US2833990A - Controlled oscillator means utilizing gated-beam tubes - Google Patents

Description

May 6, 1958 J. D. VAN TILBURY 0 CONTROLLED OSCILLATOR MEANS UTILIZING GATED-BEAM TUBES Filed Nov. 21, 1955 3 Sheets-Sheet 1 50022: Or FREQUENCY INVENTOR.

Iacx D. I/AN 7715012) w im Ar roRNE vs May 6, 1958 J. D. VAN TILBURY 2,833,990

CONTROLLED OSCILLATOR MEANS UTILIZING GATED-BEAM TUBES Filed Nov. 21, 1955 5 Sheets-Sheet 2 PULSE SOURCE flunlo INPUT IN VEN TOR.

Jack D. Mq/v Tizsunv BY May 6, 1958 J. D. VAN TILBURY Filed Nov. 21, 1955 3 Sheets-Sheet 3 Iza5fC) iii INVENTOR. Jack D. Jwfizsmz M a ll J ATTORNE ys United States Patent CONTROLLED OSCELLAT-DR MEANS UTILIZING GATE-BEAM TUBES Application November 21, 1955, Serial No. 548,028

Claims. (Cl. 332-45) This invention relates to a versatile gated-beam oscillator, and teaches how such oscillator may be adapted for many particular uses, such as, frequency division, frequency modulation, and gated oscillation.

The invention requires a gated-lbeam electron tube, which, for example, might be a type generally designated in the electronic industry as a 6BN6 vacuum tube. A basic operational difierence between the gated-beam tube and a more conventional tube is that the former has a relatively constant cathode current which is not substantially affected by the voltage applied to its. grids, while the latter has its cathode current varied by an alternating voltage received on its control grid.

The gated-beam tube used herein difiers structurally from more conventional vacuum tubes in that the gated beam tube has an accelerator electrode and does not have a grid of the type generally designated as a control grid.

The accelerator grid of the gated-beam tube is an enclosed metallic structure formed with two relatively small openings, wherein one opening is adjacent to and the other opening is opposite the cathode. A positive directvoltage bias is applied between the accelerator and cathode as an operating condition. A limiter grid is contained within the accelerator electrode; and a control voltage is applied to the limiter grid. However, the limiter grid voltage does not substantially affect the total cathode current, but rather acts as a deflecting medium for the cathode current. A very negative voltage between the limiter grid and cathode deflects the cathode current entirely to the accelerator; while a more positive limiter grid voltage permits the cathode current to pass, in part,

through both accelerator openings so that the current may reach a plate electrode. A second grid, called herein the gating grid, is interposed between the plate electrode and accelerator electrode; and the gating grid controls whether or not that cathode current, which is permitted to escape from the accelerator electrode, can go to the plate or is deflected back to the accelerator.

Gated-beam tubes are known other than the type generally designated as the 6BN6, and any of them may be used in this invention when they have analogous electrodes, as taught by this specification.

It is, accordingly, an object of this invention to provide a gated-beam oscillator having very simple construction, although its theory of operation is complex, which will provide a substantially constant voltage output with varia tion in loading.

It is another object of this invention to provide an oscillator which can be used over an extreme range of frequencies from the audio frequencies into the very high frequencies.

It is still another object of this invention to provide an oscillator capable of being almost instantaneously keyed on and 01f by a gating signal.

It is yet another object of this invention to. provide an oscillator that has a substantially undarnped rise characteristic and a highly damped decay characteristic, which corn'ers that are almost perfectly square without regard to.

the value of the duty cycle of the pulses.

It is a further object of this invention to provide an oscillator circuit that, without substantial modification, can be used as a frequency divid'er, which will divide an input frequency by integer multiples of two.

It is a still further object of this invention to provide an oscillator that can be frequency modulated by. almost adirect connection to a modulating source.

