A broadband circularly polarized antenna fed by a coplanar waveguide

Abstract

The application discloses a kind of coplanar waveguide feed's broadband circularly polarized antennas, including rectangular dielectric substrate;The upper surface of the rectangular dielectric substrate is provided with rectangular plate, the upper surface of rectangular plate is etched with a circular slot in middle part, the inside left and right sides of circular slot are provided with Z-shaped branch two and Z-shaped branch one respectively, the lower end of circular slot is provided with L-shaped feed belt;The lower surface of the rectangular plate is provided with rectangular slot one for the antenna of L-shaped feed belt to pass through middle part;The upper left end of the rectangular plate and its lower right end are etched with triangular slot;The upper right end of the rectangular plate and its lower left end are etched with arc long slot;This coplanar waveguide feed's broadband circularly polarized antenna, coplanar waveguide feed's broadband circularly polarized antenna is widened by optimization design axial ratio band, cover multiple wireless communication frequency band, meet the demand of modern communication system to high bandwidth and multiple frequency band work.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of communication, in particular to a wideband circularly polarized antenna fed by a coplanar waveguide. BACKGROUND

[0002] With the progress of communication systems, in recent decades, scholars have become more and more in-depth study of circularly polarized antennas. It is because of the orthogonal nature of circularly polarized antennas in the polarization direction, so it is often used in combination with other antennas, circularly polarized antenna elements are usually used for satellite applications, whether as a low-gain unit antenna, high-gain array antenna, or reflector antenna feed. The main advantages of circularly polarized radiation technology are: 1. Reduce polarization loss: Even if the corresponding terminal of the communication only uses a linearly polarized antenna, it can ensure electromagnetic wave reception, thereby improving the stability of the communication link; 2. Avoid Faraday rotation phenomenon: In satellite communication, due to the influence of the earth's ionosphere's strong magnetic field, linearly polarized signal waves will produce a rotation of the polarization plane, which is called Faraday rotation, and the two orthogonal polarization components of the circularly polarized wave are simultaneously affected by the Faraday rotation effect, thereby eliminating the influence caused by the rotation effect. Circularly polarized antennas are often used in satellite communication systems. Satellite signal transmission is often disturbed by the atmosphere and ground objects. Compared with traditional single-polarized antennas, circularly polarized antennas can more effectively suppress multipath fading and reduce the loss caused by polarization mismatch, providing more stable signal transmission and reception quality.

[0003] Due to the growing demand for communication services, many researchers are now committed to expanding the communication capacity, and according to Shannon's theorem, to expand the channel capacity, the communication channel bandwidth needs to be increased, or the signal-to-noise ratio needs to be improved. Higher frequency bands such as K-band, Ka-band, etc. have larger bandwidths, and the application of various multiple access technologies can greatly improve the channel capacity, especially suitable for high-speed transmission services, which is undoubtedly of great research value in the face of today's frequency resource shortage. In addition to expanding the bandwidth, multi-frequency sharing technology of the antenna is also the main development direction of satellite communication at present. A set of antenna system can work in multiple frequency bands, which not only can reduce the number of satellite earth stations to be built and control the operating cost, but also can increase the communication capacity to provide better communication services.

[0004] At present, the antenna of UHF band is often used in the fields of RFID reader, military communication, broadcast television and medical equipment due to its strong signal penetration, strong terminal practicability, global coverage and broadcast networking, guaranteed access and other advantages. The antenna of UHF band is often designed to circularly polarized radiation. Many slot antennas with CP radiation have been proposed to be applied to the RFID reader of UHF band. However, like the RFID reader antenna, the 840-960MHz band is the most common application band in the UHF band, and the 485-503MHz band is not used much. The antennas working in the super high frequency band are mainly stereo antennas, but such antennas are not conducive to integration and small size design. Moreover, the current wideband circularly polarized antenna cannot meet the demand of modern communication system for high bandwidth and multi-band operation. SUMMARY

[0005] The purpose of the present application is to provide a wideband circularly polarized antenna fed by a coplanar waveguide. The wideband circularly polarized antenna fed by a coplanar waveguide expands the axial ratio band by optimization design, covers multiple wireless communication frequency bands, meets the demand of modern communication system for high bandwidth and multi-band operation, and can effectively solve the problems in the background art.

