SHORT PULSE GENERATOR
United States Patent 3798461
A spark generator is provided which is reentrant, can deliver all output to a single load while being either balanced or unbalanced to ground, as desired. The structure is operable over a wide frequency and power level range.
US Patent References:
SPARK GAP DEVICE WITH IGNITION ELECTRODE
Marx et al. - July 1969 - 3454823
Multiple spark gap switch
Schofield - July 1958 - 2844740
Electrical suppressor
Dubilier - April 1959 - 2884605
APPARATUS FOR PROVIDING A STEEP VOLTAGE STEP ACROSS A LOAD IN ELECTRIC HIGH-VOLTAGE CIRCUIT
Nilsson - December 1971 - 3629605
SPARK GAP DEVICE WITH IGNITION ELECTRODE
Marx et al. - July 1969 - 3454823
Multiple spark gap switch
Schofield - July 1958 - 2844740
Electrical suppressor
Dubilier - April 1959 - 2884605
APPARATUS FOR PROVIDING A STEEP VOLTAGE STEP ACROSS A LOAD IN ELECTRIC HIGH-VOLTAGE CIRCUIT
Nilsson - December 1971 - 3629605
Application Number:
05/308483
Publication Date:
03/19/1974
Filing Date:
11/21/1972
View Patent Images:
Export Citation:
Assignee:
Stanford Research Institute (Menlo Park, CA)
Primary Class:
Other Classes:
315/36, 313/325
International Classes:
H03K3/537; H03K3/00; H03K3/00; H03K3/64
Field of Search:
313/325,198 315/207,209,36 333/31C 317/69,70 307/106,108,109,110
Primary Examiner:
Smith Jr., David
Attorney, Agent or Firm:
Lindenberg, Freilich & Wasserman
Claims:
What is claimed is
1. A spark gap pulse generator comprising:
2. A spark gap pulse generator as recited in claim 1 wherein each of said spaced conductive circular, structure constitutes a disc, and
3. A spark gap pulse generator as recited in claim 1 wherein each of said spaced conductive circular structures constitutes a drum,
4. A spark pulse generator comprising:
5. A spark gap pulse generator as recited in claim 4 wherein there is included:
6. A spark gap generator comprising:
7. A spark gap generator as recited in claim 6 wherein said conductor has a surface area which substantially parallels the surface area of each notch in said circular drum periphery.
8. A spark gap pulse generator as recited in claim 7 wherein there is included a load which is connected to the two ends of said conductor,
1. A spark gap pulse generator comprising:
2. A spark gap pulse generator as recited in claim 1 wherein each of said spaced conductive circular, structure constitutes a disc, and
3. A spark gap pulse generator as recited in claim 1 wherein each of said spaced conductive circular structures constitutes a drum,
4. A spark pulse generator comprising:
5. A spark gap pulse generator as recited in claim 4 wherein there is included:
6. A spark gap generator comprising:
7. A spark gap generator as recited in claim 6 wherein said conductor has a surface area which substantially parallels the surface area of each notch in said circular drum periphery.
8. A spark gap pulse generator as recited in claim 7 wherein there is included a load which is connected to the two ends of said conductor,
Description:
BACKGROUND OF THE INVENTION
This invention relates to spark pulse generators and, more particularly, to improvements in the construction thereof.
Spark pulse generators are circuits comprising inductances, capacitors and resistors connected in the manner of a filter or transmission line. The capacitors are first charged, then discharged into the inductances. The inductances thereafter discharge into the capacitors. Thus, a number of cycles or oscillations occur providing pulses which can be applied to a load. Examples of such pulse generators are shown in a patent to Samsel, U.S. Pat. No. 2,792,508, or in articles by Hellar and Holter, on Pages 161-170 of the 1953 Proceedings of the National Electronics Conference, entitled, "A Transmission Line Oscillatory Pulse Generator," or in an article by Weibel in the Review of Scientific Instruments, Pages 173-175, February 1964, entitled, "High Power Pulse Generator."
Spark gap generators normally find use in radar, ionosonds and other applications, where very short, high power, rf pulses are required.
OBJECTS AND SUMMARY OF THE INVENTION
An object of this invention is the provision of a simpler and more compact construction for a spark gap pulse generator, then has been available heretofore.
