Патент USA US2120998код для вставки
June 21, 1938. A. w. BARBER 2,120,998 COUPLED CIRCUITS Filed Feb. 3, 1936 INVENTOR gums Patented June 21, 1938 UNITED STATES PATENT OF'FlCE " 2,120,998 COUPLED CIRCUITS Alfred W. Barber, Flushing, N. Y. Application February 3, 1936, Serial No. 62,074 15 Claims. (Cl. 179-171) This present invention of mine concerns im provements in carrier wave receiver circuits. It the automatic control of radio or carrier wave receiver response by means of automatic inter stage circuit coupling control. with manual control. particularly concerns methods of, and means for, One object of my invention is to provide means for the automatic control of radio or carrier wave receiver or ampli?er response. Another ob 10 15 20 25 30 35 ening response when receiving conditions permit. Since the possibility of using broadened response usually occurs on strong stations‘, I have found it possible to control coupling automatically as a function of signal strength and thus do‘ away ' In my copending application, I have shown how automatic coupling may be provided in the con- ' trol of thermionic vacuum tube input capacity. ject is to provide automatic control of interstage The dynamic input capacity of a thermionic circuit coupling in carrier wave ampli?ers. A vacuum; tube depends mainly on the grid to plate capacity and grid to plate gain of the tube. further object is to provide automatic circuit cou pling means easily controlled over a wide range Since the tube gain‘may be controlled by means of its grid bias, the input capacity may also be of responses. In my copending application for Letters Pat- controlled by grid bias changes. If the bias is ent dated January 2'7, 1936 and entitled “Coupled ' derived, in part, from the recti?ed signal travers circuit systems” Serial No. 61,458, I have shown, ing the receiver or ampli?er, the couplingand circuit coupling means consisting of the grid hence band-pass characteristics may be made to to cathode capacity of a thermionic vacuum ‘automatically follow the received signal strength. My present‘ invention makes use of this same tube. I have also shown how the grid to cath ode capacity and hence the coupling may be‘ controlled tube input capacity‘ but the sensitivity of the control is greatly increased by using controlled by varying the grid bias in the cou resonant or partly resonant coupling means. pling tube. Further, I have shown how this con trol may be effected from‘ the recti?ed signal, The tube input capacity is used in conjunction and hence the coupling and ampli?er response ‘with inductive coupling means and by ‘means of made to automatically vary with the strength of series resonance, the coupling is made to vary the, received signal. My present invention is a more rapidly as a function of tube gain than in system devised for thesame purpose but showing the simple common impedance type of coupling. I have found it possible to vary a 500 k. c. tuned a more sensitive control characteristic. pair'of circuits from a single peaked response In radio and carrier wave ampli?ers the inter stage selective means usually consists of pairs of to a 30 k. c. band-pass by varying the grid bias tuned circuits. If ‘the two circuits comprising of a 1500 micromho mutual conductance vacuum each pair are coupled together by varying tube by an amount to cause the plate current to amounts, three general types of response are change from zero to 5 milliamperes. The appended claims set forth, in particular, possible. With less than a particular coupling called “critical”, the response of two circuits the novel features to be found in this invention. tuned to the same frequency is a single peak but The following ‘description, however, when taken the amplitude of transmission becomes less as in connection with the drawing, will serve to the coupling is decreased. At critical coupling set forth the theory and mode of operation of 40 the response is still a single peak but with some broadening of the peak and a maximum ampli tude of transmission. If the coupling is “in creased above critical, the amplitude of response remains the same but asecond peak appears and 45 as the coupling is increased, the frequency of my invention. ' - obtainable selectivity in a radio receiver which 7 ation of my invention. Due to receiving condi 50 requires critical coupling or less between inter stage circuits. However, under this condition most systems produce serious attenuation of speaker. ?rst detector I, intermediate frequency ampli?ers some receivers manual means have been pro 55 vided for increasing coupling and hence broad 30 ~ 40 In Fig. 1, I have shown a superheterodyne re ceiver exclusive of the audio ampli?er and loud modulationfrequencies above 3000 cycles. In > ‘ Fig. 1 shows the circuit of a radio receiver, tions, it is often necessary to use the maximum the tuning frequency. _ In the drawing, up. to and including the second detector, em bodying my invention. Fig. 2 shows the equivalent circuit of two tuned circuits coupled by my present system. Fig. 3 shows a circuit equivalent to 'Fig. 2. 