[0006] To achieve the above purpose, the present application provides the following technical scheme: a wideband circularly polarized antenna fed by a coplanar waveguide, comprising a rectangular dielectric substrate; the upper surface of the rectangular dielectric substrate is provided with a rectangular plate, the upper surface of the rectangular plate is provided with an etched circular slot with a radius of R1 in the middle, Z-shaped branch two and Z-shaped branch one are arranged on the left and right sides of the inside of the circular slot, and an L-shaped feeding strip is arranged at the lower end of the circular slot;

[0007] A rectangular slot one is arranged on the lower surface of the rectangular plate for the antenna of the L-shaped feeding strip to pass through;

[0008] A triangular slot is etched on the upper left end and the lower right end of the rectangular plate;

[0009] An arc-shaped long slot is etched on the upper right end and the lower left end of the rectangular plate;

[0010] The triangular slot and the arc-shaped long slot are communicated with the circular slot through a rectangular slot two;

[0011] The lower end of the L-shaped feeding strip extends to the lower edge of the upper surface of the dielectric substrate to form a feeding end;

[0012] A coupling branch is arranged at the lower end of the left side of the inside of the circular slot.

[0013] Compared with the prior art, the wideband circularly polarized antenna fed by a coplanar waveguide has the following advantages:

[0014] (1) Miniaturization design: By adding Z-shaped branches and long slots on the circular slot, the current distribution and flow direction are adjusted, achieving a reduction in frequency and circularly polarized radiation characteristics. This design allows the antenna to reduce the operating frequency without increasing the size, thereby achieving miniaturization design;

[0015] (2) Multi-band performance: By changing the position and shape of the radiation branches on the dielectric substrate, and using multi-slot technology, the current size and direction flowing through the branches can be adjusted to excite different resonant frequencies. This method facilitates the realization of multi-band performance of the antenna.

[0016] (3) Wideband characteristics: The interaction between the L-shaped feed strip and the patch produces inductance and capacitance, which interact to produce resonance, so the operating frequency and bandwidth of the antenna can be flexibly controlled by adjusting the size and size of the L-shaped feed strip, facilitating design and optimization.

[0017] (4) Good circular polarization performance: By loading two Z-shaped branches in the center of the circular slot, the electric field and current direction in the circular slot are disturbed, further improving the circular polarization radiation performance. In addition, by selecting appropriate W4 and L8 sizes, a wider axial ratio bandwidth can be achieved.

[0018] (5) Easy to process and integrate: The antenna structure of the coplanar waveguide feed is simple, has a wide operating bandwidth, and is easy to process and manufacture. This makes it more suitable for applications that require miniaturization and integration.

[0019] (6) Wide range of applications: Due to its miniaturization, multi-band, wideband and good circular polarization performance, the coplanar waveguide-fed wideband circularly polarized antenna is suitable for a variety of communication systems, such as UHF band RFID readers, military communications, broadcast television, medical devices and maritime communications, etc.

[0020] (7) Cost-effective: Due to the use of coplanar waveguide feed technology, the antenna reduces costs while maintaining high performance, improving economic efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The structure diagram of the present application.

[0022] Figure 2 The size diagram of the present application when removing the extension branch one, the extension branch two and the triangular short section.

[0023] Figure 3 The curve of the return loss of the present application with L3.

[0024] Figure 4 The curve of the return loss of the present application with L5.

[0025] Figure 5 The return loss curve versus q of the present application.

[0026] Figure 6 The axial ratio curve versus W4.

[0027] Figure 7 The axial ratio curve versus L8.

[0028] Figure 8 The return loss curve and the axial ratio curve simulation results.

[0029] Figure 9 The E-plane and H-plane gain diagram of the antenna of the present application.

[0030] Figure 10 The surface current distribution diagram of four phases with 90° phase difference.

[0031] In the figure: 1-triangle slot, 2-arc long slot, 3-Z-shaped branch 1, 4-L-shaped feed strip, 5-coupling branch, 6-rectangular plate, 7-Z-shaped branch 2, 8-extended branch 1, 9-extended branch 2, 10-triangle short section. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0033] In the description of the present application, if the orientation description such as "upper", "lower", "front", "back", "left", "right" and the like is involved, the orientation or positional relationship indicated is based on the drawings shown, only for the convenience of describing the present application and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application. When a certain feature is referred to as "set", "fixed", "connected" to another feature, it can be directly set, fixed, connected to the other feature, or indirectly set, fixed, connected to the other feature. Figure 1 The orientation or positional relationship shown is only for the convenience of describing the present application and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application. When a certain feature is referred to as "set", "fixed", "connected" to another feature, it can be directly set, fixed, connected to the other feature, or indirectly set, fixed, connected to the other feature.

