A broadband multi-mode planar directive antenna and a design method thereof

Abstract

The application discloses a broadband multi-mode planar directive antenna design method and belongs to the field of antennas and microwave technologies. The antenna is composed of a main vibrator, a reflector, tuning branches, a feeding cable and a balance branch. The main vibrator is in a fan shape structure, the length of the circular arc of which is about one wavelength corresponding to a center frequency, and a pair of tuning branches are arranged on the outer periphery of the main vibrator; the reflector is in a ring shape structure, the length of the outer circular arc of which is about 1.5 times of the wavelength corresponding to the center frequency, and the available mode of the reflector can be determined through an eigen equation. The main vibrator and the reflector are attached to the same plane of a dielectric substrate, the feeding cable and the analog cable are attached to the main vibrator and the reflector, and the balance branch connects the outer conductors of the feeding cable and the analog cable to suppress the unbalanced current on the cable. The application has the characteristics of wide bandwidth, simple structure and coplanar easy integration, and has a wide application prospect in the fields of phased array, radar system, vehicle-mounted system and other wireless mobile communication fields.

Description

Technical Field

[0001] This invention relates to a design method for a broadband multimode planar directional antenna, belonging to the field of mobile communication and microwave technology. Background Technology

[0002] In today's increasingly complex communication environment, it is essential not only to ensure high-quality information transmission but also to enhance confidentiality and anti-interference capabilities. This necessitates antennas with wide bandwidth and good directivity, as well as planarization and miniaturization for application in portable devices. Currently, a common approach to designing directional antennas is to use reflectors and directors, essentially converting omnidirectional or bidirectional antennas into directional antennas. Traditional directional antennas are primarily single-mode resonant, with narrow bandwidth, and require a large number of elements to achieve high gain. Log-periodic dipole antennas require even more elements to simultaneously achieve wide bandwidth and moderate gain. Therefore, the "single-cavity multimode" approach from multimode analysis can be employed. By fully exciting all modes within a single resonant cavity and perturbing the resonant nulls, the resonant points are brought closer together, thus widening the antenna bandwidth.

[0003] In broadband directional antenna design, the reflectors used are often large in size and perpendicular to the plane of the antenna, which makes the antenna occupy a lot of space and is not conducive to coplanar integration in new devices. However, coplanar reflectors can suppress the back radiation of the antenna and significantly improve the front-to-back ratio and end-fire gain of the antenna. Planarly integrated directional antennas have received great attention in recent years due to their advantages such as light weight, small size, simple structure and easy conformal integration.

[0004] Therefore, with the development of new high-capacity mobile communication systems, there is an urgent need to develop new planar directional antennas that are broadband, have a high front-to-back ratio, simple structure, and small size. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a directional antenna that uses a simple fan-shaped and loop structure. It exhibits multimode resonance characteristics within the operating frequency band, a relative impedance bandwidth exceeding 60%, and achieves a front-to-back ratio of over 10 dB with a directional radiation bandwidth exceeding 20%. It possesses a series of advantages, including simple structure, excellent performance, and ease of fabrication.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A design method for a broadband multimode planar directed antenna, wherein the directed antenna employs a multimode resonant current-strip operating mode, and the current distribution resonant modes of the sector and ring patches are controlled by a Bessel-Fourier doublet series; the antenna design method specifically comprises:

[0008] Two identical and symmetrical sector-shaped patches are disposed on the surface of the dielectric substrate to form the main element of the directional antenna.

[0009] Two identical annular patches, symmetrical about the central axis of the dielectric substrate, are disposed on the surface of the dielectric substrate to form the reflector of the directional antenna. The reflector achieves resonance by coupling with the main oscillator.

[0010] Two coaxial cables are arranged on the surface of the main oscillator and the reflector. One coaxial cable is used for power feeding and is called the power feeding cable. The other coaxial cable is not used for power feeding and is called the virtual cable. The outer conductor of the power feeding cable is attached to the right arm of the main oscillator and the reflector, and the inner conductor is connected to the left arm of the main oscillator. The virtual cable is symmetrically attached to the left arm of the main oscillator and the reflector.

[0011] Furthermore, the resonant mode orders of the master oscillator and the reflector described above can be independently adjusted.

[0012] Furthermore, both of the aforementioned sector-shaped patches and the two aforementioned annular patches are disposed on the same surface of the dielectric substrate, and the aforementioned first sector-shaped patch and the aforementioned second annular patch are disposed on the same surface of the dielectric substrate.

