CN102694231A - Novel high-power microwave antenna - Google Patents

Abstract

The invention provides a radial line slot array antenna for high-power microwave radiation. By connecting the radial line slot array structure at the end of the circular waveguide transmitting the TM ₀₁ mode, it can make the TM with zero axial energy _{The 01} mode forms a radiation field whose energy is concentrated in the axial direction. The invention works in the X wave band, the bandwidth is within 5.8%, and the reflection coefficient is less than -10dB. When there are two gaps, the gain in the frequency band is not less than 20dB. From the simulation results, the radiation efficiency at the working frequency can reach 92%, and the power capacity is on the order of GW. Radiation surface radius is 4λ _g . The longitudinal length from the end of the feeding circular waveguide to the end of the antenna is 1.35λ _g . The invention has the advantages of small longitudinal length, large power capacity, coaxial input and output, axial radiation, high radiation efficiency, easy adjustment and the like.

Description

A New High Power Microwave Antenna

technical field

The invention belongs to the technical field of high-power microwave radiation system design, and relates to technologies such as mode conversion, axial radiation, axial length shortening, high-power capacity and high-efficiency radiation in high-power microwave radiation.

Background technique

High power microwave technology is a new discipline that emerged with the combination of plasma physics and pulse power technology in the 1970s. The pursuit of higher power, higher energy and higher frequency microwave sources in military research has promoted the development of high power microwaves.

The output of the high-power microwave source is the TM _0n and TE _0n modes of the circular waveguide, or the TEM mode of the coaxial waveguide, and the axial field of these modes is zero. If these modes are radiated directly, there will be problems such as zero axial radiation, energy dispersion, and high side lobe level, and the energy cannot be effectively concentrated on the target. Therefore, how to realize the axial radiation of high-power microwave energy is the primary problem. With the continuous development of military and other scientific research, higher requirements are put forward for the power capacity and volume miniaturization of high-power microwave radiation devices.

Using a mode converter or a mode conversion antenna can convert the field mode into the center with the strongest energy, so that the high-power microwave can be effectively concentrated in the axial radiation. The power capacity, volume and orientation of these devices have become the top priority of research.

Contents of the invention

The object of the present invention is to provide a high-power microwave antenna working in the X-band. For the case where the fed electromagnetic wave is the TM ₀₁ mode in the circular waveguide, the structural form of the radial line slot array is adopted, and an adjustable cylindrical cavity is added at the center of the radiation surface. The invention has the advantages of simple structure, short axial length, coaxial input and output, high power capacity and high radiation efficiency.

Traditional high-power microwave radiators need to perform mode conversion, but general mode converters are not only complex in structure and usually have an axial length of more than five wavelengths, the present invention does not need to perform mode conversion, so the axial length is greatly shortened. And because there is no medium added to the structure, the slit width is appropriately increased in the slit of the radiation surface and the two ends of the slit are rounded, so it has a high power capacity. Add a height-adjustable cylindrical cavity at the center of the radial line, and the standing wave characteristics can be improved by adjusting the height of the cavity; by adjusting the size of the slit, the radiation characteristics of the antenna can be improved, so that the radiation of high-power microwaves has a high s efficiency.

The high-power microwave antenna invented in this paper is composed of a feeding circular waveguide, a metal base plate, a slot radiation surface, a radial terminal short-circuit side wall and a cylindrical cavity. By controlling the height of the radial waveguide, only the TEM mode electromagnetic wave propagating in the radial direction exists when the electromagnetic wave of the TM ₀₁ mode in the circular waveguide is transmitted into the radial waveguide. Slits are opened on the metal radiating surface according to certain rules. By adjusting the size, radial distance, azimuth angle and angle with the radial direction of the slit, the slit can be radially polarized or circularly polarized in the axial direction. electromagnetic waves. Then through a certain number of slits in the form of forming an array and superimposing them in the axial direction, high-efficiency axial radiation of electromagnetic waves can be realized. Adding a height-adjustable cylindrical cavity at the center of the radiation surface can adjust the standing wave characteristics of the antenna. Compared with the traditional high power microwave antenna with mode conversion structure, the antenna has the following advantages:

(1) The form of radial lines is adopted, so that the axial length of the antenna is greatly reduced.

