Left-handed material extended interaction klystron

Abstract

A left-handed material extended interaction klystron includes: an input cavity, a middle cavity, an output cavity, first-section drift tube and a second-section drift tube; wherein the input cavity, the middle cavity and the output cavity are all cylindrical resonant cavities having arrays of Complementary electric Split-Ring Resonator (CeSRR) unit cells provided therein; wherein a first side of the input cavity is an input channel of an electron beam, a second side connects the middle cavity via the first-section drift tube; a first T-shaped coaxial input structure is provided in the input cavity; a first side of the output cavity is for connecting a collector, a second side of the output cavity connects the middle cavity via the second-section drift tube, a second T-shaped coaxial output structure is provided in the output cavity.

Claims

1. A left-handed material extended interaction klystron, comprising: an input cavity, a middle cavity, an output cavity, a first-section drift tube and a second-section drift tube; wherein the input cavity, the middle cavity and the output cavity are all cylindrical resonant cavities having arrays of Complementary electric Split-Ring Resonator (CeSRR) unit cells provided therein; wherein a first side of the input cavity is an input channel of an electron beam, a second side of the input cavity connects the middle cavity via the first-section drift tube; a first T-shaped coaxial input structure is provided in the input cavity; a first side of the output cavity is for connecting an electronic output terminal of an electron collector, a second side of the output cavity connects the middle cavity via the second-section drift tube; a second T-shaped coaxial output structure is provided in the output cavity.

2. The left-handed material extended interaction klystron, as recited in claim 1, wherein a layer of attenuator with uniform thickness is provided on an external side of the first-section drift tube.

3. The left-handed material extended interaction klystron, as recited in claim 1, each array of adjacent CeSRR unit cells of the input cavity, the middle cavity and the output cavity has equal period

4. The left-handed material extended interaction klystron, as recited in claim 1, wherein period of the arrays of the CeSRR unit cells in the input cavity, the middle cavity and the output cavity are reduced in sequence.

5. The left-handed material extended interaction klystron, as recited in claim 3, wherein period of the arrays of the CeSRR unit cells in the input cavity, the middle cavity and the output cavity are reduced in sequence.

6. The left-handed material extended interaction klystron, as recited in claim 1, wherein the input cavity, the middle cavity and the output cavity all have four CeSRR unit cells.

7. The left-handed material extended interaction klystron, as recited in claim 3, wherein the input cavity, the middle cavity and the output cavity all have four CeSRR unit cells.

8. The left-handed material extended interaction klystron, as recited in claim 1, wherein the CeSRR unit cells comprise an external metal ring, two coupling gaps, an internal metal ring and two sections of metal bridge for connecting the internal metal ring and the external metal ring; wherein grooves are provided on a joint of the metal bridge and the internal metal ring; a center of the internal metal ring has an electron beam channel and the first section internal drift tube is provided on an external side of the electron beam channel.

9. The left-handed material extended interaction klystron, as recited in claim 8, both the first-section drift tube and the second-section drift tube a circular waveguide structure, wherein an internal radius of the drift tube structure is equal to a radius of the electron beam channel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1-a is a front view of a CeSRR; FIG. 1-b is a left view of the CeSRR; FIG. 1-c is a schematic structural view of an EIK input cavity; FIG. 1-d is an overall structural diagram of the Left-Handed Materials EIK.

[0020] FIG. 2 is a peak output power diagram of an EIK amplified signal.

[0021] FIG. 3 is a spectrum diagram of an output signal of the EIK.

[0022] FIG. 4 is a diagram of gain and electronic efficiency of the output signal versus the input power of the EIK.

[0023] FIG. 5 is a diagram of peak output power versus the input signal of different frequency.

[0024] FIG. 6 is a peak output power diagram corresponding to different axial focusing magnetic field.

REFERENCES OF THE DRAWINGS

[0025] 1external metal ring; 2coupling gap; 3electron beam channel; 4metal bridge; 5groove; 6internal drift tube; 7internal metal ring; 8T-type coaxial input structure; 9input channel of an electron beam; 10metal shell of the cylindrical resonant cavity; 11attenuator; 12first section drift tube; 13second section drift tube; 14T-type coaxial output structure; 15electron beam output terminal; Ainput cavity; Bmiddle cavity; Coutput cavity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0026] Further description of the present invention is illustrated combining with the accompany drawings and the preferred embodiments.

