A vertically polarized omnidirectional radiation notch antenna for WLAN

Abstract

The present invention discloses a vertically polarized omnidirectional radiating notch antenna for WLAN, which comprises a dielectric substrate and a coaxial feed cable. A pair of dipoles are printed along the z-axis direction on the upper layer of the dielectric substrate, and a pair of split ring resonators are printed along the y-axis direction. A coplanar waveguide structure is printed on the upper layer of the lower arm of the dipole, and a layer of metal is printed on the lower layer of the lower arm. The inner conductor of the coaxial cable passes through the dielectric substrate and is connected to the upper metal layer of the lower arm of the dipole, while the outer conductor is connected to the lower metal layer of the lower arm. The dipole is fed by the coaxial cable. A metal layer with the same size and shape as the lower part of the upper layer dipole is printed on the lower layer of the dielectric substrate. The planar notch antenna proposed by the present invention can achieve stable omnidirectional radiation characteristics and small circularity. Within the working frequency band, the antenna has high gain and small cross-polarization components in the horizontal plane. It is suitable for omnidirectional coverage WLAN applications that require notch function.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technologies, and particularly to a vertically polarized omnidirectional radiation notch antenna for WLAN. Background Art

[0002] Planar processed broadband monopoles are designed for communication applications that require miniaturization. As Figure 1 shown, a planar processed monopole antenna is composed of a planar monopole and a ground plane. This planar monopole antenna with a ground plane has broadband characteristics and can cover the UWB frequency band. Compared with a broadband monopole antenna with a three-dimensional structure having a ground plane, the planar structure monopole has the advantages of small volume and low processing cost. A planar processed broadband vertically polarized omnidirectional radiation antenna does not require a ground plane, and the ground plane of the antenna is in the same plane as the antenna, as Figure 2 shown. The shape of the monopole antenna can be various shapes, and shapes such as rectangular, triangular, and curved can all achieve a wide frequency band. These planar processed vertically polarized omnidirectional radiation antennas all have an ultra-wideband operating frequency band, but the horizontal component of these vertically polarized antennas is relatively high, especially in the high-frequency band, and the horizontal component is almost of the same order of magnitude as the vertical component. In addition, the shapes of such antennas are diverse, and there is a lack of guidance on design and optimization methods.

[0003] Through the above analysis, it can be known that although the existing planar processed broadband vertically polarized omnidirectional radiation antennas have advantages such as wide frequency band and miniaturization, in the face of the further requirements of modern communication systems for the wide frequency band and miniaturization of antennas, a vertically polarized omnidirectional radiation antenna with excellent electrical indexes such as miniaturization and wide frequency band is still the current application demand and research difficulty. Selecting a suitable notch method and designing a notch antenna that meets broadband miniaturization according to different communication systems and corresponding index requirements are the research contents of this invention patent. Summary of the Invention

[0004] In view of the problems in the background art, the present invention has studied a vertically polarized omnidirectional radiation notch antenna for WLAN, introduced an open resonator into the omnidirectional radiation vertically polarized antenna, and has a radiation null at 3.5 GHz. In the notch frequency band, the maximum gain in the horizontal plane can be suppressed from 3 dBi to -15 dBi.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A vertically polarized omnidirectional radiation notch antenna for WLAN, comprising a dielectric substrate and a coaxial feed cable. A pair of dipoles are printed along the z-axis direction on the upper layer of the dielectric substrate, and a pair of split ring resonators are printed along the y-axis direction. A coplanar waveguide structure is printed on the upper metal layer of the lower arm of the dipole, and a layer of metal is printed on the lower layer of the lower arm. The inner conductor of the coaxial cable passes through the dielectric substrate and is connected to the upper metal layer of the lower arm of the dipole, while the outer conductor is connected to the lower metal layer of the lower arm. The dipole is fed by the coaxial cable. A metal layer with the same size and shape as the lower part of the upper layer dipole is printed on the lower layer of the dielectric substrate.

