Crossed field device

Abstract

A crossed field device for generating electromagnetic emissions includes an anode having a first slow-wave structure having a plurality of first vanes separated by cavities formed therebetween and a second slow-wave structure having a plurality of second vanes separated by cavities formed therebetween. At least one of the first vanes is laterally aligned with one of the second vanes. The first vanes are offset from the second vanes by an offset distance so that at least one of the first vanes is not laterally aligned with a second vane and at least one of the second vanes is not laterally aligned with a first vane. The device further includes a cathode disposed in a space located between first and second vanes. A magnetic element generates a magnetic field (B), which is oriented orthogonally to an electric field (E) formed by the anode and cathode to generate EM emissions.

Claims

1. An anode for use in a crossed field device operating in a selected mode of operation for generating electromagnetic (EM) emissions, the anode comprising: a first slow-wave structure having a plurality of first vanes separated by cavities formed therebetween; and a second slow-wave structure having a plurality of second vanes separated by cavities formed therebetween, the second vanes being vertically spaced apart from the first vanes to provide a space therebetween, wherein at least one of the first vanes is laterally aligned with one of the second vanes, and wherein the first vanes of plurality of first vanes are offset from the second vanes of the plurality of second vanes by an offset distance so that said at least one of the first vanes is not laterally aligned with a different second vane and at least one of the second vanes is not laterally aligned with a different first vane.

2. The anode of claim 1 wherein the offset distance is equal to the width of an odd number of half-periods of the electromagnetic (EM) emissions generated in the selected mode of operation.

3. The anode of claim 1 wherein the offset distance is equal to the width of one vane and one cavity.

4. The anode of claim 1 wherein the offset distance is sized such that a first vane having a predetermined EM polarity is laterally aligned with a second vane having an equivalent EM polarity.

5. The anode of claim 1 further comprising one or more apertures formed in one or more of the cavities between each of the first and second vanes, said apertures being sized and configured to permit extraction of EM emissions from said cavities.

6. The anode of claim 5 further comprising extractors coupled to said apertures to transfer EM emissions away from the anode to an intended load.

7. The anode of claim 6 wherein each extractor is a waveguide and each waveguide is joined together with at least one other waveguide to form a combined waveguide.

8. The anode of claim 1 further comprising a short connection member and a long connection member extending outwards from opposing ends of each of the first and second slow-wave structures, wherein the long connection member is longer than the short connection member by a distance equal to the offset distance such that, by joining the short connection member of each slow-wave structure to the long connection member of the opposite slow-wave structure, the first and second slow-wave structure are joined together and the first vanes are offset from the second vanes by the offset distance.

9. A crossed field device for generating electromagnetic (EM) emissions as the cross product of an electric field (E) and a magnetic field (B), the crossed field device operating in a selected mode of operation and comprising: an anode comprising: a first slow-wave structure having a plurality of first vanes separated by cavities formed therebetween; a second slow-wave structure having a plurality of second vanes separated by cavities formed therebetween, the second vanes being vertically spaced apart from the first vanes to provide a space therebetween, wherein at least one of the first vanes is laterally aligned with one of the second vanes, and wherein the first vanes of plurality of first vanes are offset from the second vanes of plurality of second vanes by an offset distance so that said at least one of the first vanes is not laterally aligned with a different second vane and at least one of the second vanes is not laterally aligned with a different first vane; a cathode disposed in the space located between first and second vanes; and a magnetic element for generating a magnetic field (B), which is oriented orthogonally to an electric field (E) formed by the anode and cathode to generate EM emissions.

10. The crossed-field device of claim 9 wherein the offset distance is equal to the width of an odd number of half-periods of the EM emissions generated in the selected mode of operation.

11. The crossed-field device of claim 9 wherein the offset distance is equal to the width of one vane and one cavity.

12. The crossed-field device of claim 9 wherein the offset distance is sized such that a first vane having a predetermined EM polarity is laterally aligned with a second vane having an equivalent EM polarity.