This invention utilizes a series circuit comprising a resistor, capacitor, and tank circuit, which are respectively connected in series between a positive. direct-voltage supply and ground. The tank circuit, which is a parallel-resonant circuit, has its ungrounded side connected to the limiter grid of the gated-beam electron tube; The resistor has an end, which is opposite from its end connected to the direct-voltage supply, connected to the accelerator elec trode of the gated-beam tube. Also, the gatedabeam tube. may have its cathode connected to ground, its gating grid connected to ground through a. resistor, and. its plate connected to a positive direct-voltage supply through a plate impedance. The oscillating output may the removed; from the plate or from a point in the series; circuit.

The tuned frequency of the tank circuit primarily determines the frequency of oscillation, of t e invention. Oscillatory feedback is provided as a result of complex inter; actions within the gated-beam tube, wherein a negative resistance characteristic is provided between accelerator electrode alternating current and limiter grid alternating voltage. The oscillatory feedback current is transferred from the accelerator electrode through, the series capacitor to the tank circuit to sustain oscillation. I

When the tank circuit is tuned to the frequency f/N, where N is a positive integer multiple of two, the, tank circuit frequency will lock with a frequency of f applied to the gating grid; and, therefore, a frequency division of N occurs. A sinusoidal divisional output'may 'be removed from the tank circuit. If it is required to quench the oscil! lation during periods when no input frequency f is applied, it is necessary to bias the gating grid to a substantially negative direct voltage, which is easily done by connecting a resistor between the cathode. and ground. How-, ever, the limiter grid is biased above cutoff for this .condition.

The invention can provide a gated oscillator by biasing the gating grid substantially negative to prevent free oscillation. This may be done either by usinga cathode resistor or by applying a negative bias to the gating grid. An input gating signal, which has positive polarity pulses, may be applied to the gating grid to provide an oscillatory output having a pulsed envelope. Also, an, input gating signal, which has negative polarity pulses, may be applied to the cathode to obtain the oscillatory Pulsed, output, if a cathode impedance is provided, such as, for example, an unbypassed cathode resistor. A distinctive characteristic of the gated osci lator, in this invention, is that it provides very sharp leading and trailing edges for the envelope of the gated bursts of oscillation. Thus, almost instantaneous rise times and ecay times are provided-for each pulse burst; and this is believed to be due to the extremely small time constant provided by the electron stream coupling involved. An exceptional damping char acteristic of the gated oscillator. prevents jitter and parasitic oscillation from occurring in the envelope of the pulsed output bursts. V p

Furthermore, the invention can provide a frequency modulated output. A high-frequency oscillation, which may be a radio-frequency oscillation and which is generated as described above, canbe rna de to vary with an -applied audioinput voltage properly applied tothe gati g grid. The audio input signal can b ery ,smal,l.ither by.

l atented May 6, 1958 eliminating the need for modulator amplifiers; and the radio-frequency output may be relatively large, which in some cases may eliminate the need for additional stages of radio-frequency amplification. Furthermore, the gated-beam tube automatically limits the amplitude of the output and, hence, reduces amplitude modulation upon the frequency-modulated output to, therefore, reduce the need for amplitudelimiters which are generally used to purify frequency-modulated signals.

Further objects, advantages, and features of this invention will be apparent to a person skilled in the art upon further study of the specification and drawings, in which:

Figure l is a schematic diagram of one form of oscillator utilizing this invention;

Figure 2 is a schematic diagram of a frequency divider utilizing the invention;

. Figure 3 is a schematic diagram of a gated oscillator utilizing this invention;

Figure 4 illustrates a schematic diagram of frequencymodulation means made according to this invention;

' Figures 5(A), 5 (B) and 5(C) illustrate wave forms that may be found in the frequency divider form of the invention; and,

Figures 6(A) and 6(B) illustrate wave forms that may be associated with the gated oscillator form of the invention.

Now referring to the invention in more detail, Figure 1 illustrates schematically a circuit of an oscillator made according to this invention and utilizes a gated beam tube 10, which has its cathode 11 connected to ground and its plate 12 connected to a B plus direct-voltage supply through a plate resistor 13.