[0013] Furthermore, the inner conductor of the power supply cable is connected to the power supply point on the left arm of the main oscillator, and the power supply point is located on the straight edge of the left arm of the main oscillator closest to the central axis.

[0014] Furthermore, the feed point is not the vertex of the sector patch.

[0015] Furthermore, a pair of open-circuit tuned stubs are provided on the main oscillator to excite and perturb higher-order modes.

[0016] Furthermore, the outer arc length of the annular patch is an odd multiple of half the wavelength of the arc length of the sector patch.

[0017] Furthermore, there is a gap between the two fan-shaped patches and a gap between the two annular patches.

[0018] Furthermore, unbalanced currents are suppressed by connecting the outer conductors of the feed cable and the analog cable through balancing stubs.

[0019] A broadband multimode planar directional antenna is fabricated using the method described above.

[0020] Furthermore, the antenna also includes a director disposed on the side of the main oscillator away from the reflector.

[0021] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0022] This invention proposes a novel design method for planar directional antennas, focusing on the use of two-dimensional dipole technology with multimode resonance to achieve an impedance bandwidth of over 60% and a directional radiation bandwidth of over 20%. By using a coplanar integrated reflector, the antenna structure is greatly simplified, the manufacturing process is simple, and the cost is low, thus meeting the application requirements of next-generation broadband mobile communication. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a broadband multimode planar directional antenna consisting of one main element, one reflector, a feed cable, a virtual cable, a tuning stub, and a balancing stub.

[0024] Figure 2 It is a side view of a broadband multimode planar directional antenna consisting of one main element, one reflector, a feed cable, a virtual cable, a tuning stub, and a balancing stub.

[0025] Figure 3 This is a schematic diagram of a three-element planar directional antenna with a director, consisting of one main element, one director, one reflector, a feed cable, a virtual cable, a tuning stub, and a balancing stub.

[0026] Figure 4 This is a specific implementation dimension of a broadband multimode planar directional antenna;

[0027] Figure 5 The S11 diagram of the broadband multimode planar directional antenna is obtained using HFSS simulation calculations.

[0028] Figure 6 This is the antenna gain diagram obtained from HFSS simulation calculations for the broadband multimode planar directed antenna end-fire.

[0029] Figure 7 This is a graph showing the front-to-back ratio change of a broadband multimode planar directional antenna, obtained through HFSS simulation calculations.

[0030] Figure 8 The specific implementation dimensions are of a three-element planar antenna with a director;

[0031] Figure 9 The S11 diagram of the three-element planar directional antenna is obtained from HFSS simulation calculations.

[0032] Figure 10 This is the antenna gain diagram of the three-element planar directional antenna end-fired antenna obtained by HFSS simulation calculation;

[0033] Figure 11 This is a schematic diagram showing the specific dimensions of the antenna with a metal reflector.

[0034] Figure 12The S11 diagram is obtained from the specific implementation of the antenna with a metal reflector.

[0035] Figure 13 This is a schematic diagram showing the specific dimensions of a traditional Yagi antenna.

[0036] Figure 14 This is the S11 diagram obtained from the specific implementation of a traditional Yagi antenna;

[0037] Figure 15 This is a gain curve obtained from a specific implementation of a traditional Yagi antenna. Detailed Implementation

[0038] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0039] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0040] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings:

[0041] This invention proposes a novel design method for a broadband multimode planar directional antenna. It focuses on achieving multimode resonance by combining two-dimensional sector and ring elements, and uses a coplanar ring reflector instead of a vertical reflector to achieve an impedance bandwidth of over 60% relative bandwidth. This simplifies the antenna structure and meets the application requirements of next-generation broadband mobile communication.

[0042] The broadband multimode planar directional antenna of the present invention adopts a two-dimensional resonant current patch operating mode. The current distribution resonant modes of the sector and ring patches are controlled by the Bessel-Fourier double series, rather than the one-dimensional sine (cosine) distributed current characteristics of the conventional bowtie (sector oscillator).

[0043] The present invention designs the main oscillator as a fan-shaped structure, that is, the main oscillator is composed of two identical fan-shaped patches, and the central angle of the fan-shaped patches ranges from 30 to 175 degrees.

