Патент USA US2411166код для вставки
Nov. 19, 1946. Rl H_ QLSON 2,411,166 FREQUENCY MULTIPLIER Filed Oct. 2, 1942 2 Sheets-‘-Sheet l 6 //. //d ? Z6 1559.2 I /J =34’ Z? 2% V‘ U 36 UU Z695 a - I ' 171067555", Nov. 19, 1946. R, |-|_ CLSON 2,411,166 FREQUENCY MULTIPLIE'R Filed Oct. 2(1942 '0 I 2 Sheets-Sheet 2 . J7Zv67z757". 17%;? also/'7, Patented Nov. 19, 1946 Lilhltt UNETED STATES PATENT OFPEQE 2,411,166 FREQUENCY MULTIPLIER Roy H. Olson, Marion, Iowa, assignor to Collins Radio Company, a corporation of Iowa Application October 2, 1942, Serial No. 460,560 10 Claims. (01. 250-36) 1 2 This invention relates to a frequency mu1ti~ plier, and more particularly to means for mini~ phase to the undesired variations in the harmonic mizing undesired voltage variations at funda~ mental frequency. put circuit as viewed from the tube to present considerable capacitative reactance at the funda One feature of this invention is that it provides output. This is accomplished by causing the out mental frequency. an improved output for driving a class C ampli?er In the particular embodiment of my invention from a frequency multiplier, particularly where illustrated in Figure 1, a tube lEl andxits asso the frequency multiplier is operated at a higher ciated circuits provide oscillations at a desired order of multiplication as, for example, quad fundamental frequency. The tube ii and its rupling; another feature of this invention is that 10 associated circuits comprise the multiplier stage. it minimizes or eliminates undesired frequency The oscillator output is coupled to the grid circuit components or variations in the desired multiple of the multiplier stage and causes periodic pulses frequency component in the output of the class C of plate current in the multiplier stage, being ampli?er operating from a frequency multiplier under conditions where such variations are trans ferred by the circuit tuned at multiple frequency; sufficiently biased to work as a class B or class C 15 ampli?er, in accordance with conventional multi~ plier practice. The output circuit of the tube E 1, still another feature of this invention is that it includes a tank circuit comprising the induc enables the use of the same variable inductance tance I2 and the condenser i3 in parallel, this with different ?xed condensers for different orders being tuned to any desired harmonic, as the of multiplication from an oscillator of limited 20 fourth. This circuit, then, presents inductive re frequency range without the output of a class C actance to a lower frequency, as the fundamental, ampli?er driven from the frequency multiplier and to overcome this and cause the output circuit containing undesired frequency components nor~ to present capacitative reactance at the funda mally present due to the lower Q values in the metal frequency, a, condenser M is connected in frequency multiplier tank circuit at the higher 25 series with ‘the tank circuit. This condenser multiplications such as quadrupling; and other should have a capacity somewhat less than that‘ features and advantages will be apparent from which would be required for series resonance at the following speci?cation and the drawings, in the fundamental frequency, preferably having a which: capacity such that its reactance exceeds that Figure l is a circuit diagram of one embodiment 30 of the tank circuit at fundamental frequency by a fraction of one over the order of multiplication, of my invention; Figure 2 is a schematic repre but is less than the order of multiplication at sentation of decaying voltage oscillations; Fig which the stage is operating times such tank ure 3 is a schematic representation of plate cur circuit reactance, less than four times in the rent pulses in a multiplier stage; Figure 4 is a schematic representation of the fourth harmonic output of a multiplier stage with the peak Values Varying periodically at fundamental frequency; quadrupler here being described. I have found in a particular case that best’ results are secured, in a quadrupler, with a condenser having a ca pacity of approximately one-third of that which Figure 5 is a schematic representation of plate would be required for series resonance with the current variations at fundamental frequency, and of voltage variations in the output circuit nor 40 tank circuit at fundamental frequency. mally associated therewith; Figure 6 is a sche Where it is desired to tune the tank circuit matic representation of the undesired accentua of the multiplier stage, as is usually the case, tion of the variations of the positive peaks; and best results are secured by tuning by inductance Figure 7 is a schematic representation of the variation where the condenser M is a fixed con» output from a quadrupling stage embodying my 45 denser, as this tends to best keep the proper ratio invention, showing elimination of variation in of values between the circuit elements over a the crest values of the positive peaks. reasonable band of frequencies. The output of The output of higher order multiplication stages, particularly