(2) There is no dielectric material in the structure, and the shape of the gap with rounded corners is adopted, which has high power capacity.

(3) The antenna input and output are coaxial.

(4) By adjusting the arrangement of the radiation slits, the linear polarization or circular polarization of the radiation wave can be realized.

(5) An adjustable terminal short-circuit circular waveguide is set at the center, which can adjust the standing wave in the required frequency band.

Description of drawings

Fig. 1 is three views of structure of the present invention;

Among them, 1 is the feeding circular waveguide, 2 is the metal bottom plate, 3 is the radiating surface of the slot, 4 is the short-circuit side wall of the radial terminal, and 5 is the cylindrical cavity.

Figure 2 is an explanatory diagram of the arrangement of the gaps;

Fig. 3 is a graph of the reflection coefficient of the antenna;

Fig. 4 is φ=0 ° in-plane gain pattern;

Fig. 5 is φ=90 ° in-plane gain pattern;

Fig. 6 is the main polarization and cross polarization direction diagrams within the range of the main lobe in the plane of φ = 45°.

Detailed ways

Referring to FIG. 1 , the radial line high-power microwave antenna of the present invention consists of a feeding circular waveguide 1 , a metal base plate 2 , a slot radiation surface 3 , a radial terminal short-circuit side wall 4 and a cylindrical cavity 5 .

The invention works in the X wave band, feeds the electromagnetic wave of TM ₀₁ mode from the circular waveguide, and forms the electromagnetic wave of TEM mode transmitted along the radial direction when the electromagnetic wave propagates to two metal plates. During the transmission of electromagnetic waves in the radial direction, the outward traveling wave and the inward traveling wave reflected by the short-circuit side wall respectively radiate energy through the gaps of the radiation surface, and the radiation of each pair of slots can be made in the axial direction through the proper slot arrangement. The direction is superimposed, so that the energy is concentrated and radiated in the axial direction.

What is designed here is a linearly polarized antenna, and the relevant parameters of the slot are shown in Figure 2. Each slot pair is composed of two slots whose centers are at the same azimuth and are perpendicular to each other. The length of the slot is L, the width is t, and the azimuth angle is Φ. The distances from the center of the gap to the center of the circle are ρ ₁ and ρ ₂ , and the included angles with the radial direction of the azimuth are ψ ₁ and ψ ₂ respectively. To make the slot polarize electromagnetic waves to radiation, the phase difference between the slots should be 0° or 180° (180° is selected here), that is, ρ ₁ and ρ ₂ should satisfy the following relationship:

${\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Where λ _g is the waveguide wavelength.

To make the slot pairs at different angles radiate linearly polarized electromagnetic waves in the same polarization direction, ψ ₁ and ψ ₂ should respectively satisfy the following relations:

${\mathrm{<span\; class="notranslate">\; \&psi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; \&Phi;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

According to the above conclusions, the slit pairs can be arranged in a circular form, and the slit pairs can be arranged on several circles, and the radii of these circles are:

ρ _m1 = ρ ₁ ±mλ _g (4)

ρ ₂ = ρ ₂ ±mλ _g (5)

Among them, _ρm1 and _ρm2 are the radial distances from the first and second slits of any slit pair to the center of the circle respectively, and m is the circumference of the slit pair (the slit represented by ρ _m1 and ρ _m2 ) and the reference slit pair (the gap represented by ρ ₁ and ρ ₂ ) is the difference in the number of weeks of the circumference. Therefore, the radial distance S _ρ between adjacent slot pairs is λ _g . On the other hand, the distance S _φ between slot pairs can be selected arbitrarily according to the actual slot arrangement, as long as the grating lobe suppression condition is satisfied. At no time, the number of turns required for the slot is determined according to the requirements of the gain index. If high gain is required, the goal can be achieved by appropriately increasing the antenna aperture and increasing the number of turns of the slot pair. Adding terminal short-circuit sidewalls in the radial waveguide can suppress the lateral radiation of the antenna, and at the same time make the unradiated electromagnetic waves radiate again after reflection, thereby improving the gain of the antenna.

So far the slot arrangement principle of the linearly polarized antenna has been fully determined, and the specific selection of the relevant parameters of the design steps of the present invention will be described in detail below:

1. The thickness h of the radial waveguide should be selected to ensure that only radial electromagnetic waves of a single TEM mode are transmitted in the radial waveguide, so h<λ _g /2, here is 12mm.

