Broadband monopole antenna

Abstract

The utility model provides a broadband monopole antenna, and relates to the technical field of antennas. The antenna comprises a rectangular dielectric substrate, wherein the upper surface of the rectangular dielectric substrate is provided with two circular metal patches and an antenna feed network, and the lower surface of the rectangular dielectric substrate is provided with a metal ground plane. A hollow-out area is arranged in the circular metal patch, and the hollow-out area is composed of a square and small circles located at the four vertex angles of the square. The antenna feed network adopts a one-to-two structure to connect the circular metal patch and the port; the metal ground plane is rectangular, and rectangular defect areas are arranged at the two ends and the terminal of one long side of the metal ground plane. The antenna has a good broadband characteristic and a good gain effect, and is simple in structure and low in processing difficulty.

Description

Technical Field

[0001] The utility model relates to the technical field of antennas, in particular to a broadband monopole antenna. Background Art

[0002] In recent years, as society enters the era of mobile Internet and big data, people have increased their demands for wireless communication services and systems, and therefore have made higher requirements on the performance of WI-FI router antennas. The utility model meets the requirements of wideband, high transmission rate and strong resistance to multipath fading in wireless communication through the design of broadband monopole antenna.

[0003] In the existing technology, although broadband antennas such as Vivaldi antennas have broadband characteristics, their gain is relatively low and their anti-interference ability is weak; the use of high-gain planar quasi-Yagi antennas requires the addition of parasitic patches and other methods to achieve broadband characteristics, which is complex in design, difficult to process, and has high design costs; slot-coupled patch antennas have certain broadband capabilities, but multi-layer dielectrics increase the difficulty and cost of processing. In short, in the existing technology, antennas with broadband characteristics either have low gain or are more complex in structure and more difficult to process. Utility Model Content

[0004] In order to solve the above technical problems existing in the prior art, the utility model aims to provide an antenna with simple structure, low processing difficulty and wide operating frequency band.

[0005] To achieve the above-mentioned purpose, the utility model provides a broadband monopole antenna. The broadband monopole antenna includes a dielectric substrate, an antenna feeding network and a metal ground plane;

[0006] The dielectric substrate is rectangular, and two circular metal patches of equal size are symmetrically arranged on its upper surface parallel to the long side; wherein the radius R1 of the circular metal patch is:

[0007]

[0008] In the formula, c is the speed of light, f is the resonant frequency, ε r is the relative dielectric constant of the dielectric substrate;

[0009] Each circular metal patch is provided with a hollow area including a square; the center point of the square coincides with the center of the circular metal patch, and the four vertex corners are provided with small circles whose centers are located on their diagonals; wherein,

[0010]

[0011] In the formula, R2 is the radius of the small circle, W1 is the side length of the square, and L1 is the distance from the center of the small circle to the center of the square;

[0012] The antenna feeding network is arranged on the upper surface of the dielectric substrate, and includes a first microstrip line, a second microstrip line and a third microstrip line; one end of the first microstrip line is connected to a feeding port located at the midpoint of a long side of the dielectric substrate, and the other end is connected to one end of two left-right symmetrical second microstrip lines, the other end of each second microstrip line is vertically connected to one end of a third microstrip line, and the other end of each third microstrip line is radially connected to a circular metal patch; the first microstrip line and the third microstrip line are both perpendicular to the long side of the dielectric substrate, and the second microstrip line is parallel to the long side of the dielectric substrate; wherein the impedance values ​​of the second microstrip line and the third microstrip line are equal, and a quarter-wavelength impedance transformation line is arranged between the first microstrip line and the second microstrip line, and between the third microstrip line and the circular metal patch;

[0013] The metal ground plane is located on the lower surface of the dielectric substrate; the metal layer plate is rectangular, the first long side of which coincides with the long side of the dielectric substrate where the feeding port is located, and the second long side is circumscribed to the circular metal patch;

[0014] On the second long side, a first rectangular defect area, a second rectangular defect area and a third rectangular defect area of ​​equal width are symmetrically arranged; the first rectangular defect area and the second rectangular defect area are respectively arranged at both ends of the third long side, and the sum of their areas is equal to that of the third rectangular defect area arranged in the middle section of the third long side; wherein,

[0015]

[0016] Where W2 is the width of the first rectangular defect area, L2 is the length of the first rectangular defect area, and W M is the width of the metal ground plane, L M is the length of the metal ground plane.

