Патент USA US2390768код для вставки
Deco-1,1, 1945. 2,390,768 ‘K. B.‘ AUSTlN ETAL VARIABLE SELECTIVITI AMPLIFIER Filed Oct; '7, 1944 T 3 —o 32 I 0 RAD/O SECOND DE TEC TOR All/D UT/L/ZA?U/V DEV/CE FREQUENCY AMPLIFIER All/D CONVERTER —L, _: Tg‘zy ‘Fi g2. lu 3 :‘K 50 37 519 ‘s 40 _ _ m _ _ _ a g 30 | E20 :I E /0 Q 0 L ' ' COUPLING Fig.3. Fug/l’. 45’ | 4.? 42 42 I | I | \1 92 I § E w : 2 I H117’UAL 42 | ' 44 g R g 45 b k I & w | I l k | I ‘t FREQUENCY L w 4 | | | x k . '4; I 45 g k g a w |\ k ‘I FREQUENCY FREQUE/YC Y I r-wventow 5: Kirby 15. Austin, ' George G.Young., by Their" Attorney. V ‘2,390,768 Patented Dec. 11, 1945 umrsp STATES PATENT ' OFFICE ascents VARIABLE SELECTIVITY Kirby B. Austin and George G. Young, Bridge- * ' port, Conn, assignors to General Electric Com5 pany, a. corporation of New York 1 Application October 7, 1944, Serial No. 557,.tt9 ' 8 Claims. writs-171) This invention relates to" high frequency am pll?ers and particularly to such ampli?ers which are provided with. switching devices for selec tively changing the resonance bandwidth. It is an object of this invention to provide a variable selectivity high frequency amplifier in cluding an improved arrangement for changing the resonance bandwidth of the ampli?er. v . Referring now to the drawing. the ampli?er shown in Fig. 1 includes ?rst and second stage . electron discharge devices I and 2, respectively. The device I is coupled to the output of a radio frequency ampli?er and converter 3 through a pair of tuned circuits 4 and 5. The circuit a is the primary circuit and includes a main induct ance 8 and a main capacitance ‘l. The second ary circuit 5 includes a main inductance 8 and It is another object of this invention to provide a variable selectivity high frequency ampli?er 10 a main capacitance 9. and the two circuits are directly coupled through an inductive reactance including an improved bandwidth selection ar rangement of simpli?ed construction. v element “I which is connected in series with the main inductance it of the circuit s. In the posi The novel features which are believed to be ‘tion shown the direct coupling is effected through characteristic’ of this invention are set forth with particularity in the appended claims. The in 15 the left-hand contact of a double-throw switch vention itself, however, both as to its organiza tion and method of operation, together with fur ther objects and advantages thereof, may best be it so that only a portion‘ of the reactance III is . common to both circuits. The main inductance elements 8 and t are provided with movable cores l2 and M respectively‘ for tuning purposes, tion taken in connection with the accompanying 20 and these circuits are tuned to resonance at a predetermined frequency when switch It is in its drawing in which Fig. 1 represents an embodi left-hand position as shown. The circuit 571s ment of the invention, and Figs. 2, 3, 4, and 5 represent certain operating characteristics of the _' connected across-a resistor ll to a control grid it apparatus of Fig. 1. of the device 9, which also includes an anode it and a cathode it. The devices I and 2 are cou Brie?y the apparatus illustrated in the draw~ pled by a pair of tuned circuits l8 and it. The ing comprises a two-stage intermediate fre circuit It includes a main capacitor 29 and a quency electronic ampli?er provided with tuned main inductance M which may be tuned by circuits directly coupled through suitable react-v movement of a core 22. The circuit 19 includes ance elements, one pair of tuned circuits being arranged in the input of the ?rst stage of the 30 a main capacitance 23 and a main inductance 24 ampli?er and a second pair of tuned circuits in which may be tuned by movement of a core 25. understood by reference to the following descrip the output thereof. The coupling reactances are associated with the primary tuned circuits of A capacitive reactance element comprising ca: 'pacitors 26 and 2? connected in series with the main capacitor it is provided for coupling the each pair and are of opposite sign; that is, one is inductive and the other is capacitive. " A 35 circuits l8 and I8, and the circuit i9 is connected switching arrangement is provided for simul in common with the capacitor 21 through the taneously changing the coupling of the ‘second left-hand contacts of the gouble-throw switch 28. ary circuits from, the position including only a A suitable source ofano' e voltage indicated as portion of the reactance elements to the position a battery 28 is provided and is connected to . including all of the reactance elements, together 40 the plate It through the inductance 2| and a » resistor 30. The battery 20, is also connected with an additional resistance element included only in the secondary circuits. The values of through the inductances 6 and ill to supply the the reactances are selected so that when the anode voltage for the last tube in the ampli?er and converter 3. ' units are tuned to resonance with only portions of the elements common to the two circuits, the 45 _ The pair of circuits l! and i9 is similar to the changing of the control to include the entire ele pair 4 and 5 except that the direct coupling is ments provides a wide resonance bandwidth, one capacitive rather than inductive, and the circuits of the secondary circuits being detuned below the Ill and II are tuned to resonance at the same resonance frequency and the other above the res predetermined frequency when the switch 20 is onance frequency so that