Broadband circularly polarized microstrip antenna with E-type defected ground structure

Abstract

The invention relates to the technical field of microwave antennas, in particular to a broadband circularly polarized microstrip antenna with an E-shaped defected ground structure. Comprising a dielectric substrate, two radiation metal patch layers arranged on the top layer of the dielectric substrate and a grounding plate metal patch layer arranged on the bottom layer of the dielectric substrate, the center of the grounding plate metal patch layer is provided with a feed source point connected to the radiation metal patch layers, and the two radiation metal patch layers are arranged in parallel. The number of the feed source points is two, the two feed source points are right opposite to the center of the radiation metal patch layer, two E-shaped defected ground structures which are in plane central symmetry are etched on the radiation metal patch layer, openings of the two E-shaped defected ground structures are oppositely arranged, signals are fed in through the feed source points, and the two E-shaped defected ground structures are arranged in the radiation metal patch layer. Therefore, the dielectric substrate, the radiation metal patch layer and the grounding plate metal patch layer form an antenna structure. The broadband circularly polarized microstrip antenna is simple in manufacturing structure, convenient to integrate and miniaturize, wide in axial ratio bandwidth and impedance bandwidth, and remarkable in working frequency band gain.

Description

Technical Field

[0001] The invention relates to the technical field of microwave antennas, and in particular to a broadband circularly polarized microstrip antenna with an E-shaped defect ground structure. Background Art

[0002] The BeiDou satellite navigation system is an infrastructure that provides all-weather, high-precision positioning services to the world. The transmission and reception waves of the BeiDou satellite navigation system are multi-path propagated and are easily affected by the environment. Among them, the ultra-wideband circularly polarized antenna has attracted widespread attention because of its better anti-interference ability and signal reception stability in a multi-path propagation environment. The circularly polarized wave of the antenna is an electromagnetic wave whose electric field vector changes in a circular trajectory during propagation. The circularly polarized antenna is insensitive to the direction of the receiving device, which makes it more advantageous in a dynamic environment. When the circularly polarized wave hits a planar obstacle, the rotation direction will change. This feature can reduce rain and fog interference and resist multipath reflection. Therefore, the design of an ultra-wideband circularly polarized antenna that is easy to integrate is of great significance to the BeiDou satellite navigation system.

[0003] In the prior art, ultra-wideband microstrip antennas have the advantage of small size, but there is still room for further improvement in antenna miniaturization. The antenna structure design that achieves circular polarization and ultra-wideband performance in the prior art is relatively complex. For example, some antennas achieve circular polarization radiation through complex radiation unit combinations and etching of multiple slot structures. For example, in the design of patent CN114865298B, it is necessary to design the coordination between a quarter-circular monopole radiation patch, a bent microstrip branch line, a circular patch, and an asymmetric coplanar waveguide ground plane to achieve a larger axial ratio bandwidth and a wider bandwidth. The complex design of the circularly polarized antenna increases the manufacturing difficulty and cost.

[0004] Therefore, it is required to have better axial ratio characteristics and radiate circularly polarized waves, which puts higher requirements on the antenna's wide bandwidth, simplified structure and miniaturization. The design of circularly polarized microstrip antennas with wide axial ratio bandwidth and impedance bandwidth is still a challenge faced by antenna designers. Summary of the invention

[0005] In order to solve the problem of manufacturing a broadband circularly polarized microstrip antenna with a simple structure and easy integration and miniaturization, having a wider axial ratio bandwidth and impedance bandwidth, and significant working frequency band gain, the present invention provides a broadband circularly polarized microstrip antenna with an E-type defect ground structure.

[0006] The present invention provides a broadband circularly polarized microstrip antenna with an E-type defective ground structure, comprising a dielectric substrate, a radiating metal patch layer arranged on the top layer of the dielectric substrate, and a grounding plate metal patch layer arranged on the bottom layer of the dielectric substrate. The dielectric substrate, the radiating metal patch layer, and the grounding plate metal patch layer are closely connected as a whole. A feed point connected to the radiating metal patch layer is provided at the center of the grounding plate metal patch. There are two radiating metal patch layers. There are two feed points that are directly opposite to the center of the radiating metal patch layer. The radiating metal patch layer is etched with two E-shaped defective ground structures that are symmetrical in the center of the plane. The openings of the two E-shaped defective ground structures are arranged opposite to each other. Signals are fed into the antenna by the feed points, so that the dielectric substrate, the radiating metal patch layer, and the grounding plate metal patch layer form an antenna structure.