[0007] Preferably, the dielectric substrate uses Rogers-4350, with a dielectric constant of ε r = 3.66, a side length of 37.7 mm, and a thickness of 0.787 mm.

[0008] Preferably, the antenna arms of the dipole are fan-shaped, and an exponential antenna arm is used to achieve broadband characteristics.

[0009] Preferably, the expression of the exponential function is Y(x) = Ce kx + B, where k is the constant coefficient of the exponential function, B is the parameter of the exponential function, and the smaller the coefficient k, the closer the exponential function line is to a straight line.

[0010] Preferably, the pair of split ring resonators are C-shaped split ring resonators.

[0011] Preferably, the upper and lower layer metals of the lower arm of the dipole are connected by four metallized vias.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] The planar notch antenna proposed by the present invention can achieve stable omnidirectional radiation characteristics and small circularity. Within the working frequency band, the antenna has high gain and small cross-polarization components in the horizontal plane. It is suitable for omnidirectional coverage WLAN applications that require notch functions. Description of the Drawings

[0014] Figure 1 It is a structural diagram of a monopole antenna for planar processing.

[0015] Figure 2 It is a shape type diagram of a monopole antenna.

[0016] Figure 3 It is an overall structural diagram of the present invention.

[0017] Figure 4 It is a structural diagram of the upper and lower metal layers of the notch antenna of the present invention, where (a) is the upper metal layer and (b) is the lower metal layer.

[0018] Figure 5 This is the simulation and measurement result diagram of the VSWR and isolation of the present invention.

[0019] Figure 6 This is the simulation and test result of the radiation pattern of the present invention. Detailed implementation manners

[0020] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following will, in conjunction with the accompanying drawings and preferred embodiments, describe in detail the specific implementation manners, structures, features and their effects of the present invention as follows.

[0021] As Figure 3 shown, a vertical polarization omnidirectional radiation notch antenna for WLAN of the present invention is composed of a dielectric substrate and a coaxial feed cable. The dielectric substrate uses Rogers-4350, with a relative dielectric constant of εr = 3.66, a side length of 37.7 mm, and a thickness of 0.787 mm. The size parameters of each part of the antenna in the figure are:

[0022] D1 = 0.7 mm, G1 = 8.2 mm, G2 = 0.23 mm, L1 = 36.8 mm, L2 = 8.7 mm, S1 = 0.2 mm, W1 = 1.3 mm, k = 0.2.

[0023] As Figure 4 (a) and (b) show the structures of the upper and lower metal layers of the notch antenna. On the upper layer of the dielectric substrate, a pair of dipoles are printed along the z-axis direction, and a pair of split ring resonators are printed along the y-axis direction. The dipole arms are fan-shaped, and an exponential antenna arm is used to achieve broadband characteristics. The expression of the exponential function is Y(x) = Ce kx +B, where the smaller the coefficient k, the closer the exponential function line is to a straight line. A pair of split ring resonators are C-shaped split ring resonators. The dipole is fed by a coplanar waveguide structure, and the coplanar waveguide structure can be designed in these two metal layers. Therefore, the coplanar waveguide structure is printed on the upper metal layer of the lower arm of the dipole, and a layer of metal is printed on the lower layer of the lower arm. The upper and lower layers of metal of the lower arm of the dipole are connected by four metallized vias. The dipole first feeds the signal to the coplanar waveguide through a coaxial cable, and then continues to be fed to the antenna by the coplanar waveguide. The inner conductor of the coaxial cable passes through the dielectric substrate and is connected to the upper metal layer of the lower arm, and the outer conductor is connected to the lower metal layer of the lower arm.

[0024] In order to verify the performance of the proposed vertical polarization omnidirectional radiation notch antenna of the invention, the simulated antenna is processed and tested, and the measured results are compared with the simulation results. The measurement results of this antenna are obtained by testing with an Agilent network analyzer (Agilent N5230A) and a far-field measurement system (NSI 2000).