the combined or over 50 in its left-hand position. The output of the cir all characteristic is symmetrical about the res cuit I0 is connected'to a control electrode it of the device 2 which ampli?es the output and sup onance frequency. The voltage gain for the two positions of the control is made substantially plies it to a. suitable utilization device 32 con cqual so that no adjustment of the gain is nec nected between the anode 33 and the cathode 84 cssary. of device 2. ' 2 I . ' 2,890,768 The ampli?er of Fig. 1 when operated with the being plotted against attenuation. In each of switches H and 28 in their left-hand position these ?gures, the sharp resonance characteristic is sharply tuned and highly selective. Under curve is indicated at 42, this being the desired certain conditions, however, it is desirableto con-v sharp resonance curve with the switches in their nect the ampli?er to operate with ‘a broad res left-handjposition and at a frequency indicated onance bandwidth. This may be accomplished by the dotted line 43. Fig. 3 represents at 44 the by moving the switches II and 28 to their right selectivity curve of the pair of circuits 4 and 5 . hand positions. To facilitate the simultaneous when the switch II is in its right-hand position, movement of the switches, they may be con _ the secondary circuit 5 producing detuning in nected by a suitable mechanical coupling indi 10 the range'of frequencies below the frequency 43. cated by a dotted line 35. When the switches are Fig. 4 represents at 45 the selectivity curve of in their right-hand positions, the entire react the circuits l8 and I9 when-the switch 28 is in‘ ance elements I!) and 23, 21 are connected in common with their respective primary and sec its rightehand position, this curve showing that . the circuit 5, and a resistance 31 is connected inductive reactance I'll and the capacitive re actance 26, 21, a symmetrical over-all curve may be obtained as indicated at 46 in Fig. 5. The the secondary circuit is detuned for.frequencies ondary circuits. Furthermore a‘ resistance 35 15 above the frequency 43 due to the capacitive cou pling. .By proper selection of the values of the is connected in_ series with the reactance ill in in series with the condensers 26 and 21 in the circuit l9. _These resistors reduce the eifective ratio of the energy stored in the resonance cir 20 curve 46 is a broad over-all resonance curve re sulting from the combined operating character cuits to the energy dissipated therein, and thus Y reduce the - sharpness of resonance. Further istics of the two pairs of tuned circuits 4, 5 and more when the entire coupling reactance ele l8, l9. » ments are included in common in both circuits, After selecting the desired values of _the cou the pairs of circuits are overcoupled. The tun 25 plingreactances ‘I0 and 26, 21, the circuit of Fig. ingof the primary circuits is not appreciably dis 1 is prepared for operation by placing the turbed. However the secondary circuits 5 and I9 are detuned to some extent, the circuit 5 be switches II and 28 in their left-hand positions as ‘shown in the drawing and. then tuning the circuits 4, 5, l8, and 19 to resonance at the de ing detuned oppositely from the circuit l8 since the reactance added to the circuit 5 is inductive 30 sired predetermined frequency 43. This simple tuning operation is the only tuning required, it whereas that added to the circuit' 19 is capaci tive. The values of the portions of the coupling. being unnecessary to make anyfurtheradjust ments of the tuning when the coupling 35 is reactances connected in the secondary circuits may be selected so that the voltage gain, that is changed to place the switches I l and 28 in ,their ratio of the input voltage to the output voltage, 35 right-hand positions. It is readily apparent from the foregoing that of each pair of circuits remains the same for both a simple and e?’ective circuit has been provided positions of the double-throw switches. That this may be accomplished is illustrated in Fig. 2 for securing either a broad or a sharp resonance where the mutual coupling curve for the pair of bandwidth in a high frequency ampli?er and that circuits 4 and 5 is illustrated. It will be noted 40' a minimum number of circuit components areyre that the curve has a hump 31 which has a maxi _quired. Furthermore only a single tuning opera mum value of gain at the point of critical cou tion is necessary for bothpositions of the band pling where the transfer of energy is maximum. " width selecting‘ device. Furthermore all the By selecting two points 38 and 39 respectively switching may be effected on the low voltage end below and above the critical couplingvalue, it is ' 45 of the tuned circuits and it is unnecessary to I possible to provide two points of equal gain with different values of coupling and ‘the values of shield the switching mechanism. Furthermore this circuit makes it possible to provide constant the two portions of the reactance l0 are selected gain for both positions of the selectivity chang accordingly, the value of the portion of the re ing device. By way of illustration only and not , actance connected when the switch II is in its 50 by way of limitation, there are listedbelow values left-hand position being that at 38 and the value of circuit constants which have been found to be when the entire reactance is included in the cir suitable for the circuit of Fig. 1 when employed _ cuit and the switch II is in its right-hand posi-_ in a particular