2. According to the gain requirement of the present invention, it is designed to be two rings of slots, the radial distance of the first slot of the first ring of slots should be greater than the radius of the feed waveguide, and because there are higher-order modes near the center, in order to reduce the higher-order mode , the initial radial distance should be a larger distance away from the center, where Here the superscript (m, n) represents the corresponding parameter in the nth slot pair in the mth ring slot pair.

3. The selection principle of the slot size is the same as that of the traditional rectangular waveguide slot antenna, the slot length should be equal to the half wavelength corresponding to the resonance frequency. Here in order to reduce the abrupt structure, rounded slits are used, so the slit length L=18.8mm, which is slightly larger than half the wavelength. Here the gap width t=3mm.

后，根据(4)式可确定再根据(1)式即可确定4. OK

After that, according to formula (4), it can be determined that Then according to formula (1), it can be determined that

${\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="g"\; filenames="HSA00000456284700023.png"\; state="\{\{state\}\}">g</figure-callout></span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ,</span>$

${\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="g"\; filenames="HSA00000456284700023.png"\; state="\{\{state\}\}">g</figure-callout></span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; .</span>$

5. According to the radial distance of the two circles of slits and the selected slit length, 20 and 32 slit pairs are evenly arranged in the two circles of slit pairs respectively, that is, Φ ^{(1, n)} = 360(n-1)/20, (n =1, 2, ..., 20), Φ ^{(2, n)} = 360(n-1)/32, (n = 1, 2, ..., 32) the angle between each slot in the slot pair and the radial direction is given by (2) (3) determined,

6. The standing wave and resonance frequency can be adjusted by changing the radius and height of the cylindrical cavity. Here, the radius is 46.5mm and the height is 34.5mm. The position of the radial terminal short-circuit sidewall in the radial waveguide should make the reflected wave and the incident wave superimpose in phase at the slot, so the distance between the short-circuit wall and the outermost ring gap is 17.5mm≈λ _g /2.

Through the above design, the length of the high-power microwave antenna from the metal bottom plate to the top of the cylindrical cavity is 47mm=1.35λ _g , the radius of the metal plate is 140mm, and the distance between the center of the outermost gap and the center of the metal plate is 122.5mm. The working frequency is 8.6GHz. The bandwidth with reflection coefficient less than -10dB reaches 5.8%, as shown in Figure 3. The gain patterns in the two planes of φ=0° and φ=90° are shown in Figure 4 and Figure 5, and the gain is 20.8dB when the slot pair is two turns, and the gain is not low in the bandwidth of 5.8% At 20dB, the cross polarization is less than -35dB, as shown in Figure 6. From the simulation results, the total efficiency of the antenna can reach 92%. From the known radio frequency breakdown field strength of the metal surface in vacuum at the MV/cm level, the maximum field strength value of the gap surface can be estimated that the power capacity of the antenna can reach the GW level.

Above, the description of the present invention is provided for those skilled in the art so that they can easily understand and use the present invention. Various modifications to these implementations will be apparent to those skilled in the art without requiring inventive effort. Accordingly, the invention is not intended to be limited only by the arrangements described herein, but only in accordance with the scope of the appended claims.

Claims (5)

1. novel high-power microwave antenna comprises circular waveguide 1, metal base plate 2, gap radiation face 3, radially terminal short circuit sidewall 4 and cylindrical cavity 5.

2. novel high-power microwave antenna according to claim 1 is characterized in that, at transmission TM ₀₁The end of the electromagnetic circular waveguide of pattern adds radial transmission line gap array irradiation structure, and the high power microwave radiation device that utilizes the mode conversion structure compared to traditional has reduced radiator length longitudinally greatly.

3. novel high-power microwave antenna according to claim 1 is characterized in that, there is regulating action the size of center short board and position to the standing wave of radiator in working band.

4. novel high-power microwave antenna according to claim 1 is characterized in that, the arrangement mode of adjustment radiating slot can form the radiated wave of linear polarization or circular polarization.

5. novel high-power microwave antenna according to claim 1 is characterized in that metal sidewall has reduced the side direction radiation, utilizes reflected wave to improve gain.

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