13. The crossed-field device of claim 9 further comprising: one or more apertures formed in one or more of the cavities between each of the first and second vanes, said apertures being sized and configured to permit extraction of EM emissions from said cavities; extractors coupled to said apertures to transfer EM emissions away from the anode to an intended load.

14. The crossed-field device of claim 13 wherein each extractor is a waveguide and each waveguide is joined together with at least one other waveguide to form a combined waveguide.

15. The crossed-field device of claim 9 further comprising a short connection member and a long connection member extending outwards from opposing ends of each of the first and second slow-wave structures, wherein the long connection member is longer than the short connection member by a distance equal to the offset distance such that, by joining the short connection member of each slow-wave structure is to the long connection member of the opposite slow-wave structure, the first and second slow-wave structure are joined together and the first vanes are offset from the second vanes by the offset distance.

16. The crossed field device of claim 9 wherein the device is configured to operate in pi mode such that the polarity of the EM field in each of the first cavities and each of the second cavities changes by pi radians in each successive cavity.

17. The crossed field device of claim 9 wherein the cathode is a segmented mode control cathode comprising a plurality of gaps formed in the cathode.

18. The crossed field device of claim 17 wherein the gaps formed in the cathode are centered on the cavities of the first and second slow-wave structures of the anode vanes.

19. The crossed field device of claim 17 wherein the device is configured to operate in even pi mode such that laterally-aligned first and second vanes have an equivalent EM polarity and the polarity of the EM field in each of the first cavities and each of the second cavities changes by pi radians in each successive cavity.

20. A method of generating electromagnetic (EM) emissions and for carrying the EM emissions to an intended load, the method comprising the steps of: providing a crossed field device comprising: an anode comprising a first slow-wave structure having a plurality of first vanes separated by cavities formed therebetween; a second slow-wave structure having a plurality of second vanes separated by cavities formed therebetween, the second vanes being vertically spaced apart from the first vanes to provide a space therebetween; one or more apertures formed in the cavities between each of the first and second vanes, said apertures being sized and configured to permit extraction of EM emissions from said cavities; wherein at least one of the first vanes is laterally aligned with one of the second vanes, and wherein the first vanes of plurality of first vanes are offset from the second vanes of plurality of second vanes by an offset distance so that said at least one of the first vanes is not laterally aligned with a different second vane and at least one of the second vanes is not laterally aligned with a different first vane; extractors coupled to said apertures to transfer EM emissions away from the anode to an intended load; a segmented mode control cathode comprising a plurality of gaps formed in the cathode, the cathode disposed in the space located between first and second vanes; and a magnetic element for generating a magnetic field (B) that is oriented orthogonally to an electric field (E) formed by the anode and cathode to generate EM emissions; generating EM emissions using the crossed-field device; and carrying EM emissions to the intended load via the extractors.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages of the invention are apparent by reference to the detailed description when considered in conjunction with the figures, which are not to scale so as to more clearly show the details, wherein like reference numbers indicate like elements throughout the several views, and wherein:

(2) FIG. 1 is a cross sectional view of an anode and cathode configured for use in a recirculating planar magnetron (RPM);

(3) FIG. 2 is a cutaway perspective view of an RPM having an anode and cathode installed;

(4) FIG. 3 depicts a front elevation view and a perspective view of an anode;

(5) FIG. 4A is a sectional view of a portion of an anode and a solid cathode;

(6) FIG. 4B is a sectional view of a portion of an anode and a segmented or mode control cathode;

(7) FIG. 5 shows dispersion plots of an RPM having a mode control cathode in even and odd modes;

(8) FIG. 6A depicts an RPM having a solid cathode and operating in pi mode;

(9) FIGS. 6B and 6C depict an RPM having a mode cathode and operating in even and odd pi modes, respectively;

(10) FIGS. 7A and 7B depict an RPM operated in even and odd pi modes and including RF electric field lines resulting from those modes of operation;

(11) FIG. 8 is a plot of the operating space of the even and odd pi modes for an RPM;

(12) FIGS. 9A and 9B depict an extracted RPM operating in even and odd pi modes, respectively;

(13) FIGS. 10A and 10B depict separate waveguides joined together in a combined waveguide, where the EM waves are out of phase and in phase with one another, respectively;

(14) FIG. 11 is a perspective view of an anode for use in a crossed field device operating in a selected mode of operation for generating electromagnetic (EM) emissions according to an embodiment of the present invention;

(15) FIG. 12 depicts an extracted RPM having an anode and mode control cathode according to an embodiment of the present invention; and

(16) FIG. 13 depicts the RPM of FIG. 12 after apertures in the anode have been blocked off.