[0007] Furthermore, the defective ground structure is formed with a first vertical groove, a second vertical groove and a third vertical groove arranged parallel to each other, and a fourth tree-shaped groove arranged perpendicular to the first vertical groove, the first vertical groove, the second vertical groove and the third vertical groove are flush at one end away from the collapse source point, the first vertical groove, the second vertical groove and the fourth vertical groove are connected to form an F shape, the first vertical groove is arranged on the side away from the feed point, the third vertical groove is arranged on the side close to the feed point and is spaced apart from the fourth vertical groove.

[0008] Furthermore, the widths of the first vertical groove, the second vertical groove, the third vertical groove and the fourth vertical groove are the same.

[0009] Furthermore, the first vertical groove and the fourth vertical groove have the same length, the first vertical groove and the fourth vertical groove are the longest among the four vertical grooves, and the second vertical groove is the shortest among the four vertical grooves.

[0010] Furthermore, the gap distance between the third vertical groove and the fourth vertical groove is 0.2mm, the width of the first vertical groove, the second vertical groove, the third vertical groove and the fourth vertical groove is 2mm, the length of the first vertical groove and the fourth vertical groove is 5mm, the length of the second vertical groove is 3mm, and the length of the third vertical groove is 4mm.

[0011] Furthermore, the top surface of the radiation metal patch layer is a rectangle, the diagonals of the rectangle are connected to form a first diagonal line and a second diagonal line, the E-type defective ground structure is distributed on the first diagonal line, and the diagonals of the second diagonal line form a cut angle.

[0012] Furthermore, the thickness of the circularly polarized microstrip antenna is 1.4 mm, and the size of the rectangle on the top surface of the radiating metal patch layer is 18 mm×18 mm.

[0013] Furthermore, the length of the hypotenuse of the cut angle is 4 mm.

[0014] Furthermore, the dielectric substrate is a FR4 dielectric substrate, and the length of the dielectric substrate is 46 mm and the width is 26 mm.

[0015] Furthermore, there are two first vertical grooves in the same radiation metal patch layer, wherein the first vertical groove far away from the center of the dielectric substrate is 15 mm away from a perpendicular line of a long side of the dielectric substrate.

[0016] Furthermore, a feed point at the center of the ground plate metal patch is connected with an SMA connector.

[0017] In summary, the present invention has the following beneficial technical effects: 1. The broadband circularly polarized microstrip antenna with an E-type defective ground structure proposed in the present invention has a compact structure. The E-type defective ground structure is easy to process and manufacture. The feeding structure adopts a coaxial feeding method in which two central feed points are connected to an SMA connector. The feeding structure is simple and direct, which reduces the complex feeding line design, reduces the cost and manufacturing difficulty, and provides convenient conditions for its integrated application in various electronic devices.

[0018] 2. The broadband circularly polarized microstrip antenna with an E-type defect ground structure proposed in the present invention has excellent radiation performance. The top surface of the radiating metal patch layer is rectangular and the first diagonal formed by the diagonal connection is distributed with the E-type defect ground structure. At the same time, the diagonal of the second diagonal forms a cut angle, so that the phase difference of the surface current is controlled at 90°, which optimizes the radiation characteristics, enables the antenna to efficiently radiate circularly polarized waves, and realizes the ability to stably and uniformly radiate signals outward within a wide frequency band, effectively improving the radiation efficiency and coverage range of the antenna.

[0019] 3. The invention proposes a broadband circularly polarized microstrip antenna with an E-shaped defect ground structure, which adopts four E-shaped defect ground structures. The introduction of this structure can greatly broaden the axial ratio bandwidth, and excite two degenerate modes with equal amplitude and orthogonal to each other at the feeding point, so that they produce a phase difference of 90°, thereby realizing the circular polarization performance of the antenna and the ultra-wideband characteristics of the microstrip antenna, and effectively avoiding the signal fading and distortion problems caused by frequency changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure is a top view of a broadband circularly polarized microstrip antenna with an E-type defect ground structure according to the present invention.

