RU2593910C2 - Vivaldi antenna with printed lens on single dielectric substrate - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: Vivaldi antenna comprises a dielectric substrate, a metal layer, a slit in the metal layer with divergent walls along the longitudinal direction and forming an antenna aperture, a lens placed in the antenna aperture and made from scatterers. The scatterers are in the form of electroconductive plates placed on the dielectric substrate between the divergent walls, and are free of contact with the walls of the slit for compensation of phase distortions in the aperture.

EFFECT: device reduces longitudinal and transverse dimensions of the antenna and has a simple design.

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Description

The invention relates to antenna technology, in particular to ultra-wideband antennas, and can be used in various broadband radio systems.

Known polarization converter containing a dielectric substrate on which are placed conductive plates made in the form of squares, rectangles, ellipses, polygons, in particular regular hexagons arranged in parallel rows (US patent No. 3267480).

This converter is used in antenna-feeder devices to convert, for example, linear polarization to circular, and vice versa.

Vivaldi's antenna design was first proposed by Gibson (Gibson P.J., "The Vivaldi aerial", Proceeding 9th European Microwave Conference, 1979, pp. 101-105). The Vivaldi antenna contains a dielectric substrate, a metal layer located on the dielectric substrate, a slot made in a metal layer with expanding walls along its longitudinal direction, forming the opening of the antenna. An antenna of the TSA type (abbreviation from the English. Tapered Slot Antenna - an antenna with an expanding slot) has a shape resembling a tuning fork, therefore, because of the musical association, the TSA is commonly called the Vivaldi antenna.

The established TSA patterns are as follows.

Its slit width determines the lower frequency, like a dipole.

The length of the expanding walls of the slit determines the gain in the middle and on the upper edge of the strip, as in a log-periodic antenna or horn.

The shape of the slit determines the frequency band (as in a log-periodic antenna). The shape may be different, but it has been established that the exponential increase in the width of the gap gives the widest band.

Where power is applied to the supply gap affects the matching at the bottom of the frequency band.

The classic Vivaldi antenna design has the following disadvantages: a high level of side lobes and a high level of phase distortion. The phase distortions are due to the spherical shape of the phase front of the wave, i.e. the phase on the expanding walls of the gap lags behind the phase in the center of the aperture of the antenna.

Vivaldi antenna designs are known, characterized by powering means located in the power slot (US Pat. No. 4,837,004; US Pat. No. 5,014,466).

The disadvantage of these designs is the significant phase distortion of the electromagnetic field in the aperture of the antenna between the expanding walls, which leads to a significant level of lateral radiation of the antenna in the plane of the electric field lines.

A known Vivaldi antenna design capable of emitting in the forward and reverse direction (US patent No. 7071888).

This is achieved through the use of a surface with a non-uniform controlled impedance, which is irradiated by the Vivaldi antenna. This surface is a dielectric substrate coated with metal plates, the electrical contact between which is controlled by p-i-n diodes. However, the said surface is located both in the aperture of the Vivaldi antenna and beyond, at a distance from the Vivaldi antenna, which is the irradiator of this surface, the reflective properties of which are controlled by p-i-n diodes. The controllable surface is used for electronic scanning by the radiation pattern of the antenna system. Metal plates located in the aperture and in contact with the expanding walls of the slit lead to a sharp distortion of the wall shape itself, which leads to additional phase distortions compared to the “classical” surface of the Vivaldi antenna walls when compared with known technical solutions (Gibson P.J. "The Vivaldi aerial", Proceeding of the 9th European Microwave Conference, 1979, pp. 101-105; US patent No. 483704; US patent No. 5081466). In principle, the part of the metal plates located in the aperture and in the supply gap should be isolated from the planar strip line.