[0017] Preferably, a connection between the second microstrip line and the third microstrip line is chamfered.

[0018] In summary, in the technical solution provided by the present invention, the circular metal patch with a hollow area and the metal ground plane with a defective ground structure can ensure that the antenna has good broadband characteristics and gain effects, and has a simple structure and low processing difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a top view of the broadband monopole antenna in the utility model.

[0020] Figure 2 It is a bottom view of the broadband monopole antenna in the utility model.

[0021] Figure 3 This is a schematic diagram of the effect of square hollow areas with different side lengths on antenna return loss in the utility model.

[0022] Figure 4This is a schematic diagram of the effect of small circular hollow areas of different radii on antenna return loss in the utility model.

[0023] Figure 5 This is a schematic diagram of the effect of first rectangular defect areas of different widths on antenna return loss in the present invention.

[0024] Figure 6 This is a schematic diagram of the effect of first rectangular defect areas of different lengths on antenna return loss in the utility model.

[0025] Figure 7 It is the return loss curve of the antenna in the utility model.

[0026] Figure 8 It is the S parameter curve of the antenna feeding network in the utility model.

[0027] Fig. 9 It is the phase curve of the output port of the antenna feeding network in the present utility model.

[0028] Fig.10 : The E-plane (phi=0°) radiation diagram of the utility model at different frequency points.

[0029] Fig.11 : H-plane (phi=90°) directional diagram of the utility model at different frequency points.

[0030] The symbols in the figure are as follows: circular metal patch - 1; hollow area - 2; first microstrip line - 3; second microstrip line - 4; third microstrip line - 5; microstrip line cut corner - 6; dielectric substrate - 7; metal ground plane - 8; first rectangular defect area - 9. DETAILED DESCRIPTION

[0031] In order to solve the above technical problems existing in the prior art, the utility model aims to provide an antenna with broadband characteristics, simple structure and low processing difficulty.

[0032] The technical solution proposed by the present utility model will be further explained below in combination with embodiments and drawings.

[0033] The utility model provides a broadband monopole antenna, comprising a dielectric substrate 7, an antenna feeding network and a metal ground plane 8;

[0034] The dielectric substrate 7 is rectangular. Figure 1 As shown, two circular metal patches 1 of equal size (i.e., two monopole antenna units) are symmetrically arranged on its upper surface parallel to the long side;

[0035] Among them, the radius R1 of the circular metal patch 1 is:

[0036]

[0037] In the formula, c is the speed of light, f is the resonant frequency, ε r is the relative dielectric constant of the dielectric substrate 7;

[0038] Each circular metal patch 1 is provided with a hollow area 2 including a square; the center point of the square coincides with the center of the circular metal patch 1, and the four vertices are each provided with a small circle with the center located on the diagonal thereof.

[0039] in,

[0040]

[0041] Where R2 is the radius of the small circle, W1 is the side length of the square, and L1 is the distance from the center of the small circle to the center of the square.

[0042] The antenna feeding network is arranged on the upper surface of the dielectric substrate 7, and includes a first microstrip line 3, a second microstrip line 4 and a third microstrip line 5; one end of the first microstrip line 3 is connected to a feeding port located at the midpoint of a long side of the dielectric substrate 7, and the other end is connected to one end of two left-right symmetrical second microstrip lines 4, the other end of each second microstrip line 4 is connected to one end of a third microstrip line 5, and the other end of each third microstrip line 5 is radially connected to a circular metal patch 1; the first microstrip line 3 and the third microstrip line 5 are both perpendicular to the long side of the dielectric substrate 7, and the second microstrip line 4 is parallel to the long side of the dielectric substrate 7; wherein the impedance values ​​of the second microstrip line 4 and the third microstrip line 5 are equal, and a quarter-wavelength impedance transformation line is provided between the first microstrip line 3 and the second microstrip line 4, and between the third microstrip line 5 and the circular metal patch 1.