'Fig. 4 shows curves characteristic of the oper the second response moves further away from a The tube complement consists of, a ‘ 2 and 3, second detector 4, oscillator 5 and cou pling tubes v6 and l. The ?rst detector-oscillator 2 2,120,998 circuits are conventional. +EB denotes points of connection of plate voltage supply and +En de notes points of connection of screen voltage sup ply. Between plate 8 of the ?rst detector l and the plate voltage supply is connected a tuned cir cuit consisting of coil 9 tuned by condenser l0. Coil 9 and condenser [0 form the tuned primary of an interstage transformer. Coil H tuned by condenser 12 forms the tuned secondary of the proached and by proper choice of circuit elements a wide range of control slopes may be obtained. Fig. 3 shows a circuit equivalent to Fig. 2 in terms of mutual and leakage inductance all re duced to unity turns ratio. M12 is the mutual in ductance between L1 and L2 and m4 is the mu tual inductance between L3 and L4. This circuit shows that the series resonant coupling imped magnetically coupled to primary coil and coil . l5 ance is not accurately L2, L3 and C23 but is LziMiz plus L3iM34 and C23 in series. ‘Looking at 10 the system thus from the standpoint of an equiv alent circuit, C23 is equivalent to a “high side” coupling reactance and resonates with the leak magnetically coupled to secondary coil H and an age reactance of L2 and In to provide a sharp 10 interstage transformer feeding .grid l3 of the fol lowing ampli?er tube 2. Coupling between coils 9 and II is accomplished by means of coil l4 15 external series impedance thru condenser VI 6. The voltage induced in coil l4 from coil .9 causesa current to ?ow in coil ill of a magnitude de pending on the impedances of coils ‘I4 and ‘I 5 ‘and the impedance between the lower end of coil. 20 l4 and ground. This impedance is condenser [6 in series with the ‘input‘or grid to cathode dynamic ‘impedance of tube *6. This input im pedanceis essentially a capacity reactance. Con denser i6 is shown as a'blocking- condenser having 25 -a capacitylarge compared 'to the tube input ca pacity. The controlled current ?owing in the series circuit ?owsvthru 'coil I5 inducing a volt agelinlcoil'll whichis afunction of the current. The equivalent "circuit-of this coupling system 30 .isshown in Fig. 2 where the primary-circuit con sists-of inductance Lrtunedby condenser 01, and the secondary circuit consists'of inductance L4 tuned byrcondenserC-i. Coupling between L1 and L4 is:accomplished by ‘thecoupling ‘link consist .35 ing-of inductances L2 and L3 and condenser C‘zs .all in series. vL2 iscmagnetically'coupled to L1 .and Lsis .magneticallycoupled toL4. L1 induces a .voltageinLz. and a'current ?owsin the L2, L3, C23 seriescircuit. Since-Czsis variable ‘the current depends on .the value ofCza ‘and ‘the'voltage vin duced in Lil-depends on thiscurrent ?owing in L3. It should be.noted that if at the operating frequency, C23 resonates L2 and L3 in series, a series resonant circuit is produced in which the 45 series current increases very rapidly as C23 is varied. C23 represents the grid to-cathode ‘ca pacity of tube 6 or 1 in Fig. 1. Fig. 4 shows .aplot of reactance against bias where bias designates the variable component of the bias'appliedto the-grids of thecoupling tubes .6 or .1. Thehorizontal axis may also. be con denser capacity inorderzto explain Fig. 2. Luis the reactance of Lz-and L3 (or'coil “and coil H3) in series. __1_ Co: is the reactance of C23 (orthe input capacity of tubes “6 or 1) as the'capacity is'varied. The re actance of the series circuit is then shown by the 60 curve - 1 Leo ~65 The increase in sensitivity of the tuning eiiect over the simpleself-reactance coupling is shown by comparingthelast two curves. Starting with a bias or condensersetting athe bias-or capacity alone mustbevaried to point 0 in order to halve the series coupling reactance. However, with the 70 inductance added the reactance is halved in go ing from a to b on the 1 Leo-a curve. The apparent sharpening of control be 75 comes greateras the series resonant point is ap coupling eiTect. 