[0025] The results of VSWR and isolation for antenna simulation and measurement are as follows Figure 5 shown. For VSWR < 2, the measured frequency bands are 2.3 - 2.78 GHz and 5.2 - 6 GHz, covering the 2.4 - GHz and 5 - GHz WLAN frequency bands. The measured VSWR of the antenna is greater than 16 within the notch frequency band of 3.4 - 3.6 GHz. Figure 6 The maximum gain in the horizontal plane is given. Within the notch frequency band of 3.4 - 3.6 GHz, there is a radiation null, and all the measured gains within the notch frequency band are less than -6 dBi. Within the 2.4 - GHz WLAN frequency band, the measured gain is approximately 2 dBi, and within the 5 - GHz WLAN frequency band, the measured gain is 3.5 - 4.2 dBi. In summary, for VSWR < 2, the proposed antenna can cover the two WLAN operating frequency bands of 2.4 - 2.5 GHz and 5.15 - 5.85 GHz, while in the notch frequency band of 3.4 - 3.6 GHz, the minimum measured gain is -16 dB. The measured results are in good agreement with the simulation results. The deviation between the simulation results and the measured results is mainly caused by manufacturing, installation, and broadband measurement tolerances.

[0026] Figures (a), (b), and (c) respectively depict the radiation patterns in the horizontal plane at 2.4 GHz, 5.2 GHz, and 5.8 GHz. It can be seen from the figures that the proposed antenna has good circularity of the vertical polarization component at these three frequency points, less than 2.2 dB. At the 2.4 - GHz frequency point, the cross - polarization ratio of the antenna is greater than 21 dB. At the 5.2 - GHz and 5.8 - GHz frequency points, the cross - polarization ratios of the antenna are greater than 19 dB and 16 dB respectively. Generally speaking, the proposed planar notch antenna can achieve stable omnidirectional radiation characteristics and small circularity. Within the operating frequency band, the antenna has high gain and small cross - polarization components in the horizontal plane. Therefore, the vertically polarized omnidirectional radiation notch antenna proposed in the present invention is suitable for omnidirectional coverage WLAN applications that require a notch function.

[0027] The above - mentioned are only the preferred embodiments of the present invention and do not impose any form of limitation on the present invention. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above - disclosed technical content to obtain equivalent embodiments with equivalent changes, but as long as they do not depart from the technical content of the present invention, any brief modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A vertically polarized omnidirectional radiation notch antenna for WLAN, comprising a dielectric substrate and a coaxial feed cable, characterized in that: A pair of dipoles is printed along the z-axis direction on the upper layer of the dielectric substrate, and a pair of C-shaped open resonator rings is printed along the y-axis direction; the antenna arms of the dipoles are fan-shaped, and an exponential antenna arm is used to achieve broadband characteristics. The expression of the exponential function is Y(x) = Ce kx + B, where k is the constant coefficient of the exponential function, B is the parameter of the exponential function, and the smaller the coefficient k, the closer the exponential function line is to a straight line; a coplanar waveguide structure is printed on the upper layer of the lower arm of the dipole, and a layer of metal is printed on the lower layer of the lower arm. The upper and lower layers of metal of the lower arm of the dipole are connected by four metallized vias; the inner conductor of the coaxial feed cable passes through the dielectric substrate and is connected to the upper metal layer of the lower arm of the dipole, and the outer conductor is connected to the lower metal layer of the lower arm. The dipole is fed by the coaxial feed cable; Print a metal layer with the same size and shape as the lower part of the upper dipole on the lower layer of the dielectric substrate.

2. The omnidirectional radiation notch antenna with vertical polarization for WLAN according to claim 1, characterized in that: The dielectric substrate uses Rogers-4350 with a dielectric constant of ε r = 3.66, a side length of 37.7 mm, and a thickness of 0.787 mm.

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