate fre out and distinctly claimed the part, improvement quency ampli?er, resulting in interference and or combination which I claim as my invention of cross-talk with the desired signal. The frequency discovery and I have explained the principles of the undesired signal is termed the “image” fre thereof and the best mode in which I have'cons quency, and it is equal to the frequency of the de sired signal plus twice the intermediate fre 35 templated applying those principles so as to dis tinguish my invention from other inventions. ' In the drawing' It is usual to provide a signal selecting circuit The figure is a circuit diagram of one form‘ of in advance of the ?rst detector, and this circuit is ordinarily arranged to be tuned to the frequency circuit in accordance with my invention. " I quency. , 2 In the practice of my invention, for some pur-. of the desired signal. However, even when such 40 poses I prefer to employ what is known as “per-I a circuit is used, image interference may still be meability tuning,” although this invention is not encountered and it has been proposed in the past limited thereto. If such permeability tuning is to eliminate or reduce this imagev interference by providing preselecting circuits and the like, and also by providing one or more wave traps asso ciated with the antenna and variably tuned. The employment of wave traps for image sup pression increases the cost of the receiver, since employed, the variation in resonant frequency is 45 obtained, not by rotation of a variable ‘condenser, but by movement of a core of magneticmaterial in the ?eld of an inductance. Such cores’ are sat isfactorily formed of iron dust mixed with a suit able insulating and binding material and pressed it is necessary to provide an additional coil and‘ an additional condenser, one or the other of, 50 or otherwise processed to form what appears as a solid bar. > which is usually variable. The provision of such Since they are easily obtainable on the marke , parts increases the cost of the receiver, from the and their construction is per se, not a part of my standpoint of material and parts employed and invention, they are not described in detail. also the labor of assembly, I have discovered that it is possible to provide 554 If such a core is moved axially into and out‘ 2,412,244 3 of a solenoid in a resonant circuit, there is ob- ‘ 3 and condenser. 5, forming a closed loop circuit, served a variation in the inductance of the sole noid, and a variation of the resonant frequency of the circuit in which said solenoid is connected, are resonant to the image-producing signal and , cause extreme attenuation thereof while not inter this change of resonant frequency being due, to a . very considerable extent, to the variation in the value of the inductance‘of' the" solenoid with the positionof the: core, and probably‘ also, in some. “ arrangements, to some extent at least, to the variation of the capacity of the circuit resulting; "19 from change of position of the core,.. fering with the‘ selection by resonance of the desired signal. ‘I have found that movement of thecore 4 into and out of the coil 3 varies the tuning of . the entire circuit and: also, the; tuning of the'imagesuppressor 3+5. in a satisfactory ap proximation to the desired manner. "In order for the signal or mainvtuning circuit to vary from 500 to 1500 kilocycles, i. e., 3 to 1 I represents an antenna of any suitable typew, . ratio; the» inductance of that circuit must vary ‘ in a. 9. to 1 ratio. It will be noted, however, which may be connected to groundz'throug‘ni that. while the resonant circuit varies from 5037 _Referring more particularly to the ?gure; ‘ ‘ coupling condenser 2. C'urrnntsprodirceidihthe 15' to. 150.0 kilocycles,_v the image frequency varies antenna I by incoming signals will ?ow to some‘ extent through inductance 3, shunted by con denser 5, and the voltage thereby produced‘ may be supplied to the grid 9 of the ?rst.» tube 'l,.. whichmay be connected to ground through con 20 from. 1460. tn» 2510} kilocycles when the inter mediate frequency is455 kilocycles. In this case the ratio of frequencychange is 1.72 to 1 and the changeiwofiinductance required to make the image denser 6; this ratio, or. 2.96-1. V circuit track exactly should be in the square of ~ From. this it iwill‘beseen that. if the main tuning: The antenna side of coil 3, may be connected through resistance ll, having a_high resistance, circuit is tuned to the lowest broadcast fre to ground or to the automatic volume control quency, i. e., 