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Publication numberUS3594603 A
Publication typeGrant
Publication dateJul 20, 1971
Filing dateApr 29, 1968
Priority dateApr 29, 1968
Publication numberUS 3594603 A, US 3594603A, US-A-3594603, US3594603 A, US3594603A
InventorsGuckenburg Walter P
Original AssigneeDesoto Inc
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Field emission circuit element and circuit
US 3594603 A
Abstract  available in
Images(5)
Previous page
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Claims  available in
Description  (OCR text may contain errors)

United States Patent Inventor Walter P. Guckenburg Linthicum, Md. AppL No. 724,845 Filed Apr. 29, 1968 Patented July 20, 1971 Assignee DeSoto, Inc.

Des Plaines, [11.

FIELD EMISSION CIRCUIT ELEMENT AND CIRCUIT 12 Claims, 13 Drawing Figs.

Primary Examiner-Roy Lake Assistant Examiner-E. R. LaRoche AnorneyDressler, Goldsmith, Clement & Gordon ABSTRACT: A field emission circuit element adaptable for use at the millimeter wave range of'the frequency spectrum. The field emission element may take the form of a diode embodiment including a pair of electrodes presenting opposing emitter and collector surfaces bounding a vacuum gap having a configuration defining a regular field region terminating at the surfaces. The circuit element is characterized by minute gaps and high vacuums whereby the regular field region is capable in the presence of applied electric potential of providing an electric field for producing at the emitter surface electron field emission controllable at the millimeter wave range.

PATENTEUJULZOIBH 3,594,603

SHEET u Ur" S j Z 12 DIODE PARAMETER FOR THREE EMITTING AREAS d=|o cm, =4.5eV lo RF A=lO' crn 4 z A-IO cm lNVlFNTOI? er 3 1' HOW FIELD Emission cmcurr ELEMENT AND CIRCUIT BACKGROUND The desirability of and the need for electronic systems operable in the millimeter wave region of the frequency spectrum has long been recognized and appreciated. Significant advantages of millimeter wave systems include high channel each of these windows. Each of these windows theoretically permits about 2,000,000 independent voice channels in a phase locked transmission system, assuming a 5 kHz. voice channel. Due to the nature of millimeter wave propagation, such transmission systems are point to point communication links.

The wide carrier bands available in the millimeter wave region are particularly suitable for FM modulation. For example, a modulation index of 100 can be easily employed not only to reduce the noise figure but to eliminate distortion due to frequency drift. Greater carrier band separation can be provided to enable interference-free communication systems.

Millimeter wave communication systems utilize miniature, lightweight components and exhibit highly directive properties so that the transmission power is low and the intelligence is confined to small regions of space. For millimeter waves, antennas comprise a source element for transforming high frequency current energy into radiation energy and a director element such as a parabolic reflector, horn, lens dielectric rod or a slot. Portable equipment becomes practical and convenient by reason of the properties of millimeter waves.

By way of example, for operation at l millimeter wavelength, a beamwidth of one-half degree can be obtained with a parabolic reflector having a diameter of about cm. (6 inches). lf the same parabolic reflector were used at a wavelength of 1 cm., the beamwidth would be increased to 5 with a drop in power gain from 52 db. to 32 db. Thus, millimeter wave systems make it possible to provide portable equipment of high efficiency and accuracy and of useful range. ln the case of fixed equipment for millimeter wave communication systems, a reflector 3 feet in diameter can provide a beamwidth of less than 0.025 with a power gain of about 80 db.

Efforts to develop equipment, such as diode structures, for microwave and millimeter wave systems have been extensive and have taken many forms. The problems of generating, transmitting and detecting millimeter wave energy signals have been approached by application of principles from numerous disciplines, such as classical electronics, quantum electronics, semiconductors, solid state physics, ferrites, ferroelectrics, field emission, tunneling, superconductors, physical optics, electromagnetic theory, acoustics, relativistic physics, nonlinear phenomena, plasmas and electroscopy. No significant advances have heretofore made it likely that practical operational millimeter wave systems can be expected in the foreseeable future.