Another object of this invention is the provision of a unique construction for a spark gap pulse generator.
Still another object of this invention is the provision of a spark gap pulse generator which is operable over a wide frequency range and can be operated over a wide power level range.
These and other objects of the invention may be achieved in an arrangement wherein a spark gap pulse generator comprises, in one embodiment, a pair of spaced parallel discs having centrally positioned opposed protuberances or bosses, which form a spark gap therebetween. The discs have a purality of opposed openings disposed around their surfaces out of which tubes extend outwardly. A conductor is threaded through the tubes without touching their walls. A load is attached to the ends of the conductor. The tubes and conductors are coaxially related. A voltage is applied to the discs until a spark occurs across the spark gap formed between the two opposed bosses. In a second embodiment, a pair of opposed spaced drums have opposed bosses therebetween defining a spark gap. A plurality of radial notches are formed in the periphery of each drum. A conductor threads through all of the radial notches of both drums without touching the walls and a load is connected to the ends of the conductor.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a circuit diagram of an embodiment of the invention employing lumped circuit components.
FIG. 1A is a waveform representative of the load current available with the structure shown in FIG. 1.
FIG. 2 is a top view of one embodiment of the invention.
FIG. 3 is a side view of the embodiment of the invention as seen in FIG. 2.
FIG. 4 is a top view of another embodiment of the invention.
FIG. 5 is a side view of the embodiment of the invention shown in FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIG. 1, there may be seen a circuit diagram of a lumped constant arrangement of this invention. A load 10 is represented by a resistor. On either side of the resistor are inductances 12, 14, which are connected in series therewith. Each of these inductances has the value 1/2L. Connected in series with the inductance 12 are three other inductances respectively 16, 18, 20, which have the value L, or twice that of the inductance 12. Connected in series with the inductance 14 are inductances 22, 24, 26 and 28 which have the value L. The inductance 28 is connected back to the end of the inductance 20 at the point designated by the letter A.
Between the junction of the inductances 22 and 24, and a bus line 30, there is connected in series a capacitor 32, and an inductance 34. Connected in series between the junction of an inductance 14 and 22 and the bus 30, is a capacitor 36, and an inductance 38. Connected between the junction of inductances 18 and 20 and the bus 30 are the capacitor 40 and the inductance 42. A serially connected capacitor 44 and inductance 46, are connected between the point A and the bus 30.
A serially connected capacitor 48, and inductance 50, are connected between the junction of inductances 16 and a bus 52. A serially connected capacitor 54 and inductance 56, are connected between the junction of inductances 12 and 16. A serially connected capacitor 58 and inductance 60, are connected between the junction of inductances 24 and 26, and the bus 52. A serially connected capacitor 62 and inductance 64, are connected between the junction of inductances 26 and 28 and bus 52.
Capacitors 32, 36, 40, 44, 48, 54, 58 and 62 all have the value C. Inductors 34, 38, 42, 46, 50, 52, 60, 64 all have the value L'. The function of the eight capacitors designated C and numbered 32, 36, 40, 44, 48, 54, 58 and 62 is to store energy provided by voltage sources 68 and 70 for subsequent delivery to the load resistor 10. The associated inductances designated L' are unavoidable parasitic elements, recognized and integrated into the design in such a way as to be harmless.
Between the busses 30 and 52, there are serially connected a current limiting resistor 66, a voltage source 68, another voltage source 70, and another current limiting resistor 72. Voltage sources 68 and 70 are preferably equal. Between the point A and the junction between the two voltage sources, there is connected a resistor 74. A normally open shorting switch is connected across the busses 30 and 52. Energy stored in the capacitors C is delivered to the load 10 when the switch is closed. The resulting current has the waveform shown in FIG. 1A.
To operate the line shown in FIG. 1, a switch 76 is open until such time as the capacitors become charged up. At that time, the switch is closed, whereby the shunt capacitors discharge into the series connected inductances, which thereafter again discharge into the capacitors. The oscillation which is thereby generated continues over a number of cycles determined by the values and the number of sections selected in the construction of the line. The frequency of the oscillation is also determined by the values of the components which have been selected. Those skilled in the art know how to select the inductance, capacitance, and resistance values required to produce the desired frequency of oscillation in a desired number of cycles. It should be noted that the inductors L'are provided to accommodate any parasitic elements that may be present.