DETAILED DESCRIPTION

(17) Referring now to the drawings in which like reference characters designate like or corresponding characters throughout the several views, there is shown in FIG. 11 an improved anode 200 for use in a crossed field device operating in a selected mode of operation for generating electromagnetic (EM) emissions according to a first embodiment of the present disclosure. The anode 200 includes generally a first slow-wave structure 202 having a plurality of first vanes 204 separated by cavities 206 formed therebetween and a second slow-wave structure 208 having a plurality of second vanes 210 separated by cavities 212 formed therebetween. The second vanes 210 are spaced apart from the first vanes 204 to provide a space 214 therebetween. As shown in FIG. 12, that space 214 is suitably sized for a cathode 224. Although five vanes 204, 210 are illustrated on the slow-wave structures 202, 208, this is not intended to be limiting of the disclosed inventions. For example, any number of vanes 204, 210 could be provided depending on the application and desired output. In addition, there may be more or less vanes 204, 210 provided in one slow-wave structure as compared with the opposite slow-wave structure, depending on the application and desired output As in the prior art anodes 104 (FIG. 1) discussed above, the anode 200 includes at least one first vane 204 that is laterally aligned with one of the second vanes 210. This positional relationship is shown by solid and dashed lines 240 extending laterally across the anode 200 in FIG. 11. However, unlike the prior art anodes discussed above, the first vanes 204 of this anode 200 are laterally offset from the second vanes 210 by an offset distance D so that at least one of the first vanes is not laterally aligned with a second vane and at least one of the second vanes is not laterally aligned with a first vane.

(18) In this particular case, the offset distance D is equal to one period of the slow wave structures 204, 208 or the width of one cavity 206, 212 and one vane 204, 210. Put another way, the offset distance D is equal to the width of one half-period of the EM emissions generated in the selected mode of operation. Since, in this case when operating in pi mode, two cavities and two vanes are required for the polarity of the EM emission to repeat with the slow wave structure of this anode 200, the width of a half period is equal to the width of one cavity 206, 212 and one vane 204, 210. However, in other embodiments, the offset distance may be increased to any odd number of half-periods of the EM emissions generated in the selected mode of operation. In each case, the lateral shift may be performed in either direction. For example, as shown, the lower planar magnetron section 208 is shifted to the right by one period, with respect to the upper planar magnetron section 202. The anode 200 would also function as intended if the lower planar magnetron section 208 was shifted to the left by one period, with respect to the upper planar magnetron section 202.

(19) At the instant in time represented by FIG. 12, the RF electromagnetic field configuration would result in EM waves 216 oriented in a downward direction within the upper extraction waveguides 218 and EM waves 220 oriented in a downward direction within the lower extraction waveguide 222. In this regard, this RPM configuration is similar to the RPM illustrated in FIG. 9B, where the EM waves 130, 132 were each oriented in the same direction. As discussed above, having EM waves 216, 220 oriented in the same direction is important because it enables EM energy to be extracted and then constructively combined, thereby resulting in the transmittal of power in the output waveguide to the intended load, as shown in FIG. 10B.

(20) As discussed above, however, in order to achieve EM waves that are each oriented in the same direction, use of the odd pi mode was necessary. Recall that during odd pi mode operation (FIG. 7B), opposing vanes 114C, 114D in the upper planar magnetron section 108 and lower planar magnetron section 110 have opposite polarity. Likewise, in the embodiment illustrated in FIG. 12, the left-most vane 226 of the upper magnetron section 202 has a + polarity and the left-most vane 228 of the lower magnetron section 208 has a polarity. Therefore, this structure is similar to the RPM in FIG. 7B that is operating in odd pi mode. Therefore, if the upper and lower planar magnetron sections 202, 208 were not shifted by the offset distance D, this structure would result in the same structure shown previously in FIG. 9B and would have the same disadvantages of that structure.