quadrupling stages where the multiplier stage is coupled to the input cir cuit of a succeeding tube 15, and since it is the higher values of effective reactance to resistance 50 crest values of the positive peaks of the harmonic ratio is used in the tank circuit or ‘Where the oscillations which are leveled 01f, this succeed decay of the circuit is high, has heretofore con~ ing tube must be sufficiently biased so that its tained periodic variations‘ at fundamental fre operation is not affected by the negative harmonic quency which could not be minimized or elimi peaks. That is, there is still variation in the nated. I have found that these periodic unde-‘ 55 negative peaks of the harmonic output, as will sired variations can be completely eliminated or be more fully described later, but operating the minimized to a negligible value by combining succeeding stage with the proper cutoff value with the harmonic output another voltage vary eliminates any difficulty with these variations. ing at fundamental frequency and being sub In the particular circuit shown, the induct stantially equal in amplitude and opposite in 60 ance l6 could have a value variable between 2411,166 4 3 oscillator arrangement employed, or the oscil- . about 40 and 60 microhenries, and condensers I‘! and I3 values of about 800 mmf., providing for some variation of the oscillator frequency in the neighborhood of one megacycle. Conventional values would be used for the coupling condensers I9 and 20, the grid leak 2|, and the radio fre quency choke 22 connected'to the plate voltage this specification and the accompanying claims, supply. the theory of operation of the present invention, lator and multiplier stage combined in a single tube. Moreover, as the word “plate” is used in it is intended in a broad sense covering any anode element as a screen grid operating as an anode. Figures 2 to 7 are intended as illustrative of The tube It is illustrated as a triode, and this will be described in connection with a as type 801 having cathode, grid and plate ele~ 10 quadrupler.‘ When the periodic energy pulses at ments Illa, lilb and I00. oscillator fundamental frequency energize the The output of the oscillator is ‘coupled through tank circuit in the multiplier output, fourth har a condenser 23, which may have a value of 500 monic oscillations are induced, and the peak val mmf., to the input circuit of the tube II, here ues ‘of these oscillations decrease, as is illustrated in Figure 2. This ?gure is not intended as an illustrated as a type 802 pentode having an in directly heated cathode element I Ia, control, . screen, and suppressor grid elements Ilb, H0, and Ild, and a plate element He. The grid leak 24 should have a value considerably higher than that usually associated with such a tube, prefer accurate representation, since the peak variations follow an exponential decay curve; but it does illustrate what happens when a very brief energy pulse is admitted periodically to a tank circuit ably between 50,000 and 200,000 ohms. The by 20 of reasonably good Q tuned to four times the energy frequency. The decay per oscillation is given by the formula have conventional values, as .002 mi. and 20,000 ohms. Where the multiplier stage is to operate as a quadrupler, the inductance I2 may have a value variable between about 9 and 14 microhenries, 25 where R'is the resistance and L the inductance of the circuit. Since t=1/F, and since and the condenser I3 a value of about 110 mmf. for this inductance. These values may, of course, be varied with relation to each other; but the tank circuit must be tuneable through a band of 30 substituting gives frequencies four times that of the oscillator, the pass condenser 25 and screen grid resistor 26 may D=e_2_Lt band having a corresponding range. It will be D=e understood that, in accordance with conventional Q practice where the transmitter is intended to op Using this formula, the decay for a given num erate in a number of different hands, a plurality 35 ber of cycles would be K times the power in this of condensers I3 of different values may be pro formula, so that where the circuit is tuned to vided and selectively connected into this circuit. the fourth harmonic, the amount of decay in the These may provide different multiples of the same ‘crest values of the positive peaks, before another frequency, or the same multiple of widely dif energy pulse is received, is given by the formula ferent fundamental frequencies. Condenser M, 40 t 41 ‘in. connection with a tank circuit having a Q of about 50 and the values stated, would have a D=e Q In a quadrupler where the tank circuit has a Q of 50 at the harmonic frequency, it will be " seen that the decay for four cycles, in accordance with the above formula, is from whatever the ini tial crest value was to .777 of such value. This ate value may be used to connect the plate to a is a substantial change, amounting to about 20% plate voltage source 28. modulation of the harmonic oscillations at fun The output of the multiplier tube