Tube includes an accelerator electrode 14 having a pair of openings 16 and 17. A limiter grid 18 is mounted within accelerator 14, and a gating grid 19 is supported between accelerator 14 and plate 12.

A series circuit 21 comprising a resistor 22, a capacitor 23, and a tank circuit 24, is connected in series between the B plus source and ground. Parallel-resonant circuit 24 comprises an inductor 26 and a capacitor 27 and any distributed capacitance that is across the tank circuit. At high frequencies, the distributed capacitance may provide the entire capacitance in tank circuit 24. Also, a piezoelectric crystal may be substituted for tank circuit 24. At low frequencies, an inductor may be substituted for resistor 22 if the inductor is connected to a lower positive direct voltage source than the plate source.

The accelerator electrode 14 of tube 10 is connected to point 28, which is common to resistor 22 and capacitor 23; and the limiter grid 18 is connected to point 29, which is common to capacitor 23 and tank circuit 24. The gating grid 19 has a resistor 31 connected between it and ground.

The circuit of Figure 1 will oscillate at the tuned frequency of tank circuit 24. However, capacitance in the tube between the accelerator and cathode electrode is coupled into the tank circuit through series capacitor 23 to affect the tuned frequency. Also, the resistivity of the electron stream between the cathode and accelerator electrodes is coupled into the tank circuit through series capacitor 23 to lower the Q of the resonant circuit. Thus, it is desirable, although not critical, to provide series capacitor 23 with a value that is a compromise between being as small as possible, on the one hand, and being sufliciently large, on the other hand, to permit necessary feedback energy to pass into tank circuit 24 to sustain oscillation, as will be described below.

The bias between cathode 11 and gating grid 19 is zero in Figure 1 because both are grounded. However, a relatively large variation in bias is permissible, and a positive bias is generally preferable to a negative bias. The gating grid bias should not be biased below cutofi if freerunning oscillation is required.

As stated above, the current provided by cathode 11 is I not substantially affected by the bias on either limiter grid 4 18 or gating grid 19. vWhen limiter grid 18 is biased sufficiently negative, the entire electron stream is deflected '1 to accelerator electrode 14 and flows as a current through series resistor 22 to the B plus voltage source. This condition is defined herein as the cutoff condition for limiter grid 18.

When the limiter grid voltage rises above its cuoff state, some of the electrons are permitted to pass by limiter grid 18 and to pass out of accelerator 14 through opening 17.

The cutoff state for gating grid 19 is that bias voltage which causes the electron stream, that passes through accelerator opening 17, to be deflected back to accelerator 14. The backward deflected electrons then flow through series resistor 22 as occurred when limiting grid 18 was biased to cutoff. Thus, the current through series resistor 22 remains the same when either limiter grid 18 or gating grid 19 is below cutoff, or when both are below cutoff.

However, when gating grid 19 and limiter grid 18 are both biased above cutoff, electrons are permitted to pass them and to reach plate 12, because of the higher positive direct-voltage on plate 12 than on accelerator 14.

Accordingly, while gating grid 19 is biased above cutoff, the accelerator current has the following limiting values: it is maximum when the limiter grid voltage is below cutoif (which deflects the entire electron stream to accelerator 14) and is minimum when the limiter grid voltage and gating grid voltage are above cutoff (which deflects only part of the electron stream to accelerator 14 with the remaining going to plate 12). Hence, when the limiter grid voltage varies above and below cutotf in an alternating manner, an alternating current will be generated by accelerator 14 and is designated as voltage E Tank circuit 24 will act as a load on the alternating current generated by accelerator 14; since they are coupled through capacitor 23. A voltage drop E will occur across capacitor 23, and a final voltage drop B, will occur across tank circuit 24, so that the following relationship exists;

a c'i' t When capacitor 23 is relatively large, voltage E becomes negligible, and tank circuit voltage E will be approximately equal in magnitude and in-phase with generated voltage E,,.

