RU2486642C1 - Symmetrical polyconic antenna - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: symmetrical polyconic antenna has two metal-coated composite cones which are mounted on an insulator with vertices facing each other have a common axis of symmetry, and each composite cone consists of M straight truncated conical surfaces with different values of generatrix angles α_m, m= 1, 2,…, M. The edge of the previous conical surface has electrical contact with the edge of the next conical surface, and the outermost edges of both composite cones are connected to edges of corresponding metal-coated spherical surfaces and have electrical contact; further, each composite cone includes M-1 metal-coated annular spherical surfaces. The vertices of all straight truncated conical surfaces are superimposed. The edges of the conical surfaces are electrically connected by corresponding annular spherical surfaces.

EFFECT: efficient reception and transmission of signals in a wider frequency band while retaining overall dimensions.

12 dwg

Description

The invention relates to radio engineering, in particular to broadband polyconic antennas, and can be used in metrology, in communication systems, in radio monitoring, in solving problems of electromagnetic compatibility.

Known "Biconical antenna with shortening" (see Pat. RF №2336614, IPC H01Q 9/28, publ. 20.10.2008). It contains upper and lower cones made of rods, with both cones facing each other and mounted on an insulator, and each of the M rods of both cones is shortened by making N similar segments from a high-frequency feeder in the form of N, each of which is formed by a connection the central core with a braid at the end of its segment, and the segments are interconnected in series, and the free ends of the central veins of each of the rods are attached to the vertices of the corresponding cones mounted on the insulator.

The antenna provides a certain decrease in the overall dimensions and mass of the antenna in comparison with the known analogues, and the irregularity of its radiation pattern in the horizontal plane also decreases.

The main disadvantage of the analog device is the large overall dimensions.

The well-known "Biconical antenna" (see Pat. RF №2168248, IPC H01Q 13/04, publ. 05.27.2001). It contains N shunts made in the form of segments of conductors connecting the edges of the bases of the cones, while the segments of the conductor are made of two equal parts, offset from one another by an angle α = 360 ° / 2N, located with equal angular displacement around the axis of the cones and connected by one on the other, by means of conductive jumpers placed in a plane passing through the tops of the cones perpendicular to their axis, and reflectors are installed above the bases of the cones.

The analogue provides an increase in gain in the direction of the horizon line. However, the antenna has a significant drawback: significant overall dimensions and heavy weight.

Closest to the technical nature of the claimed device is a "Symmetric polyconic antenna" (see Kaloshin VA, Skorodumova EA Research symmetric polyconic antenna // IV All-Russian Conference "Radar and Radiocommunication." Abstracts and reports. - M : V.A.Kotelnikov Institute of Radio Engineering and Electronics, Russian Academy of Sciences, 2010, p.531-534).

It contains two combined cones with a metal coating, while both combined cones are mounted on the insulator with their vertices facing each other and have a common axis of symmetry, and each combined cone consists of M truncated straight conical surfaces with different values of the forming angles α _m , m = 1, 2, ..., M, and the edge in the previous conical surface coincides with the edge of the subsequent conical surface and has electrical contact with it.

In the prototype device, a significant reduction in the size of the antenna is achieved due to the implementation of the forming cones in the form of a broken line (the implementation of combined cones).

The prototype antenna also has a significant drawback. It is unsuitable for working with a significant class of broadband signals due to insufficient broadband. Modern communication systems use wide bands of operating frequencies: 6.6% for the GSM range 450-480 MHz; 7.6% for the GSM band 890-960 MHz; 9.5% for the DCS band 1780-1880 MHz; 7.5% for the PCS band 1850-1990 MHz and 12.2% for the UMTS band 1920-2170 MHz (see Kin-Lu Wong. Compact and Broadband Microstrip Antennas. - New York: Awiley - Interscince Publication. John Wiley & Cons, inc . 2002). In addition, the WiMAX 3G family of mobile wireless standards is widely used, allowing subscribers to freely move between base stations of the network without a break in communication (see http://www.mforum.ru/analit/802_16.htm). This standard is implemented in the frequency ranges 2300-2400 MHz, 2496-2690 MHz and 3400-3600 MHz (see ibid.). It is also worth noting that the fourth-generation LTE cellular communication is developing in the framework of TD-LTE technology (http://www.mforum.ru/news/article/100520.htm), which uses the 3.5 GHz band (band 42 ) (see http://www.mforum.ru/news/article/100356.htm).