[0043] like Figure 2 As shown, the metal ground plane 8 is located on the lower surface of the dielectric substrate 7; the metal ground plane 8 is rectangular, one long side coincides with the long side where the feeding port is located on the dielectric substrate 7, and the other long side is circumscribed to the circular metal patch 1.

[0044] A first rectangular defect area 9, a second rectangular defect area and a third rectangular defect area of ​​equal width are symmetrically arranged on the long side of the circular metal patch 1; the first rectangular defect area 9 and the second rectangular defect area are respectively arranged at both ends of the third long side, and the sum of their areas is equal to that of the third rectangular defect area arranged in the middle section of the third long side; wherein,

[0045]

[0046] Wherein, W2 is the width of the first rectangular defect area 9, L2 is the length of the first rectangular defect area 9, and W M is the width of the metal ground plane 8, L M is the length of the metal ground plane 8.

[0047] Furthermore, in order to avoid more electromagnetic wave reflections at the corners of the antenna feed network, the corners are processed as microstrip lines with a cut angle of 6 to minimize the insertion loss of the feed network. Insertion loss: usually used to describe the transmission characteristics of the antenna, which refers to the phenomenon that when the antenna transmits a signal, the signal is lost during the transmission process inside the antenna due to factors such as the internal structure of the antenna and the transmission line. The size of the insertion loss is usually expressed in decibels (dB) to measure the degree of loss of the antenna during signal transmission.

[0048] The dimensions of the dielectric substrate 7 and each microstrip line satisfy the following relationship:

[0049]

[0050] In the formula, ε re is the effective relative dielectric constant of the equivalent medium, ε r is the relative dielectric constant of the dielectric substrate 7, W is the width of the microstrip line, h is the thickness of the dielectric substrate, and Z0 is the preset impedance value of the microstrip line. In other words, the width of each microstrip line is calculated based on its preset impedance value, combined with the relative dielectric constant of the microstrip line, the thickness of the dielectric substrate 7 and the relative dielectric constant.

[0051] Example 1

[0052] In this embodiment, all metals are etched on 0.762 mm thick Roger 4350B (with a dielectric constant of ε r =3.66, loss angle tanδ=0.004) on a dielectric substrate with a substrate size of 150mm×100mm, which has the characteristics of low profile and low cost.

[0053] (1) Antenna array: Figure 1 As shown, the front monopole antenna unit uses a petal-shaped slot in the center of a circular metal patch to change the inductance and capacitance distribution of the antenna, thereby affecting the surface current distribution of the antenna, thereby adjusting the resonant frequency and impedance matching of the antenna and improving the radiation characteristics of the antenna.

[0054] (2) Antenna feeding network: Figure 1As shown in the figure, in order to enhance the anti-interference ability of the antenna, a binary array design is adopted to improve the antenna gain. The two units are connected by a microstrip T-shaped power divider. The impedance matching of the feeding network uses a quarter-wavelength impedance transformation line. At the same time, in order to avoid more electromagnetic wave reflections at the corners of the microstrip T-shaped power divider, the microstrip line at the corner is cut to minimize the insertion loss of the feeding network. Among them, the quarter-wavelength impedance transformation line is used to transform a specific input impedance into another specific output impedance. It is usually used to match the impedance between the antenna and the transmission line and between the transmission lines to ensure the maximum energy transmission of the signal. The length of the microstrip line is exactly one-quarter of the wavelength of the input signal to achieve impedance matching.

