RU2495518C2 - Dual-band circularly polarised microstrip antenna - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: dual-band circularly polarised microstrip antenna has a metal shield, two radiating elements in form of rectangular metal plates placed on over the other in parallel to the metal shield and separated by dielectric substrates, and a coaxial transmission line with one feed point; linear dimensions of the sides of the plates are defined by relationships X_L=(0.94-0.97)×Y_L; X_u=(0.94-0.97)×Y_u, where X_L, Y_L, and X_u, V_u are dimensions of the sides of the lower and upper plates, and the location of the feed point is defined by the following relationships: N_L=(0.35-0.40)×X_L; M_L-(0.25-0.30)×Y_L; N_u=(0.32-0.36)×X_u; M_L=(0.23-0.28)×Y_u, where N_L, M_L and N_u, M_u are coordinates of the feed point relative edges of the lower and upper plates, respectively.

EFFECT: design of a small-sized dual-band circularly polarised microstrip antenna which is suitable for operation with a single-input receiver.

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Description

The invention relates to antenna-feeder devices, in particular, to airborne antennas for satellite navigation.

For antennas placed on aircraft, size requirements are imposed. They should have minimal weight and size characteristics and be non-protruding or low protruding to preserve the aerodynamic properties of the object. In addition, to receive radio signals having a circular or randomly oriented linear polarization, it is necessary to have a receiving antenna also circular (elliptical) polarization.

A known dual-band antenna containing a metal screen, the lower and upper radiating elements in the form of disks separated by dielectric substrates and a coaxial transmission line [RF patent No. 2089017, IPC H01Q 1/28, publ. August 27, 1997]. To ensure circular polarization of radiation, both radiating elements are closed to the screen by conductive support posts (short-circuit pins), formed in two groups. Racks are located between the lower radiating element and the metal screen, and between the upper and lower radiating elements. This device is intended for use as an on-board antenna with undirected uniform radiation in the horizontal (azimuthal) plane, and can be used in radio communication systems between mobile objects, in particular, for transmission and reception in a radiotelephone cellular communication system at two separated frequencies.

However, this antenna is dual-band with linear polarization, i.e. such an antenna cannot work with circular polarization, which is especially important when using a microstrip dual-frequency antenna on aircraft.

Known dual-band microstrip circular polarized antenna containing a metal screen, two radiating elements in the form of square metal plates located one above the other parallel to the metal screen and separated by dielectric substrates, and a coaxial transmission line (coaxial feeder) with two excitation points [USSR copyright certificate No. 1771016, IPC H01Q 1/38, publ. 10.23.1992]. To increase the bandwidth of the working frequencies and the scanning sector according to the ellipticity coefficient, the plates have inhomogeneities in the form of slots cut diagonally from the corners of the plates and have heterogeneities in the form of protrusions designed to adjust the operating frequencies.

However, the implementation of inhomogeneities in the plates of this antenna complicates its manufacture. In addition, this antenna contains two excitation points and two inputs corresponding to these points, which makes it impossible to use it when working with a single-input receiver.

Known microstrip antenna with circular polarization, implemented in the patent under the name "Microstrip antenna, in particular for satellite telephone transmissions" [RF patent No. 2117366, IPC H01Q 1/38, publ. 08/10/1998]. This device is selected as a prototype of the invention, as the closest in combination of features. This microstrip antenna containing a metal screen (ground plane), two radiating elements in the form of square metal plates located one above the other parallel to the metal screen and separated by dielectric substrates, and a coaxial transmission line (power line) with one excitation point, has a power divider ( Wilkinson divider) with an additional fee for its placement.

To provide elliptical (circular) polarization with one coaxial transmission line (single-input receiver), a microstrip power divider with an additional board for its placement is introduced into this device. The bottom plate is powered by probes at two selected points. The second plate is excited by the radiation field of the first. An additional substrate with the separation of the exciting element is introduced into the antenna design.

However, the construction of a microstrip antenna according to such a design scheme leads to an increase in its dimensions (thickness) due to the appearance of an additional power divider board and probes, complicating its design and manufacturing.

The objective of the invention is to provide a small microstrip dual band antenna with circular polarization, suitable for operation with a single-input receiver.

The technical result to which the proposed invention is directed is to achieve circular polarization (ellipticity coefficient of at least 0.5) in two frequency ranges L1 (1575 ÷ 1610 MHz) and L2 (1245 ÷ 1257 MHz), in which the standing wave coefficient voltage (VSWR) not more than 2, when using one coaxial transmission line and, accordingly, one excitation point of two radiating elements due to the introduction of slight asymmetry in the design and the choice of a specific location of the excitation point, refer no ribs radiating elements.