In the case of field emission, the trend of the current work has been directed towards field intensification structures utilizing a tiny needle-shaped cathode and a relatively large anode. The needle is about 1 micron square to achieve highintensity field strengths at the needle with reasonable values of anode voltage. Cathode heating is a factor limiting the current density at the needle so that multiple needle cathode arrays are used where any useful current flows are desired.

This approach to the use of field emission had led only to special purpose applications such as X-ray equipment. lt has serious drawbacks that preclude its application with millimeter wave communication systems. Among the drawbacks are lack of uniformity in tip geometry, shielding effects between adjacent needle tips, nonuniform electron emission conditions and excessive electron transit times 'due to the large anodecathode gap.

Other prior art arrangements of general relevancy to field emission and to the problem of producing millimeter wave systems are shown in US. Pats. Nos. 2,090,033, 2,279,872, 2,887,606 and 2,897,396. An article of general interest appeared in the Aug. l964 issue of Journal of Applied Physics, Vol. 35 No.8, pages 2324-2332.

SUMMARY OF lNVENTlON This invention relates to electric circuit elements utilizing field emission, their energization and their operating characteristics.

The circuit element of the present invention utilizes as pair of electrically insulated emitter and collector electrodes 0 conductive material presenting opposing emitter and collector surfaces that bound a vacuum gap having a configuration defining a regular field region which terminates at the opposing surfaces. Such a regular field region is capable, in the presence of an applied electric potential, of providing an electric field for producing at the emitter surface high field emission of electrons controllable at the millimeter wave range of the frequency spectrum to deliver the electrons to the collector surface.

In operation as a field emission device, the control energy applied 0 the conductive surfaces provides a gap voltage that produces a transmit time for the high field emission electrons compatible with the frequency of millimeter waves, while avoiding gap voltages that result in deterioration or destruction of the collector. These relationships and the requisite balance of these operational factors are primarily a function of the gap configuration, while also being a function of electrode geometry, electrode material and environment, all of which are interdependent.

In accordance with this invention, the gap configuration is characterized by the use of minute spacing between the electrode surfaces and careful control of surface irregularity and purity. Extremely high vacuum conditions are also characteristic of the gap region during operation.

The gap configurations utilized in this invention are those which define a regular field," the characteristics of which are illustrated and described in the disclosure which follows. In the case of a regular field," the field strength pattern and the field emission current are predictable and controllable. The minute spacing and configuration that characterize the gap permit use of acceptable levels of voltage for creation of an electric field that can cause high field emission and short transit time at current densities that do not result in the generation of objectionable heating at the emitter and at voltages that do not result in adverse effects at the collector.

In its simplest forms, a high field emission gap structure in accordance with this invention is utilized in a'diode embodiment having a strongly nonlinear current-voltage characteristic and is applicable in rectifier and harmonic multiplier Circuits operable at frequencies up to the cutoff frequency determined by the transit time for the gap. Since this cutoff frequency is readily arranged to be at or above the millimeter wave range, the device can handle impulse wave forms with high fidelity.

The small dimensions for the gap arrangement and the characteristics of operation at millimeter wave frequencies enable self-contained miniaturized structures of simplified physical form and arrangement.

More specifically, the high vacuum, high field emission gap structure of the present invention defines a regular field region between closely spaced emitter and collector electrodes supplied with electrical control energy to establish high field emission of electrons from the emitter electrode. A regular" field may be defined in part by its properties such as those which permit control of the electron emission at the millimeter wave range of the frequency spectrum under conditions of gap spacing sufficiently small to achieve desired field strength for producing the electron field emission at levels of applied voltage capable of providing the requisite small electron transit time without excessively high values of voltage.