The desirability for having the capacitance of capacitor 23 as small as possible was explained above; however, it is noted'here that capacitor 23 should not be so small that it unduly shifts the phase and unduly lowers the magnitude of the tank circuit voltage 13,. Therefore, the size of series capacitor 23 is a compromise depending upon many factors including the range of operating frequencies.

The value of series resistor 22 is determined in part by the value of D. C. voltage required to bias accelerator electrode 14. Also, resistor 22 also leads the accelerator voltage source and should have a relatively high impedance.

The operation of the oscillator in Figure 1 may be explained by observing what happens during a cycle of tank circuit voltage 13,, which is applied to limiter grid 18. (It is noted that gating grid 1? has zero bias and is therefore above cutoff.) If the positive going portion of the cycle is taken first, the voltage on limiter grid 18 will increase and rise above cutoff to permit electrons to leave accelerator 14- and pass to plate 12. Accordingly, accelerator current decreases during the positive halfcycle of voltage E, to cause a positive voltage across tank circuit 24 which causes a regenerative build-up of the positive half-cycle of tank circuit voltage. Thus, a regenerative voltage is provided by the accelerator current variation, since it is in-phase with the tank circuit voltage. The positive half-cycle regeneration within tank circuit 24 reaches a maximum voltage that is limited when a maximum portion of the electron stream reaches plate 12. A further positive increase beyond this limiting value of limiter grid voltage does not substantially change the accelerator current.

Tank circuit voltage B, then begins a negative swing and limiter grid 18 is driven below cutoff. Accordingly, when the entire electron stream is diverted to accelerator 14, the accelerator current reaches an opposite limiting value, allowing no further increase in feedback voltage E Therefore, one regeneration cycle is completed. This cycle is repeated to sustain free-running oscillation.

The output of the oscillator may be taken from a terminal 32 connected to plate 12, when it is connected to the B plus supply through an impedance, such as, plate resistor 13 or a tank circuit. An output removed from plate 12 will be a pulsed wave rich in harmonics, since the substantially sinusoidal excitation of the limiter grid switches a substantially constant current stream on and off plate 12. The pulse-repetition-rate of the output is determined by the tuning of tank circuit 24. Furthermore, the pulsed output will have a substantially constant amplitude because of the essentially constant electron density reaching plate 12.

If a sinusoidal output wave is desired, a filter may be connected to the output or a tank circuit may be substituted for plate resistor 13. Also, a substantially sinusoidal output may be taken from tank circuit 24. Furthermore, an output voltage may be taken from a point on series resistor 22 or from tank circuit 24 which will have an opposite phase from an output taken from plate terminal 32. Thus, the invention provides an oscillator which uses a single ended tuned circuit that can provide simultaneous opposite phased outputs. In some cases, it may be preferable to remove the output from the plate because of its isolation from the frequency controlling tank circuit; and, therefore, loading of the oscillator will not substantially aifect its frequency.

The frequency-divider circuit shown in Figure 2 is similar to the oscillator circuit shown in Figure 1, and like circuit elements are identified by like reference numerals. The' only additional features shown are an input frequency source 33 connected to gating grid 19 and a biasing resistor 34, connected between ground and cathode 11. The lower end of tank circuit 24 remains connected to cathode 11. Resistor 34 biases gating grid 19 below cutolf but permits the bias between limiter grid 18 and cathode 11 to remain zero.

Also, gating grid 19 may be biased below cutoff by other ways than shown in Figure 2, such as, by connecting a negative direct-voltage supply in series with gating grid 19.

When gating grid 19 is biased below cut-elf, the oscillator is no longer a free-running type but is a controlled-output type. It will be recalled from the above described operation of Figure 1 that gating grid 19 was biased above cutofI so that the electron stream could be alternately switched to plate 12. With the gating grid biased below cutoff, the electron stream cannot reach plate 12 and free-running oscillation cannot be obtained in described embodiment. Consequently, oscillation occurs only in response to an input voltage that exceeds the gating grid cutoff state.