[0034] In combination with Figure 1 , Figure 2The application provides a wideband circularly polarized antenna fed by a coplanar waveguide, which comprises a rectangular dielectric substrate; a rectangular plate 6 is arranged on the upper surface of the rectangular dielectric substrate; a circular slot with a radius of R1 is etched in the middle of the upper surface of the rectangular plate 6; Z-shaped branch 2 and Z-shaped branch 1 are arranged on the left and right sides of the circular slot respectively; and an L-shaped feeding strip 4 is arranged at the lower end of the circular slot.

[0035] A rectangular slot 1 is arranged in the middle of the lower surface of the rectangular plate 6 and used for passing the antenna lobe of the L-shaped feeding strip 4.

[0036] A triangular slot 1 is etched on the upper left end of the rectangular plate 6 and a triangular slot 1 is etched on the lower right end of the rectangular plate 6.

[0037] An arc-shaped long slot 2 is etched on the upper right end of the rectangular plate 6 and an arc-shaped long slot 2 is etched on the lower left end of the rectangular plate 6.

[0038] The triangular slot 1 and the arc-shaped long slot 2 are communicated with the circular slot through a rectangular slot 2.

[0039] The lower end of the L-shaped feeding strip 4 extends to the lower edge of the upper surface of the dielectric substrate to form a feeding end.

[0040] A coupling branch 5 is arranged at the lower end of the left side of the inner part of the circular slot.

[0041] Specifically, the Z-shaped branches are arranged on the left and right sides of the middle feeding strip of the circular slot, long slots are arranged around the circular slot, the distribution and flow direction of the current are adjusted, and thus the frequency point is reduced and the circular polarization radiation characteristic is realized.

[0042] More specifically, four asymmetric slots are etched on the outer side of the circular slot to increase the magnetic current path, and thus the working frequency of the antenna is reduced without increasing the size of the antenna.

[0043] Further, the Z-shaped branch 1, the L-shaped feeding strip 4, the coupling branch 5, the rectangular plate 6 and the Z-shaped branch 2 are all copper-clad plates.

[0044] Specifically, the thickness of the copper-clad plate is preferably 1.2 mm.

[0045] Further, the working mode of the wideband circularly polarized antenna fed by the coplanar waveguide is UHF band circular polarization.

[0046] The dual-frequency working frequency band of the antenna is 485-503 MHz.

[0047] The standing wave ratio of the antenna is less than 2.

[0048] The characteristic impedance of the antenna is 50 Ω.

[0049] The polarization mode of the antenna is left-handed circular polarization.

[0050] The antenna gain is greater than 0 dBi ± 50°.

[0051] The axial ratio of the antenna is less than 6dB±50°.

[0052] Furthermore, the Z-shaped branch 3 is provided with an extension branch 8.

[0053] Furthermore, the end of the coupling branch 5 is provided with an extension branch 2 9.

[0054] Furthermore, a triangular short segment 10 is provided at the lower end of the L-shaped power supply strip 4 near the coupling stub 5.

[0055] Specifically, the combination of extension stub 1 (8) and extension stub 2 (9) with the triangular short segment 10 at the lower end of the L-shaped feed band allows for a smooth transition between the two frequency bands.

[0056] Specifically, see the instruction manual. Figure 2 As shown, the specific structural dimensional parameters of this application are as follows:

[0057]

[0058]

[0059] Figure 1 This is a schematic diagram of the antenna structure. The antenna is etched onto an FR-4 dielectric substrate with a thickness of 1.2 mm, a dielectric constant of 4.4, and a loss tangent of 0.02. A circular slot with a radius of 52.8 mm is etched at the center of the antenna. A rectangular slot of 4.2 mm × 18.7 mm is left at the lower end of the circular slot to accommodate the antenna feed line. Four asymmetrical slots are etched on the outer sides of the circular slot to increase the magnetic current path, thereby reducing the operating frequency of the antenna without increasing its size. The purpose of using an asymmetrical layout is to give the antenna specific functions by adjusting the ground plane and radiating elements. Based on the observation of current distribution, areas with weak current or symmetrical current distribution are removed, thereby minimizing the negative impact on radiation characteristics while reducing the antenna size. The antenna dimensions are calculated using the following formula:

