RU2435260C2 - Plane antenna - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: in plane antenna the plane waveguide (1) is dielectric, and on its outer side there located is slot array (3) consisting of metal bands parallel to each other, with period of about the length of wave in plane dielectric waveguide (1); at that, communication slot (4) serves for excitation of surface waves in plane dielectric waveguide (1) throughout its width. Excitation device is made in the form of linear array of emitters; metal reflecting boards (5) are located on edges of plane waveguide (1) parallel to metal bands of slot array (3) and made in the form of solid walls or rows of metal pins.

EFFECT: increasing antenna efficiency, enlarging operating frequency band, improving compatibility with transmission feed line and improving compactness of the design.

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Description

The proposed device relates to antenna technology and can be used in radio communication systems, radar systems and in security devices and systems of the microwave (ultra-high frequency) and EHF (extremely high frequencies) ranges.

Known flat antenna using a surface wave [1], made on the basis of a shielded radial waveguide with a grid of concentric metal rings, excited through a slot in the center of the screen, over which on the outer surface of the dielectric waveguide is a matching element in the form of a metal disk. An antenna is an antenna array with central power and radiation normal to the aperture plane.

The disadvantage of this antenna is its low efficiency (defined as the product of the coefficient of performance (COP) and the utilization of the surface (KPI) of the aperture of the antenna), which, as a rule, does not exceed 50%. This is due to the fact that when the azimuthal amplitude distribution of the field is implemented in the antenna in the aperture of its field, the instrumentation usually does not exceed 50%. In addition, the radiation of this antenna inevitably contains a significant orthogonally polarized component. Another known flat antenna with the possibility of radiation normal to the aperture plane [2], which contains, in particular, two slotted sublattices excited in the center using a linear array based on a non-emitting dielectric waveguide (NRE), has a narrow operating frequency band, since the excitation of the NRD produced from its end, which leads to the rapid splitting of the main lobe of the radiation pattern.

The closest analogue is a slot antenna array with radiation normal to the aperture plane [3], adopted as a prototype.

Figure 1 presents a drawing of the antenna of the prototype, where indicated:

1 - waveguide cavity;

2 - upper and lower metal plates;

3 - lattice of radiating slits;

4 - communication gap;

5 - metal (reflective) sides;

6 - excitation device (power distribution).

The prototype antenna contains a waveguide cavity 1 formed by parallel metal plates 2, the lower one plays the role of a screen, and the upper one contains a lattice of radiating slots 3. In the lower plate 2 there is a communication gap 4 of the waveguide cavity with the excitation (power distribution) device 6, which is made in the form of a sectorial horn antenna. Metal reflective edges 5 are located between the edges of the upper and lower metal plates 2 and are electrically connected to them.

The disadvantages of the prototype antenna are the bulkiness of the design and narrowband due to the problem of matching the antenna with the supply line, inherent in resonant slot antenna arrays, and low efficiency, i.e. the product of the antenna efficiency and the surface utilization coefficient of the radiating aperture.

The objective of the proposed technical solution is to increase the antenna efficiency, expand the operating frequency band, improve coordination with the power transmission line and increase the compactness of the design.

Figure 1 presents a drawing of the antenna prototype; figure 2 is a drawing of the proposed antenna; figure 3 is an embodiment of the structural elements of the proposed antenna; figure 4 is a diagram of the proposed antenna, explaining the principle of its action.

To solve the problem in a flat antenna containing a flat waveguide, the bottom plate of which is a metal screen, provided with a communication gap with an excitation device, as well as a slotted grating and reflecting metal sides electrically connected to a metal screen and located on opposite edges of the plane waveguide, according to the invention a flat waveguide is made dielectric, on the outside of which there is a slotted grating consisting of metal strips parallel to each other, a period of the order of the wavelength in a plane dielectric waveguide, and the coupling gap serves to excite surface waves in a plane dielectric waveguide over its entire width, while the excitation device is made in the form of a linear array of emitters, metal reflecting edges are located along the edges of the plane waveguide, parallel to the slotted metal tapes lattice, and made in the form of solid walls or rows of metal pins.

Figure 2 presents the drawing of the proposed flat antenna, where indicated:

1 - flat dielectric waveguide (PDV);

2 - a metal plate (screen);

3 - slotted (diffraction) grating of metal ribbons;

4 - communication gap;

5 - metal reflective sides;

6 - metal grooved waveguide:

7 - dielectric substrate;

8 - a system of metal strip elements.

Figure 3 shows a drawing of the structural elements of the proposed antenna, where the designations 1 to 8 are similar to the designations in figure 2, and 9 is the hole in the center of the metal groove waveguide 6.

The proposed antenna contains a flat dielectric waveguide (PDV) 1 located on a metal screen 2, on the outer surface of the PDV 1 there is a diffraction grating 3 made of metal strips, in which the edges of adjacent ribbons form emitting slits, and the central ribbon of the diffraction grating 3 has a width of the order of the grating period (distances between the centers of adjacent tapes). In addition, in the center of the screen 2 there is a communication gap 4 with an excitation device in the form of a combination of a metal groove waveguide 6, in which a linear antenna array based on a comb strip line is placed - a dielectric substrate 7 and a system of metal strip elements 8 (Fig. 3).