In a regular field capable of causing electron emission, the electrons emitted from the emitting electrode have the same transit time in traveling to the collector electrode assuming the applied voltage remains constant. In its ultimate form, an ideal regular field would exist between a pair of infinite perfectly smooth uniformly fiat emitter and collector electrodes.

It should be understood that for any given applied voltage, gap spacing and gap configuration, there is a corresponding minimum transit time (T) which delineates the maximum frequency at which the high field emission, high vacuum gap structure may e utilized. Furthermore, for a given gap spacing and applied voltage, this minimum transit time (1') is shorter in the case of an ideal regular field than for any other regular field.

In high frequency systems which, for example, include radio frequencies in the order megahertz, the transit time of electrons is very very small in relation to the wave lengths of the frequencies of concern. However, in the microwave and millimeter wave systems, the transit time of electrons between the emitter and collector electrodes approaches the same order of magnitude as the period of one cycle.

This relationship defines a cutoff frequency, the highest frequency with which the electron emission structure can be used. The cutoff frequency, however, is not that frequency whose period is the same as the minimum electron transit time. The cutoff frequency is dependent on the function sin rot/mt. (See, for example, Microwave Engineering by T. Korym lshii, Ronald Press Company, 1966, Chapter 7).

The value of this function becomes zero at transit times equal to one-half the period (T) of the frequency in question. Therefore, in order to achieve reasonable efficiency of operation, the period (T) of the cutoff frequency" with which any device of the present invention is utilized should be about from to 10 times the frequency whose period is identical to the minimum transit time (1) for a given structure.

For the purposes of this application f =ll 10 where:

f is the cutoff frequency;

-r=3.37Xl0"'dV',,, nanoseconds for an ideal regular field;

d is the gap spacing between the electrodes in centimeters;

and V is the voltage applied between the electrodes, assuming that the gap is space charge free.

The above equations would appear to indicate that for a given gap spacing d the desired minimum transit time (1') can simply be achieved by increasing the voltage V.

The various parameters which define the gap structure of the present invention are all interrelated and changes in one value cannot be made without considering its effect on the other parameters. Increasing the voltage also increases the strength of the electric field, which between parallel plate electrodes is defined by the equation E=V/d. Thus, increases in the voltage are restricted by limitations on the electric field strength.

Maximum values of electric field strength in the gap are limited by the gap breakdown level, by the requirement that the circuit element operate in a space charge-free environment and by the maximum current density which the emitter electrode can withstand before sufficient heat is generated at the emitter to convert the field emission, at least in part, to thermionic emission. Thermionic emission is not acceptable since uniform transit time between the electrodes is not maintained under such conditions.

The current density at the emitter is a function not only of field strength but of the material used as the emitting electrode. A number of materials may be used for the emitter electrode, e.g., tungsten, tantalum and alloys thereof. It is clear from the above that one characteristic which is to be considercd in selection of the emitter electrode is its work function (4 The work function is selected to keep in tolerable limits the field strength required to sustain fieldemission at selected current densities. Thus, the lower the work function I the higher the field emission current density for a given electric field. On the other hand, the work function ofthe emitting electrode cannot be so low as to reduce the voltage applied across the gap to a point where transit time (1-) becomes too high for frequencies of interest.

For clarity and ease of understanding, the field emission circuit element of the present invention will be described with tungsten used as its emitting electrode. Tungsten has a work function of about 4.5 ev which requires an electronic field of 3X10 volts/cm. to sustain field emission current. For pertinent gap spacings d, applied voltages remain within practical levels.

Another criterion in selecting the electrode emitting material is its physical characteristics. The surface of a tungsten electrode can be freed from unwanted gases by subjecting the electrode to increasingly high vacuums along with the application of progressively stronger electric fields. Such a clean tungsten electrode can be formed with anoptically smooth sur face having variations plus or minus 0.1 micron. This surface smoothness is, of course, important at the small gaps under consideration to obtain the desired uniform transit time.

