RU2578660C1 - Planar dielectric radiator - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to microwave antenna engineering. Disclosed planar dielectric radiator consists of exciting single-mode rectangular dielectric waveguide dielectric flat wedge and dielectric plate with two slots, end of which is aperture of radiator, a wedge is connected to side of tops with exciting its single-mode rectangular dielectric waveguide with polarisation of electric field along wide side of cross section, on other side to wedge is attached plate with two slits format (ratio of sides) cross section of f which is selected from condition F_kr15≤F≤F_kr17, where F_kr15 and F_kr17 - critical values format cross-section rectangular dielectric waveguide for waves HE₁₅ and HE₁₇ respectively, wedge vertex angle must not be more than 15 degrees, thickness of wedge and plates are equal to narrow side section of exciting waveguide slot in plate are arranged symmetrically and parallel to its axis and can have an arbitrary shape.

EFFECT: technical result is possibility of obtaining radiation with amplitude distribution, described by one of transverse spatial coordinates of Gauss-Hermitic function of zero-order.

2 cl, 4 dwg

Description

The invention relates to the antenna technique of the EHF range, can be used in probing devices of diagnostic equipment, in exciters of quasi-optical transmission lines of the millimeter wavelength range and is intended for the formation of localized radiation in the form of a zero-order Gaussian-Hermite wave beam that preserves beam properties at distances up to tens of lengths waves.

Known dielectric emitters in the form of an end face of a regular single-mode dielectric waveguide (DW) or DW, smoothly tapering or expanding at the end [1].

The disadvantage of such emitters is the formation of a rapidly diverging wave beam that preserves the beam properties of the radiation at distances of not more than 5 wavelengths from the end of the emitter.

Closest to the proposed invention is a planar emitter selected for the prototype, consisting of an exciting single-mode dielectric waveguide and a flat wedge connected to it by its apex, passing into the plate, the end of which is the aperture of the emitter [2].

The emitter selected for the prototype provides a distribution of the radiation field along one of the transverse coordinates, close to the Gauss-Hermite beams, at distances up to tens of wavelengths from the aperture of the emitter.

However, for a number of applications, in particular, problems of multichannel diagnostics, to increase the accuracy of measurements and the possibility of an analytical description of the radiation field, it is necessary to form an amplitude distribution that is approximated to the maximum degree by a zero-order Gaussian-Hermite beam.

The disadvantages of the emitter selected for the prototype are the limited possibilities of the formation of a Gaussian-Hermite wave beam of zero order due to the small amplitude of the higher types of waves excited at the input of the plate. The ability to control the amplitudes of the higher types of waves in the prototype emitter is limited only by the choice of the angle at the top of the wedge and its length.

The technical result of the proposed invention is the ability to obtain radiation with an amplitude distribution, described in one of the transverse spatial coordinates by the Gaussian-Hermite function of zero order.

The technical result is achieved in that in a planar dielectric radiator, consisting of an exciting single-mode rectangular dielectric waveguide with polarization of the electric field along the wide side of the cross section and a dielectric flat wedge made of the same material, with an angle at the apex not exceeding fifteen degrees, turning into dielectric plate width b, which is the end of the radiator aperture and a thickness equal to the thickness of the plate and the narrow side of the wedge and transverse ce eniya exciting the waveguide plate has a cross-sectional format F = b / a, which is selected from the condition F _{kr15 kr17} ≤Φ≤Φ where F and F _{kr15 kr17} - critical values of the cross-sectional size of the rectangular dielectric waveguide for ΗΕ waves ₁₅ and _17, respectively NO , at the transition point of the wedge into the plate, two slots are made, located symmetrically and parallel to the axis of the plate, the dimensions of which are selected from the condition for the transformation of the HE ₁₁ wave into waves ΗΕ ₁₃ and HE ₁₅ with an amplitude ratio of 1: 0.3: 0.1, and the plate length is selected from the phase condition inhronizma wave is not _11, not _13, and ₁₅ ΗΕ on her butt.

≤d≤0,8λ/

и 19,7λ/

≤L≤22,2λ/

, где λ - длина волны излучения, ε - диэлектрическая проницаемость излучателя, которая должна быть в пределах от 2,1 до 2,3, размеры щелей - ширина δ и площадь S удовлетворяют соотношениям 0,18λ/

≤δ≤0,27λ/

и 0,3(λ/

)²≤S≤0,5(λ/

)².A planar dielectric emitter can be characterized in that the slots have the shape of a hexagon elongated along an axis passing through diametrically opposite vertices, with an angle at these vertices of no more than fifteen degrees, and the distance d from the axis of each slot to the axis of the plate and L from the ends of the slots to the aperture emitter selected from the conditions of 0.6λ /

≤d≤0.8λ /

and 19.7λ /

≤L≤22.2λ /

where λ is the radiation wavelength, ε is the dielectric constant of the emitter, which should be in the range from 2.1 to 2.3, the dimensions of the slits are the width δ and the area S satisfy the relations 0.18λ /

≤δ≤0.27λ /

and 0.3 (λ /

) ² ≤S≤0.5 (λ /

) ² .