Along the ends of the PDV 1, parallel to the edges of the tapes of the slotted grating 3, there are metal reflecting edges 5 electrically connected to the screen 2. Moreover, the metal edges 5 can be installed along the other ends of the PDV 1, perpendicular to the metal tapes of the slotted grating 3, to reduce the level of lateral radiation of the antenna . The hole 9 is located in the center of the metal grooved waveguide 6, as shown in Fig.3.

The principle of operation of the proposed antenna is illustrated using figure 4, on which are indicated: 1 - PDV, 2 - metal screen, 3 - slotted lattice of metal bands; 4 - communication gap with the excitation device (located under the central ribbon and stretched along the OY axis).

In the inventive flat antenna, upon excitation of the communication gap 4 by a wave with polarization of the electric field vector E, perpendicular to the wide edges of the communication gap 4, a surface wave of the TM type is excited in PDV 1, propagating in both directions from the metal central ribbon of the slotted grating 3. When it is scattered by Diffraction grating 3 generates radiation with H-polarization (the vector E in the aperture plane is oriented along the OX axis, i.e., is perpendicular to the edges of the slit grating ribbons 3).

The radiation directions of both halves of the antenna aperture (which lie at the central working wavelength in the XOZ plane) are determined by angles Θ _nmax relative to the normal to the aperture plane:

sinΘ _nmax = γ (λ) + nλ / d,

where γ (λ) = c / v _f - deceleration of the phase velocity of the surface wave of the MPE;

λ is the working wavelength; d is the lattice period; n is the number of spatial harmonics (GH) of the radiation field.

Reception and emission of electromagnetic waves by the antenna are provided in the operating mode at minus the 1st GHG. Obviously, at the wavelength at which the deceleration of the surface wave of the MPE 1 is equal to the ratio of the wavelength to the lattice period, Θ _-1max = 0, the radiation of both halves of the _aperture is in phase in the direction normal to its plane, i.e. along the OZ axis (second-order Bragg resonance diffraction takes place). Due to the fact that the central ribbon of the grating 3 has a width of the order of the grating period, and the PDV 1 thickness is selected on the order of a quarter of the wavelength in the dielectric, minimal reflection from the antenna input is ensured, so that the SWR at this wavelength can be close to 1. Moreover, good agreement is maintained in frequency band greater than 5%. The use of surface waves PDV 1 allows for high antenna efficiency. With a relative PDV 1 thickness of not more than 0.2–0.3 of the maximum radiation wavelength, an almost single-mode wave propagation mode of the TM type is ensured, which makes it possible to obtain radiation from an antenna with a very low level of spurious (orthogonal) polarization. The excitation device can be made in the form of a compact linear antenna array (in the form of a combination of a metal grooved waveguide 6, in which a linear antenna array based on a comb-strip line is placed — a dielectric substrate 7 and a system of metal strip elements 8), which minimizes the dimensions and weight of the antenna generally.

An example of a specific implementation of the antenna is illustrated in Fig.3. In this example, a device in the form of a comb-shaped strip line (7-8) placed in a rectangular grooved waveguide 6 and fed in the center by a rectangular metal waveguide through aperture 9 is proposed to excite a gap in the PDV screen 1. The operability of this variant of the antenna was tested by computer simulation and experimentally in the microwave range at frequencies of 9-10 GHz. It was found, for example, that the operating frequency band at the SWR level of ≈2 was 5%, and with a maximum gain of 28.7 dB, the maximum antenna efficiency was 74%.

Thus, the proposed antenna has a wider frequency band, better matching with the supply line of transmission, a reduced level of orthogonally polarized radiation and increased compactness of the design.

Information sources

1. Microwave directional antenna using a surface wave (US Patent No. 4536767), 08/20/1985.

2. An electromagnetic emitter using a non-emitting dielectric waveguide with a leaky wave (US Patent No. 5416492, 05.16.1995).

3. Slit antenna array (US Patent No. 5173714, 12/22/1992).

Claims (5)

1. A flat antenna containing a flat waveguide, the bottom plate of which is a metal screen equipped with a communication slot with an excitation device, as well as a slotted array and reflecting metal sides electrically connected to the metal screen and located on opposite edges of the plane waveguide, characterized in that the plane the waveguide is made dielectric, on the outside of which there is a slotted grating consisting of metal strips parallel to each other, with a period of the order of the wavelength a glossy dielectric waveguide, and the coupling slit serves to excite surface waves in a planar dielectric waveguide over its entire width, while the excitation device is made in the form of a linear array of emitters, metal reflecting edges are located at the edges of the plane waveguide, parallel to the metal tapes of the slotted array, and are made in as solid walls or rows of metal pins. 2. The device according to claim 1, characterized in that along the ends of the plane waveguide, perpendicular to the tapes of the slit lattice, metal boards are installed with a height of the order of the thickness of the waveguide, and having electrical contact with the screen. 3. The device according to claim 2, characterized in that the opposite narrow edges of all the tapes or only one central tape have electrical contact with the metal sides. 4. The device according to claim 1, characterized in that the linear array of emitters is made in the form of a lattice of slits in a metal waveguide. 5. The device according to claim 1, in which the linear array of emitters is made with power in its center.

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