Tank circuit 24 is tuned to a frequency f/N where N is a positive integer multiple of two. Thus, if the circuit of Figure 2 were not biased below cutoff, it would oscillate at approximately a frequency of f/N, as described for Figure 1.

If a voltage having a frequency f is provided by source 33, and if a portion of each cycle has suflicient amplitude to exceed the gating grid cutoff state, the frequency of oscillation will lock in with input frequency f to provide an exact divisible relationship of 1/N between the input and output frequencies. The output frequency may be taken at any point in the series circuit, such as across tank circuit 24, or may be taken from plate 12.

The operation of the frequency divider in Figure 2 may be explained by using the specific situation where a frequency division by two is required. A sinusoidal input voltage of the type shown in Figure 5 (A) and having a frequency f is'injected on gating grid 19 by fre-. quency source 33. Also, tank circuit 24 is tuned to the frequency f/2.

It may be assumed in Figure 5 (A) that gating grid 19 has a cutoff voltage 37 and is biased to a lower voltage 36.

A positive one-half cycle 33 in Figure 5(A) begins the sinusoidal input, and it raises the gating grid voltage above cutoflf level 37 for a period less than one-half cycle. During this period, the electron stream is permitted to reach plate 12, since the initial bias on the limiter grid is above cutoff; and the accelerator current will drop from an initial value 41, shown in Figure 5(B), to a lower value 42 for the same period which is less than the duration of the positive one-half cycle of input signal. Negative pulse 42 of accelerator current will pass through series resistor '22 and shock excite tank circuit 24 to begin a positive one-half cycle 43 of voltage in tank circuit 24 atits tuned frequency of f/2 shown in Figure 5 (C).

During the following negative one-half cycle of input voltage, the gating grid is below cutoff and no electron current can reach plate 12; and, hence, all the cathode current is deflected to accelerator 14 to maintain the accelerator current at itsmaximum value 41. Thus, the negative one-half cycle of input does not have anyaffect upon the tank circuit other than causing the electron stream to load the tuned circuit.

When the next positive one-half cycle 44 of input exceeds cutoff level 37, the tank circuit voltage will begin a negative half-cycle atfrequency f/ 2 to bias limiter grid 13 below cutoff; and, hence, positive input one-half-cycle 44 has no affect upon the tank circuit output.

When a third positive one-half cycle 46 reaches cutoff, both the limiter grid and gating grid are simultaneously positive to form another negative pulse 47 of accelerator current to shock excite tank circuit 24 for another cycle at frequency f/ 2.

Thus, tank circuit 24 completes one full cycle for every two full cycles of input voltage.

A frequency division of four way may be obtained by tuning the tank circuit to a frequency of f/4. Then, the voltages on the gating grid and limiter grid will be simultaeously positive only once during each'four cycles of input current to shock excite the tank circuit at the division frequency f/4.

The controlled type of oscillator, used in Figure 2, may, with almost no change except for the tuning of tank circuit 24, be used as a gated-oscillator circuit, which is shown in Figure 3. Like components are identified by the same reference numerals in Figure 3 as in Figures 1 and 2. i

In Figure 3, a pulse source 51 is provided and is connected to the gating grid 19 through a blocking capacitor 52. Pulse source 51 may provide an input voltage wave form similar to that shown in Figure 6(A). The am-' plitude of the input pulses 53 is sufficient to drive gating grid 19 above the cutoif level 54 for the duration of each pulse; and for the pulse duration, the oscillator is placed in a free-running state, since gating grid 19 becomes positively biased.

The leading edge of a pulse shock excites the oscillator into immediate oscillation which lasts for the duration of the pulse, and which stops at the trailing edge of the pulse where the pulse type of bias on gating grid 19 instantaneously drops below cutoff.