The aim of the proposed technical solution is the development of a symmetric polyconic antenna that provides efficient reception and transmission of signals in a wider frequency band while maintaining overall characteristics.

This goal is achieved by the fact that in the known device containing two combined cones with a metal coating, while both combined cones are mounted on the insulator with their vertices facing each other and have a common axis of symmetry, and each combined cone consists of M straight truncated conical surfaces with different values forming angles α _m , m = 1, 2, ..., M, and the edge in the previous conical surface has electrical contact with the edge of the subsequent conical surface, and the extreme edges of both These cones are connected to the edges of the corresponding metal-coated spherical surfaces and have electrical contact; in addition, M-1 annular metal-coated spherical surfaces are introduced into each combined cone. The vertices of all straight truncated conical surfaces in the combined cones are combined. The electrical connection of the edges of the nearest truncated conical surfaces is carried out by the corresponding annular spherical surfaces.

The listed new set of features due to the fact that the implementation of the combined cones is changed (the vertices of all straight truncated conical surfaces are aligned, and the electrical connection of their edges is carried out using the additionally introduced annular spherical surfaces) allows to achieve the purpose of the invention: to develop a broadband symmetric polyconic antenna while maintaining the overall characteristics .

The technical result in the proposed antenna is achieved due to the transition from a cascade connection of waveguides with a smoothly changing wave resistance in the prototype to their connection, structurally corresponding to a transformer at a wave resistance jump. When the overall dimensions are equal with the prototype and the specified coordination, for example, SWR = 2.5, the working frequency band increases by 40% or more.

The inventive antenna is illustrated by drawings, in which:

figure 1 shows a schematic illustration of a biconical antenna;

figure 2 illustrates the equivalent circuit of a biconical antenna;

figure 3 shows an embodiment of the manufacture of the antenna prototype;

figure 4 shows the equivalent circuit of the antenna prototype;

figure 5 shows the antenna in accordance with the claimed invention;

6 illustrates an equivalent circuit of the claimed antenna;

figure 7 shows the dimensions of the antenna prototype;

Fig. 8 shows the overall dimensions of the claimed antenna;

figure 9 shows a graph of the frequency characteristics of the antenna prototype (the dependence of the SWR from the frequency used);

figure 10 shows the values of the input resistance of the antenna of the prototype on the Smith chart;

figure 11 illustrates the dependence of the SWR from the frequency used in the inventive antenna;

in Fig.12 shows the values of the input resistance of the claimed antenna in the Smith diagram.

The extension of the working frequency band in the inventive antenna is illustrated as follows. It is known (see L. Felsen, N. Markuvets. Radiation and scattering of waves. - M .: Mir, 1978) that free space can be considered as a special case of a biconical waveguide formed by conical surfaces with a common vertex and zero angles between the axis and generators. The biconical antenna in this case is a matching segment between the field in the feeder line connected to the antenna and a semi-infinite conical waveguide with a wave resistance of 120π Ohms (free space). A schematic representation of a biconical antenna, an equivalent circuit comprising a feeder line segment, an antenna, and a load describing the effect of free space are shown in FIGS. 1 and 2, respectively. The upper limit of the working range of such an antenna is determined by the thickness of the central conductor of the coaxial line, which should be no more than 0.05λ _min . The lower limit of the working range depends on the size of the conical surface or on the radius of the spherical surface R, closing the base of the cone. If the SWR of the antenna should not exceed 2, then it is necessary that R≥0.15λ _max . In the lower part of the decimeter range, and even more so in the meter range, the sizes of the biconical antenna can reach 1 meter or more. The resulting large windage leads to the need for a significant strengthening of the central part of the antenna (to increase the thickness of the central conductor of the coaxial line supporting the upper arm). In addition to reducing the upper limit of the operating range, large dimensions pose serious problems in the operation of such antennas in mobile complexes, since they require the allocation of large volumes in vehicles for storage and transportation.