In FIG. 1 presents the proposed planar dielectric emitter.

In FIG. 2 shows a planar dielectric emitter with slots having the shape of an elongated hexagon.

In FIG. Figure 3 shows the dependences of the amplitudes of the excited waves on the length of the slits.

In FIG. 4 presents the results of a theoretical calculation and measurement of the amplitude distribution of radiation at a distance from the emitter aperture of 6λ.

In FIG. 1 and FIG. 2 shows a planar dielectric radiator, consisting of a single-mode exciting dielectric waveguide 1 of rectangular cross section ( a × b ₁ ) connected in section I to wedge 2 with an angle at the apex of α≤15 °. Wedge 2 in section II passes into the plate 3 with two slots 4, the end of which is the aperture of the emitter. The electric field Ε of the main wave of waveguide 1 is polarized along the wide side b _{1 of the} transverse section of waveguide 1 and is stored in the wedge 2 and in the plate 3 along their wide sides b (z) and b, respectively. The wide side b (z) of the cross section of the wedge 2 increases linearly. The thicknesses of the wedge 2 and plate 3 are the same and equal to the narrow side a of the cross section of the waveguide 1.

The cross-sectional format of the plate 3 Ф = b / а , equal to the cross-sectional format of the wedge 2 in section II, is selected from the condition

Ф _кр15 ≤Φ≤Ф _кр17 ,

where Φ _cr15 and Φ _cr17 are the critical values of the cross-sectional format of a rectangular dielectric waveguide for waves NOT ₁₅ and NOT _17, respectively.

The waveguide 1, the wedge 2 and the plate 3 are made of the same material with a dielectric constant ε in the range from 2.1 to 2.3.

The slots 4 are made at the transition point of the wedge 2 into the plate 3 and are located symmetrically and parallel to the axis of the plate 3. In the general case, the slots 4 can have an arbitrary shape, in particular rectangular, hexagonal, lentil grain shape, etc.

In FIG. 2 shows a planar dielectric emitter with slots having the shape of a hexagon elongated along an axis passing through diametrically opposite vertices. The angle at these vertices is selected no more than 15 °. The distances d from the axis of each slit to the axis of the plate and L from the ends of the slits to the aperture of the emitter, as well as the dimensions of the slits — width δ and area S — are selected from the conditions

≤d≤0,8λ/

;0.6λ /

≤d≤0.8λ /

;

≤L≤22,2λ/

;19,7λ /

≤L≤22.2λ /

;

≤δ≤0,27λ/

;0.18λ /

≤δ≤0.27λ /

;

)²≤S≤0,5(λ/

)²,0.3 (λ /

) ² ≤S≤0.5 (λ /

) ² ,

where λ is the radiation wavelength.

волн от продольной координаты z/λ щели, имеющей форму прямоугольника: 5 - для волны НЕ₁₁, 6 - для волны НЕ₁₃, 7 - для волны ΗΕ₁₅, 8 - суммарная мощность указанных волн.In FIG. Figure 3 shows the dependences of the modules of complex amplitudes

waves from the longitudinal coordinate z / λ of the slit, having the shape of a rectangle: 5 - for the wave HE ₁₁ , 6 - for the wave HE ₁₃ , 7 - for the wave ΗΕ ₁₅ , 8 - the total power of these waves.

Planar dielectric emitter operates as follows.

In a single-mode rectangular dielectric waveguide 1 (Fig. 1), the main wave HE _{11 is} excited with polarization of the electric field Ε along the wide side of the cross section. Wedge 2 plays the role of a smooth transition from a single-mode waveguide 1 with a small cross-sectional format to a larger plate 3, which makes it possible to excite higher types of waves in the latter.

To minimize energy losses associated with reflection and radiation at irregularities of the waveguide structure of the emitter (sections I and II), the angle at the tip of the wedge should not exceed 15 ° [2].

In the plate 3, which is a segment of a multimode rectangular DW, due to the presence of irregularities in the structure of the emitter, along with the main wave HE ₁₁ , surface waves of higher types HE _{1,2m + 1 are excited} , where m = 1, 2, 3, ..., the number of which is determined by the size of the format Ф = b / а of the cross section of the plate.