The transmission line circuit shown in FIG. 1 is reentrant; therefore, a single load represented by the resistor 10 will absorb all of the power stored in the line. The arrangement is such that the output is balanced to ground and no blocking capacitors are required. The arrangement shown generates an even number of half-cycles. The waveform for the load current is represented in FIG. 1A. By altering the number of capacitors employed, that is, by substituting a load in place of one of the shunt capacitors, an unbalanced output can be obtained, but at a lower impedance level.
FIGS. 2 and 3 respectively, show top and side views of a coaxial line and disc structure which has distributed circuit components and which realizes the circuit arrangement shown in FIG. 1. It comprises a pair of conductive discs respectively 80, 82, which are parallel with one another and spaced from one another. At the centers of the discs, at their opposite faces, lumped protuberances or bosses, respectively 84, 86 are provided. These bosses and the spacing therebetween constitute a spark gap switch.
To assist in triggering a discharge between the bosses provision may be made at one or both of the bosses for a trigger electrode. By way of example, this can constitute a pin 85 extending into an opening 87 in the boss 84. A voltage applied between the trigger electrode 85 and the disc 80 from a trigger voltage source 89, which causes an arc discharge between the electrode and the edge of the opening 87, in the boss. This arc triggers a discharge in the main gap between bosses 84 and 86.
Both top and bottom discs have openings, from which conductive tubes extend at right angles from the plane of the discs. In the top view, these tubes have reference numerals 88A, 90A, 92A and 94A, applied thereto. In the side view of these tubes, only 88B and 94B may be seen.
A single conductor 96, extends into the space between the two discs, thereafter extends upward through the tube 88A and across and downward through the tube 94A, through 94B, then across and upward through tube 92B (not shown), upward through tube 92A, across to tube 90A through which it proceeds downwardly through tube 90B (not shown), then across, upward through tube 88B and then out adjacent to the input lead. The ends of the conductor 96 are connected to a load 10. It should be recognized that the conductor and tubes form a series of coaxial lines connected to the discs which form a spark gap switch.
A source of potential 98 is connected through the upper disc 80 through a charging resistor 100. A second and preferably equal source of potential 102 is connected to the upper disc through a charging resistor 104. The lead 96 is connected to ground through a resistor 106.
In operation, the sources of charging potential are connected across the discs. When the potential between the protuberances 84, 86 attains a sufficient value, and with the assistance of the trigger electrode 85, a discharge is made to occur, which has the same effect as the shorting switch 76 in FIG. 1. The inductances designated with the values L in FIG. 1, are distributed throughout the length of the zigzag circuit formed by the conductor 96. The capacitors are formed by the spacing between the conductor 96 and the tubes 88-94, A and B. Additional design flexibility is available by tapering the diameters of the conductors that make up the inductances and coaxial capacitance. At relatively high frequencies, it may prove desirable to add tubular conductors that shield the open inductive connections which bridge between the tubes, for example 94A, 88A.
By way of example, and not to serve as a limitation upon the invention, for operation at a frequency of 30 MHz, the spark gap section was made about 50 percent larger than that shown. The coaxial sections were made of flexible coaxial cable each about 10 feet long. The cable was of a type designated as "RG8", now widely used for cable TV. A second model, was made and tested in which cable lengths were doubled (as well as stored energy) and the frequency of operation was lowered by the same ratio.
In many situations, it is possible and desirable to enclose the entire structure shown in FIGS. 2 and 3 in a sealed vessel containing a liquid of gaseous dielectric. Nitrogen at high pressure is an excellent dielectric that is favorable for high speed, high power spark switching.