[0021] Figure 2 The figure is a front view of a broadband circularly polarized microstrip antenna with an E-type defective ground structure according to the present invention.

[0022] Figure 3 It is a schematic diagram of the evolution process of the antenna of the present invention.

[0023] Figure 4S is the evolution process of the antenna of the present invention 11 Schematic diagram.

[0024] Figure 5 Schematic diagram of the effect of the patch cutting angle on the axial ratio of the present invention.

[0025] Figure 6 The rectangular slot position of the present invention is the antenna S 11 Schematic diagram of the impact.

[0026] Figure 7 Schematic diagram of antenna current distribution at 4.8 GHz of the present invention.

[0027] Figure 8 The radiation patterns of xoz and yoz of the present invention are compared at 4.8 GHz and 5.2 GHz.

[0028] Fig. 9 The antenna S of the present invention 11 Schematic diagram of the comparison between measured and simulated data.

[0029] Fig.10 It is a schematic diagram comparing the measured and simulated data of the antenna axial ratio of the present invention.

[0030] Among them, 1. Radiating metal patch layer; 2. SMA connector. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0032] Example 1 A broadband circularly polarized microstrip antenna with an E-type defective ground structure in the present embodiment includes a dielectric substrate, a radiating metal patch layer arranged on the top layer of the dielectric substrate, and a grounding plate metal patch layer arranged on the bottom layer of the dielectric substrate. The dielectric substrate, the radiating metal patch layer, and the grounding plate metal patch layer are closely connected as a whole. A feed point connected to the radiating metal patch layer 1 is provided at the center of the grounding plate metal patch. There are two radiating metal patch layers 1. There are two feed points that are directly opposite to the center of the radiating metal patch layer 1. The radiating metal patch layer 1 is etched with two E-shaped defective ground structures that are symmetrical in the center of the plane. The openings of the two E-shaped defective ground structures are arranged opposite to each other. The signal is fed into the antenna structure by the feed point, so that the dielectric substrate, the radiating metal patch layer, and the grounding plate metal patch layer form an antenna structure.

[0033] The ultra-wideband circularly polarized microstrip antenna designed in this embodiment adopts a rectangular radiation patch, that is, a radiation metal patch layer, and the ground plane material is selected to have a relative dielectric constant of FR4 dielectric substrate, dielectric loss tangent , using coaxial line feeding for excitation. The three-dimensional structure diagram of the antenna is shown in Figure 1 and Figure 2 The two array metal patch layers of this antenna are L1 in length and W1 in width. The two radiating patches are printed on a FR4 dielectric substrate with a length of L and a width of W. The overall thickness of the antenna is 1.4 mm. The antenna operates at a frequency of 3.8 GHz -6.2 GHz, covering the frequency bands of satellites, mobile phones and other communication equipment. Among them, by cutting the corners on the radiating patch, two degenerate modes with equal amplitudes and orthogonal to each other are excited at the feeding point, causing a phase difference of 90°, thereby achieving the circular polarization performance of the antenna in this embodiment. In addition, the defective ground structure of the improved rectangular slot ultra-wideband circularly polarized array antenna is to utilize four E-shaped defective ground structures etched on the radiating patch to achieve the ultra-wideband characteristics of the microstrip antenna.

[0034] The defective ground structure is formed with a first vertical groove, a second vertical groove and a third vertical groove arranged in parallel with each other, and a fourth tree-shaped groove arranged perpendicular to the first vertical groove. The first vertical groove, the second vertical groove and the third vertical groove are flush at one end away from the collapse source point. The first vertical groove, the second vertical groove and the fourth vertical groove are connected to form an F shape. The first vertical groove is arranged on the side away from the feed point, and the third vertical groove is arranged on the side close to the feed point and is spaced apart from the fourth vertical groove.

[0035] The widths of the first vertical groove, the second vertical groove, the third vertical groove and the fourth vertical groove are the same.

[0036] The first vertical groove and the fourth vertical groove have the same length, the first vertical groove and the fourth vertical groove are the longest among the four vertical grooves, and the second vertical groove is the shortest among the four vertical grooves.