In the prototype device (see Fig. 3), a reduction in dimensions is achieved by replacing one segment of the biconical waveguide with several cascade-connected ones. Moreover, as can be seen from figure 4, the second and subsequent segments are heterogeneous due to the fact that their cross section (π-2θ) increases with distance from the center of the antenna (from the top of the first conical surface). The cascade connection of segments of biconical waveguides, starting from the second, is a line whose wave resistance continuously increases from the input to the output (to the connection point) of the load. From the theory of circuits it is known (see Serkov V.P. Propagation of radio waves and antenna devices. - L .: YOU, 1981, p. 352) that the minimum length of a transformer with an exponentially varying wave impedance, ensuring coordination of the SWR ≤K ₀ at waves λ ≤λ _max should be selected from the condition

, $$l\ge \frac{{\lambda }_{\max }}{\mathrm{four}\pi }\frac{{\mathrm{TO}}_0+\mathrm{one}}{{\mathrm{TO}}_0-\mathrm{one}}\left|\ln N\right|$$

,

where N = Z _H / ρ is the transformation coefficient; Z _H - load resistance; ρ is the wave resistance of the feeder. If K ₀ = 2, a Z _H = 120π, then from this expression it follows that l≥λ _max / 2. Therefore, the antenna length should be increased by more than 3 times. The solution of the optimization problem showed that while maintaining the same heights (radii of the outer conical surfaces), the three-stage polyconic antenna ensures matching with the SWR no worse than 2.5 in the fivefold frequency range.

The inventive antenna design (see figure 5) can be considered as a transformer on the jumps of wave impedance (see figure 6). It is known from circuit theory that such transformers with a given strip and matching level have a minimum length (see ibid.). To go from segments of biconical waveguides with smoothly varying wave resistances (see Fig. 4) to segments with constant wave resistances (see Fig. 6), the vertices of all conical surfaces are combined in the proposed antenna. For the same purpose, additionally introduced annular spherical surfaces are used. The simulation results using the CST MICROVAWE STUDIO program (see www.cst.com) and subsequent practical tests showed the following. A three-stage polyconic antenna at jumps in the wave resistance at the same overall dimensions with the prototype provides matching in a sevenfold frequency range. The latter corresponds to a gain in broadband of 40%.

The appearance of the antenna with overall dimensions is shown in Fig. 8. A symmetric polyconic antenna contains the first 1 and second 2 combined cones with a metal coating, while both combined cones 1 and 2 are mounted on the insulator 3 with their vertices facing each other and have a common axis of symmetry, and each combined cone 1 or 2 consists of M straight truncated conical surfaces 4.1, 4.2, ..., 4.M with different values of the generatrix angles α _m , m = 1, 2, ..., M, and the edge in the previous conical surface 4.W-1 has electrical contact with the edge of the subsequent conical surface 4.m . In addition, the extreme edges of both combined cones 1 and 2 are connected to the edges of the corresponding spherical surfaces with a metal coating 5.1 and 5.2 and have electrical contact.

To ensure efficient reception and transmission of signals in a wider frequency band while maintaining dimensional characteristics, M-1 annular spherical surfaces 6.m, m = 1, 2, ..., M-1, with a metal coating, are additionally introduced in each combined cone 1 and 2 . The vertices of all straight truncated conical surfaces 4.m, m = 1, 2, ..., M, are combined. The electrical connection of the edges of the nearest straight truncated conical surfaces 4.m, m = 1, 2, ..., M, is carried out by the corresponding annular spherical surfaces 6.m, m = 1, 2, ..., M-1. The Central core 7 of the coaxial cable 8 is electrically connected to the top of the upper combined cone 1, and the screen of the cable 8 is electrically connected to the lower combined cone 2.

A comparative analysis of the prototype (see Fig.7) and the inventive antenna (see Fig.8) was performed with the coincidence of their main physical characteristics:

the overall overall dimensions of the antennas are 170 × 64 mm;

the same number of truncated conical surfaces, m = 3;

coinciding dimensions of spherical surfaces 5, R = 85, ⌀64.

Combined cones 1 and 2 can be made of brass grade L-60. The dimensions of the first straight truncated conical surface 4.1 are: the generatrix angle α ₁ = 65 °, the generatrix length R ₁ = 22 mm.

The second truncated straight conical surface 4.2 has the following dimensions: the generatrix angle α ₂ = 45 °, and its equivalent length (the length of the generatrix from the second annular spherical surface 6.2 to the top of the combined cone 1 (2)) R ₂ = 45 mm. The first annular spherical surface 6.1 has a radius R ₁ = 22 mm In this case, the function of the first annular spherical surface 6.1 includes the electrical connection of the edges of the first straight truncated conical surface 4.1 with the second straight truncated conical surface 4.2.

The third straight truncated conical surface 4.3 is formed using a generatrix with an angle α ₃ = 22 °, and its equivalent length R ₃ is 85 mm. The lower edges of the combined cones 1 and 2 are electrically connected to the corresponding spherical surfaces 5.1 and 5.2.