[0027] Referring to FIG. 1-a, FIG. 1-b, FIG. 1-c and FIG. 1-d, wherein a size of the left-handed materials EIK is as follows. Inner diameters of three cylindrical resonant cavities are all 36 mm. A radius of the electron beam channel is 4 mm. A wall thickness of the cavities is 2 mm. A length of an input cavity A is 68.5 mm; a period of adjacent CeSRR is set as 20 mm; lengths of internal drift tubes are all 8.5 mm, a length of a T-shaped head is 11 mm; a distance of the T-shaped head to a central axis is 10 mm. An internal radius and an external radius of a coaxial input structure are respectively 0.5 mm and 3.5 mm. A length of a middle cavity B is 66.8 mm. A period length of an adjacent CeSRR in the middle cavity is 19.5 mm, wherein an internal drift tube thereof has a length of 8.3 mm. A length of an output cavity C is 63.8 mm. In the output cavity, a the length of a T-shape head is 12 mm, a distance of the T-shape head to a central axis is 9 mm, A period of an adjacent CeSRR in the output cavity is 18.5 mm and corresponded internal drift tubes are respectively 8.5 mm, 8.5 mm, 8.0 mm and 8.0 mm. A length of a first section drift tube is 45 mm and a length of a second section drift tube is 50 mm. A diameter of an external metal ring of the CeSRR is 36 mm; a width of the external metal ring is 2 mm; a diameter of an internal metal ring is 26 mm; a diameter of an electron beam channel is 8 mm; a width of a coupling gap is 3 mm; a width of a metal bridge is 2 mm; a width and a depth of grooves on double sides of a metal bridge are respectively 3 mm and 2 mm; thicknesses of both the CeSRR and internal drift tube are 1 mm. In addition, an external side of a first section drift tube is filled with an attenuating material of beryllium oxide (BeO) having a thickness of 3 mm; wherein the relative permittivity of the attenuating material is 6.5 and a loss angle tangent is 0.5. Thus, the high-frequency oscillation is suppressed and the electron beam entering into the middle cavity is easier for further modulation.

[0028] Based on the structure parameters mentioned above, for a three-cavity left-handed material EIK, when a voltage of the electron beam is 33.5 kV, a current of the electron beam is 4 A, a magnetic induction density of the focusing electron beam is 0.15 T. As shown in FIG. 2, when the input power is 0.72 W, a peak output power is 102.3 kW, and a corresponding average output power is 51.15 kW. The spectrum of the output signal is obtained using Fourier transform. As shown in FIG. 3, it can be seen that the spectrum is very pure and there is no clutter signal, and the operating frequency is 2.4574 GHz, which only has a small difference with a frequency of the input signal (2.457 GHz). This difference is come from the electron beam load. In addition, when a frequency of the input signal is fixed at 2.457 GHz, the electronic efficiency and gain corresponding to different input power is as shown in FIG. 4. The FIG. 4 shows that a maximum electronic efficiency of the three-cavity EIK is 39%, and a corresponding gain is 48.5 dB. Here, the input cavity is a three-gap extended interaction structure, in such a manner that the electron beam which enters the output cavity obtains a greater modulation current of the fundamental wave. Hence, the electronic efficiency is further improved. When the beam voltage and current are 33.5 kV and 4 A, respectively, the focusing magnetic field is 0.2 T, and the input power is 0.5 W, the simulation results show the peak output power as a function of the input signal frequency (FIG. 5). FIG. 6 shows the peak output power versus the axial focusing magnetic field. It can be seen that the left-handed material EIK can obtain a larger output power with a lower axial uniform magnetic field (0.1 T) relative to conventional klystrons.

[0029] In summary, the left-handed material EIK provided by the present invention based on the mechanism of the transition radiation in left-handed materials is a low-band EIK with a high gain, high efficiency and small size. The EIK is easy achieving and has excellent performances in a three-cavity structure. The left-handed material EIK can achieve high gain, high efficiency, and wide bandwidth by using multiple left-handed material extended interaction cavities. Thus, the four or even more left-handed material extended interaction cavities can further improve the performance of the proposed EIK. Meanwhile, adopting unequal period and unequal high-frequency gaps has the potential of further enhancing the electronic efficiency. The output power can be further enhanced by improving period. Thus, resonant cavity with multiple gaps has advantages in tuning bandwidth, increasing efficiency, and shortening the axial length. Based on the left-handed material, similar left-handed material extended interaction oscillator (EIO) can be further designed. The three-cavity or multiple-cavity left-handed material EIK has wide application prospects in radar, industrial heating and satellite communications. In addition, the present invention provides new design ideas for developing other vacuum electronic devices with small size and high performance in other frequency bands.

[0030] One skilled in the art will understand that the embodiment of the present invention as shown in the drawings and described above is exemplary only and not intended to be limiting.

[0031] It will thus be seen that the objects of the present invention have been fully and effectively accomplished. Its embodiments have been shown and described for the purposes of illustrating the functional and structural principles of the present invention and is subject to change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.