The oscillation output at plate 12, which is shown as gated oscillations 54 in Figure 6(B), almost instantaneously damps when the pulse terminates, because the elec tron stream has very little mass and is immediately diverted to accelerator electrode 14 by the negative voltage on the gating grid, caused by the trailing edge of each pulse. Hence, although the current in tank circuit 24 may take more time to decay, the tank circuit oscilla- 7 tions are not coupled to plate 12 by the electron stream and, therefore, cannot affect the output. Thus, there is little or no parasitic oscillation, which is sometimes called jitter.

Another form of the invention is shown in Figure 4. It includes the free-running oscillator circuit of Figure l,- and enables the oscillation frequency to deviate in response to an audio input signal, thereby providing frequency modulation.

Like components in Figure 4 have the same reference numerals as were used in Figure 1. An additional tank circuit 61, comprising a capacitor 62 and an inductor 63, is provided, which has one side connected to gating grid 19 and its other side connected to an audio input terminal 64. Of course, capacitor 62 might be the distributed capacitance of inductor 63. Another capacitor 66 is connected bet 'een ground and audio input terminal 64. Capacitor 66 has a value wherein its capacitive reactance is large at audio frequency, but is substantially zero at the tank circuit frequency 1 A resistor 67 is connected across capacitor 66 to maintain the directvoltage on gating grid 19 at ground potential.

Both tank circuits 61 and 24 are tuned to a center frequency f which is the free-running carrier frequency of the oscillator. Tank circuit 61, which is connected to gating grid 19 should have a high Q, which might, for example, exceed 100, while tank circuit 24 may have a medium to high Q.

The frequency modulation operation of the invention may be explained as follows: The tuned frequency of tank circuit 24 is not only dependent upon the values of inductor 26 and capacitor 27, but is also dependent upon all distributed and stray reactances across the tank circuit. One stray reactance circuit across tank circuit 24 is a capacitive reactance circuit comprising series capacitor 23, and the resistive electron stream between accelerator 14 and cathode 11 to ground. The efiective resistance of the accelerator to cathode electron stream is controlled by the gating grid voltage which varies with the audio input.

It is this variation of the electron stream effective resistance that provides the frequency modulation. Part of the cathode current is being switched at the carrier frequency between plate 12 and accelerator 14, and it is the amplitude of this part that is varied by the gating grid modulated bias voltage. The remaining part of the substantially constant cathode current provides the electron stream between cathode 11 and accelerator 14.

The audio voltage on limiter grid 18 changes slowly compared to carrier-frequency variations, and, therefore, the instantaneous audio signal acts as a varying bias on the gating grid. When the audio cycle is most positive, the portion of the cathode current diverted to plate 12 is maximum; thus, the electron coupling between cathode and accelerator is at a miniurn, and, accordingly, the effective resistance between cathode and accelerator is maximum. On the other hand, when the. audio input signal is most negative, a minimum of cathode current reaches plate 12.; accordingly, the electron coupling between cathode and accelerator 14 is maximum; and, therefore, the effective resistance between cathode and accelerator is minimum.

The capacitance of series capacitor 23 is, hence, variably coupled across the tank circuit by the accelerator to cathode eifective electron stream resistance, which varies in correlation with the audio input. As a result, the reactance across tank circuit 24 varies, and its frequency deviates about its carrier frequency f in an amount corresponding to the amount of effective capacitance of series capacitor 23 coupled into the tank circuit.

The frequency modulated output may be removed from plate 12 and will be richin the harmonics of the instantaneous signal. A filter may be connected to the outut to select either the fundamental frequency modulation or any harmonic frequency modulation. A tank 8 circuit substituted for plate resistor 13 and tuned to the carrier frequency will attenuate splatter frequencies. The output will be substantially free of amplitude modulation because of the limiting action within the tube.