intermediate frequency ampli?er. tion being that at 39. A similar curve may be The electronic discharge devices I and 2 were drawn to illustrate the variation of gain with 55 12sG7 pentodes, and the circuits 4, a. la, and I3 mutual coupling for the pair of circuits l8 and were tuned to an intermediate frequency of 1225 I8, the values of the condensers 26 and'21 being kilocycles when the switches I l and 28 were in - selected‘ to provide equal gain in a manner simi - their left-hand positions. The other values were lar to the selection of the two portions of the in I ductance l0. as follows: ' ‘ " - 'Inductances 8, 8, 2|, 24____'__'_- 85 microhenries Capacitors 1, 9, 20, 23_-___ 200 micromicrofarads The coupling between the primary and second ary circuits of each pair may be made entirely dependent upon the impedance of the coupling ' element by electromagneticallyand electrostati Inductance l0 ____ __ 1.8 microhenries, tapped at ' ' I _ 0.7 or 07.8 microhenrles cally isolating the _circuits of each pair from each c5 Capacitor 26____.._____-___.._____ .01 microfarad Capacitor 21_..___'_______ _'_ ____ .._ .05 microfarad other and from the ‘other circuits by suitable Resistor 38, 31 _____ _'. _______ __'_'_'_____ 3.3 ohms shielding indicated by dotted lines 40 and 41, the switches [I and 28 and the coupling reactances While the invention has been illustrated in con i0 and 26, 21 being located outside the shielding. nection with an intermediate frequency ampli?er The manner in which the circuit shown in Fig. 70 for a superheterodyne receiver, ‘other applica 1 operates toprovide a broad resonance band tions will readily be apparent to those skilled in width when the switches, II and 2,8 are in their the art. Therefore, it is not desired that the in right-hand positions is illustrated in Figs. 3, 4 vention be limited to the specific vcircuit arrange- and 5 which are selectivity curves, the frequency . - ment described and illustrated, and it is intend above and below the mean resonant frequency, 75, ed by the appended claims to cover all modiacas; 2,390,768‘ f ' ' ‘\ 3 means movable into one position for connecting tions within the spirit and scope of the invention. the other circuit of each of said pairs across a What we claim as new and desire to secure by predetermined portion of the corresponding one -of said elements in the pair and movable into a second position for connecting said other circuits to include a greater portion of each of therespec tive ones of said elements, said circuits being tuned to resonance when said selectively operable Letters Patent of the United States is: 1. A variable selectivity high frequency amplié ?er comprising in combination, ?rst and second pairs of tunable circuits, means for interconnect ing said pairs of circuits, a reactance of one sign connected in ‘one circuit of said ?rst pair and having a portion common to the other circuit of said ?rst pair for coupling said circuits of said ?rst pair, a reacta'nce of the opposite sign con ‘ means is in said ?rst position whereby in said 10 nected in one circuit of said second pair and hav ing a portion common to the other circuit of said second pair for coupling said circuits-of said sec , (and pair, said circuits being tuned to a predeter second position said other circuits are detuned oppositely to provide a broad over-all resonance bandwidth. ' - 5. A variable selectivity high frequency ampli ?er comprising in combination, ?rst and second 15 pairs of tuned circuits, each comprising a primary ’ mined resonance frequency, and selectively oper tuned circuit and a secondary tuned circuit, means for interconnecting the secondary circuit = actances common to said other circuits whereby of said first pair and the primary circuit of said said other circuits are detuned in opposite direc second pair, each of said pairs of circuits includ tions and the resonance bandwidth of said am 20, ing a reactance element connected in the primary pli?er is broadened, ‘ ' ‘ circuit and having a portion thereof common to 2. A variable selectivity high frequency ampli- ' both the primary and secondary circuits for di ?er comprising in combination, ?rst and second ‘rectly coupling the primary and secondary cir pairs of tunable circuits, means for interconnect cuits of each pair, one of said reactance elements ing said pairs of circuits, one of the circuits of 25 being an inductance and the other a capacitance, each of said pairs including a reactance element, and selectively operable means for varying said the one of said reactance elements in one pair - common portions of said reactance elements being inductive and that in the other‘ pair being. solelyby changing the portions of said elements capacitive, each of said elements having a por included in said secondary circuits whereby the tion connected in the other circuit of its respec 30 resonance bandwidth of said ‘amplifier .may'be able means for increasing the portions of said rc tive pair for directly~ coupling the circuits in each - pair, said circuits being tuned to resonance at a varied. ‘ , ' 6. A variable-selectivity high frequency ampli predetermined frequency, and selectively operable ?er comprising in combination, ?rst and second means for increasing the portions of said elements pairs of tunable circuits, means for interconnect common to said other circuits whereby both. said 35 ing said pairs of circuitsfone of the circuits of pairs of-circuits are overcoupled and said other each of said pairs including a reactance element, circuits are detuned in opposite directions to DI'O-r the one of said reactance elements in one pair vide an over-all broad resonance bandwidth. 