15 Returning to Fig. 1 the input capacity of tube ‘6 is equivalent to condenser C23 of Figs. 2, 3 and 4. This input capacity depends on the tube characteristics, operating voltages, plate load and grid to plate capacity. Actually it depends 20 on the-tube grid to plate gain and grid to plate capacity. With no external applied bias the tube gain'depends on the tube characteristics, plate voltage ‘EB, cathode bias E0 and plate load re sistor I1. While I .have found the simple re 25 sistor I‘! to be a satisfactory load, a complex im pedance may be used. The‘tube is not limited to ~a triode although I prefer'one. Tube'? is shown having a cathode 18, heated'by means not shown, a control grid l9 and a plate .20. The grid to :30 plate capacity 2! maybe taken to represent the internal tube capacity plus external added ca pacity. The initial bias is provided by battery E0 in the cathode circuit. The control bias is supplied thru the resistor 22. Condensers 23 and 35 Marc by-pass condensers. The circuit ‘is de signed so that With no external applied bias thru resistors 22 and 25, the circuit coupling is the minimum desired which will'in general be-criti .cal- coupling, for maximum selectivity and gain. 40 If an external positive bias is applied to grid IS, the gain of tube 6 is increased increasing its in put capacity. Increasing the input capacity in creases the current ?owing in the coupling cir cuit increasing the coupling. As the coupling is 45 increased over critical, a-double peak appears in the response :producing a band-pass character istic. The same coupling system is shown between tubes 2 and 3 that was shown and described be 50 tween tubes 1 and 2. Tube 3~feeds a tuned out put circuit consisting. of inductance'26 tuned by condenser 21. The double diode second detector '4.is fedfrom coils 28 and 29 magnetically coupled to coil 26. The voltageacross coil 28 is impressed 55 on the diode formed by plate 30 and cathode 3| thru'the load by-pass condenser 32. The load resistor 33 develops a recti?ed current voltage drop which maybe used for automatic volume control of tubes 2 and '3 by applying the drop to 60 grids l3 ‘thru‘the ?lter consisting of resistors 34 and .35 and the condensers 36 and .31. The audio voltage for actuating the audio ampli?er and speaker may also be obtained from the drop across resistor 33 or a separate recti?er may be employed. 65 The voltage across coil 29 is applied to the diode consisting of plate 38 and cathode '39 thru the by-pass condenser 40. The recti?ed output is a drop thru resistor ‘4| and the direct current component is ?ltered out by means of resistors 25 and condensers 23. This direct current com ponent is proportional to the signal output from tube 3 and is a function of the signal picked up by antenna A. Since the cathode 39 end of load resistor-‘4| becomesmore positive thegreater the 2,120,998 signal received, the external bias supplied by recti?cation to tubes 6 and ‘I is more positive the greater the signal. As shown above the more positive the externalbias, the greater the input capacity to tubes 6 and 1 and the greater the coupling between the interstage circuits. Thus the system provides a response which is a func- ' tion of the received signal and the stronger the received signal the wider the response band and the better the ampli?er ?delity. While not in any way. intended to limit the scope of my invention, I have found the following con stants to give the indicated expansion: Tube 0 or ‘I mutual conductance at normal 15 bias 1450 Resistor-22 ______ -l ___________ __ohms__ 500,000 Bias Ec _______________________ __volts__ Plate voltage Eb _______________ __do____ 25 250 Resistor ll _____________ _‘_ ____ __ohms__ 400 Internal part of condenser 2|____mmf__ 50 6 20 External part of condenser 2l____mmf__ Condenser l6 _____ __, ___________ __mmf__ 25 2000 _ Coil 9 __________________________ __mh__ 1 Coil l I ____________ _'_ ___________ __mh__ Coil I4 ___________ __-_ ___________ __mh__ 0.3 .Coil l5 _________________________ __mh__ 0.3 1 Condenser It to tune coil 9 to 547 k. c. Condenser, it to tune coil H to 547 k. c. coils ii and I5 close. Coupling with no external grid bias very nearly critical giving single response peak, with plate current zero. With external bias to give plate current 5 ma. over coup-ling produced giving two ‘peaks sepa rated 30 k. c. s 1 A set of typical results is here shown as peak frequencies for various coupling tube plate cur 40 rents. apparent to one skilled in the art that many modi?cations are possible without departing from ' its spirit and scope as set forth in the appended claims. What I‘claim is: 1.