[0055] (3) Antenna ground plane: Two rectangular grooves are opened at the left and right corners of the bottom metal ground of each unit to form a defective ground structure. The defective ground structure is achieved by etching a defect pattern on the ground plane of the circuit to change the distribution of the effective dielectric constant of the circuit substrate material, thereby changing the distributed inductance and distributed capacitance of the microstrip line based on the medium, thereby making such microstrip lines have bandgap characteristics and slow wave characteristics, so that the transmission line generates a resonant frequency with filtering characteristics, and realizing the broadband characteristics of the antenna. Among them, the microstrip power divider is a common power division network, which is used in RF and microwave systems to evenly distribute RF signals from one input port to multiple output ports. It has the advantages of simple structure, low cost, easy integration and manufacturing. The defective ground (Defected Ground Structure) is achieved by etching a defect pattern on the ground plane of the circuit to change the distribution of the effective dielectric constant of the circuit substrate material, thereby changing the distributed inductance and distributed capacitance of the microstrip line based on the medium, thereby making such microstrip lines have bandgap characteristics and slow wave characteristics.

[0056] like Figure 1 As shown, 2 represents the hollow area of ​​the petal-shaped slot. The petal-shaped slot consists of a square slot with a width of W1 and four circular slots with a radius of R2 at the top corners of the square. The radius of the circular patch calculated according to the resonant frequency is R1, as shown in Figure 3 As shown in the figure, the square slots with different widths have an effect on the antenna return loss (S 11 ) has different effects. When W1 = 20mm, the improvement of antenna impedance matching is most obvious. Figure 4The figure shows the effect of circular slots of different radius sizes on the antenna return loss. When R1 = 5mm, the improvement of antenna impedance matching is most obvious. Therefore, the utility model uses a petal-shaped slot formed by a square slot with a width of 20mm and a circular slot with a radius of 5mm to slot the circular patch, so as to improve the impedance matching of the antenna. Among them, return loss refers to the reflection coefficient parameter of the antenna, which is usually used to describe the reflection characteristics of the antenna. Return loss represents the reflection coefficient of the input port of the antenna in the receiving mode, usually expressed in decibels (dB), which is used to measure the degree of reflection loss of the antenna.

[0057] In order to realize omnidirectional radiation characteristics of the monopole antenna provided in this embodiment, the metal ground on the lower surface of the dielectric substrate cannot exceed the radiation unit (that is, the circular metal patch and the metal ground do not overlap in the vertical direction). Figure 2 As shown, in this embodiment, two rectangular grooves are opened at the left and right corners of the bottom metal ground of each antenna unit to form a defective ground structure.

[0058] The effect of changing the length of the defective rectangular slot on the antenna return loss is as follows: Figure 5 As shown in the figure, when L2 = 19 mm, the antenna impedance matching is improved most significantly. The effect of the length of the defective rectangular slot L1 on the antenna return loss is shown in the figure. Figure 6 As shown, when W2=18mm, the antenna operating frequency band and impedance matching are best improved. Therefore, this embodiment uses square grooves with L2=19mm and W2=18mm to groove the metal ground, so as to widen the antenna's operating frequency band and improve the antenna's impedance matching.

[0059] The return loss curve (S) of the monopole antenna provided in this embodiment is 11 )like Figure 7 As shown, the -10 dB bandwidth of the monopole antenna covers 1.57-3.32 GHz, and the return loss of the feeding port at 2.4 GHz is less than -20 dB. This result shows that the monopole antenna provided in this embodiment has a good return loss characteristic.

[0060] The S parameters of the microstrip T-shaped power divider used in the binary array are as follows: Figure 8 As shown in the figure, within the antenna operating frequency band, the return loss of the power divider input port (port 1, i.e., the feeding port) is less than -10dB, and the insertion loss of the output port (ports 2 and 3, i.e., the two ports connecting the two circular metal patches) is about -3dB. Fig. 9 The output phase curve of the T-type power divider is shown in Figure 2. The output phase of the two output ports is consistent, and the power divider can feed the antenna unit with equal amplitude and phase. In other words, the insertion loss S of the two ports is 21 and the 3-port insertion loss S 31 The output phase and amplitude are consistent.