FIGS. 4 and 5 show a variation of the structure shown in FIGS. 2 and 3, and differs in that a parallel strip transmission line is substituted for the coaxial arrangement shown in FIGS. 2 and 3. FIG. 4 is a top view and FIG. 5 is a side view. The two discs 80 and 82 in FIG. 5, are thickened to essentially resemble two drums, respectively 110, 112. A plurality of radial notches exemplified by notch 114 are formed in the periphery of the upper and lower drums, respectively 110, 112. Bosses, 118, 120 are formed opposite one another at the centers of the drums 110, 112, and establish a base therebetween which is the spark gap. A trigger electrode (not shown) such as is shown in FIGS. 2 and 3, may also be employed at one or both of the bosses to insure the occurrence of timely discharges and also, since energy from the trigger generator is used to form the spark that makes the gap conductive, a larger fraction of the energy stored in the transmission line is available for conversion into the useful oscillatory wave delivered to the load.
Only fragments of the line, 122, which threads through the twenty slots in the drums is shown in order to avoid confusion in the drawings. In FIG. 4, reference numeral 122A is applied to an illustration of a cross-section of the line. It may be seen that the line is broadened to extend approximately parallel to the surface of a slot. The geometry of the structure shown in FIGS. 4 and 5 is that of a parallel strip transmission line in place of the coaxial arrangement shown in FIGS. 2 and 3. This geometry is especially attractive when the number of cycles to be generated is moderately large. The structure shown in FIGS. 4 and 5 has twenty slots and is therefore appropriate to form a pulse that is ten cycles long. The length of the radial path from each line section to the switch can be made small compared to a wavelength without seriously reducing the stored energy.
The charging potential sources and the load are given the same reference numerals, as in the previous drawings.
It should be noted, by way of example, and not as a limitation upon the invention that the size of the embodiment of the invention shown in FIGS. 4 and 5 is correct for operation at a frequency near 1,200 MHz, corresponding to a wavelength of about 10 inches.
There has accordingly been described and shown herein, a novel and useful structure for a spark gap transmission line.
This invention relates to spark pulse generators and, more particularly, to improvements in the construction thereof.
Spark pulse generators are circuits comprising inductances, capacitors and resistors connected in the manner of a filter or transmission line. The capacitors are first charged, then discharged into the inductances. The inductances thereafter discharge into the capacitors. Thus, a number of cycles or oscillations occur providing pulses which can be applied to a load. Examples of such pulse generators are shown in a patent to Samsel, U.S. Pat. No. 2,792,508, or in articles by Hellar and Holter, on Pages 161-170 of the 1953 Proceedings of the National Electronics Conference, entitled, "A Transmission Line Oscillatory Pulse Generator," or in an article by Weibel in the Review of Scientific Instruments, Pages 173-175, February 1964, entitled, "High Power Pulse Generator."
Spark gap generators normally find use in radar, ionosonds and other applications, where very short, high power, rf pulses are required.
OBJECTS AND SUMMARY OF THE INVENTION
An object of this invention is the provision of a simpler and more compact construction for a spark gap pulse generator, then has been available heretofore.
Another object of this invention is the provision of a unique construction for a spark gap pulse generator.
Still another object of this invention is the provision of a spark gap pulse generator which is operable over a wide frequency range and can be operated over a wide power level range.
These and other objects of the invention may be achieved in an arrangement wherein a spark gap pulse generator comprises, in one embodiment, a pair of spaced parallel discs having centrally positioned opposed protuberances or bosses, which form a spark gap therebetween. The discs have a purality of opposed openings disposed around their surfaces out of which tubes extend outwardly. A conductor is threaded through the tubes without touching their walls. A load is attached to the ends of the conductor. The tubes and conductors are coaxially related. A voltage is applied to the discs until a spark occurs across the spark gap formed between the two opposed bosses. In a second embodiment, a pair of opposed spaced drums have opposed bosses therebetween defining a spark gap. A plurality of radial notches are formed in the periphery of each drum. A conductor threads through all of the radial notches of both drums without touching the walls and a load is connected to the ends of the conductor.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a circuit diagram of an embodiment of the invention employing lumped circuit components.
FIG. 1A is a waveform representative of the load current available with the structure shown in FIG. 1.
FIG. 2 is a top view of one embodiment of the invention.
FIG. 3 is a side view of the embodiment of the invention as seen in FIG. 2.
FIG. 4 is a top view of another embodiment of the invention.