Calculations show that for the formation of a wave beam with an amplitude distribution of radiation along the y coordinate in the form of a zero-order Gaussian-Hermite function in plate 3, it is sufficient to excite three surface waves HE ₁₁ , HE ₁₃ and HE ₁₅ with an amplitude ratio of 1: 0.3: 0, one. The contribution of the waves of higher types is NOT ₁₇ , NOT ₁₉ , etc. can be neglected.

Thus, the format Φ of the cross section of the plate 3 should be chosen from the condition

Ф _кр15 ≤Φ≤Ф _кр17 ,

where Φ _cr15 is the critical value of the cross-sectional format of a rectangular dielectric waveguide (PDV) for the HE ₁₅ wave, Φ _cr17 is the critical value of the cross-sectional format of the _PDF for the HE ₁₇ wave.

The indicated format values can be selected from the dispersion dependences of waves ΗΕ ₁₅ and HE ₁₇ PDV [3].

Since the irregularities in the structure of the emitter are weak, the amplitudes of the waves of higher types HE ₁₃ and ΗΕ ₁₅ , excited at the junction of the wedge 2 into the plate 3 (section II), are insufficient to form the required radiation distribution. To obtain the necessary ratio of the wave amplitudes of HE ₁₁ , HE ₁₃ and HE ₁₅ , inhomogeneities are introduced into the plate 3 in the form of two slots 4, which can have an arbitrary shape. Slots 4 are located symmetrically and parallel to the axis of the plate 3.

Considering slots 4 as local inhomogeneities in the form of a perturbation of the dielectric properties of the PDW, in accordance with the theory of coupled waves [4], from the numerical solution of the equations of coupled modes, the relationship between the HE ₁₁ , HE ₁₃ and HE ₁₅ waves is determined depending on the parameters of the slits and the location of the slits in the plate 3.

As an example, for the case where the slots are rectangular in shape, in FIG. Figure 3 shows the dependences of the moduli of the complex wave amplitudes on the longitudinal coordinate of the gap for the HE ₁₁ (5), HE ₁₃ (6) and ΗΕ ₁₅ (7) waves, as well as the total power of these waves (8).

The calculation was performed for the MPE with a cross section of 4λ × 0.3125λ. From FIG. Figure 3 shows that, with a slit length of 1.328λ, the amplitudes of the HE ₁₁ , HE _13, and ΗΕ ₁₅ waves excited in the plate provide the necessary relationships between them to obtain the field amplitude distribution along the y coordinate close to the zero-order Gaussian-Hermite distribution.

The field distribution along the second of the transverse coordinates (x coordinate) will be close to the field distribution of the HE ₁₁ wave due to the choice of the thickness of the wedge 2 and plate 3 equal to the thickness of the single-mode exciting waveguide 1.

In order to form the required radiation distribution in the beam, in addition to providing a given amplitude ratio, it is also necessary to ensure that these waves are in phase, which is achieved by choosing the distance L from the ends of the slits to the aperture of the emitter.

The distance L can be determined from the system of equations

where U ₁₁ , U ₁₃ and U ₁₅ are the deceleration coefficients of the waves NOT ₁₁ , NOT ₁₃ and ΗΕ _15, respectively, in the plate 3; φ ₁₁ φ ₁₃ and φ ₁₅ - phase waves at the boundary of the site with heterogeneities; k = 0, 1, 2, ...; n = 0, 1, 2, ... As the p000000 state L, it is advisable to choose the smallest solution of the indicated system.

Thus, when introducing gaps in the proposed planar dielectric emitter when choosing the plate format, the parameters of the gaps and their location in the plate from the above conditions, the amplitude distribution of the emitted wave beam can be analytically described by the Gaussian-Hermite function of zero order in the y coordinate of the cross section, and the amplitude distribution along coordinate x - distribution of the main wave NOT _{11 of the} rectangular DW.

The choice of the shape of the slits is determined by the technological capabilities of manufacturing and the requirements for the emitter in a particular application - the requirements for the level of reflection, the accuracy of the approximation of the emitted wave beam by the zero-order Gaussian-Hermite function.

To minimize the level of reflections and ensure the minimum possible standard deviation of the amplitude distribution of the emitted beam from the zero-order Gaussian-Hermite distribution, a planar dielectric radiator with slots in the form of a hexagon elongated along an axis passing through diametrically opposite vertices shown in FIG. 2. It has been experimentally established that to minimize reflection from slots, this angle should be no more than 15 °.