In the above configurations, a regular field has been discussed for uniform transit times between the electrodes absent the consideration of fringe effect. As a practical matter, it is not possible to construct devices capable of generating ideal regular electric fields. While the spacing between two parallel plate electrodes can be held constant, the electrodes do terminate, resulting in edge field intensification and fringe field effects. Such fringe field effects can be reduced by forming at least the emitting electrode with its edges abutting or continu ous with adjacent elements having higher work function, i.e., materials selected so as not to generate field emission when subjected to the same conditions that create field emission from the emitting electrode. The configuration of such elements may be selected to provide increased gap spacing as compared with the gap between the emitting and collecting electrodes in order to reduce the strength of the field to which such adjacent elements are subjected, thereby further reducing the chances of field emission therefrom.

Based on the above discussion, a regular electric field is defined with respect to a number of factors. For electrode configurations producing uniform transit time, an electric field is considered to be a regular field when the ratio of the field strength at each of the electrodes is no more than 1.]. Alternatively, when compared with an ideal regular field, the field strength at the collector electrode for an ideal field to the field strength at the collector electrode for the field in question is no more than 1.1 for structures having thesame gap dimension and the same field strength at the emitter electrode.

Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and of several embodiments thereof, from the claims, and from the accompanying drawings in which each and every detail shown is fully and completely disclosed as part of this specification, in which like reference numerals are employed to designate like parts throughout the same.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the basic component making up one embodiment of the high field emission circuit element of the present invention;

FIG. 2 is a transverse sectional view of one embodiment of a field emission circuit element in the form of a diode;

FIG. 3 is an enlarged fragmentary sectional view showing the relationships between the surfaces of the electrode-supporting bodies and the facing surfaces of the electrodes;

FIG. 4 is a sectional view of an alternative embodiment of the circuit element taken along lines 4-4 of FIG. 5;

FIG. Sis a sectional view taken along lines 5-5 of FIG. 4;

FIG. 6 is an enlarged transverse section of another embodiment utilizing electrodes deposited on the supporting bodies and taken along lines 6-6 of FIG. 7;

FIG. 7 is a transverse section of the embodiment of FIG. 6 taken along lines 7-7 of FIG. 6;

FIG. 8 is an enlarged fragmentary sectional view of FIG. 6;

FIG. 9 is an enlarged fragmentary sectional view of another embodiment;

FIG. 10 is an enlarged fragmentary view similar to FIG. 9 showing another alternative embodiment; and

FIGS. 11, 12 and 13 are characteristic curves for various configurations of the circuit element.

DETAILED DESCRIPTION In accordance with the invention in one of its preferred fonns, the circuit element takes the form of a diode, having an emitter electrode 22 and a collector electrode 24. The surfaces 26, 28 of the electrodes 22, 24 are obtained by forming truncated cones at the ends of wire elements 30, 32, the surfaces 26, 28 being formed as flat planes.

By way of specific example and referring to FIGS. 1, 2 and 3, there is shown one embodiment of the present invention including a pair of lower and upper mating glass body members 34, 36, for supporting the wires 30, 32, only one body being shown in perspective in FIG. 1. Each of the glass bodies 34, 36

' is formed with confronting outer sidewall portions 37, 38 and with a central transverse trough 39, 40 into which extends the tungsten wires 30, 32 each embedded in the glass body, 34, 36, respectively. The ends 26, 28 of the tungsten wires 30, 32 and the abutting surfaces 42, 44 of the sidewall portions 37, 38 are ground flat in the same plane until the surfaces 26, 28 of the wires 30, 32 achieve the desired area and surface smoothness. Typically, the surface of the electrode should be optically smooth and, in the case of tungsten irregularities in the surfaces 26, 28 my be as little as 0.] micron.

The abutting surfaces 42, 44 of the sidewall portions 37, 38 of glass bodies 34, 36 are each coated with a spacer deposit 46, 48, the combined thickness of which defines the gap between the electrode surfaces 26, 28. The glass bodies 34, 36 are sealed together with the coatings 46, 48 abutting in sealing engagement to define a vacuum region 52 in the recessed area formed by the mating troughs 38, 40 including the gap 50.

