Sept. 24, 1946. w D. o. GRIEG 2,408,061 STABLE PULSE GENERATOR _ Filed Dec. 20, 1941 17/6” VOLMGE' - BY - DOA/ALP a 6/?76'6' _ . ‘Am , Patented Sept. 24, 1946 2,408,061 UNITED" STATES PATENT OFFICE 2,408,061 STABLE PULSE GENERATOR Donald D. Grieg, New York, N. Y.,‘ assignor to Federal Telephone and Radio Corporation, a corporation of Delaware Application December 20, 1941, Serial No. 423,862 2 Claims. (Cl. 250——'36) This invention relates to improved means for the generation of short impulses of relatively high energy and periodically recurrent. It is an object of the invention to provide rel atively simple means for the generation of im pulse energy. Another object is to provide an improved sta bilized impulse generator wherein it is not nec 2 of tube T1 to produce a sinusoidally varying volt age of the form shown in Fig. 2a. The remaining elements of tube T1 preferably form an ampli?er for amplifying portions of the voltage generated by the above—described oscil lator. Preferably, in accordance with the in vention, the suppressor grid of tube T1, which forms an effective control grid for the ampli essary to synchronize the generator to an ex ?er, is biassed below cutoff so that class C oper ternal frequency standard. A further ebject is to provide an improved 10 ation of the ampli?er results. It will be clear that the output of tube T1 will then comprise a impulse generator wherein the impulse frequency series of current surges or pulses, the duration’ is independent of load or supply-voltage varia tions. of which is determined by the degree to which the ampli?er portion of tube T1 is operated class It is also an object to provide an improved im pulse generator wherein the impulse width is 15 C, that is, the magnitude of negative bias ap constant over a range of supply voltage or load conditions. plied to the suppressor grid across the used por tion of resistance Rs. Preferably, this bias is relatively great so that only very short current A still further object is to provide an improved surges are derived in the output of tube T1. These impulse generator wherein the impulse recur rence frequency may be varied and the width 20 current surges may be of the form shown in Fig. 2b. of impulses at the same time maintained con In. accordance with features of the invention, stant in spite of such frequency variation. Other objects and further features of novelty _ the output of tube T1 is applied directly across an inductance L2. Now, when the above-men and invention will hereinafter be pointed out or will become apparent from a reading of the 25 tioned short pulses of current ?ow through in~ ductance L2, voltage surges of high value may following speci?cation in conjunction with the appear thereacross, as will be clear. Inasmuch drawing included herewith. In said drawing, as there is unavoidably some capacity associated Fig. 1 is a schematic diagram of a circuit in with inductance L2 and its associated circuit, the corporating features of the invention, and Fig. 2 illustrates graphically the progressive treatment 30 nature of the voltage pulses appearing across L2‘ will be damped oscillations, as shown for ex of wave forms in the circuit of Fig. 1. ample, in Fig. 2c. Broadly speaking, the invention contemplates ‘ Now, in order to obtain relatively high voltage pulses of short duration from these damped os-“t regularly recurrent current surges across an in ductance whereby correspondingly recurrent 35 cillations, I propose to use appropriate shaping means for eliminating all of the voltage varia damped oscillations are set up in the circuit of tions but the initial surge associated with these the inductance. Appropriate shaping means pulses. Several methods for so shaping the out thereafter serve to remove all of such oscilla put appearing across inductance L2 will naturally tions but the first current surge thereof. 40 occur to those skilled in the art. For example, Speci?cally, and in accordance with the pre it would be possible to shunt inductance L2 with ferred form shown in Fig. 1, an oscillator feeds resistance, thereby increasing the damping and an electron-coupled device to supply the reg further reducing any effect of the undesired volt ularly recurrent current ‘surges. In the form age variations. The objection to this method is shown, the circuit of this oscillator includes a 45 that the. initial pulse is likewise considerably vacuum tube T1 of known form having a cath reduced in amplitude, and at the same time its ode, control grid, screen grid, suppressor grid, and width at the base is substantially broadened due the generation of impulse energy by applying anode. The oscillatory circuit further comprises the parallel impedance combination of an in ductance L1, a variable capacitance C1, and an other capacitance C2. The frequency of oscil lation of this circuit is largely determined by the magnitudes of elements L1, C1 and C2, and this frequency may be de?ned as to the effect of such a shunt resistor on the time 50 constant of the damped oscillation circuit. In accordance with thejinvention, however, I propose to employ thermionic damping means shunted across inductance L2 in order to remove the undesired voltage variations following the 55 initial pulse. In the form shown, a diode T2 is connected across inductance L2, and a resistor R3 is preferably in series therewith to reduce the effect of the plate-cathode capacitance of the diode. The operation of such a connection will In operation the oscillator functions with the screen grid, control grid, and. cathode circuits 60 be