FIG. 5 is a side view of the embodiment of the invention shown in FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIG. 1, there may be seen a circuit diagram of a lumped constant arrangement of this invention. A load 10 is represented by a resistor. On either side of the resistor are inductances 12, 14, which are connected in series therewith. Each of these inductances has the value 1/2L. Connected in series with the inductance 12 are three other inductances respectively 16, 18, 20, which have the value L, or twice that of the inductance 12. Connected in series with the inductance 14 are inductances 22, 24, 26 and 28 which have the value L. The inductance 28 is connected back to the end of the inductance 20 at the point designated by the letter A.
Between the junction of the inductances 22 and 24, and a bus line 30, there is connected in series a capacitor 32, and an inductance 34. Connected in series between the junction of an inductance 14 and 22 and the bus 30, is a capacitor 36, and an inductance 38. Connected between the junction of inductances 18 and 20 and the bus 30 are the capacitor 40 and the inductance 42. A serially connected capacitor 44 and inductance 46, are connected between the point A and the bus 30.
A serially connected capacitor 48, and inductance 50, are connected between the junction of inductances 16 and a bus 52. A serially connected capacitor 54 and inductance 56, are connected between the junction of inductances 12 and 16. A serially connected capacitor 58 and inductance 60, are connected between the junction of inductances 24 and 26, and the bus 52. A serially connected capacitor 62 and inductance 64, are connected between the junction of inductances 26 and 28 and bus 52.
Capacitors 32, 36, 40, 44, 48, 54, 58 and 62 all have the value C. Inductors 34, 38, 42, 46, 50, 52, 60, 64 all have the value L'. The function of the eight capacitors designated C and numbered 32, 36, 40, 44, 48, 54, 58 and 62 is to store energy provided by voltage sources 68 and 70 for subsequent delivery to the load resistor 10. The associated inductances designated L' are unavoidable parasitic elements, recognized and integrated into the design in such a way as to be harmless.
Between the busses 30 and 52, there are serially connected a current limiting resistor 66, a voltage source 68, another voltage source 70, and another current limiting resistor 72. Voltage sources 68 and 70 are preferably equal. Between the point A and the junction between the two voltage sources, there is connected a resistor 74. A normally open shorting switch is connected across the busses 30 and 52. Energy stored in the capacitors C is delivered to the load 10 when the switch is closed. The resulting current has the waveform shown in FIG. 1A.
To operate the line shown in FIG. 1, a switch 76 is open until such time as the capacitors become charged up. At that time, the switch is closed, whereby the shunt capacitors discharge into the series connected inductances, which thereafter again discharge into the capacitors. The oscillation which is thereby generated continues over a number of cycles determined by the values and the number of sections selected in the construction of the line. The frequency of the oscillation is also determined by the values of the components which have been selected. Those skilled in the art know how to select the inductance, capacitance, and resistance values required to produce the desired frequency of oscillation in a desired number of cycles. It should be noted that the inductors L'are provided to accommodate any parasitic elements that may be present.
The transmission line circuit shown in FIG. 1 is reentrant; therefore, a single load represented by the resistor 10 will absorb all of the power stored in the line. The arrangement is such that the output is balanced to ground and no blocking capacitors are required. The arrangement shown generates an even number of half-cycles. The waveform for the load current is represented in FIG. 1A. By altering the number of capacitors employed, that is, by substituting a load in place of one of the shunt capacitors, an unbalanced output can be obtained, but at a lower impedance level.
FIGS. 2 and 3 respectively, show top and side views of a coaxial line and disc structure which has distributed circuit components and which realizes the circuit arrangement shown in FIG. 1. It comprises a pair of conductive discs respectively 80, 82, which are parallel with one another and spaced from one another. At the centers of the discs, at their opposite faces, lumped protuberances or bosses, respectively 84, 86 are provided. These bosses and the spacing therebetween constitute a spark gap switch.
To assist in triggering a discharge between the bosses provision may be made at one or both of the bosses for a trigger electrode. By way of example, this can constitute a pin 85 extending into an opening 87 in the boss 84. A voltage applied between the trigger electrode 85 and the disc 80 from a trigger voltage source 89, which causes an arc discharge between the electrode and the edge of the opening 87, in the boss. This arc triggers a discharge in the main gap between bosses 84 and 86.
Both top and bottom discs have openings, from which conductive tubes extend at right angles from the plane of the discs. In the top view, these tubes have reference numerals 88A, 90A, 92A and 94A, applied thereto. In the side view of these tubes, only 88B and 94B may be seen.