550. kilocycles, and’the. image circuit voltage source, if such ispresent, thereby provid ing, a; direct. current grid return path. The. 3-.51 then tuned, by varying.v condenser 5,. to. the. image. frequency,.then as; the. main tuning circuit. frequency is increased by movement. of‘the core 4‘. out of the inductance,.the. reduction of; inductance sistance-- L2,. shunted by condenser l3;- or directly in the image trap proceeds too fast,‘ and. the. grounded if desired; Sincemy invention is? not concerned with the 30 resonant? frequency of the. image circuit. rises? cathode of=~tube 11» may be grounded through re construction of the superheterodyne beyond this , above the image'frequenc'y. point, and the same is well known in the'art, only This. departure from. the theoretical image. value is, in most cases, not-a serious. matter,_.be the ?rst tube 1 is indicated. ' - cause, ordinarily, themost harmful-image. inter‘ ' The desired- signals may be selected by, move~ ment of the core 4 into and out of the ?eld of coil 3, and at? the same time the‘ frequency of the local oscillator is: varied. in such" 'a manner that the signalselected in the antenna. circuit by movement of the coil 4 is heterodyned to-pro» f'erence is. obtained when. the. main-tuning circuit is- tuned to thelow frequency end of. thebroadcast band. . 'It may be noted that under certain. conditions the value of condenser "2. may be. zero; that. is, d-ucev oscillations of the desired intermediate fr - ‘ that physical condenser may be omitted; quency. In adjusting the circuit for operation, the con denser. 5: may be omitted and the desired num beriofqturns in. inductance 3 provided so that’ instance. of this is in automobile radio installa tions where the. running-board's are used as. an. aerial. In this. instance, the antenna capacity; ' whichis in parallel with condenser 2 is so large, movement of? they core 4 causes the circuit to i ; comparatively, that condenser 2, may be‘omitted. Condenser 2. may be'omitted with an aerialof tune’ over the range desired, in this instance from small capacity also; such as av “?shpole.” 500 to 1500 kilocycles, and» the tuning. circuit formed ‘by-inductance- 3-.and its associated‘ ele ments, herein called the “signal tuning circuit,” is-preferably ‘ftracked” withthe- oscillator tuner will. now operate’ as a- conventional superhetere» ody'neand imageinterferencemay be experienced. In» this-instance condenser 6- may be adjusted. to compensate: for'the variation- in antenna capac~ ity; bytrinnner condenser-‘6”. so that thereceiver may be operated: by- a single control as indicated by theconnected arrowsin the drawing. The circuit._ One. . I r V ' ‘While I have shownand- described certain. pre-. ferred» embodiments of my» invention, it? will. be apparent that modi?cations.» and changes may be. made. without departing from the spirit and scope. ~‘ of my invention, as will beelear to those skilled. If now condenser 5 be connected across coil 3 and chosen of the proper value, a very great im movement in signal: to image ratio is noticed. In in the art. I claim: _ ‘ ~ . l . , » I g, 1; In-a superheterodyne receiver, incombina-r tion, inductance and capacity elements: associ: choosing the value? of condenser 5, it is picked of such magnitude as to cause the inductance 3 to 60 ated. together to form a resonant circuit, tun resonate with condenser 5 at the image frequency able as a whole by variation of one of- saideleej (which, as stated, is equal to the desired signal ‘ ments to select desired. signal. frequencies, said frequency, plus twice the intermediate frequency) variable element forming, with another. of said. ~ whengthe- tuning circuit is tuned to a desired signal; frequency; » elements, a parallel tuned. resonant circuit which .. is maintained resonant to the image ofthe SE‘: The connection of thiscondenser, which will ' ordinarily be quite small, for instance of the 1 order of. two to twelve mmf., may slightly disturb: 1 the tracking of the main tuning circuit with the i oscillator tuner, in which case: it may be neces-v sary to retrim the main tuning circuit by varia- ‘ ‘ tion' of. the trimmer‘ condenser 6, but it will be found that when the operation is completed the ' entire input. circuit; as a whole, is resonant ‘fe thedesired'signal frequency; whereas, inductance 75. lected signal frequency. I v - 2. In a superheterodyne receiver, in. combina tion, inductance and capacity elements associ» ated togetherv to form a resonantlcircuit, tunable’ as. a whole by variation of said inductance to_ se lect; desired signal