Feb‘ 2'2, 1944- J. A. RANKIN 'ETAL - 2,342,492 .

‘ ' ULTRA-j-iIGH-FREQUENCY AMPLIFIER '

Filed April 4, 1942 >

14/14/341

' INVENTOR c/aHlv A RANK/IV. ' 14? THUR E. NEWL 0N

TTORNEY , Patented Feb. 22, 1944 ' 2,342,492,

2. UNITED STATES‘ PATENT omcs

’ I I ULTRA-lllGll-Fiztiggrqclf AMPLIFIER - I i I John’A. Rankin, Port Washington, and Arthur E. Newlon, Rochester, N. Y.I assign ors to Radio a Corporation of America, a corporation of Dela ware Application April 4, 1942, Serial No. 437,638 ‘

6 Claims. (Cl. 179-471) ‘ I , This invention relates generally to ultra-high pended claims. ‘The invention itself, however, frequency ampli?ers for operation at such high . both as to its organization and mode of oper frequencies that the conductance of the input ation together with further objects and ‘advan circuit of the ampli?er is an appreciable factor . tages thereof will best be understood by reference in determining the response characteristic of the to the following description taken in connection stage. with the accompanying drawing in which the It is well known that circuits using convention single ?gure illustrates an ultra-high frequency al vpentode- tubes, while having satisfactory per- ‘ ampli?er embodying the invention. formance at low and medium-high frequencies, Referring to the circuit shown in the draw have certain drawbacks at frequencies in excess l0 ing, T is a tube known as a pentagrid-converter of about 10 me. For example, such tubes ex and is provided with a K, successive ‘grids hibit a low positive input conductance as a result G1 - ->- to G5 and a plate P. The tube of transit time losses and'the effect of which is T may be of the type presently known °as the toload the tuned circuit connected to the sig “6A8,” although other types such as the “6K8” nal grid of the tube. - The input loading is made‘ and "6SA7” may also be successfully used. manifest by a decrease in the gain and selectivity Signal frequencies from a suitable source such of the circuit. ~ . ‘ as the antenna A which may be a dipole or According to. the invention the input loading ' other type are transferred through the coupling of the tube employed in an ampli?er circuit is coil B to the tunable input circuit’ Ii which is not only reduced, but bya proper choice of oper connected to the signal inputvgrid G4. ating conditions is made negative in sign. The output circuit I0 is resonant to the same It is therefore an object of the invention to. signal frequency is as the input circuit Ii and is provide an improved ultra-high-frequency‘ am connected through the couplingcondenser C to pli?er stage, the response of which is not sub the plate P. Positive potential is supplied to the stantially limited by the‘ input conductance of 25 plate through a choke coil CH and to the screen the tube included in the stage. - grids G3, G5 by way of the resistance R. Suit Another object is to provide a pentagrid- or able condensers C1 and C: for by-passing radio oscillatoreconverter to function as an RF am frequencies to ground are connected to the screen pli?er of frequencies above about 10 inc. in order grids and to the plate. The signal - to obtain high antenna circuit gain‘ andfselec 30 G4 is supplied with a bias derived from an A. V. C. tivity and in which the input loading is effectively source through the conductor L, and if desired a reduced or even made negative. ?xed or other bias maybe employed. The out A further object is to" operate'a pentagrid-' or put of the ampli?er may be coupled to a second oscillator-converter as an RF ampli?er in a man similar R.v F. ampli?eror else to a converter stage ner such that at frequencies above about .10 me. 35 of conventional design, bias to the signal control ' itsperformance is 'far superior to that obtain grid of the second ampli?er or converter being able with the conventional tube. ‘ similarly supplied. The condensers C3 serve to - In superheterodyne receivers the use of an provide a radio frequency path for the signal oscillator-converter tube and circuit is known frequencies in the tunable circuits I1 and 10. to produce aninput conductance which may be 40 The cathode K, ?rst or oscillator grid G1 and . negative‘ thereby effectively reducing losses in second or oscillator -grid G2 constitute the the circuit connected to the input, terminals of oscillator section of the tube‘. The oscillator the oscillator-converter. . _ which for the purpose of illustration is shown to According to the present invention, however, be of the‘ Hartley type comprises a. ?xed-tuned we make useyof the above phenomenon by em 45 circuit 0 resonant to the oscillator frequency in. ploying a converter-oscillator as the radio fre It will be understood of course that other forms quency ampli?er in an ultra-high frequency of oscillators may be used equally aswell without receiver to obtain greater gain and selectivity in departing from the invention. The oscillator the ?rst tuned circuit.’ The oscillator portion of grid G1 is connected through the grid condenser the tube needinot be tuned and may be at some 60 Cg to‘ the high potential side of the circuit 0. frequency suf?ciently removed from the signal The cathode K is tapped to an intermediate point -, and I. F. frequencies so as not to introduce on the'coil of the circuit 0. The grid spurious responses. _ 'R¢.i_s connected between the ‘oscillator grid G1 The novel features characteristic of our inven-q and cathode, the combination of C; and R; pro tlon are set forth with particularity in the ap viding suitable operating @as for the grid \Gl. 2 2,342,492 The G: serves as the oscillator anode and with re region contribute ai‘positive component to the spect to high frequencies is connected to ground input conductance. . through the condenser Ci. As heretofore stated The net input conductance of the tube will the oscillator section of the tube is adjustedv depend in sign and in magnitude upon the rela to oscillate at some frequency remote from the li tive importance of the two effects operating simul signal and I. F. frequencies. Unlike the local taneously within the signal-grid-screen space.‘ oscillator in superheterodyne receivers, the fre The average potential of the signal grid will affect ' quency of the oscillator circuit‘ above described the distribution of electrons within the signal is not varied with’tuning, but rather it is adiusted grid-screen space, and the avierage vpotential of to a fixed value, preferably outside the frequency l0 the oscillator-grid will determine the number of rarige of the received signals. Its- only purpose electrons passing through the screen. Therefore, is its effect in the production of negative input ' the bias on the oscillator grid and that on the conductance, the theory of which wilinow be , . signal. grid will both affect the magnitude of the described. _ t I‘ ' . input conductance. However, the Qscillator fre The space current between Grand G3 is rela-‘ quency no effect upon the magnitude of the tively independent of the bias on the signal‘ grid, input conductance. “ i G4, due to the interposed screen, Ga. That is to ' For purpose of comparison there is given in the say the sum of the currents in the plate P and the following table the values of input conductance at screens G3 and G5 is relatively constant. The ' speci?ed frequencies of the 6A8 and 6J7, con electrons passing through G: will be subject to the 20 verter and pentode tubes, respectively. influence of G4, and at some high negative bias on G4 will be completely ‘prevented. from passing I 6A8 ‘ 6J7 through this grid, resulting in- plate-current cut oil‘ as in the ordinary . "However, as the Anode volts ______'_; ..... ______- 250 .‘ 250 negative bias on G4 is decreased, from some high Screen volts: ~ ' -, ~ \ - a 1 v value the plate current will not increase linearly Gzof657 ______'______._'., .;..‘_._. 100 because the supply of'electrons getting'through Signal grid bias _ _ . . _ _ . _ _ _ _ . . ______._ *3 ;-—3 Osc. grid voltage (G: of 6A8.» ' ...... _ , , ,250 .r ____ .. G3 is limited. ‘ ' ‘V Input conductance at'5 mc_. .unihos +.'25‘ +2. 75 This limitation is brought about as follows: Input conductance at 10 mc..-_. __.do.;_ _ ~ +2. 0 +8. 0 The potential of the oscillator grid G1 ‘and the 30 Input conductance at 20 me ______. .7 .__l.rio__.._| -—l4. 0 +26. 0 anode-grid G2 exert the primary in?uence in determining how many electrons shall be avail l Supplied through 20,600 ohm dropping resistor. I I _ v, able for the plate. ' The grid Ga by virtue of its While we have shown and described a preferred potential and its position will draw some value of embodiment of our invention, it will be under current, which current will be relatively inde 35 stood that modi?cations and changes may be pendent of the potential of G4, with the remainder made without departing from the spirit and scope of the current passing to the plate. Therefore, of our invention, as will be understood by those by a proper choice of potentials for-v G2 and G3 skilled in the art. ' there will be a scarcity of electrons on the G4 side ‘ What we claim is: of G3 for some range of ‘potentials on G4 (low 40 1. A high frequency ampli?er circuit compris values of negative bias). This de?ciency of elec ing a tube provided with a cathode, a plurality trons will cause the‘Ip vs. En4 characteristic to of grid and an anode, an input cir ?atten out at low negative bias values on G4. cuit resonant to a desired signal frequency con Then, with electrode potentials selected to cause nected to one of the grids, said input circuit an electron de?ciency in the G3——G4 space over a having appreciable conductance at the operating certain range of bias values on G4, we may say to frequency, means connected to certain of the a ?rst approximation that the current passing