The lower and upper glass bodies 34, 36 are held together by suitable glass clamps 54 which in turn are fused to a vacuum envelope 56. The vacuum region 52 is evacuated through a nipple 58 in the envelope 56 which is sealed when the desired vacuum of about 10" to about 10" torr is achieved. The electrode surfaces 26, 28 are cleaned as explained above, before the nipple is sealed.

The volume of the vacuum region 52 is substantially greater than the volume in the gap region 50. Since the diode 20 is operated at very high vacuums, as indicated above, any residual molecules tend to accumulate in larger area 52, thereby minimizing the probability of gas ions being formed in the gap 50.

In FIG. 2, the diode structure is shown connected in a simple rectifier circuit including a DC voltage bias source 60, a load 62 and means for applying an AC signal 64. The bias source is connected across the electrodes 22, 24 to polarize the emitter 22 as a cathode. The DC voltage is selected to achieve required field strength at the emitter surface 26 for producing high field emission of electrons across the gap to the collector surface 24. Referring to FIGS. 11, 12 and 13, there are shown the characteristic curves of the field emission circuit element for a tungsten emitter plotted as a function of electric field intensity at the emitter electrode.

Another embodiment of the diode device is disclosed in FIGS. 4 and S in which the separate envelope chamber is omitted and the lower and upper glass bodies 34', 36' are sealed at their juncture about their periphery by a head 66 to provide an airtight enclosure. The desired vacuum is drawn through a nipple 68 formed in one of the bodies until the desired vacuum is achieved at which point the nipple 68 is sealed.

The diode structure of FIG. 4 is shown connected in a harmonic multiplier circuit arrangement which includes a bias voltage source 70, a tuned tank circuit 72 and a source of AC signals 74. The tuned circuit may be tuned, for example, to a frequency that is a multiple of the frequency of the AC input signals.

Since the characteristic curves shown in FIGS. 11, 12 and 13 of a field emission circuit element are strongly nonlinear, the element can produce strong third or higher harmonic components rendering it particularly suitable for use in harmonic multiplier circuits.

Where the circuit element is used as a rectifier or harmonic multiplier, the applied AC signal may be of any frequency value. The particular merit of the device, however, is its ability to handle signal at the millimeter wave range of the frequency spectrum.

For ideal regular fields, the following performance characteristics result for various assumed values of gap spacing d and voltage V where the emitter electrode material is tungsten and the area of the electrodes is about 10 sq. cm.

CHARACTERISTICS OF IDEAL REGULAR FIELD EMISSION CIRCIUIT ELEMENT [Plate area.=l0- sq. cm.

Emitter mateiial=Tungsten (=4.5)

Current density Transit Gap Voltage Field (10 (amps/sq. Current Power time fc y,

(10' em.) (10 volts) volts/cm.) em.) a) (watts) (1O- secs.) (gHz.) (111111.)

3.6 a 1. mom 1, 750 6.3 5. s2 1, 780 .168

2 s 1. 2x10 12,000 96 7. as 1, 324 .226

28. S 3 l. 75X10 1, 750 50. 4 15. 9 630 476 ctrsgxggsarsrtcsor IQAL REGQEQjLIQI D EMISSION cmcur'r ELEMENT (unrinut-d {Plate area=l" sq. cm.

Emitter material==Tungsten (o -4.6)]

Current density Transit Gap "oltage Field (amps/sq. Current Power time I, (tocm.) (10 volts) volts/era.) cm.) Ora.) (watts) (IO- secs.) (gHz.) (mm.)