[0044] The feed point of the left arm of the main oscillator is located on one side of the fan-shaped patch near the central axis, about 0.18 wavelengths from the center. The feed point should not be located at the apex of the fan-shaped patch to fully excite the TE mode, that is, the electric field direction should be parallel to the plane of the oscillator.

[0045] This invention designs the reflector as a ring structure, meaning the reflector consists of two identical ring patches. The central angle of the ring patches ranges from 45 to 90 degrees, and the ratio of the outer diameter to the inner diameter is greater than 1. The outer arc length of the ring patch is an odd multiple of half the wavelength of the arc length of the fan-shaped patch.

[0046] The antenna's main element and reflector can be fabricated on a dielectric substrate with any dielectric constant. The central angles of the sector patch constituting the main element and the annular patch constituting the reflector can be flexibly selected based on the intrinsic equations and boundary conditions.

[0047] In this invention, the arc length of the reflector is selected to be 1.4-1.6 times the wavelength corresponding to its center frequency, while the arc length of the main oscillator is 0.9-1.1 times the wavelength corresponding to its center frequency.

[0048] Furthermore, tuning branches can be set on the fan-shaped patch of the main oscillator to tune its operating mode.

[0049] This invention designs a planar directional antenna using a coplanar two-dimensional sector dipole and a ring reflector. The design process involves: first, deriving approximate analytical formulas through eigenvalue equations to determine all initial values ​​for key antenna parameters; then, studying two-element and three-element designs to verify the correctness and versatility of the design method. Without using an additional 3D reflector, a full-plane, broadband directional antenna is achieved using a full-wavelength sector dipole and a coplanar ring reflector under multi-TE mode resonance. It exhibits multi-mode resonance characteristics within the operating frequency band, a relative impedance bandwidth exceeding 60%, and directional radiation characteristics with a front-to-back ratio exceeding 10dB, a directional radiation bandwidth exceeding 20%, and a series of advantages including simple structure, excellent performance, and ease of fabrication.

[0050] In one embodiment, such as Figure 1 , 2 As shown, this broadband multimode planar directional antenna consists of a reflector, a main element, a pair of tuning stubs, a feed cable, and a balancing stub. The length of the open-circuit tuning stub of the main element is L, and the width is w. The distance from the feed point on the main element to the center of the main element is c. The spacing between the two sector patches forming the main element and the spacing between the two sector patches forming the reflector are h. The central angle of the two sector patches forming the main element is β. The distance between the main element and the reflector is D.

[0051] Specific implementation dimensions are as follows: Figure 4As shown, the main vibrator is a full-wave vibrator. The central angle of the fan-shaped patch constituting the main vibrator is 135 degrees, and the radius is 0.21 wavelengths. The distance from the feed point on the main vibrator to the center of the main vibrator is 0.182 wavelengths. A pair of open-circuit tuned stubs with a length of approximately 0.1 wavelengths and a width of approximately 0.05 wavelengths are introduced on the outer circumference of the main vibrator. The distance between the main vibrator and the reflector is 0.25 wavelengths. The central angle of the reflector is 150 degrees, and the ratio of its outer diameter to its inner diameter is 2. The S11, the gain diagram of the antenna end-fire direction, and the front-to-back ratio of the broadband multimode planar directional antenna are obtained through simulation calculation using HFSS software, as shown below. Figure 5 , 6 As shown in Figures 7 and 8.

[0052] In one embodiment, such as Figure 3 As shown, this three-element planar directional antenna with a director consists of a director, a reflector, a main element, a pair of tuning stubs, a feed cable, and a balancing stub. The length of the open-circuit tuning stub of the main element is L, and the width is w. The distance from the feed point on the main element to the center of the main element is c. The spacing between the two sector patches forming the main element and the spacing between the two sector patches forming the reflector are h. The central angle of the two sector patches forming the main element is β. The distance between the director and the main element is d. The distance between the main element and the reflector is D. The radius of the director is r.

[0053] Specific implementation dimensions are as follows: Figure 8 As shown, the director has a radius of 0.213 wavelengths, the distance between the director and the main element is 0.024 wavelengths, the main element is a full-wave dipole, the central angle of the fan-shaped patch constituting the main element is 135 degrees, and the radius is 0.21 wavelengths; the distance from the feed point on the main element to the center of the main element is 0.182 wavelengths; the distance between the main element and the reflector is 0.25 wavelengths, the central angle of the reflector is 150 degrees, and the ratio of its outer diameter to its inner diameter is 2; a pair of open-circuit tuned stubs with a length of approximately 0.1 wavelengths and a width of approximately 0.05 wavelengths are introduced on the outer circumference of the main element. The S11 and gain diagram of the antenna end-fire direction of the three-element planar directional antenna are obtained by simulation calculation using HFSS software, as shown below. Figure 9 , 10 As shown, by comparing the gain diagrams, it can be found that this invention can combine a director to realize a multi-element planar directional antenna, thereby further improving the antenna performance.