i I is con 50 damental frequency; and this modulation is an neoted through a coupling condenser 29 to the undesired-variation which goes through with the capacity of about 830 mmf. This condenser value is not sharply critical, although the closer it is held to the calculated value, the more complete ly undesired positive peak variations are elimi nated. A radio frequency choke 27 of appropri~ grid circuit of the tube I5, here schematically harmonic oscillations and is produced rather than eliminated by the tuned tank circuit. illustrated as a triode, although in commercial practice this would normally be a multi-element Where the multiplier stage is being operated tube, the present representation being intended 55 with an angle of ?ow of about 180 degrees, the as a generic one. This tube 15 might comprise plate current pulses are as illustrated in Figure 3. If a situation is conceived where these plate cur part of another multiplying stage, again multi plying the output of the tube I I ; or it might com, rent pulses delivered energy to the tank circuit prise an intermediate stage between the multi without any variation in the plate voltage at fun plier and the power ampli?er of a transmitter. 60 damental frequency, that is, where the tank cir If operating as another multiplier stage, another cuit presents zero impedance at fundamental fre type 802 might be employed with circuit con~ quency, there would be a situation like that illus nections similar to those of the tube I I; and if as trated in Figure 4, with the harmonic oscillations an intermediate ampli?er, a beam power tube 30 swinging about a ?xed voltage base line here such as a type 813 tube might be used. In either 65 indicated as 3|, with upper and lower envelope case, it is essential that this stage be operated curves 32 and 33 resulting from the decay modu as a class C ampli?er, that is, that the control lation effect. Because of the decay action, the grid be provided with su?icient negative bias that bottom or minimum point of the modulation the negative grid voltage peaks are all below the curve 32 occurs approximately at the point of cutoff level. 70 zero plate current flow, and the positive peak of It will be understood that the preceding detailed this modulation envelope occurs approximately description of the circuit of Figure 1 is intended at the point of zero plate current flow 90 degrees as illustrative only, since this invention may be in phase after maximum current, Figures 3 and 4 showing the relationships in this regard over two embodied in any number of different circuits. Different type tubes might be used, a different 75 cycles. > ' ' , ‘ 5 2,411,166 The plate voltage, however, does vary at the fundamental frequency, this being illustrated in current is substantially independent of plate voltage, and the control grid current is negligible, the plate current is- given by the formula Figure 5 where the line 34 indicates current flow in the output circuit at fundamental frequency, the amplitude shown in Figure 5 being approxi where Eg is the control grid voltage, Esg the mately in correct relationship to the harmonic screen grid voltage, [.Lsg the voltage ampli?cation oscillations 36 shown in Figure 4. Under output circuit conditions heretofore employed, the out factor of the screen grid, k the tube constant, and a, a constant between 1 and 2 and normally put circuit presents inductive reactance to the about 1. An explanation of the theory behind fundamental frequency, and therefore plate volt this formula, and of‘ the relationship between age variations, indicated by the line 35, are ap current harmonics at various frequencies, is proximately 90 degrees ahead of plate current contained in an article by Terman and Ferns in flow. It should be noted that, even though a by pass condenser has heretofore been frequently the March, 1934, Proceedings of the Institute of used in the output of a multiplier stage, this con 15 Radio Engineers, volume 22, No. 3, and will not be gone into here. denser has always had such a large capacity (in Where the voltage applied to the grid of the order to provide low impedance to ground) that tube consists of ‘a ?xed negative bias Ec- and an the reactance of the output circuit has always alternating potential of crest amplitude Es and been inductive, even when such a condenser was employed. angular velocity w, as is the case in a frequency The result of combining the crest voltage varia multiplier stage actuated by an oscillator, this formula becomes tions illustrated in Figure 4 with the plate volt age variations at fundamental frequencies has always heretofore resulted in accentuating the By Fourier analysis, the components of the positive peak variations of the harmonic oscilla 25 plate current at various frequencies can be de tions, as illustrated in Figure 6, giving an unde termined for various angles of current ?ow. sirable amount of fundamental frequency in the Where a. is 1 and the angle of ?ow is about 180 output of the stage. By making the total re degrees, the