[0037] The feed point at the center of the ground plate metal patch is connected with an SMA connector 2 .

[0038] The defect ground structure is composed of four E-shaped gap structures composed of sixteen vertical grooves, and the E-shaped structures are symmetrically distributed about the center of the feed source position. The positions of the two feed elements are symmetrical about the center of the y-axis, L is the length of the dielectric substrate of the microstrip array antenna, W is the width of the dielectric substrate of the microstrip array antenna, L1 is the length of the radiating metal patch layer, W1 is the width of the radiating metal patch layer, L3 is the width of the vertical groove, L4 is the length of the cutting angle of the radiating metal patch layer, L5 is the distance between the first vertical groove and the vertical line of the long side of the dielectric substrate, and the distance between the gap between the third vertical groove and the fourth vertical groove is 0.2mm. The simulated thickness of the radiating patch is 0.57mm. The above parameters are optimized by HFSS electromagnetic simulation software, and the specific parameter values ​​of the final improved vertical groove defect ground structure are shown in Table 1.

[0039] Table 1 Parameters and dimensions of the antenna parameter Value / mm parameter Value / mm W 26 L 46 <![CDATA[W1]]> 18 <![CDATA[L1]]> 18 <![CDATA[W2]]> 4 <![CDATA[L2]]> 5 <![CDATA[W3]]> 3 <![CDATA[L3]]> 2 <![CDATA[W4]]> 5 <![CDATA[L4]]> 4 h 1.4 <![CDATA[L5]]> 15 Regarding the improved rectangular slot defect ground structure, in order to find the optimal defect ground decoupling structure layout for the ultra-wideband circularly polarized antenna array, refer to Figure 3 , the evolution process of the rectangular slot defect ground decoupling structure is listed. Let the original microstrip antenna be antenna 1 (a), and after loading a symmetrically distributed L-shaped slot structure on the basis of the original antenna 1, it evolves into antenna 2 (b). Based on antenna 2, a small rectangular slot is loaded on the radiating metal patch layer to form antenna 3 (c), and a vertical rectangular slot is loaded on the basis of antenna 3 to form the final defect ground structure antenna 4 (d). It is modeled using the electromagnetic simulation software HFSS, and each parameter is analyzed in detail. During the design process, the influence of the cutting angle of the radiating metal patch layer on the circular polarization performance is also given, so that the overall performance of the antenna is finally relatively optimal.

[0040] Reference Figure 4 , showing the parametric analysis process of the above antenna evolution, the resonant frequency of antenna 1 to antenna 4 gradually moves to low frequency, and the impedance bandwidth gradually increases. Compared with the other three antennas, the antenna loaded with improved rectangular slot defect ground structure can better improve the reflection coefficient of the antenna. S 11 , and at the same time, new resonance points are generated at low and high frequencies, thereby improving the impedance matching of the array as a whole. S 11 The impedance bandwidth is increased from the original 11.8% (4 GHz, 5.5 GHz, 5.7-5.8 GHz) to 65.8% (3.8-3.9 GHz, 4.5-5.5 GHz, 6.4GHz). This is mainly because loading the improved rectangular slot is equivalent to expanding the length and width of the slot, changing the propagation of the surface wave, making the frequency band move to low frequency and have ultra-wideband characteristics. In addition, by cutting the corners of the radiation patch, the ultra-wideband characteristics are met, and the circularly polarized wave radiation is stimulated.

[0041] This embodiment shows the effect of the cutting angle of the radiating metal patch layer on the circular polarization characteristics of the antenna. To achieve circular polarization characteristics while ensuring that the antenna has ultra-wideband characteristics, the radiating metal patch layer is cut. The cutting angle treatment will cause the patch current to produce a 90° phase difference to achieve circular polarization. This method is simple and easy to implement. The size of the cutting angle is parametrically analyzed using the electromagnetic simulation software HFSS. Figure 5When the cutting angle of the radiation patch is 0, the axial ratio of the antenna does not meet the working requirement of less than 3dB. When the cutting angle increases, the axial ratio gradually decreases, and the axial ratio bandwidth gradually increases. When it increases to 6mm, the axial ratio is greater than 3dB near 5GHz. Based on the above parameter analysis, the relative optimal value of the cutting angle is 4mm. At this time, the axial ratio bandwidth is 3.8-6.2GHz, accounting for 46.8%, which meets the working requirement of relative bandwidth greater than 20%.