frequencies/said inductance-v forming with a capacity element a secondreso nant circuit parallel tuned. to the image ofthe selected signal frequency; 7 ' ‘ r ' > 3. In a superheterodyne. receiver, inzcombinal tion, inductance and capacity elements associ stantially “equal, to ‘_ ated together to form. a resonant circuit tunable twice the intermediate frequency, desired 5' frequency _f plus _ I v , as a whole to select desired signal frequencies, a 9. In ajsuperheterodyne radio'lre‘ceivingi cir core of magnetic material movable into the, ?eld of said inductance to tune said ‘circuit, said in ductance having a capacity connected thereto selector circuit comprising an inductance coil, a ?rst capacitor across theends of said induct‘ and forming therewith 'a second resonant cirf cuit maintained parallel resonant to the image of inductance coil atone end, an impedance in the selected signal frequency. ' . cuit, an audion tube having a control grid,'-a ance coil,,a second capacitor in series ‘with the series with the inductance coil at the other end, an aerial operatively connected to the inductance coil and to the impedance, the opposite ends of ' » 4.‘ In a superheterodyne receiver, in combina tion, inductance and capacity elements associ ated tog’ether’to form a resonant circuit, tun-' able as a whole by variationof said inductance the impedance and capacitor being‘ grounded, means for impressing a received signal across the terminals of the impedance, the second‘ ca pacitor and inductance coil being connectedto the grid, and-means for varying theinductance to select desired signal frequencies, and a cir“ cuit comprising a condenser in shunt with said inductance, the circuit formed byv said induc tance and said condenser in shunt therewith be of theicoil to tune the circuit as a whole to a desired frequency and to tune the image trap composed of thejinductance coil and ‘the, first 5. In a superheterodyne receiver, a combined 20 capacitor to a frequency substantially vequaljton the desired frequency ‘plus twice the.interrne' signal selecting and image rejecting circuit com , ing parallel tuned to the image of the selected signal frequency. ' - prising a plurality of reactance elements forming diate frequency. a resonant circuit, at least one of said reactances being variable to select signals of a desired fre quency, said variable element being shunted by a vacuum tube with a control electrode, includ an additional reactance of opposite sign of such value as to constitute a second resonant circuit parallel resonant to the image of the resonant frequency of the ?rst resonant circuit, and means for varying the value of said variable reactance to simultaneously vary both resonant frequencies while maintaining the second at the image value of the ?rst. 6. In a superheterodyne receiver, an input tuning circuit comprising a pair of capacity ele ments, a connection between said capacity ele ments, said connection including, in series, a closed tuned circuit, the inductance and capacity of said closed tuned circuit being so chosen that 4-0 said closed tuned circuit is resonant to the im age frequency, and one of the reactance elements of said closed tuned circuit being variable over a range such as to tune the input tuning circuit as a whole to desired signals while maintaining said closed circuit resonant to said image frequency. 7. In a superheterodyne receiver, an input tuning circuit comprising a pair of capacity ele ments, 9, connection between said capacity ele ments, said connection including, in series, a closed tuned circuit, the inductance and capac ity of said closed tuned circuit being so chosen that said closed tunedcircuit is resonant to the image frequency, and one of the reactance ele ments of said input tuning circuit being variable over a range such as to tune the input tuning circuit as a whole to desired signals while main taining said‘ closed circuit resonant to said image frequency. 8. In a superheterodyne radio receiving cir cuit, an audion tube having a control grid, a selector circuit comprising an inductance coil, a ?rst capacitor across the ends of said induc tance coil, a second capacitor in series with the inductance coil at one end, an impedance in series with the inductance coil at the other end, the opposite ends of the impedance and capac itor being grounded, means for impressing a received signal across the terminals of the im¢ pedance, the second capacitor and inductance coil being connected to the grid, and means for varying the inductance of the coil to tune the circuit as a whole to a desired frequency and to tune the image trap composed of the inductance coil and the ?rst capacitor to a frequency sub ‘ . j '. j'_ ' 10. An image suppression system'for a super: heterodyne radio receiver having an antenna and ing a ?rst resonant circuit a portion of which is connected between said control electrode and ground, and a second resonant circuit in series between said antenna and said control elec trode, said resonant circuits being tuned by in ductance variation respectively to a signal fre quency and to the corresponding image fre quency. 