Also known is the design of a planar lens used as the basis for rectenna (US patent No. 7456803). At the focus of each of the lenses that form the antenna array are diodes that convert the energy of a focused electromagnetic field into an electric current. A printing lens, consisting of electrically small (compared to the wavelength) metal diffusers, is used to concentrate the lines of force of the electric field on the detector diodes. As in the previous technical solution, the printing lens is located both in the aperture of the Vivaldi antenna (Fig. 8a) and outside it (Fig. 8a, 10) at a distance from the antenna, which is the irradiator of the printing lens. The metal diffusers located in the aperture and in contact with the expanding walls of the slit (Fig. 8a) lead to a distortion of the most generalized shape of the walls (walls of the expanding slit + metal diffusers), which leads to additional uncontrolled (chaotic) phase distortions when compared with known technical solutions (Gibson P.J., "The Vivaldi aerial", Proceeding of the 9th European Microwave Conference, 1979, pp. 101-105; US Patent No. 483704; US Patent No. 5081466).

Closest to the proposed technical solution is a Vivaldi antenna containing a dielectric substrate, a metal layer located on the dielectric substrate, a slot made in a metal layer with expanding walls along its longitudinal direction and forming the antenna opening, a lens mounted in the antenna opening and made of diffusers (Bin Zhou, Yan Yang, Hui Li, and Tie Jun Cui, "Beam-steering Vivaldi antenna based on partial Luneburg lens constructed with composite materials", Journal of Applied Physics, V. 110, no. 8, pp. 084908-084908 -6, 2011).

The known device contains a circular Luneberg lens in the aperture between the expanding walls of the slit from the outer and inner surfaces of the dielectric substrate, and outside the aperture. This antenna device consists of a Vivaldi antenna tuned to operate in the frequency band 8-11 GHz and a Luneberg lens (Fig. 2, 3). A Luneberg lens is made in the form of several disks of dielectric material and diffusers, in the form of perforation of disks with round holes, due to which the necessary distribution of the refractive index is realized. In addition, the Luneberg lens disks are located on both sides of the E-polarization plane of the antenna, and the use of eight Luneberg lens disks (four above and below the E-polarization plane of the antenna) is required to satisfactorily reduce the side lobe level and improve the gain.

The advantages of this technical solution when compared with the known ones (Gibson P.J., "The Vivaldi aerial", Proceeding of the 9th European Microwave Conference, 1979, pp. 101-105; US patent No. 483704; US patent No. 5081466) are reduced level of side lobes and increase in gain due to the use of Luneberg lens.

The disadvantages of the known device are:

- the complexity of manufacturing and cumbersome design;

- large longitudinal and transverse dimensions.

The problem solved by the invention is the improvement of technical and operational characteristics.

The technical result that is obtained using the invention is to simplify the device, reducing the longitudinal and transverse (height) dimensions.

To solve the problem with achieving the specified technical result in the known Vivaldi antenna containing a dielectric substrate, a metal layer located on the dielectric substrate, a slot made in a metal layer with expanding walls along its longitudinal direction and forming the antenna opening, a lens installed in the antenna opening and made of scatterers, according to the invention, the scatterers are made in the form of conductive plates located on a dielectric substrate I am waiting for expanding walls, and free from contact with the walls of the slit to correct phase distortions in the aperture.

Additional embodiments of the device are possible, in which it is advisable that:

- conductive plates were located symmetrically with respect to the axis of the longitudinal direction of the slit;

- the conductive plates were arranged in rows relative to the axis of the longitudinal direction of the slit and in transverse rows relative to it;

- conductive plates were made in the form of triangles, squares, rectangles, circles, ellipses, polygons, including pentagon or hexagon, closed or open rings and their combinations;

- a slot made in a metal layer with expanding walls along its longitudinal direction, in the place of its narrowing was associated with a power slot, which is made narrow and with parallel walls;

- the outer profile of the conductive plates formed by their surfaces facing the expanding walls of the slit was made tapering in the direction from the maximum aperture of the antenna to the power gap.