It is, therefore, apparent that this invention provides an oscillator circuit that can be used for many different purposes with very little circuit variation. Accordingly, the oscillator may be used as a free-running oscillator, a gated oscillator, a frequency dividing means, or a frequency modulation means.

While particular forms of the invention have been shown and described, it is to be understood that the invention is capable of modifications. Changes, therefore, in construction and arrangement may be made without departing from the full scope of the invention, as given by the appended claims.

What is claimed is:

1. Oscillatory means comprising a gated-beam electron tube having at least a cathode, an accelerator electrode,

a limiter grid, 3. gating grid and a plate, a parallel resonant circuit connected between said limiter grid and said cathode, a first direct-voltage potential level connected to said cathode, a second direct-voltage potential level that is positive with respect to said first level operably connected to said plate, first impedance means capable of conducting direct-current connected between said second potential level and said accelerator electrode, second impedance means capable of passing alternatingcurrent and blocking direct-current connected between said accelerator electrode and said limiter grid, and third impedance means connected between said gating grid and said first potential level, whereby oscillatory feedback is provided from said accelerator electrode to said parallel resonant circuit.

2. Oscillatory means comprising a gated-beam electron tube having at least a cathode, an accelerator electrode, a limiter grid, a gating grid and a plate, a tank circuit connected between said limiter grid and said cathode, a capacitor connected between said limiter grid and said accelerator electrode to pass feedback voltage, a resistor connected at one end to said accelerator electrode, a given direct-voltage potential level connected to said cathode, a direct-voltage source positive with respect to said potential level connected to the other end of Said first resistor, said plate also operably connected to said positive direct-voltage source, and resistance means connected between ground and said gating grid, whereby oscillation occurs in said tank circuit due to feedback from the accelerator electrode.

3. Oscillatory means comprising a gated-beam electron tube having at least a cathode, an accelerator electrode, a limiter grid, 21 gating grid, and a plate, a tank circuit connected between said cathode and said limiter grid, said cathode being connected to ground, first resistance means connected between ground and said gating grid,

a plate-voltage source, a second resistor connected between said plate and said plate voltage source, a third resistor connected between said voltage source and said accelerator electrode, and a capacitor connected between said limiter grid and said accelerator electrode, whereby oscillator feedback passes through saidcapacitor to excite said tank circuit.

4. Controlled oscillator means for dividing an input frequency by a multiple of two, comprising a gated beam tube having a cathode, an accelerator electrode, a limiter grid, a gating grid and a plate, a first direct-voltage potential level connected to said cathode, a frequency source connected to said gating grid, resistance means connected in series with said gating grid, a parallel resonant circuit connected between said cathode and said limiter grid, said parallel resonant circuit tuned to a frequency that is an even integer divisible of the frequency of said frequency source, capacitor means connected between said accelerator electrode and limiter grid, a second directvoltage potential level positive with respect to said first potential level and operably connected to said plate, and

an impedance means capable of conducting direct-current connected between said second potential level and said accelerator electrode, wherein the frequency of oscillation of said parallel resonant circuit is an even integer divisible of the input frequency.

5. Controlled oscillator means for dividing an input frequency by even integer divisibles, comprising a gated beam tube having a cathode, an accelerator electrode, a limiter grid, a gating grid and a plate, a frequency source connected to said gating grid, a first resistor connected between ground and said gating grid, 21 plate resistor connected between said plate and a B plus voltage source, a cathode resistor connected between ground and said cathode, an accelerator resistor connected between said accelerator grid and the B plus voltage source, a capacitor connected between said accelerator electrode and said limiter grid, and a parallel resonant circuit connected between said limiter grid and said cathode, said parallel resonant circuit being tuned to an integer divisible of the frequency of said frequency source, whereby the oscillation in said parallel resonant circuit is an even integer divisible of said input frequency.