[0060]

[0061] Where ε ris the dielectric constant, c is the speed of light in free space, and f is the resonant frequency. According to this formula, the antenna size working at 485MHz-503MHz is about 180mm, but in order to reduce the overall size of the antenna, facilitate processing and integration, so in reducing the size of the antenna while the need to open a long slot around the circular slot to increase the magnetic current path, reduce the operating frequency. Finally the size of the antenna is 136.5mm x 146.5mm, the side length is about equal to 0.5λ g .λ g is the wavelength of the center frequency designed at 500MHz, which can be calculated as follows:

[0062]

[0063] where c0is 3x10 8 m / s, ε eff is the dielectric constant of FR-4 dielectric material.

[0064] In the antenna structure of the present application, the middle feeding L-shaped feed strip 4 is adopted, which produces resonance through interaction with the patch, can broaden the operating bandwidth of the antenna, and makes it present multi-band or wide-band characteristics. When the resonant frequency needs to be adjusted, the inductive reactance is produced between the vertical part of the L-shaped feed strip 4 and the patch, and the capacitive reactance is produced between the horizontal part and the patch, and the resonance is produced through the interaction of the two, so this design can flexibly control the operating frequency and bandwidth of the antenna by adjusting the size and size of the L-shaped feed strip 4, and is convenient for design and optimization.

[0065] Specifically, the resonant frequency and bandwidth in different L3and L5cases are as shown in Figure 3 and Figure 4 From Figure 3 and Figure 4 it can be seen that when L3is widened from 19mm to 21mm, the return loss at the lower frequency in the antenna operating band is reduced, but the larger L3is, the smaller the bandwidth of the antenna is. Although reducing L3, the return loss can also be maintained at a good level while increasing the bandwidth, but the smaller L3is, the size of the axial ratio bandwidth will also be affected. Therefore, considering comprehensively, the value of L3is finally selected to be 23.4mm. Compared with L5, the change of the return loss amplitude caused by the change of L5is smaller, and with the increase of L5from 7mm to 9mm, the return loss increases and the bandwidth gradually narrows. Therefore, without affecting the axial ratio, the value of L5should be selected to be a lower value. Considering comprehensively, the value of L5is finally selected to be 7.2mm.

[0066] The slot around the circular slot mainly functions to increase the magnetic current path, and is very important for the miniaturization design of the antenna. Therefore, the length of the slot has a great influence on the operating frequency of the antenna. From Figure 5It can be seen that when q is reduced from 15° to 5°, the slot line becomes longer, the antenna surface magnetic current path increases, the antenna operating frequency is obviously reduced, but the return loss is also increased, when q becomes larger, the frequency point of the antenna is obviously right shifted, so when the long slot is used to reduce the operating frequency, the return loss performance of the antenna should also be considered, and the q value is selected as 13° after comprehensive consideration.

[0067] Two Z-shaped branches in the center are arranged in the circular slot, the two branches are used to disturb the electric field and current direction in the circular slot, so that the circular polarization radiation performance is further improved, and the influence of the two Z-shaped branches on the axial ratio will be analyzed by specific simulation data.

[0068] Figure 6 and Figure 7 is the axial ratio bandwidth curve of the antenna with W4 and L8, when W4 is changed from 9mm to 14mm, the operating frequency band gradually moves left, and the axial ratio bandwidth gradually becomes narrow, so the operating frequency band and the axial ratio width should be considered when selecting the size of W4, and the appropriate size of W4 is selected. At the same time, it can be observed from the figure that when L8 is changed from 32mm to 38mm, the operating frequency band also gradually moves left, but the axial ratio bandwidth becomes wide first and then narrow, and the axial ratio bandwidth needs to be designed as wide as possible, so the appropriate size of L8 needs to be selected. It can be seen that the Z-shaped branches on the left and right sides have a great influence on the axial ratio performance.