[0042] This embodiment gives the effect of the slot position and structure of the radiation metal patch layer on the reflection coefficient of the microstrip antenna. S 11 The return loss of the microstrip antenna array is mainly affected by the size of the radiation patch, among which the length of the radiation patch mainly affects its resonant frequency, and the width mainly affects its impedance matching. However, simply changing the size of the radiation patch to adjust the resonant frequency and impedance matching will often lead to deterioration of the radiation performance of the antenna. Therefore, without changing other parameters of the antenna, after loading the defective ground structure, it is only necessary to analyze the main size parameters of the defective ground structure to increase the bandwidth of the array antenna. This is because the defective ground structure changes the distributed capacitance and distributed inductance on the antenna floor, thereby reducing the quality factor of the antenna and widening the working bandwidth. Figure 6 In order to study the influence of defect location on its bandwidth, the location of current concentration distribution in the antenna array is found, and the rectangular slot location and the arrangement location of the small rectangle are parametrically scanned and analyzed. First, the rectangular slot location and structure are parametrically scanned and analyzed. It can be seen that the closer the rectangular slot is to the coordinate center, the narrower the bandwidth is, and the resonant frequency is not generated at low frequencies. As the small rectangle moves away from the coordinate center, the resonant frequency moves toward low frequencies, but when it exceeds 10mm, the resonant frequency moves toward high frequencies. When L 5 When 10mm is selected, the effect is relatively the best, but it does not meet the bandwidth requirements. Therefore, in order to make the antenna have ultra-wideband characteristics, while keeping other parameters unchanged and fixed L 4, and then perform parameter analysis on the structural arrangement of the defective ground according to the same steps as above, and obtain the following Figure 4 The parameter analysis diagram is shown, and the structural form is shown in Figure 3 (c) Antenna 3 and Figure 3 (d) Antenna 4 is shown.

[0043] This example provides a comparative analysis of radiation performance. Figure 7 , the surface current distribution diagram of the improved rectangular slot ultra-wideband circularly polarized antenna at 4.8GHz is given. Figure 6It can be seen that the radiation patch generates two orthogonal electric fields in the range of 0° (e), 90° (f), 180° (g), and 270° (h), which are orthogonal to each other, thus forming a circularly polarized wave and a circularly polarized characteristic. When the port is excited, the superimposed surface current rotates counterclockwise as the phase increases, and the antenna radiation presents right-hand circular polarization.

[0044] Reference Figure 8 , showing the radiation patterns of the antenna at 4.8 GHz (i) and 5.2 GHz (j). The dotted line represents the radiation pattern in the xoz plane, and the solid line represents the radiation pattern in the yoz plane. It can be seen that the main polarization is right-hand circular polarization, which is the same as the previous Figure 7 The radiation intensity of the surface current distribution shown in each direction is consistent, and the maximum radiation gain is 5.6 dB, indicating that the radiation characteristics of this antenna are very stable.

[0045] This embodiment provides physical testing and analysis. In order to verify the simulation results, the antenna is processed in a 1:1 ratio according to the simulation model size. The ultra-wideband circularly polarized antenna based on the improved rectangular slot defect ground structure is tested by a vector network analyzer. 11 The actual measurement of the parameters. The axial ratio of the antenna is tested in a microwave darkroom. Fig. 9 , represents the S of the simulated and measured antennas 11 From the data comparison in the figure, it can be seen that at 3.5-4.5 GHz, the measured impedance matching is about 5dB lower than the simulated impedance matching, and the lowest resonant frequency at 4.8 GHz is not as low as the simulated value. There is a small frequency deviation between the bandwidth and the actual measured data, but the test results are basically consistent with the simulated data, and the agreement is also relatively good. The reason may be due to the loss of the dielectric substrate feed itself or the error caused by the welding interference of the SMA connector.