For the latter additional option, it is advisable that:

- the envelope of the outer profile of the conductive plates was made parabolic, either in the form of a branch of a hyperbola, or in the form of a part of an ellipse;

- the outer profile of the conductive plates from the maximum aperture was made in the form of a straight line that does not protrude beyond the maximum aperture of the antenna and parallel to it.

These advantages, as well as features of the present invention are illustrated by a variant of its implementation with reference to the accompanying drawings.

FIG. 1 - view of the classic Vivaldi antenna, prior art (prior art);

FIG. 2 - image of a dielectric substrate for mounting a Luneberg lens, prior art (prior art);

FIG. 3 is the same as FIG. 2, with a mounted Luneberg lens;

FIG. 4 - the claimed design of the Vivaldi antenna (outside view);

FIG. 5 - various types of printing lenses: a - with triangular conductive plates, b - in the form of squares, c - circles, d - hexagons, e - open and closed rings;

FIG. 6 - frequency dependence of the gain G of the claimed antenna (solid line) compared with the analogue without a printed lens (dashed line);

FIG. 7 is a radiation pattern of the claimed antenna in a vertical plane at a frequency of 1, 2 and 3 GHz with a printing lens;

FIG. 8 is the same as FIG. 7, without a lens.

The Vivaldi antenna (Fig. 1-4) contains a dielectric substrate 1, a metal layer 2 located on the dielectric substrate 1, a slot 3 made in a metal layer 2 with expanding walls along its longitudinal direction and forming an opening 4 of the antenna. Lens 5 is installed in the aperture 4 of the antenna and is made of diffusers. In accordance with the invention, the lens diffusers 5 (Figs. 4, 5) are made in the form of conductive plates 6 located on the dielectric substrate 1 between the expanding walls of the slit 3, and are made free from contact with the walls of the slit 3 to correct phase distortions in aperture 4.

The term "conductive plate 6, free from contact with the walls of the slit 3" means their location with a small gap relative to the expanding walls of the slit 3 in the transverse direction and the absence of electrical contact with the walls of the slit 3 in the longitudinal direction.

The conductive plates 6 are located symmetrically relative to the axis of the longitudinal direction of the slit 3.

The conductive plates 6 can be arranged in rows relative to the axis of the longitudinal direction of the slit 3 and in transverse rows relative to it.

The conductive plates 6 can be made in the form of triangles (Fig. 5a), rectangles (Fig. 4), squares (Fig. 5b), circles (Fig. 5c), ellipses (not shown in Fig. 5), polygons, for example hexagons (Fig. 5d), closed or open rings (Fig. 5d) and their various combinations (Fig. 5d).

As in analogs, a slot 3 made in a metal layer 2 with expanding walls along its longitudinal direction, in the place of its narrowing is conjugated with a power gap 7, which is narrow and with parallel walls (Fig. 1-4).

The outer profile of the conductive plates 6, formed by their surfaces facing the expanding walls of the slit 3, is made tapering in the direction from the maximum aperture 4 of the antenna to the power gap 7 (Fig. 4).

The envelope S of the outer profile of the conductive plates 6 is made parabolic (Fig. 5 a, b, c), either in the form of a branch of a hyperbola (Fig. 5 g), or in the form of a part of an ellipse (Fig. 5e).

The outer profile of the conductive plates 6 (or its envelope S) from the side of the maximum aperture 4 is made in the form of a straight line L, not protruding beyond the dimension of the maximum aperture 4 of the antenna and parallel to it (Fig. 4, 5).

The claimed Vivaldi antenna (TSA) (Fig. 1, 4) operates as follows. An electromagnetic wave propagates from the power gap 7 along the aperture 4 of the antenna. In the area where the distance between the expanding walls of the gap 3 is small compared to the wavelength in free space, electromagnetic waves are well “connected” with the walls of the gap 3. But as the distance between the conducting surfaces of the expanding walls of the gap 3 increases, the radiation resistance increases, and when threshold wavelengths are emitted by the antenna. It can be noted that at different frequencies different parts of the walls of the Vivaldi antenna emit, so theoretically it can have a very wide frequency band. In practice, the frequency band is limited by the size of the antenna.