9.. 36 l l. 2X10 12, 000 432 16. 0 625 .480 3'2. 4 3. 6 1.75Xl0 I, 750 56.7 16.9 592 .507 27 3.0 .36 36 0. 972 18.4 542 .533

10 40 4 1. 2X10 12, 000 480 16. 8 595 .504 36 3.6 1. 75x10) 1,750 63 17. 8 563 532 30 3.0 36 36 I. 08 19. 5 512 .585

In each of the embodiments discussed above, the field between the opposed electrode surfaces formed by the wire tips approaches the ideal regular" field and, therefore, the desired uniform field emission current and uniform transit time is substantially achieved in this region. Any fringe field that exists between the exposed conical surface of the wires is substantially weaker due to the increased spacing therebetween and the resultant lower field strength. Additionally, this portion of the wire may be coated with a higher work function material to further reduce or eliminate field emission.

Since, as indicated above, the dimensions of the high field emission device of the present invention are quite small, the electrodes may also be produced by deposition of the metallic elements on a glass substrate or base material. Referring to FIGS. 6, 7 and 8, there is shown one embodiment of such a deposited electrode configuration in which the lower and upper glass bodies 76, 78 are formed in a generally E-shaped transverse section to provide confronting external sidewall portions 80, 82 and confronting central peninsulas 84, 86 extending along one axis of each of the bodies 76, 78. The confronting surfaces 80, 82 and 84, 86 are ground to desired smoothness and suitable coatings are deposited thereon. Insulative spacer coatings 88, 90 are deposited on the facing surfaces of the external sidewall portions 84, 86 and are of such a thickness as to separate the facing body surfaces by an amount sufficient to allow the opposed surfaces of the deposited electrodes 92, 94 to be separated by a gap 96 of distance d.

Referring to FIG. 7, it can be seen that each electrode coating 92, 94 is deposited on its respective peninsula 84, 86 and extends from the center of the peninsulas outwardly in opposite directions. The inner ends of the coatings 92, 94 overlap each other to define the pair of opposed electrodes having a desired surface area.

Since smoother surfaces are achieved in the deposition of the electrode materials on a glass substrate rather than on a metallic substrate, the deposited electrodes extend away from the gap region to a point where the electric energy may be conducted away by suitable conductors I02, I04 embedded in the glass bodies 76, 78.

The electrode coatings can take any number of forms. As seen in FIG. 9, the emitter coating 92' may be somewhat thicker in the area of the vacuum gap 50 to reduce fringe field effects and the emission from the remainder of the conductive coating by increasing the spacing between the deposited coating in areas other than across the gap. Alternatively, as shown in FIG. 10, the deposited emitter electrode 92 may be surrounded by a higher work function material 106 which, as explained above, greatly reduces fringe field emission since any fringe emission that might otherwise occur is restricted by the higher work function material 106 surrounding the emitter 92". Any emission from the higher work function material 106 is of lower strength and depending upon the work function of such material may in fact be almost nonexistent.

The deposited electrode structures of FIGS. 6-l0 can be incorporated in the same electrical circuits in which the other embodiments have been disclosed and are particularly suitable for low power applications.

It will be readily observed from the foregoing detailed description and the illustrated embodiments thereof that numerous other variations and modifications may be effected without departing from the true spirit and scope of the novel concepts and principles'of this invention.

What I claim is:

I. In an electric circuit having a source of DC voltage, a high field emission circuit element having an evacuated envelope, a pair of electrodes of conductive material disposed within said envelope for connection across said source, said electrodes having opposed spaced apart optically smooth emitter and collector surfaces lying in parallel planes and each having an area of at least about l0 cm. said spaced apart surfaces bounding a vacuum gap defining a regular field region therebetween and terminating at said surfaces, said emitter surface responsive to sard source of DC voltage across said electrodes polarizing said emitter surface as a cathode and having a magnitude sufficient to provide a regular electric field having the minimum strength required to sustain field emission of electrons from said emitter surface for initiating said field emission to said collector surface with a transit time sufi'rciently low to render said field emission controllable-at the millimeter wave range of the frequency spectrum.

2. A circuit element as claimed in claim 1 wherein the dimensions of said gap configuration being selected to limit said voltage to a potential of about 10 kv.