The task of determining the size of the slots, their location in the emitter plate is multifactorial. Due to the approximation of the theoretical models inherent in solving the equations of coupled modes for determining the size and location of gaps, neglecting the inhomogeneous waves (gaps) of the resulting waves, the quasiperiodic nature of the dependences of the modules of the complex amplitudes of the excited waves (Fig. 3), phase relations between the modes, a precise exact solution is difficult .

For a planar dielectric emitter with hexagonal slots (Fig. 2), the basic relations are determined for choosing the distance d from the axis of each slit 4 to the axis of the plate 3, the dimensions of the slots (width δ and area S), and the distance L from the ends of the slots to the aperture of the emitter.

When choosing the specified parameters of the slits, the standard deviation of the radiated beam from the zero-order Gaussian-Hermite distribution is ensured no worse than 5 · 10 ^-3 .

A sample of a planar dielectric emitter with slots having the shape of an elongated hexagon (Fig. 2) with an angle at the tip of the wedge α = 10 °, a format of the cross section of the plate Φ = 13.1, angle β = 15 °, and a distance from the axis of the slit to the axis of the plate d = 1.52 mm, the distance from the ends of the slits to the aperture of the emitter L = 45.2 mm, the width of the slit δ = 0.45 mm, and the area of the slit S = 1.7 mm ² . A sample of the emitter is made of fluoroplastic (ε = 2.1), wavelength λ = 3.2 mm, section of the exciting waveguide a = 1.0 mm, b ₁ = 2.2 mm.

The experimentally obtained amplitude distribution of radiation along the transverse coordinate y at a distance from the emitter aperture of 6λ almost coincides with the Gaussian-Hermite distribution of zero order (Fig. 4).

Literature

1. Orekhov Yu.I. Open waveguide and resonant EHF devices for non-contact diagnostics of fast processes in multicomponent media: diss. ... doc. tech. sciences. M., 2007.314 s.

2. Planar emitter: US Pat. 2447552 RF. No. 201042590/07; declared 10/18/10; publ. 04/10/12, bull. No. 10. 2 sec

3. Gainulina E.Yu., Shtykov VV Multimode mode of dielectric planar waveguide-beam converters // Izv. universities. Physics. 2012.V. 55. No. 8/3. S. 5-10.

4. Miller S. The theory of coupled waves and its application to waveguides // Waveguide transmission lines with low losses / Per. under the editorship of B.V. Steinshleiger. M .: Publishing house of foreign countries. lit., 1960.S. 139.

Claims (2)

1. A planar dielectric radiator, consisting of an exciting single-mode rectangular dielectric waveguide with polarization of the electric field along the wide side of the cross section and a dielectric flat wedge made of the same material with an apex angle not exceeding fifteen degrees, turning into a dielectric plate of width b, whose end is the aperture of the emitter, and the plate thickness a is equal to the thickness of the wedge and the narrow side of the cross section of the exciting waveguide, characterized the fact that the plate has a cross-sectional format Ф = b / a, which is selected from the condition Ф _кр15 ≤Ф≤Ф _кр17 , where Ф _кр15 and Ф _кр17 are the critical values of the cross-sectional format of a rectangular dielectric waveguide for waves NOT ₁₅ and NOT _17, respectively at the transition point of the wedge into the plate, two slots are made, located symmetrically and parallel to the axis of the plate, the dimensions of which are selected from the conditions for the conversion of the HE ₁₁ wave into HE ₁₃ and HE ₁₅ waves with an amplitude ratio of 1: 0.3: 0.1, and the plate length is selected from the condition of phase synchronism of waves NOT ₁₁ , N E ₁₃ and HE ₁₅ at its end. 2. A planar dielectric emitter according to claim 1, characterized in that the slots have the shape of a hexagon elongated along an axis passing through diametrically opposite vertices with an angle at these vertices of not more than fifteen degrees, and the distance d from the axis of each gap to the axis of the plate and L from the ends of the slits to the aperture of the emitter selected from the conditions $$0.6\lambda /\sqrt{\epsilon }\le d\le 0.8\lambda /\sqrt{\epsilon }$$

and $$19.7\lambda /\sqrt{\epsilon }\le L\le 22.2\lambda /\sqrt{\epsilon }$$

, where λ is the radiation wavelength, ε is the dielectric constant of the emitter, which should be in the range from 2.1 to 2.3, the dimensions of the slits are the width δ and the area S satisfy the relations $$0.18\lambda /\sqrt{\epsilon }\le \delta \le 0.27\lambda /\sqrt{\epsilon }$$

and $$0.3{(\lambda /\sqrt{\epsilon })}^2\le S\le 0.5{(\lambda /\sqrt{\epsilon })}^2$$

.

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