(21) However, the first vanes 204 are offset from the second vanes 210 by an offset distance D equal to the width of one cavity and one vane. This shift results in the relative polarity on opposing (i.e., laterally aligned) vanes 204, 210 at the instant in time represented being equal, such that the shifted RPM is operating in the even pi mode. Recall from FIG. 9A that operating in the even pi mode results in opposing vanes having like charge at a given instant in time. This means that the shifted RPM shown in FIG. 12 will benefit from the aforementioned beneficial operating properties of the even pi mode, such as lower magnetic field requirements and enhanced mode stability.

(22) Shifting the upper and lower planar magnetron sections with respect to one another requires the recirculation sections 234 to be altered to maintain the electromagnetic connection between the shifted planar magnetron sections. In particular, after laterally shifting the magnetron sections 202, 208 with respect to one another one, one side of each of the recirculation sections 234 is longer than the other in order to accommodate this shift. Accordingly, the anode includes a short connection member 230 and a long connection member 232 extending outwards from opposing ends of each of the upper magnetron section 202 and the lower magnetron section 208. In FIG. 12, the connection members 230, 232 are located on the left-most and right-most ends of the upper magnetron section 202 and the lower magnetron section 208. Each of the long connection members 232 is longer than the short connection members 230 by a distance equal to the offset distance D. Thus, by joining the short connection member 230 of each slow-wave structure to the long connection member 232 of the opposite slow-wave structure, the first and second slow-wave structures 202, 208 are joined together and the first vanes 204 are offset from the second vanes 210 by the offset distance D.

(23) The anode 200 is provided with one or more apertures 236 formed in one or more of the cavities 206, 212 between each of the first and second vanes 204, 210. The apertures are sized and configured to permit extraction of EM emissions from the cavities 206, 212. Extraction waveguides 218, 222 are coupled to each of the apertures 236 for transferring EM emissions away from the anode 200 to an intended load. Preferably, the separate waveguides are joined together with at least one other waveguide to form a combined waveguide. Due to the preferred phase relationship of the RF power in the upper and lower waveguides 218, 222, the EM waves traveling into the combined waveguide would combine constructively (i.e., constructive interference), thereby resulting in efficient power extraction from the device. This is illustrated, for example, in FIG. 10B. While the apertures 236 are depicted to all be the same, in practice, a given aperture or set of apertures may differ from adjacent apertures or sets of apertures in size and geometry. This alteration of aperture size is sometimes done for the purposes of power balancing between waveguides, but would not inhibit the functionality of the present invention.

(24) Additionally, as illustrated in FIG. 13, pi mode operation and waveguide extraction could be accomplished in the case where only every other adjacent cavity includes an aperture connected to an extraction waveguide.

(25) The device illustrated in FIG. 2 includes a coaxial waveguide. The improved anode 200 of the present invention could be used as a substitute for anode 104. Additionally, the anode 200 would also work for non-coaxial waveguides as well. The cross section of non-coaxial waveguides may be rectangular, elliptical, or other more complex shapes in cross section. The waveguides may include internal structures such as single ridge structures, double ridge structures, or more complex structures. The anode 200 disclosed herein would be expected to function as intended when using any non-coaxial waveguide regardless of its cross section.

(26) Thus, as illustrated above, the anode design disclosed herein gains the preferred phase relationship of the RF power in the upper and lower waveguides, generally associated with the odd pi mode, while operating in the even pi mode. The anode 200 and cathode 224 discussed above may be substituted for the anode 104 and cathode 102 installed in the RPM 100 shown in FIG. 2.

(27) The foregoing description of preferred embodiments for this disclosure have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the disclosure to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments are chosen and described in an effort to provide the best illustrations of the principles of the disclosure and its practical application, and to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the disclosure as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.