3. A variable selectivity high frequency'ampli ?er comprising in combination, ?rst and second pairs of tunable‘ circuits, means for interconnect ing said pairs of circuits, one of the circuits of . each of said pairs including a reactance element, the one of said reactance elements in one pair be ing inductive and that in the other pair being ca pacitive, each of said elements having a portion connected in the other circuit of its respective pair for directly coupling the circuits in each ' pair, said circuits being tuned to resonance at a being inductive and that in the other pair being ‘capacitive, each of said elements, having a por tion connected in common with the other circuit of its respective pair for directly coupling the circuits in each pair, said circuits being tuned to resonance at a predetermined frequencyya re-> sistance element associated with each of said pairs of circuits, and selectively operable means for increasing the portions of said reactance elements common to said other circuits and for inserting the respective ones of- said resistance elements in said other circuits whereby both said pairs of predetermined'frequency, and selectively operable 50 circuits are overcoupled and. their resonance means for increasing the portions of said elements common to said other circuits to provide a broad er over-all resonance bandwidth for said ampli . bandwidths are broadened and said other circuits are detuned in opposite directions to provide an over-all bro'ad resonance bandwidth. " 7. A variable selectivity high frequency ampli ?er, the valuesof the common portions of said reactance elements being selected to provide over 55 ?er comprising in combination, ?rst and second coupling in one position of said selectively oper pairs of tunable circuits, each comprising a pri mary circuit and a secondary circuit, means for able means and less than critical coupling in the interconnecting the secondary circuit of said ?rst other position thereof and to provide a substan pair and the primary circuit of said second pair, tially constant ratio of input voltage to output voltage for both pairs of circuits in both posi 60 each of said primary circuits including a reac tions of said selectively operable means. ‘ tance element, the reactance element in one of 4. A variable ‘selectivity high frequency ampli said primaries being inductive and that in the other capacitive, and selectively operable cou ?er comprising in combination, ?rst and second pling means movable into one position for con pairs of tunable circuits, means for interconnect ing said pairs of circuits, each of said circuits in-, 66 necting a predetermined portion of each of said cluding a main, inductance and‘a main capaci elements in common. with the secondary circuit of its respective one of said pairs and movable into tance, means for electromagnetically and electro a second position for connecting a greater portion Istatically shielding the main inductance and ,main capacitance of each of said circuits, an inductive of each of said elements in common with the reactance element and a capacitive reactance ele 70 respective secondary circuit, said circuits being tuned to ‘a predetermined frequency when said ment arranged outside said shielding means, selectively operable means is in said one posi means for connecting one of said elements in one tion whereby said one- position provides a sharp circuit of said ?rst pair, means for connecting the other of said elements in the corresponding cir resonance bandwidth and said second position . cuit of said second pair, and selectively operable 75 provides a broad resonance bandwidth, the values 2,390,?” of the common portions of said reactance ele- ' ments being selected to provide substantiallyv equal ratios of output to input voltage for both pairs of circuits in both positions or said selectively operable means. 8. A variable selectivity high i’requency ampli fler comprising in combination, ?rst and second I pairs of tunable _gircuits, each of said pairs in cluding a primer‘? circuit and a secondary cir . , series with the main capacitance of the other of ' said primary circuits, both or said elements being arranged outside said smeldin's‘means. and selec tively operable switching means arranged outside 5 said shielding means and movable into a first position for connecting a predetermined portion 01.’ each 0! said elements in common with the _ ‘secondarycircuit 01' the respective pair and mov able into a second [position for connecting a cuit, means for interconnecting the secondary 10 greater portion of each of said elements in com mon with‘the respective secondary-circuit. said circuit of said ?rst pair and the primary circuit of said second pair, each of said circuits including a main inductance and a main capacitance, circuits‘ being tuned to resonance when said capacitance of each‘ of said circuits, an inductive , resonance bandwidth. switching means is in said ?rst position whereby means for electromagnetically and electro- ' in said ‘second position said secondary circuits are statically shielding the main inductance and main‘ 15 detuned oppositely to'provide a broad over-all reactance element connected in series with the main inductance of one of said primary circuits, a capacitive reactance element connected in Y 3. sperm. GEORGE o. YOUNG.