The technical result is achieved by the fact that in a dual-band microstrip circularly polarized antenna containing a metal screen, two radiating elements in the form of metal plates located one above the other parallel to the metal screen and separated by dielectric substrates, and a coaxial transmission line with one excitation point, according to the invention, the plates are made rectangular, the linear dimensions of the sides of which are determined by the relations X _n = (0.94 ÷ 0.97) × Y _n ; X _in = (0.94 ÷ 0.97) × Y _in , where X _n , Y _n , are the sizes of the sides of the lower plate, X _in , Y _in are the sizes of the sides of the upper plate, and the location of the point of excitation is determined from the following relations: N _n = (0.35 ÷ 0.40) × X _n ; M _n = (0.25 ÷ 0.30) × Y _n ; N _in = (0.32 ÷ 0.36) × X _in ; M _in = (0.23 ÷ 0.28) × Y _in , where N _n , M _n are the coordinates of the location of the excitation point relative to the edges of the lower plate, and N _in , M _in are the coordinates of the location of the excitation point relative to the edges of the upper plate, respectively.

The implementation of the emitting plates rectangular with the dimensions of the sides in a certain ratio and the choice of the location of the excitation point in a certain way relative to the edges of the emitting plates makes it possible to excite two orthogonal degenerate modes of vibration, providing a phase shift of ± 90 ° at one point. The location of the excitation point is chosen so that the amplitudes of the excited fields are the same, and the degeneracy is "removed" by introducing a slight asymmetry in the antenna structure. This makes it possible, having small antenna dimensions and simple geometry, to receive signals operating on two frequency ranges of the GLONASS and GPS systems L1 (1575 ÷ 1610 MHz) and L2 (1245 ÷ 1257 MHz), providing circular polarization in both frequency ranges when using one coaxial transmission line.

The presence in the claimed invention features that distinguish it from the prototype, allows us to consider it appropriate to the condition of "novelty."

New features were not identified in technical solutions for a similar purpose. On this basis, we can conclude that the claimed invention meets the condition of "inventive step".

The alleged invention is illustrated by the drawings:

figure 1 shows a design image of a dual-band microstrip antenna with circular polarization (top view);

figure 2 shows a section A-A in figure 1;

figure 3 shows the dependence of the standing wave voltage coefficient (VSWR) on the frequency for two antennas with different materials of dielectric substrates, where curve a is an antenna using FF-4 as the material of dielectric substrates; curve b — antenna using FLAN-5.0 as the dielectric substrate material (the selected region corresponds to the frequency ranges L1 and L2);

figure 4 shows the dependence of the ellipticity coefficient (CE) of the antenna on the frequency in the maximum radiation pattern (LH) in the lower frequency range for two antennas with different materials of dielectric substrates, where curve a is an antenna using FF-4 as the material of dielectric substrates; curve b — antenna using FLAN-5.0 as the dielectric substrate material (the selected region corresponds to the frequency range L2);

figure 5 shows the dependence of the FE antenna on the frequency at the maximum of the ND in the upper frequency range for two antennas with different materials of dielectric substrates, where curve a is an antenna using FF-4 as the material of dielectric substrates; curve b - an antenna using FLAN-5.0 as the dielectric substrate material (the selected region corresponds to the frequency range L1).

The proposed microstrip antenna (FIGS. 1, 2) comprises a metal screen 1 and a lower radiating element 2 and an upper radiating element 3 on dielectric substrates 4, 5 located one above the other parallel to the screen 1, respectively. In the coaxial transmission line 6, the outer conductor is connected to the shield 1, and the central core 7 is connected to the radiating element 3 at the point of excitation O. In the lower radiating element 2, at the intersection with the central core 7, a hole 8 is made for passage of the core 7 to the upper radiating element 3. Outside, the antenna is equipped with a protective radio-transparent fairing (not shown). The radiating elements 2, 3 are thin rectangular foil plates with linear dimensions of the sides according to the corresponding ratios X _n = (0.94 ÷ 0.97) × Y _n ; X _in = (0.94 ÷ 0.97) × Y _in , where X _n , Y _n - the width and length of the radiating element 2, and X _in , Y _in - the width and length of the radiating element 3. The dimensions of each radiating element 2 , 3 are designed to operate in their frequency range: the radiating element 2 operates in the frequency range L2, and the radiating element 3 operates in the frequency range L1.

The principle of operation of the proposed antenna is as follows.

The excitation is carried out by a coaxial transmission line 6, the external conductor of which is connected to the screen 1, and the central core 7 is electrically connected to the radiating element 3 at the excitation point O, thereby exciting it. The radiating element 2 is excited by the radiation field of the upper radiating element 3. Circular polarization is achieved due to slight asymmetry in the structure (aspect ratio of the rectangular radiating elements) and a certain choice of the location of the excitation point O with respect to the edges of the radiating elements 2, 3.

The possibility of industrial implementation and practical feasibility of achieving the desired technical result when using the invention is illustrated by the following examples.