‘ In a selective carrier wave ampli?er, means for varying the selectivity 'of said ampli?er com prising the combination of at least two thermionic Vacuum tube repeaters, a resonant circuit receiv ing the output of one of said repeaters, a second 10 resonant circuit connected across the input of another of said repeaters, a series circuit com prising two coils, a condenser and the grid to cathode impedance of a third thermionic vac uum tube comprising at least a grid, cathode and 15 plate wherein one of said coils is magnetically coupled to one of said resonant circuits and the other of said coils is magnetically coupled to the other of said resonant circuits whereby energy is transferred from one of said resonant circuits to the other wherein said impedance includes a ca pacity reactance component of greater magni tude than the combined inductive reactances of said two coils at the resonant frequency of at least one of said resonant circuits. ‘ 25 2. The combination as set forth in claim 1 and including means for supplying a bias to the grid of said third vacuum tube at least in part derived by rectifying the signal traversing said ampli?er. Coupling between coils 9 and I4 and between 35 3 ‘ 3. The combination as set forth in claim'l and 30 including means for applying a bias to the grid of said third vacuum tube greater than that re quired for plate current cut-off for all received signals below a predetermined level. 4. In a radio receiver employing thermionic 35 vacuum tube repeaters, an interstage coupling circuit comprising tuned input and output coils and a link circuit, a thermionic vacuum tube comprising at least a grid, cathode and plate, said link circuit including in series connection two 40 coils and the grid to cathode impedance of the 0 ma. Peak 547 k. 0. 45 last said thermionic vacuum tube all connected 20 ma. Peck 547 Peak 497 in series, wherein said link is adapted to transfer energy between said tuned circuits by virtue of c. magnetic coupling between one of said coils and 45 . 0 said output circuit, the coupling between other An eifective delayed expansion may be pro duced by increasing E0 beyond cut-off. Since no expansion will take place until the coupling tubes 50 6 and ‘i draw plate current, the delay depends on the amount the bias E0 exceeds the cut-off bias of tubes 6 and 1. Suppose for instance 25 volts is the bias required for cut-off then if EC is made 40 volts it will take 15 volts of external bias to bring 55 the 40 volts to a net 25 volt bias. If 15 volts on the recti?er corresponds to 1’ millivolt on the an tenna, no expansion will take place until the re ceived signal exceeds 1 millivolt. As the net bias is reduced below 25 volts the coupling in creases expanding the receiver response. While I have shown my automatic coupling system applied to intermediate frequency ampli ?er circuits, it is by no means thus limited but may be applied to variably tuned stages such as v65 in a tuned radio frequency receiver or in the pre selector circuits of a superheterodyne. Many combinations are possible such as equal expan sion control on two intermediate frequency stages; a control with a different delay control 70 on a third intermediate stage and a control with a still different delay value on the pre-selector circuits. - While I have described only one system whereby my invention may be carried into effect and have pointed out a few possible variations, it will be of said coils and said-input circuit and the series connected input impedance of the last said tube and including a condenser between gridand plate of the last said vacuum tube and a load resistor 50 in series with said plate whereby the input-im pedance of the last said tube exhibits a capacity reactance‘ greater than the inductive reactance of said two coilsin series at the resonant fre quency of said tuned input coil. 55 5. In a selective carrier wave ampli?er, means for varyingthe selectivity of said ampli?er com prising the combination of at least two resonant circuits and a coupling link between said circuits, 60 said link comprising in series at. least one coil magnetically coupled to each of said resonant circuits and the grid to cathode capacity of a thermionic vacuum tube, means for causing said grid to cathode capacity to vary as a function of 65 the amplitude of the signals traversing said am pli?er when said signals are greater than a pre determined amplitude. 6. The combination as set forth in claim 5 wherein at the frequency of resonance of said 70 resonant circuits the capacity reactance of said grid to cathode impedance is greater than the sum of the inductive reactances of said coils. 7.