In the classical Vivaldi antenna (Fig. 1), the wave phase is distorted on the expanding walls of the slit 3, which is caused by the spherical shape of the wave phase front, i.e. the phase on the expanding walls of the slit 3 lags behind the phase in the center of the aperture 4 of the longitudinal direction of the antenna. The distortion (lag) of the phase is greater, the greater the distance between the expanding walls of the slit 3.

It is possible to lower the level of side lobes and slightly improve the gain due to the concentration of the wave in the longitudinal direction using the Luneberg lens, as is done in the closest analogue. However, it does not allow to completely get rid of phase distortions, since the phase lag in such a design is practically preserved. Such a lens should extend beyond the aperture 4 of the antenna (Fig. 3), because it is this part that makes a significant contribution to the formation of the antenna radiation pattern.

In the claimed technical solution, lens diffusers 5 are used (Fig. 4), which are completely located in the aperture 4 of the antenna. The lens diffusers 5 are made in the form of electrically conductive plates 6 (for example, metal), which are located on the dielectric substrate 1 between the expanding walls of the slit 3, and are necessarily made free from contact with the walls of the slit 3 (not in contact with the expanding walls). In this case, the lens diffusers 5 serve to compensate for the phase lag of the wave on the expanding walls of the slit 3 and do not violate the arcuate shape of the walls. Their number is greater in the center along the longitudinal propagation of the electromagnetic wave and increases together with the opening 4 in the transverse direction.

The conductive plates 6 can be located symmetrically with respect to the axis of the longitudinal direction of the slit 3 for equal compensation of the phase lag between the expanding walls of the slit 3 and the formation of the main lobe of the radiation pattern coinciding with the longitudinal axis of the antenna (Fig. 7).

To simplify the manufacture (for example, by means of photolithography) and to calculate the correction of phase distortions in the aperture 4, the conductive plates 6 can be arranged in rows relative to the axis of the longitudinal direction of the slit 3 and transverse rows relative to it. (However, the dimensions of the electrically conductive plates 6 are chosen much smaller than the working wavelength, so they can be placed quite randomly with the symmetry of the outer profile.)

As studies have shown, the shape of the conductive plates 6 practically does not affect the compensation of phase distortions, because their sizes are chosen at a much shorter wavelength, so they can be made in the form of triangles (in Fig. 5a), rectangles (Fig. 4c), squares (Fig. 5b), circles (Fig. 5c), ellipses (in Fig. 5), polygons, including hexagons (Fig. 5d), closed or open rings (Fig. 5e), and combinations thereof.

The slot 3, made in a metal layer 2 with expanding walls along its longitudinal direction, in the place of its narrowing is associated with a power slot 7, which is made narrow and with parallel walls (Fig. 1-4). Used known means of feeding the Vivaldi antenna practically do not affect the gain G and antenna pattern.

Since the phase lag on the expanding walls of the slit 3 increases in the longitudinal direction toward the maximum aperture 4, the outer profile of the conductive plates 6 formed by their surfaces facing the expanding walls of the slit 3 is made tapering in the direction from the maximum aperture 4 of the antenna to the power gap 7 (Fig. 4).

The experiments showed that the envelope S of the outer profile of the conductive plates 6 can be made parabolic (Fig. 5a, b, c), either as a branch of a hyperbola (Fig. 5d), or as a part of an ellipse (Fig. 5d). The shape of the approximating envelope depends on the size of the Vivaldi antenna, the frequency range, and the desired radiation pattern. It was found that with increasing longitudinal dimensions of the antenna, the shape of the envelope S of the outer profile of the conductive plates 6 smoothly passes from parabolic to hyperbolic, and then even to elliptic, which is apparently due to the shape of the radiating surfaces of the expanding walls of the gap 3. Although specialists understand that in any case, optimization of the shape of the approximating envelope S of the external profile of the conductive plates 6 can be obtained by machine modeling methods depending on the technical specifications for the parameter Vivaldi antenna.