[0046] Reference Fig.10 , represents the axial ratio of the simulated and measured antennas. Compared with the simulation results, the measured axial ratio is reduced by 0.5dB and 0.8dB at 4 GHz and 6 GHz respectively. At around 6 GHz, the axial ratio of the antenna actually measured is larger than the simulated antenna value. However, the general trend is mild and meets the design requirements. This may be caused by processing errors in the manufacturing process of the antenna or dielectric constant errors of the dielectric plate. In summary, both the measured resonant frequency and impedance bandwidth are consistent with the simulation data, completely covering the 4-6GHz band, and the ultra-wideband circular polarization performance is good. The above are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A broadband circularly polarized microstrip antenna with an E-type defective ground structure, comprising a dielectric substrate, a radiating metal patch layer arranged on the top layer of the dielectric substrate, and a grounding plate metal patch layer arranged on the bottom layer of the dielectric substrate, wherein the dielectric substrate, the radiating metal patch layer, and the grounding plate metal patch layer are closely connected as a whole, and a feed point connected to the radiating metal patch layer is arranged at the center of the grounding plate metal patch, characterized in that: There are two radiating metal patch layers, there are two feed points which are directly opposite to the center of the radiating metal patch layer, the radiating metal patch layer is etched with two E-shaped defective ground structures which are symmetrical with the center of the plane, the openings of the two E-shaped defective ground structures are arranged opposite to each other, and the signal is fed by the feed point, so that the dielectric substrate, the radiating metal patch layer, and the grounding plate metal patch layer form an antenna structure.

2. The broadband circularly polarized microstrip antenna of the E-type defect ground structure according to claim 1, characterized in that: The defective ground structure is formed with a first vertical groove, a second vertical groove and a third vertical groove arranged in parallel with each other, and a fourth tree-shaped groove arranged perpendicular to the first vertical groove. The first vertical groove, the second vertical groove and the third vertical groove are flush at one end away from the collapse source point. The first vertical groove, the second vertical groove and the fourth vertical groove are connected to form an F shape. The first vertical groove is arranged on the side away from the feed point, and the third vertical groove is arranged on the side close to the feed point and is spaced apart from the fourth vertical groove.

3. The broadband circularly polarized microstrip antenna of the E-type defect ground structure according to claim 2, characterized in that: The widths of the first vertical groove, the second vertical groove, the third vertical groove and the fourth vertical groove are the same.

4. The broadband circularly polarized microstrip antenna of the E-type defect ground structure according to claim 3, characterized in that: The first vertical groove and the fourth vertical groove have the same length, the first vertical groove and the fourth vertical groove are the longest among the four vertical grooves, and the second vertical groove is the shortest among the four vertical grooves.

5. The broadband circularly polarized microstrip antenna of the E-type defect ground structure according to claim 4, characterized in that: The gap distance between the third vertical groove and the fourth vertical groove is 0.2mm, the width of the first vertical groove, the second vertical groove, the third vertical groove and the fourth vertical groove is 2mm, the length of the first vertical groove and the fourth vertical groove is 5mm, the length of the second vertical groove is 3mm, and the length of the third vertical groove is 4mm.

6. The broadband circularly polarized microstrip antenna of the E-type defect ground structure according to claim 5, characterized in that: The top surface of the radiation metal patch layer is a rectangle, the diagonals of the rectangle are connected to form a first diagonal line and a second diagonal line, the E-type defective ground structure is distributed on the first diagonal line, and the diagonals of the second diagonal line form a cut angle.

7. The broadband circularly polarized microstrip antenna of the E-type defect ground structure according to claim 6, characterized in that: The thickness of the circularly polarized microstrip antenna is 1.4 mm, and the size of the rectangle on the top surface of the radiating metal patch layer is 18 mm×18 mm.

8. The broadband circularly polarized microstrip antenna of the E-type defect ground structure according to claim 7, characterized in that: The length of the hypotenuse of the cut angle is 4 mm.

9. The broadband circularly polarized microstrip antenna of the E-type defect ground structure according to claim 8, characterized in that: The dielectric substrate is a FR4 dielectric substrate, and the length of the dielectric substrate is 46 mm and the width is 26 mm.

10. The broadband circularly polarized microstrip antenna of the E-type defective ground structure according to claim 9, characterized in that: There are two first vertical grooves in the same radiation metal patch layer, wherein the distance between the first vertical groove far away from the center of the dielectric substrate and the vertical line of the long side of the dielectric substrate is 15 mm.

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