3. A circuit element as claimed in claim 1 wherein the surface of said emitter electrode is composed of tungsten.

4. A circuit element as claimed in claim I wherein the surface irregularities of said emitter electrode are on the order of 10 percent of the distance between said electrode surfaces.

5. A circuit element as claimed in claim I wherein the surface irregularities of said emitter electrode are on the order of 0.1 micron.

6. A circuit element as claimed in claim I wherein the area of the emitter surface is on the order of 100 times the square of the distance between said electrode surfaces.

7. An electric circuit comprising a pair of electrically insulated emitter and collector electrodes of conductive material enclosed within an envelope having a pressure of about 10" to about 10 torr, said electrodes presenting spaced-apart opposed optically smooth emitter and collector surfaces lying in parallel planes, having an area of at least about 10 cm? and forming a vacuum gap therebetween defining a regular field region extending between and terminating at said opposed spaced apart surfaces, a source of DC voltage, means connecting said source across said electrodes and polarizing said emitter element as a cathode and providing an electric field in said regular field region of sufi'rcient strength to sustain high field emission of electrons from said emitter surface to said collector surface with the transit time of said electrons being on the order of one fifth to one-tenth the period of the wave length of signals having frequencies in the millimeter wave range of the frequency spectrum.

8. A circuit as claimed in claim 7 where the distance between said opposed emitter and collector surface is on the order of l0 to 10'' cm.

9. A circuit as claimed in claim 7 wherein the surface irregularities of said emitter electrode are on the order of 10 percent of the distance between said electrode surfaces.

10. A circuit as claimed in claim 7 wherein the surface irregularities of said emitter electrode are on the order of 0.1 micron.

11. A circuit as claimed in claim 7 wherein said transit time is on the order of about 5 to 20 l0 seconds.

12. A circuit as claimed in claim 11 wherein said field emission of electrons is controllable at frequencies on the order of about 500 to 1900 GHz.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent: No. 3 ,594 s 603 Dated y 20 1971 k: Inventor(s) Walter Guc burg It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col 2 line 16 "as" should be a line 17 "0" should be of line 28 "0" should be to line 29 "transmit" should be transit Col. 3 line 43 "10 dV should be 1/2 Col 5 line 35 "my" should be may line 47, "10 should be 10" line 47 "l0 should be 10* col. 6, line 47, 10 should be 10" Col 8, lines 21, 47 and 50 should be 10 line 48 "10 should be 10" line 64 "10 should be l0" line 64, "10 should be l0 line 72 "10 should be 10 Signed and sealed this 7th day of March 1972 (SEAL) Attest:

ROBERT GOTTSCHALK Commissioner of Patents EDWARD M .FLETCHER,JR. Attesting Officer FORM PO-IOSO (IO-6S) USCOMM-DC GOB'IG-PGQ 9 US GOVERNMENT PRINTING OFFICE I96! O'366*334

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2647218 *Dec 26, 1950Jul 28, 1953Eitel Mccullough IncCeramic electron tube
US2715696 *Aug 28, 1951Aug 16, 1955Northrop Aircraft IncGas-filled discharge lamp
US2887606 *Jun 12, 1953May 19, 1959Philips CorpElectron tube for decimetre-and centimetre-waves
US3066236 *May 1, 1959Nov 27, 1962Int Standard Electric CorpElectron discharge devices
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4037266 *Dec 29, 1975Jul 19, 1977Bell Telephone Laboratories, IncorporatedVoltage surge protector
US4393433 *Jul 16, 1981Jul 12, 1983Northern Telecom LimitedOvervoltage protector for telephone lines
Classifications
U.S. Classification313/104, 455/91, 313/631, 313/250, 313/267, 313/325
International ClassificationH01J1/304, H01J21/00, H01J1/30, H01J21/06
Cooperative ClassificationH01J21/065, H01J1/304
European ClassificationH01J21/06B, H01J1/304