The outer profile of the conductive plates 6 (or its envelope) from the maximum aperture 4 is made in the form of a straight line L, not protruding beyond the dimension of the maximum aperture 4 of the antenna and parallel to it (Fig. 4, 5). This is done in order to reduce the longitudinal dimension of the antenna while reducing the level of the side lobes and increasing the antenna gain, since phase distortions occur precisely in the aperture 4 between the expanding walls of the slit 3. The present invention is aimed at correcting such distortions, and not at then, to form the radiation pattern by other means, as is done in other analogues, for example, using dielectric lenses, which serve as the element focusing the radiation in us. In the present invention, the conductive plate 6 of the lens 5 is a retarding structure.

The reduction of the transverse dimensions in height is achieved by eliminating the Luneberg lens from the design of the disks and making the lens 5 with diffusers - electrically conductive plates 6 on a single dielectric substrate 1 in the E-polarization plane, which also ensures manufacturability and simplification of the design. In this case, to place the lens 5, free space is used inside the slit 3 and the same dielectric substrate 1 on which the planar strip line of the antenna device is located, which reduces the longitudinal dimensions.

Using the claimed device gives a gain in the gain G of up to 2 dB or more in the frequency band 1-3 GHz (Fig. 6). Also obtained radiation patterns in the vertical plane at a frequency of 1, 2 and 3 GHz for the Vivaldi antenna with conductive plates 6 of lens 5 (Fig. 4, 7) and without it (Fig. 1, 8). As can be seen from figures 7 and 8, the presence of lens 5 due to the compensation of phase distortion helps to focus electromagnetic energy in the direction of the main lobe of the radiation pattern. In this case, there is a decrease in the level of the back and side lobes.

The most successfully declared “Vivaldi Antenna with a Printed Lens on a Single Dielectric Substrate” is industrially applicable in broadband radio engineering systems both as a stand-alone antenna device and in antenna arrays.

Claims (8)

1. Vivaldi antenna containing a dielectric substrate, a metal layer located on the dielectric substrate, a slit made in a metal layer with expanding walls along its longitudinal direction and forming an aperture of the antenna, a lens mounted in the aperture of the antenna and made of diffusers, characterized in that the scatterers are made in the form of electrically conductive plates located on a dielectric substrate between the expanding walls, and are made free from contact with the walls of the slit for correction and phase distortion in the aperture. 2. The Vivaldi antenna according to claim 1, characterized in that the conductive plates are located symmetrically relative to the axis of the longitudinal direction of the slit. 3. The Vivaldi antenna according to claim 1, characterized in that the conductive plates are arranged in rows relative to the axis of the longitudinal direction of the slit and in transverse rows relative to it. 4. Vivaldi antenna according to claim 1, characterized in that the conductive plates are made in the form of triangles, squares, rectangles, circles, ellipses, polygons, including hexagons, closed or open rings, and combinations thereof. 5. The Vivaldi antenna according to claim 1, characterized in that a slot made in a metal layer with expanding walls along its longitudinal direction, in the place of its narrowing is associated with a power slot, which is made narrow and with parallel walls. 6. The Vivaldi antenna according to claim 5, characterized in that the outer profile of the conductive plates formed by their surfaces facing the expanding walls of the slit is made tapering in the direction from the maximum opening of the antenna to the power slot. 7. The Vivaldi antenna according to claim 6, characterized in that the envelope of the outer profile of the conductive plates is made parabolic, either as a branch of a hyperbola, or as part of an ellipse. 8. The Vivaldi antenna according to claim 6, characterized in that the outer profile of the conductive plates from the maximum aperture is made in the form of a straight line that does not protrude beyond the maximum aperture of the antenna and is parallel to it.

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