ratio of the fundamental crest value actance of the tuned output circuit capacitative, however, the phase of the voltage variation 35 30 to that of the fourth harmonic will be found to be about 12.5. Whether this ratio is derived at fundamental frequency is shifted approxi theoretically by this formula, or by direct meas mately 180 degrees, so that it is out of Phase urement and analysis of the plate current, this rather than in phase with the crest or positive relationship and the circuit Q can be used, in peak value variations of the harmonic oscilla connection with the particular decay being en tions 30. This tends to reduce rather than to in countered, to provide a formula for the amount crease such undesired positive peak variations of capacitative reactance necessary. The caused by the decay modulation effect, and if voltage developed at a given harmonic K is, of the amplitude of the voltage variation 35 is prop course, a function of the current flow at that erly adjusted and the phase relation is exactly correct, variation in the’ positive peaks will be 40 harmonic times the impedance of the tuned cir completely eliminated and the positive crest ' cuit at that harmohic, so that values of the harmonic oscillations 30 will all be equal, as shown in Figure 7. In practice, the phase relations will not be exactly correct, since the crest value of the envelope 32 and 33 will not necessarily occur 90 degrees out of phase with the crest value of the plate current pulse where Q is the reactance-resistance ratio of the tank circuit at the harmonic frequency, and XL is the reactance of the inductance at the funda mental frequency. The voltage at the fundamental frequency is also equal to the current times the impedance, practice, however, and positive peak variations ‘of 50 and is given by the formula the harmonic oscillations reduced to a negligible EFT-I amount. It will be noted that there is consid erable variation in the negative peaks of the har where X0 is the reactance of the condenser [4. monic oscillations illustrated in Figure 7, but Since the peak value of the variation of this these are completely wiped out by biasing the 55 fundamental voltage above and below its center grid of the succeeding tube to such a point that line should be equal to one-half the total decay the cutoff level is above all of these negative of the harmonic oscillation peaks, peaks, as for example, on line 36 in Figure '7. The amplitude of the voltage variations at fun 34. The theoretically perfect result illustrated in Figure '7 can be very closely approached in IG-FXC) damental frequency (illustrated as 35) can be 60 adjusted to equal the positive peak voltage varia tions of the harmonic oscillations by varying the Equating the two functions which are equal to value of the condenser l4, and thus the amount Er, with a negative sign before one to indicate of capacitative reactance, since the voltage devel proper phase relation, solving for Xe, we have oped in the output circuit is a function of the 65 current and the reactance through which it flows. l—~e Q 1K K2 While I have determined that the capacity of the condenser should preferably be such as will provide a reactance somewhat greater but less X““[(—2‘—)TKQ+T€2Ti]XL If Q is taken as 50, a value which may be than the multiplication factor times the induc 70 normal in practice, andthe angle of ?ow is 180 degrees, so that the ratio of Ix to I is as 1 is to 12, tive reactance of the tank circuit at fundamental frequency, therequired capacitative reactance in any given case can be mathematically deter and where K is 4 (quadrupling), the portion of the equation in the large parenthesis will be seen mined. to work out to a fraction over 3. 4 This is con In a pentode vacuum tube, when the plate 75 ?rmed by the experimental determination that 2,41 1,166 the capacity of the condenser It should be sub stantially less than that which would provide series resonance at the fundamental frequency, .preferably such that the capacitative reactance provided by the condenser l 4 is about three times and X1. is the reactance of the tank circuit induc tance at said fundamental frequency. 5. Apparatus of the character claimed in claim 1, including means for varying the period of said pulses, and wherein said tank circuit includes a variable inductance. 