The lower combined cone 2 contains a cavity in the form of a two-stage round straight cylinder, the axis of which coincides with the axis of the combined cone 2. Its dimensions are determined by the thickness of the coaxial cable 8 without braid, and the thickness (diameter d _c ) of the central core 7 of cable 8. Moreover, the diameter of the second straight d cylinder ₂ is selected from the condition d _2> d _n, which ensures a guaranteed absence of contact of the central core 7 with the cone 2. The diameter of the first circular straight cylinder ₁ d is chosen from the condition of providing guaranteed RE Cesky contact with the screen of the coaxial cable 8. The central conductor 7 of cable 8 extends through a hole in the insulator 3 and fixed with a reliable electrical contact to the top of the upper cone 1. Combined angle α ₁ = 65 ° is chosen so that the input impedance of the antenna at the junction with the coaxial the cable was 50 ohms.

The insulator 3 is made of fluoroplastic brand F-4 in the form of a symmetrical spherical layer with an external diameter of 22 mm. In this case, the upper and lower sections of the insulator 3 are identical and have the shape of a round straight cone with a generatrix angle α ₁ = 65 °, the vertices of which are facing each other. In the center of the insulator 3 there is a hole, the diameter of which is determined by the dimensions of the central core 7 of the coaxial cable 8.

The procedure for calculating the characteristics of biconical antennas is well known (see, for example, Makurin M.N., Chubinsky N.P. Calculation of the characteristics of a biconical antenna by the method of partial regions // Radio Engineering and Electronics, 2007, V.52, No. 10, p. 1190-1208), made using CST MICROVAWE STUDIO software (see www.cst.com). The results of calculating the frequency characteristics (SWR) and input impedance of the prototype and the claimed antenna are shown in Fig.9-12.

Figures 9 and 11 illustrate graphs of changes in frequency characteristics (SWR versus frequency used) in the prototype antenna and the claimed antenna, respectively. From their consideration it is clear that for the SWR 2.5, the prototype provides a band of operating frequencies from 0.5 to 2.5 GHz (five octaves). The inventive antenna for the same conditions implements a wider by 1 GHz frequency band of operating frequencies from 0.5 to 3.5 GHz (seven octaves), which corresponds to a 40% gain in this indicator.

The input impedance of the prototype (see Fig.10) and the claimed antenna (see Fig.12) have a similar multi-resonance nature. Outside of the mentioned operating frequency bands (with SWR = 2.5), the input impedance of both antennas is capacitive in nature.

By virtue of its symmetry, the inventive polyconic antenna generates a radiation pattern isotropic in the horizontal plane with a vertical polarization. In the elevation plane, the antenna forms a single-lobe radiation pattern, the width and shape of which depends on the frequency. The calculation of the radiation pattern of the claimed antenna based on the software product CST MICROVAWE STUDIO showed the following. In the low-frequency region, the DN has a one-petal character, which begins to collapse at λ _max / λ = 3. At higher frequencies in the elevation plane, along with the narrowing of the main lobe, the appearance of additional side lobes. The order of formation of the electromagnetic field in such antennas is widely covered in the literature (see Fradin A.Z. Antennas for microwave frequencies. - M .: Sov. Radio, 1957, pp. 203-216).

The practical test results of the antenna are in good agreement with the data obtained. All parts of the antenna according to the present invention have a simple shape and are made of a uniform conductive material of the same type. Combined cones 1 and 2 to reduce their weight, it is advisable to make using a molding or plastic molding followed by conductive coating. In addition, the manufacture and operation of the antenna is simplified if the combined cones are divided into constituent elements (straight truncated cones bounded by spherical unidirectional surfaces) having mutual threaded connections. The latter will allow you to adjust the value of the lower boundary of the working frequency band by changing their number m.

Claims (1)

A symmetric polyconic antenna containing two combined cones with a metal coating, while both combined cones are mounted on the insulator with their vertices facing each other and have a common axis of symmetry, and each combined cone consists of M straight truncated conical surfaces with different angles α _m , m = 1, 2, ..., M, and the edge in the previous conical surface is in electrical contact with the edge of the subsequent conical surface, and the extreme edges of both combined cones are connected to the edges of the respective metal-coated spherical surfaces and have electrical contact, characterized in that M-1 of annular metal-coated spherical surfaces is additionally introduced in each combined cone, the vertices of all straight truncated conical surfaces are aligned, and their edges are electrically connected by the corresponding annular spherical surfaces .

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