Example 1

As an example of a specific embodiment of the proposed antenna, an antenna was manufactured using FF-4 as a dielectric substrate with a relative permittivity ε = 2.05. The metal screen 1 was made of a conductive material aluminum 1 mm thick. The antenna had the following geometric dimensions: the thickness of the dielectric substrates 4, 5 was 4 mm, the linear dimensions of the sides of the lower radiating element 2 were 76 mm × 78.5 mm (X _n × Y _n ), the linear dimensions of the sides of the upper radiating element 3 were 60.5 mm × 62.5 mm (X _in × Y _in ). The outer conductor of the coaxial transmission line 6 was connected to the screen 1. The central core 7 of the transmission line 6 was electrically connected to the element 3 at the excitation point O. The distance from the excitation point O to the nearest edges of the upper radiating element 3 was 20.5 mm (N _in ) and 16 , 5 mm (M _in ), and the distance from the point of excitation O to the nearest edges of the lower radiating element 2 was 29 mm (N _n ) and 23 mm (M _n ).

In this case, the upper radiating element 3 was excited. The lower radiating element 2 was excited by the radiation field of the upper 3, reaching circular polarization. The experimental results are presented in Figs. 3-5 (curve a), which shows the frequency dependence of the standing wave coefficient by voltage (VSWR) and the dependence of the ellipticity coefficient (CE) at the maximum radiation pattern (LH) in the lower and upper frequency ranges of this antenna. As can be seen with these antenna sizes, the value of the VSWR of the output is no more than 2 in the frequency ranges 1230–1269 MHz and 1557–1635 MHz; FE is more than 0.5 in the frequency ranges 1232 ÷ 1253 MHz and 1575 ÷ 1615 MHz. That is, the operating frequencies L2 and L1, respectively, are included in these frequency ranges.

Example 2

As an example of a specific implementation of the proposed antenna, an antenna was manufactured using FLAN with a relative permittivity ε = 5 as dielectric substrates. The metal screen 1 was made of a conductive material aluminum 1 mm thick. The antenna had the following geometric dimensions: the thickness of the dielectric substrates 4, 5 was 3 mm, the linear dimensions of the sides of the lower radiating element were 48.5 mm × 50.5 mm (X _n × Y _n ), the linear dimensions of the sides of the upper radiating element were 39 mm × 41 mm (X _in × Y _in ). The external conductor with a coaxial transmission line 6 was connected to the screen 1, and the central core 7 of the transmission line 6 was electrically connected to the upper radiating element 3 at the excitation point O. The distance from the excitation point O to the edges of the upper radiating element was 12 mm (N _in ) and 10, 5 mm (M _in ), and the distance from the point of excitation O to the ribs of the lower radiating element was 17.5 mm (N _n ) and 13 mm (M _n ).

In this case, the upper radiating element 3 was excited. The lower radiating element 2 was excited by the radiation field of the upper 3. The experimental results are shown in Figs. 3-5 (curve b), where the frequency dependence of the standing wave coefficient with respect to voltage (VSWR) and the dependence of the ellipticity coefficient are shown ( FE) at the maximum of the radiation pattern (LH) in the lower and upper frequency range of this antenna. So, for given antenna sizes, the VSWR value is not more than 1.4 and 1.6 in the frequency ranges L2 and L1, respectively; FE more than 0.5 in the frequency ranges L2 and L1. That is, the operating frequencies L2 and L1, respectively, are included in these frequency ranges.

Thus, the experimental results confirm the solution of the problem and the achievement of the required technical result, namely, the creation of a small two-frequency microstrip antenna with circular polarization with VSWR≤2 and KE≥0.5 in the required frequency ranges L1 and L2.

So, the presented information indicates the fulfillment of the following set of conditions when using the claimed invention:

- creation of a small two-frequency microstrip antenna with circular polarization;

- for the claimed device in the form in which it is described in the claims, the possibility of its implementation using the means and methods described in the application and known prior to the priority date is confirmed.

Therefore, the claimed invention meets the condition of "industrial applicability".

Claims (1)

A dual-band microstrip circular polarization antenna containing a metal screen, two radiating elements in the form of metal plates located one above the other parallel to the metal screen and separated by dielectric substrates, and a coaxial transmission line with one excitation point, characterized in that the plates are made rectangular, linear dimensions of the sides which are determined by the relations
X _n = (0.94 ÷ 0.97) · Y _n ;
X _a = (0,94 ÷ 0,97) · Y _a,
where X _n , Y _n - the sizes of the sides of the lower plate,
X _in , Y _in - the dimensions of the sides of the upper plate,
and the location of the excitation point is determined from the following relationships:
N _n = (0.35 ÷ 0.40) · X _n ;
M _n = (0.25 ÷ 0.30) · Y _n ;
N _in = (0.32 ÷ 0.36) · X _in ;
M _a = (0,23 ÷ 0,28) · Y _in
where N _n , M _n - the coordinates of the location of the excitation point relative to the edges of the lower plate,
N _in , M _in - the coordinates of the location of the excitation point relative to the edges of the upper plate, respectively.

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