‘In the intermediate frequency ampli?er of a superheterodyne radio receiver, the combina-' 75 4 12,120,998 tion of a plurality of thermionic repeaters, at least two pairs of input and output resonant cir cuits associated with said repeaters, energy trans fer means linking said input and output circuits in said pairs, in which said transfer means com prises series circuits consisting of a coil coupled 12. The combination as set forth in claim 10 wherein the capacity reactance component of said vacuum tube input impedance is a function i to an input circuit and a second coil coupled to of the amplitude of the signal traversing said am pli?er when said signal is greater than a prede the output circuit of a pair and the input im termined value. pedance of a thermionic vacuum tube and means 13. In a radio receiver embodying thermionic vacuum repeater tubes, the combination of at 10 for causing said input impedance to exhibit a capacity reactance component greater in magni tude than the sum of the inductive reactances of .15 quired ‘to produce plate current cut-off in said vacuum tube. least one interstage coupling system comprising an input and an output tuned circuit and an in said two coils at the intermediate frequency of tercircuit coupling impedance, said coupling im said receiver. pedance consisting of inductive means resonated to a frequency greater than the resonant fre 15 ' 8. The combination as set forth in claim 7 and including means for applying a control bias to said vacuum tube which is proportional to the di?erence between an initial ?xed bias and a bias derived by recti?cation of the signal'travers v20 ing said ampli?er. 9. The combination as set forth in claim 7 in which the said vacuum tube embodies a cathode, a grid and a plate, and is associated with an ex, ternal circuit comprising a capacity connected ,25 between said grid and said plate and a resistor in series with said plate and means for applying a control bias to said grid equal to the difference between a ?xed voltage and a voltage derived by recti?cation of the signal traversing said ampli 30 ~?er. 10. In a carrier wave ampli?er, the combina tion of at least two thermionic repeaters, a reso nant circuit connected to the plate of one of said repeaters and a second resonant circuit connected to the grid of another of said repeaters, two coils and the input impedance of a thermionic vacuum tube connected in series, wherein one of said coils is magnetically coupled to said plate connected resonant circuit and the other of said coils is 40 magnetically coupled to said grid connected res onant circuit, said vacuum tubeincluding a cath ode, a grid and a plate, means associated with said vacuum tube including a capacity connected between said tube grid and said tube plate, a re V45 sistance connected between said tube plate and a source of positive potential, and external grid bias means comprising a source of ?xed-bias and the direct current component of recti?cation of the signal traversing said ampli?er acting in op 50 position wherein the input impedance of said vacuum tube exhibits a capacity reactance com ponent of greater magnitude at ‘all times than the inductive reactance of the two said coils in 55 series at the resonant frequency‘of one of said resonant circuits. ' 11. The combination as set forth in claim 10 wherein said ?xed bias is greater than that re quency of either of said tuned circuits by an elec trically controlled capacity means comprising the dynamic grid to cathode capacity of a thermionic Vacuum tube wherein, said combination includes a condenser connected between grid and plate of :20 the last said vacuum tube. 14. In a selective system, the combination of two tuned circuits and intercircuit coupling means comprising two coils and the dynamic grid to cathode impedance of a thermionic vacuum tube triode connected in series, wherein one of said coils is coupled to one of said tuned circuits and the other of said coils is coupled to the other of said tuned circuits and including a condenser connected between the grid and plate of said tri 30 ode wherein said condenser has a reactance great er than the combined inductive reactances of said two coils. 15. In a carrier wave ampli?er, automatic band-pass control means comprising a thermionic 35 vacuum tube feeding a tuned circuit, a second tuned circuit feeding into a second thermionic vacuum tube, two coils and an electronically con trolled capacity connected in series, wherein one of said c'oils is magnetically coupled to the ?rst of said tuned circuits and the second of said coils is magnetically coupled to the second of said tuned circuits and wherein said electronically controlled capacity comprises the effective grid to cathode capacity of a third thermionic vacuum tube, said third tube comprising at least acath ode, grid and plate, and further means comprising a condenser connected between plate and grid of said third tube and a load resistor in series with the plate of said third tube, means for ap~ :50 plying a bias to the grid of said third tube at least in part derived from the recti?cation of sig nals traversing said ampli?er wherein the ‘mini mum Value of said electronically controlled ca pacity resonates said two coils in series to a fre quency greater than the resonant frequency of either of said tuned circuits. ALFRED W. BARBER.