tube electrodes constituting a generator of oscil through G3 is constant with respect to the poten-. lations at a frequency remote from the signal tial of G4 over that restricted range of operation. frequency for reducing said input conductance, Expressing this in the form of an equation we and an output circuit resonant to the signal fre quency connected to the an de. ave, ’ 2. A high frequency amp er circuit compris I=kpv era constant ing a tube provided with a cathode, a plurality where, ' ' of grid electrodes and an anode, an input cir 11=charge per unit volume, (negative) cuit resonant to a desired signal frequency con v=velocity of electrons in that volume . nected to one of the grids, said input circuit hav k=a constant ing appreciable conductance at the‘ operating frequency, circuits connecting the cathode and” Now, if the signal grid potential G4 increases, the certain of the other grids constituting a genera velocity‘ v of the electrons in the space between G: '00 tor of oscillations at a frequency remote from and G4- will increase, and the charge p will ‘de the signal frequency for reducing said input crease. This decrease in charge in the Ga-G4 conductance, and an output circuit resonant to space will cause electrons to ?ow into the signal .. the signal frequency for reducing said input grid, or current to flow out. Thus, an increase in 3. A high frequency amplifier circuit compris potential of the signal grid is accompanied by a change of opposite sense in the current in that ~ ing a tube provided with a cath0de,'_a plurality of grid- electrodes and an anode, a resonant in electrode, which condition is the criterion for put circuit tunable through a range of desired negative conductance. signal frequencies connected to ‘one of the grids, The electrons moving in the space G4--G5 dur said input circuit having appreciable conduct- ing the increase in potential of the signal grid ance at the operating frequency, circuits con will- suffer a decrease in velocity, which will be necting the cathode and certain of. the other accompanied by an increase of unit charge in this grids constituting a generator of oscillations at region.‘ The increase in charge in this space will a ?xed frequency remote from the signal fre cause electrons to flow out of the signal grid, or quency forreducing said input conductance, and current to flow in. Thus, the electrons in ‘this a resonant output circuit tunable through said 2,842,492 3 range of signal frequencies connected to the ance, said means comprising circuit elements connected to the oscillator control grid and anode: ' ' , 4. A circuit for the ampli?cation of frequen anode-grid for producing oscillations at a fre vcies above about '10 megacycles comprising a quency su?iciently removed from the received tube having at least a cathode,' signal control signal frequency so' as not to introduce spurious, grid and an anode, input and output’ circuits response in the output circuit. . resonant to the same frequency connected re 6. An‘ ultra-high frequency ampli?er for fre spectively to the signal grid and anode, and quencies above about 10 megacycles comprising means for preventing loading of the input cir a tube having at least a cathode, an oscillator cuit by operating the tube with a negative input control grid, an oscillator anode-grid, a screen conductance, said means comprising _a plural grid, signal control ‘grid and an output anode ity of additional electrodes within the tube and‘ arranged in the order named, input and output circuit elements connected thereto for produc circuits resonant to the same frequency connect-v ing ‘oscillations at a frequency“ suiliciently re ,ed respectively to the signal control grid and moved from the signal frequencies to be ampli '15 anode, circuit elements connected to the oscil ?ed so as not to introduce spurious response lator control grid, anode-grid and cathode for in the output circuit. producing oscillations at a frequency outside the 5. A circuit for the ampli?cation of ultra-high range of the received signal frequencies, the po frequencies, above about 10 megacycles, compris tentials on the oscillator anode-grid and _ the ing a tube having at least a cathode, an oscilla 20 screen grid being so chosen that the tor control grid, an oscillator anode-grid, a_' between the signal control grid and the screen screen grid, a signal control grid and an output grid is such that an increase in signal grid po anode arranged in the order named, input and tential is accompanied by a. change of opposite output resonant circuits tunable to the same sense in the signal grid current, whereby the tube signal frequency connected respectively to the 25 input conductance assumes a negative value. signal control grid and anode, and means for preventing loading of the input circuit by oper JOHN A. RANKIN. ating the tube with a negative input conduct ARTHUR E. NEWLON.