[0069] The simulation results of the finally obtained circularly polarized antenna fed by the coplanar waveguide are shown in the figure, Figure 8 It can be seen that the bandwidth of the antenna is from 489MHz to 520MHz, and the axial ratio bandwidth is less than 4dB in the operating frequency band, which has good circular polarization performance. But the axial ratio bandwidth does not meet the requirement of being less than 3dB in the operating frequency band, which is because the long slot is opened around the circular slot to reduce the operating frequency of the antenna, which affects the axial ratio performance of the antenna, and a part of the axial ratio performance is sacrificed to meet the low return loss of the antenna in the super high frequency.

[0070] Figure 9 is the gain performance of the antenna in the E plane and the H plane at the two end points of the operating frequency band. It can be seen from the figure that the highest gain of the E plane and the H plane of the antenna is equal at 485MHz, reaching 2.7dBic, and at 503MHz, the highest gain of the E plane and the H plane is also equal, reaching 2.9dBic, and the antenna radiates obvious left-handed circular polarization at the two frequency points, which meets the design requirements of the antenna.

[0071] In order to explain the mechanism of circular polarization radiation, Figure 10The surface current distributions of the proposed antenna with four phase angles of 0°, 90°, 180° and 270° at 495 MHz are shown in FIG. 5. As shown, the surface current distributions of 180° and 270° phase angles are observed to be opposite to those of 0° and 90° phase angles, respectively. When the phase angle increases by 90°, the surface current rotates clockwise. Therefore, the proposed antenna excites left-handed circularly polarized (LHCP) radiation in the +Z direction and right-handed circularly polarized (RHCP) radiation in the -Z direction, with dual circularly polarized characteristics. By flipping the direction of the two Z-shaped branches and the L-shaped ground plane, the RHCP radiation can be excited in the +Z direction.

[0072] While embodiments of the application have been shown and described, it is to be understood that the application is not limited to the details of the embodiments described, since the scope of the application is defined with respect to the appended claims.

Claims

1. A broad-band circularly polarized antenna fed by a coplanar waveguide, characterized in that: The application relates to a wideband circularly-polarized antenna with a co-planar waveguide feed, which comprises a rectangular dielectric substrate; the upper surface of the rectangular dielectric substrate is provided with a rectangular plate (6), the middle part of the upper surface of the rectangular plate (6) is etched with a circular gap with a radius R1, the left and right sides of the inside of the circular gap are respectively provided with a Z-shaped branch II (7) and a Z-shaped branch I (3), and the lower end of the circular gap is provided with an L-shaped feed strip (4). The lower surface of the rectangular plate (6) is provided with a rectangular gap I for the antenna lobe of the L-shaped feed strip (4); The upper left end and the lower right end of the rectangular plate (6) are etched with triangular gaps (1); The upper right end and the lower left end of the rectangular plate (6) are etched with arc-shaped long gaps (2); The triangular gaps (1) and the arc-shaped long gaps (2) are communicated with the circular gap through rectangular gaps II; The lower end of the L-shaped feed strip (4) extends to the lower edge of the upper surface of the dielectric substrate to form a feed end; The lower end of the left side of the inside of the circular gap is provided with a coupling branch (5).

2. The broad-band circularly-polarized antenna fed by co-planar waveguide of claim 1, wherein: The Z-shaped branch I (3), the L-shaped feed strip (4), the coupling branch (5), the rectangular plate (6) and the Z-shaped branch II (7) are all copper-clad plates.

3. The broad-band circularly polarized antenna fed by co-planar waveguide of claim 1, wherein: The working mode of the wideband circularly-polarized antenna with the co-planar waveguide feed is UHF band circular polarization; the double-frequency working frequency band is 485-503 MHz.

4. The broad-band circularly polarized antenna fed by co-planar waveguide of claim 3, wherein: The standing wave ratio of the antenna is less than 2, the characteristic impedance is 50 omega, and the polarization mode is left-handed circular polarization.

5. The broad-band circularly polarized antenna fed by co-planar waveguide of claim 1, wherein: The Z-shaped branch I (3) is provided with an epitaxial branch I (8).

6. The broad-band circularly polarized antenna fed by co-planar waveguide of claim 1, wherein: The end of the coupling branch (5) is provided with an epitaxial branch II (9).

7. The broad-band circularly polarized antenna fed by co-planar waveguide of claim 1, wherein: The lower end of the L-shaped feed strip (4) is provided with a triangular short section (10) near the coupling branch (5).

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