[0061] Fig.10 and Fig.11 They are respectively the radiation patterns of the E-plane and H-plane at different frequencies of the antenna (Realized Gan). The radiation patterns of the E-plane and H-plane at 1.7GHz are relatively standard, with less electromagnetic leakage, and can achieve good persuasion radiation performance. The normal gain of the E-plane and H-plane patterns at 2.4GHz is 8.2dBi, the half-power beamwidth is 47°, and the radiation pattern is an "8" shape. The E-plane and H-plane patterns at 3.1GHz are distorted, and the simulated normal gain at this frequency is 9.3dBi. In summary, the utility model has the performance of low cost, wide bandwidth, high gain, and omnidirectional radiation.

[0062] In summary, in the technical solution provided by the utility model, the annular metal patch with a hollow area and the metal grounding surface with a defective ground structure can ensure that the antenna has good broadband characteristics and gain effects, and has a simple structure and low processing difficulty.

[0063] Furthermore, each preferred scheme has achieved the following beneficial effects on the basis of achieving the above beneficial effects: by chamfering the corners in the antenna feeding network, the insertion loss of the antenna feeding network can be further reduced; by using a relationship, the width of each microstrip line is determined based on the properties of the dielectric substrate and the microstrip line, which can further ensure that the antenna has good broadband characteristics and gain effects in different actual application environments.

[0064] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope.

Claims

1. A broadband monopole antenna, characterized in that: It comprises a dielectric substrate (7), an antenna feeding network and a metal ground plane (8); The dielectric substrate (7) is rectangular, and two circular metal patches (1) of equal size are symmetrically arranged on its upper surface parallel to the long sides; Wherein, the radius R1 of the circular metal patch (1) is: In the formula, c is the speed of light, f is the resonant frequency, ε r is the relative dielectric constant of the dielectric substrate; Each circular metal patch (1) is provided with a hollow area (2) including a square; the center point of the square coincides with the center of the circular metal patch (1), and the four vertices are each provided with a small circle with the center located on the diagonal thereof; wherein, In the formula, R2 is the radius of the small circle, W1 is the side length of the square, and L1 is the distance from the center of the small circle to the center of the square; The antenna feeding network is arranged on the upper surface of the dielectric substrate (7), and comprises a first microstrip line (3), a second microstrip line (4) and a third microstrip line (5); one end of the first microstrip line (3) is connected to a feeding port located at the midpoint of a long side of the dielectric substrate (7), and the other end is connected to one end of two left-right symmetrical second microstrip lines (4); the other end of each second microstrip line (4) is vertically connected to one end of a third microstrip line (5), and the other end of each third microstrip line (5) is radially connected to a circular metal patch (1); the first microstrip line (3) and the third microstrip line (5) are both perpendicular to the long side of the dielectric substrate (7), and the second microstrip line (4) is parallel to the long side of the dielectric substrate (7); wherein the impedance values ​​of the second microstrip line (4) and the third microstrip line (5) are equal, and a quarter-wavelength impedance transformation line is provided between the first microstrip line (3) and the second microstrip line (4), and between the third microstrip line (5) and the circular metal patch (1); The metal ground plane (8) is arranged on the lower surface of the dielectric substrate (7); the metal ground plane (8) is rectangular, a first long side of which coincides with the long side of the dielectric substrate (7) where the feeding port is located, and a second long side circumscribes the circular metal patch (1); On the second long side, a first rectangular defect area (9), a second rectangular defect area and a third rectangular defect area of ​​equal width are symmetrically arranged; the first rectangular defect area (9) and the second rectangular defect area are respectively arranged at both ends of the third long side, and the sum of their areas is equal to that of the third rectangular defect area arranged in the middle section of the third long side; wherein, Wherein, W2 is the width of the first rectangular defect area (9), L2 is the length of the first rectangular defect area (9), and W M is the width of the metal ground plane (8), L M is the length of the metal ground plane (8).

2. A broadband monopole antenna as claimed in claim 1, characterized in that: The connection between the second microstrip line (4) and the third microstrip line (5) is cut at an angle.

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