[0054] like Figure 11The illustrated directing antenna comprises a vertical metal reflector, a main element, a director, a pair of tuning stubs, a feed cable, and a balancing stub. The main element is a full-wave dipole with a fan-shaped patch forming it having a central angle of 135 degrees and a radius of 0.21 wavelengths. The distance from the feed point on the main element to its center is 0.186 wavelengths. A pair of open-circuit tuning stubs, approximately 0.1 wavelengths in length and 0.05 wavelengths in width, are introduced around the periphery of the main element. The S11 of the directing antenna is calculated using HFSS software simulation. Figure 12 As shown, compared with the broadband multimode planar directional antenna proposed in this invention, a metal reflector perpendicular to the antenna patch is required.

[0055] like Figure 13 The traditional Yagi antenna shown has the following structure: a director, a main element, and a reflector. The main element is a half-wave dipole, and the distance d3 between the director and the main element is 0.2 wavelengths. The distance between the main element and the reflector is also 0.2 wavelengths. Its S11 and gain diagram are obtained through simulation calculation using HFSS software, as shown below. Figure 14 and 15 As shown.

[0056] In summary, the planar directional antenna designed in this invention can achieve multi-mode resonance characteristics and features wide bandwidth, high front-to-back ratio, coplanar antenna elements, simple structure, and ease of fabrication. It has broad application prospects in wireless mobile communication fields such as phased arrays, radar systems, and vehicle-mounted systems.

[0057] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any transformations or substitutions that can be conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A design method for a broadband multimode planar directional antenna, characterized in that, The guiding antenna employs a multi-mode resonant current patch operating mode, where the current distribution resonant modes of the sector and ring patches are controlled by a Bessel-Fourier doublet; the antenna design method is specifically as follows: Two identical and symmetrical sector-shaped patches are disposed on the surface of the dielectric substrate to form the main element of the directional antenna. Two identical annular patches, symmetrical about the central axis of the dielectric substrate, are disposed on the surface of the dielectric substrate to form the reflector of the directional antenna. The reflector achieves resonance by coupling with the main oscillator. There is a gap between the two fan-shaped patches and a gap between the two annular patches; both the two fan-shaped patches and the two annular patches are disposed on the same surface of the dielectric substrate; both annular patches are fan-shaped ring patches. Two coaxial cables are arranged on the surface of the main oscillator and the reflector. One coaxial cable is used for power feeding and is called the power feeding cable. The other coaxial cable is not used for power feeding and is called the virtual cable. The outer conductor of the power feeding cable is attached to the right arm of the main oscillator and the reflector, and the inner conductor is connected to the left arm of the main oscillator. The virtual cable is symmetrically attached to the left arm of the main oscillator and the reflector.

2. The design method of a broadband multimode planar directional antenna according to claim 1, characterized in that, The inner conductor is connected to the feed point on the left arm of the main oscillator. The feed point is located on the straight edge of the left arm of the main oscillator closest to the central axis, and the feed point is not the vertex of the sector patch.

3. The design method of a broadband multimode planar directional antenna according to claim 1, characterized in that, The resonant mode order of the main oscillator and the reflector can be independently adjusted.

4. The design method of a broadband multimode planar directional antenna according to claim 1, characterized in that, A pair of open-circuit tuned stubs are set on the main oscillator to excite and perturb higher-order modes.

5. The design method of a broadband multimode planar directional antenna according to claim 1, characterized in that, The outer arc length of the annular patch is an odd multiple of half the wavelength of the arc length of the sector patch.

6. The design method of a broadband multimode planar directional antenna according to claim 1, characterized in that, Unbalanced current is suppressed by connecting the outer conductors of the feed cable and the analog cable through a balancing stub (7).

7. A broadband multimode planar directional antenna, characterized in that, It is prepared by the method described in any one of claims 1 to 6.

8. A broadband multimode planar directional antenna according to claim 7, characterized in that, It also includes a director located on the side of the main oscillator away from the reflector.

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