6. The method of minimizing undesired periodic variations, at fundamental frequency, in the posi tive voltage peaks of the harmonic output of a the inductive reactance of the tank circuit at the fundamental frequency. It is believed that the foregoing is a correct explanation of the theory and a correct mathe matical determination of the Various factors con 10 frequency multiplier, comprising combining therewith an alternating voltage of said funda sidered. Whatever the theory and mathematics mental frequency substantially equal in amplitude may be, however, there is no question that un but opposite in phase to said periodic variations. desired variations, at fundamental frequency, in 7. The method of minimizing undesired periodic the positive peaks of the harmonic oscillations are minimized to the point of substantial 15 variations, at fundamental frequency, in the posi tive voltage peaks of the harmonic output of a elimination by the use of a condenser in series frequency multiplier, comprising combining with the tank circuit and with a capacity low therewith an alternating voltage of said funda enough to provide a reactance substantially ex mental frequency substantially equal in amplitude ceeding that of the tank circuit at the funda but opposite in phase to said periodic variations, mental frequency. , and eliminating the negative peaks of the com‘ While I have shown and described certain bined voltages. embodiments of my invention, it, is to be under 8. The method of minimizing undesired periodic stood that it is capable of many modi?cations. variations, at fundamental frequency, in the Changes, therefore, in the construction and ar rangement may be made without departing from 25 positive voltage peaks of the harmonic output of a frequency multiplier, comprising using the the spirit and scope of the invention as disclosed current at said fundamental frequency to create in the appended claims. an alternating voltage substantially equal in am I claim: plitude but opposite in phase to said periodic 1. A frequency multiplier of the character de variations, combining said alternating voltage scribed, including: a tube having at least cathode, with the harmonic voltage, and eliminating the grid, and plate elements; means for causing negative peaks of the combined voltages. periodic pulses of plate current at a certain fre quency; and an output circuit connected to said plate, said circuit including a tank circuit tuned 9. A frequency multiplier of the character de scribed, including: a tube having at least cathode, to a multiple of said frequency and a condenser 35 grid, and plate elements; means for causing in series with said tank circuit, said condenser having a capacity such that its reactance at said frequency is at least one divided by said multiple periodic pulses of plate current at a certain fre quency; an output circuit connected to said plate, said circuit including a tank circuit tuned to a multiple of said frequency and a condenser in greater, but less than said multiple times, that which would provide series resonance with the 40 series with said tank circuit, said condenser have ing a capacity such that its reactance at said fre tank circuit at saidfrequency. quency is greater than that which would be re 2. A frequency multiplier of the character de quired to provide series resonance at said fre scribed, including: a tube having at least cathode, quency; a second tube having at least cathode, grid, and plate elements; means for causing periodic pulses of plate current at a certain fre 45 grid and plate elements; a grid circuit for said second tube coupled to said output circuit; and quency; and an output circuit connected to said means providing a negative bias on the grid of plate, said circuit including a tank circuit tuned the second tube such that the negative peaks of to four times said frequency and a condenser in the grid voltage variations’ are all below cut-oif series with said tank circuit, said condenser hav ~ ing a capacity such that its reactance at said fre 50 level. 10. A frequency multiplier of the character de quency is substantially three times that which scribed, including: a tube having at least cathode, would provide series resonance with the tank cir grid, and plate elements; means for causing cuit at said frequency. periodic pulses of plate current at a certain fre 3. Apparatus of the character claimed in claim 1, further including: a second tube having at 55 quency; and an output circuit connected to said plate, said circuit including a tank circuit tuned ,least cathode, grid, and plate elements; a grid to a multiple of said frequency and a condenser ‘circuit for said second tube coupled to said output in series with said tank circuit, said condenser circuit; and means providing a negative bias on having a capacity such that its reactance Xe at the grid of the second tube such that the negative peaks of the grid voltage variations are all below 60 said frequency is substantially equal to that deter cut-off level. 4. Apparatus of the character claimed in claim 2, wherein said condenser has a capacity such that its reactance Xe at said frequency is sub stantially equal to that determined by the formula 65 mined by the formula ’ where K is said multiple, Q is the ‘reactance resistance ratio of the tank circuit at the multiple frequency, Ik divided by I is the ratio of the crest values of the multiple and fundamental fre where Q is the reactance-resistance ratio of the 70 quency current components, and X1. is the reac tank circuit at the multiple frequency, I4 divided tance of the tank circuit inductance at said fundamental frequency. by I is the ratio of the crest values of the multiple and fundamental frequency current components, ROY H. OLSON.