11. An image suppression system for a super heterodyne radio receiver having an antenna and a vacuum tube with a control electrode, in- - eluding a ?rst resonant circuit a portion of which is connected between said control electrode and ground, and a second resonant circuit in series between said antenna and said control elec trode, said resonant circuits including in com mon a variable inductance device comprising an inductance coil and a ferromagnetic core mov able relatively thereto and being tunable simul taneously over substantially different frequency ranges by motion of said core. 12. An image suppression system for a super heterodyne radio receiver having an antenna and a vacuum tube with a control electrode, in cluding a ?rst resonant circuit a portion of which is connected between said control electrode and ground, and a second resonant circuit in series between said antenna and said control electrode, said resonant circuits including in common a variable inductance device comprising an induct ance coil and a ferromagnetic core movable rel atively thereto, said resonant circuits being simultaneously tuned by motion of said core re-‘ spectively to a signal frequency and to the cor- ’ responding image frequency. ’ 13. A preselector system for a superheterodyne radio receiver, including a variable inductance device comprising an inductance coil and a mov able ferromagnetic core, ?rst and second capac itors connected with said inductance device to secure resonance within a ?rst range of frequen cies by movement of said core, and a third capac itor in shunt with said inductance device to se cure resonance within a second range of fre quencies by movement of said core, said capac itors being so chosen that any frequency of said second range is higher than the corresponding frequency of said ?rst range by a practically constant amount throughout said core move 75 ment. 2,412,244 V8 radio receiver,v including avariable inductance able ferromagnetic ‘core, ?rst and second capac device to securev resonance within a ?rst range of , said. inductance device and ‘tunable, thereby over a second frequency. range in series between "said device comprising an inductance coil and a mov itors ‘in series shunted across said inductance‘ - ground, anda secondresonant circuit including, . 14. A preselector system for a, superheterodyne UK antenna and said input electrode, said elements being so proportioned that said resonant _cir-’ cuits are maintainedat a practically constant frequencies by movement of said core, and a frequency difference during movement of said third capacitor in shunt with said inductance de core. vice to secure resonance within a second range . a V v . '1 ‘ 16. In a superheterodyne receiver, in ‘combi; of ‘frequencies by movement of said core, said‘ 10 nation, an inductance element anda plurality of capacitors being so chosen that any frequency capacity elements connected together to‘ form a of said second range is higher than the corre single resonant signal selector circuit for con sponding frequency of said ?rst range by a prac-' nection at one pointto an antenna and at an-v tically constant amount throughout said core movement. I t s n 15, In a superheterodyne radiovreceiv'ing syse tem, an antenna, a vacuum tube having an in putelectrode, and, elements including a variable inductancedevice comprising an inductance coil and a movable ferromagnetic core, a ?rst reso other point to the control electrode'of a thermi ionic tube, said inductance having one of said capacity elements’ connected in shunt therewith and forming with said inductance a resonant circuit parallel tuned to the image of a, selec-V table signal frequency, said parallel tuned cits 20 cuit being interposed in series between the points ~ nant circuit including said inductance device of connection to said antenna and’ to said control and tunable thereby over a ?rst range of. fre electrode. quencies connected between said antenna and I _. v HOWARD J. BENNER, ' . ‘ _ "