A single conductor 96, extends into the space between the two discs, thereafter extends upward through the tube 88A and across and downward through the tube 94A, through 94B, then across and upward through tube 92B (not shown), upward through tube 92A, across to tube 90A through which it proceeds downwardly through tube 90B (not shown), then across, upward through tube 88B and then out adjacent to the input lead. The ends of the conductor 96 are connected to a load 10. It should be recognized that the conductor and tubes form a series of coaxial lines connected to the discs which form a spark gap switch.
A source of potential 98 is connected through the upper disc 80 through a charging resistor 100. A second and preferably equal source of potential 102 is connected to the upper disc through a charging resistor 104. The lead 96 is connected to ground through a resistor 106.
In operation, the sources of charging potential are connected across the discs. When the potential between the protuberances 84, 86 attains a sufficient value, and with the assistance of the trigger electrode 85, a discharge is made to occur, which has the same effect as the shorting switch 76 in FIG. 1. The inductances designated with the values L in FIG. 1, are distributed throughout the length of the zigzag circuit formed by the conductor 96. The capacitors are formed by the spacing between the conductor 96 and the tubes 88-94, A and B. Additional design flexibility is available by tapering the diameters of the conductors that make up the inductances and coaxial capacitance. At relatively high frequencies, it may prove desirable to add tubular conductors that shield the open inductive connections which bridge between the tubes, for example 94A, 88A.
By way of example, and not to serve as a limitation upon the invention, for operation at a frequency of 30 MHz, the spark gap section was made about 50 percent larger than that shown. The coaxial sections were made of flexible coaxial cable each about 10 feet long. The cable was of a type designated as "RG8", now widely used for cable TV. A second model, was made and tested in which cable lengths were doubled (as well as stored energy) and the frequency of operation was lowered by the same ratio.
In many situations, it is possible and desirable to enclose the entire structure shown in FIGS. 2 and 3 in a sealed vessel containing a liquid of gaseous dielectric. Nitrogen at high pressure is an excellent dielectric that is favorable for high speed, high power spark switching.
FIGS. 4 and 5 show a variation of the structure shown in FIGS. 2 and 3, and differs in that a parallel strip transmission line is substituted for the coaxial arrangement shown in FIGS. 2 and 3. FIG. 4 is a top view and FIG. 5 is a side view. The two discs 80 and 82 in FIG. 5, are thickened to essentially resemble two drums, respectively 110, 112. A plurality of radial notches exemplified by notch 114 are formed in the periphery of the upper and lower drums, respectively 110, 112. Bosses, 118, 120 are formed opposite one another at the centers of the drums 110, 112, and establish a base therebetween which is the spark gap. A trigger electrode (not shown) such as is shown in FIGS. 2 and 3, may also be employed at one or both of the bosses to insure the occurrence of timely discharges and also, since energy from the trigger generator is used to form the spark that makes the gap conductive, a larger fraction of the energy stored in the transmission line is available for conversion into the useful oscillatory wave delivered to the load.
Only fragments of the line, 122, which threads through the twenty slots in the drums is shown in order to avoid confusion in the drawings. In FIG. 4, reference numeral 122A is applied to an illustration of a cross-section of the line. It may be seen that the line is broadened to extend approximately parallel to the surface of a slot. The geometry of the structure shown in FIGS. 4 and 5 is that of a parallel strip transmission line in place of the coaxial arrangement shown in FIGS. 2 and 3. This geometry is especially attractive when the number of cycles to be generated is moderately large. The structure shown in FIGS. 4 and 5 has twenty slots and is therefore appropriate to form a pulse that is ten cycles long. The length of the radial path from each line section to the switch can be made small compared to a wavelength without seriously reducing the stored energy.
The charging potential sources and the load are given the same reference numerals, as in the previous drawings.
It should be noted, by way of example, and not as a limitation upon the invention that the size of the embodiment of the invention shown in FIGS. 4 and 5 is correct for operation at a frequency near 1,200 MHz, corresponding to a wavelength of about 10 inches.
There has accordingly been described and shown herein, a novel and useful structure for a spark gap transmission line.