6. Controlled oscillator means for providing a gated oscillatory output, comprising a gated beam tube having a cathode, an accelerator electrode, a limiter grid, a gating grid and a plate, a parallel resonant circuit connected between said limiter grid and said cathode, a first directvoltage potential level, a second direct-voltage potential that is positive with respect to said first level operably connected to said plate, impedance means capable of conducting direct-current connected between said second potential level and said accelerator gn'd, capacitance means connected between said accelerator electrode and said limiter grid, resistive impedance means connected between said gating grid and said first potential level, a cathode resistor connected between said cathode and said first potential level, said cathode resistor providing a voltage drop for biasing said gating grid below cutoff, and source means for providing pulses connected to said gating grid, said pulses having an amplitude which exceeds the gating grid bias.

7. Controlled oscillator means for providing a gated oscillatory output, comprising a gated beam tube having at least a cathode, an accelerator electrode, a limiter grid, a gating grid and a plate, a gating grid resistor connected between ground and said gating grid, a plate resistor connected between a B plus voltage source and said plate, a cathode resistor connected between ground and said cathode, an accelerator resistor connected between said accelerator and the B plus voltage source, a parallel resonant circuit connected between said limiter grid and said cathode, a capacitor connected between said accelerator electrode and said limiter grid to provide feedback, said gating grid biased below cutoff, a pulse source connected to said gating grid to provide pulses having an ampli tude that exceeds the gating grid cutoff and having a repetition rate that is substantially less than the tuned frequency of said parallel resonant circuit, whereby a gated oscillatory output having very steep rise and decay characteristics may be taken from the plate of said tube.

8. Controlled oscillator means wherein a modulating source provides a frequency modulated oscillatory output, comprising a gated beam tube having at least a cathode,

an accelerator electrode, a limiter grid, a gating grid, and a plate, a first parallel resonant circuit tuned to a carrier frequency and connected between said limiter grid and cathode, a first direct-voltage potential level connected to said cathode, a second direct-voltage potential level that is positive with respect to said first level operably connected to said plate, impedance means capable of conducting direct-current connected between said second potential level and said accelerator electrode, capacitance means connected between said accelerator electrode and said limiter grid, and a second parallel resonant circuit connected between said modulating source and said gating grid and also tuned to the carrier frequency, whereby the frequency of oscillation of said first parallel resonant circuit varies with the modulating input.

9. Oscillator means having its frequency varied by a modulating source comprising a gated-beam tube having at least a cathode, an accelerator electrode, a limiter grid, a gating grid and a plate, a first parallel resonant circuit connected between said cathode and said limiter grid, 21 second parallel resonant circuit tuned to the same frequency as said first parallel resonant circuit and having one end connected to said gating grid, said modulating source connected to the other end of said second parallel resonant circuit, a first direct-voltage potential level con nected to said cathode, a second direct voltage potential level that is positive with respect to said first level, impedance means capable of conducting direct-current connected between said second potential level and said accelerator electrode, capacitor means connected between said accelerator electrode and said limiter grid, and resistive impedance means connected between said second potential level and said plate, whereby an oscillatory output may be taken from said plate and will vary frequencywise in accordance with the modulating input.

10. Oscillator means having a modulated frequency comprising a gated beam electron tube having at least a cathode, an accelerator electrode, a limiter grid, a gating grid and a plate, a ground potential source connected to said cathode, a first parallel resonant circuit connected between said limiter grid and said cathode, a second parallel resonant circuit tuned to the same frequency as said first parallel resonant circuit and having one end con nected to said gating grid, a gating grid resistor connected between ground and the other end of said second parallel resonant circuit, a modulating source connected across said gating grid resistor, a capacitor connected across said gating grid resistor and having an impedance low with respect to said oscillating frequency and high with respect to said modulating frequencies, a B plus source, an accelerator resistor connected between said B plus source and said accelerator electrode, a capacitor connected between said accelerator electrode and said limiter grid, a plate resistor connected between said B plus source and said plate, whereby a frequency modulated output may be taken from said plate.

References Cited in the file of this patent UNITED STATES PATENTS

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