readily apparent. Assuming the initial pulse across inductance Le to be positive, the cathode 2,408,061 3 . of diode T2 will be positive with respect to the plate thereof. No current will then ?ow through the diode, and the ‘diode shunting e?ect will be grid bias resistor R1, variation of supply voltage‘ will change the suppressor voltage proportionally, since these voltages are obtained across a common supply resistance. Thus, for any variations in these voltages, s bstantially constant pulse width tion immediately following the initial pulse, diode will result. It follows that the circuit described T2 will be conductive, thus effectively shunting is capable of generating stable pulses without inductance L2. The removal of a voltage surge any necessity of synchronization, as by external across inductance L2 in this manner immedi monitoring circuits. The circuit obviously has ately removes any cause for ,further and lesser the added advantage of simplicity of operation. voltage variations, It follows, therefore, that only 10 AlthoughI have described my invention in par single pulses corresponding to the initial surge ticular detail'in connection with the preferred of voltage across inductance L2 will appear across form shown, it is to be understood that many , inductance L2 when diode T2 is connectedas modi?cations may be made fully within the scope shown. It is to be noted that in the preferred . thereof. For example, if it is not desired to have form of eliminating the undesired voltage surges, a flexible variation of impulse frequencies, a crys the amplitude of the initial surge is not noticeably tal oscillator may be employedinstead of the affected, and successive lesser surges are com oscillator described. Such an oscillator would, of pletely eliminated. course, furnish a permanently reliable and stable Inasmuch as the width of pulse generated in pulse frequency, ' . the above manner depends upon the damped os Furthermore, time modulation of the pulses cillation frequency, any desired control over such generated bythe circuit described may be ob width (within limits, of course) may be effected tainedby the relatively ‘simple expedient of vary by varying a circuit constant within the damped ing some circuit constant in the damped oscilla oscillation circuit. For example, inductance L2 tion circuit in accordance with ‘an intelligence negligible. During the negative cycle of oscilla ' may be controllable in any known manner as in - dicated by therarrow traversing this element. - signal. ,Such modulation may be effected in a relatively simple manner, say by varying thelin ductance of L2 in accordance with the intelli gence signaLlas will :be clear. Appropriate output may be derived from the , above-described circuit by well known means. In the form shown, a so—called cathode follower VWhat I claim is: ' ampli?er circuit is employed. This ampli?er cir V 1. Pulse'generator comprising, in combination, cuit includes a vacuum tube device T3, and the a vacuum tube having control elements includ ing an anode, a cathode and a grid, and a high output pulses may be obtained therefrom in a load P1 across a low magnitude resistor R4 in the internal plate resistance characteristic, a tank cathode, ‘circuit of tube T3. In the form shown, circuit, means interconnecting said tank circuit 35 a coupling condenser C3 in the input circuit of with elements of said vacuum tube to produce tube T3 is preferably made small in order to re oscillations therein, an output circuit connected duce the shunting effect of the input to tube T3, between the vanode and cathode of said tube, and a grid resistor R2 is also small in order not to increase the width of pulses due to the above noted undesirable damping effect of excessive re sistance. It will be noted in connection with the pulse generator described that since the pulse frequency isdetermined solely by the sinusoidal oscillator frequency, the frequency of pulse output may be varied by appropriate control of the oscillator, as by varying condenser C1, for example. The am pli?er and oscillator sections of tube T1 are iso lated from each other with the exception of a coupling by the electron stream in this tube. It means biasing an element of said vacuum tube 40 , value relatively small compared with the internal resistance of said tube, alum-directional recti?er - connected in shunt with said inductive reactor, means deriving induced voltage pulses from said reactor when said current surges from said vac uum tube are impressed thereon, and means to produce the maximum voltage pulses possible from the time duration of the applied current surges, comprising means varying the bias of the vacuum tube element and means varying the tun follows that the pulse generator will have the desirable feature that variation in load output may not affect the pulse frequency. Furthermore, in accordance with well known methods, the oscil . ing of saidreactor. lator may be made to supply a frequency sub stantially independent of supply voltage by proper adjustment of the cathode tap on inductacne L1 and adjustment of the screen grid voltage by po tentiometer R1. to sucha value as to produce periodically recur rent currentsurges in said output circuit, a tun; able inductive reactor serially connected in said output circuit, said reactor having a resistance For any ?xed value of control A - 2. The combination according to claim 1, ‘in whichsaid ‘vacuum tube includes a suppressor ‘grid, and said biasing means includes means for varying the bias on said suppressor grid. ' DONALD D. GRIEG.