Ultra-wideband planar antenna

Abstract

The utility model provides an ultra-wideband planar antenna, and relates to the technical field of antennas. In the planar antenna, the upper surface of a rectangular dielectric substrate is provided with a power feed network and four circular radiation patches with the same size, and the lower surface of the rectangular dielectric substrate is provided with a metal plate layer; the power feed network is composed of microstrip lines of a one-to-two or two-to-four symmetrical structure, the four tail ends of the power feed network are all radially connected to the annular radiation patch, and the head end of the power feed network is connected to the external port. And the circular radiation patches are in one-to-one correspondence with the hollow parts of the metal plate layer. The planar 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 an ultra-wideband planar antenna. Background Art

[0002] As a device for sending and receiving electromagnetic waves, antennas play an indispensable role in wireless communications and radar systems. Compared with traditional antennas, ultra-wideband antenna technology has the advantages of low cost and small size, and also has the characteristics of ultra-wideband, low power consumption, low cost, high transmission speed and high anti-interference. Ultra-wideband antenna technology has the characteristics of ultra-low transmission power (usually less than -41dBm), which enables this antenna technology to coexist with other radio frequency technologies and plays an important role in short-distance communications. The level of antenna gain directly affects the intensity of radiation performance. Due to the technical particularity of ultra-wideband antennas, the key lies in how to improve the antenna structure to maintain high gain within a wide frequency band, which is the key to improving the antenna radiation capability. In addition, the main technical indicators of ultra-wideband antennas also include return loss (S11), voltage standing wave ratio (VSWR), half-power beam width (HPBW), etc.

[0003] In the existing technology, a multi-layer dielectric substrate is usually used to package the antenna to achieve miniaturization and expand the working bandwidth, or a slot is made on the multi-layer dielectric substrate to change the original electric field distribution to expand the working bandwidth. Obviously, the above method has a relatively complex structure, and the processing difficulty and processing cost are relatively high. 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 object, the utility model provides an ultra-wideband planar antenna, comprising a dielectric substrate, a power division feeding network and a metal plate layer;

[0006] The dielectric substrate is rectangular, and four equal-sized circular radiation patches are arranged on its upper surface parallel to the long side and at equal distances;

[0007] A power division feeding network is arranged on the upper surface of a dielectric substrate, and includes a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line and a fifth microstrip line; one end of the first microstrip line is connected to a port located on 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 connected to one end of a third microstrip line, the other end of each third microstrip line is connected to one end of two left-right symmetrical fourth microstrip lines, the other end of each fourth microstrip line is connected to one end of a fifth microstrip line, and the other end of each fifth microstrip line is radially connected to a circular ring-shaped radiation patch; the first microstrip line, the third microstrip line and the fifth microstrip line are all perpendicular to the long side of the dielectric substrate, and the second microstrip line and the fourth microstrip line are all parallel to the long side of the dielectric substrate;

[0008] The length of all microstrip lines is much longer than the working wavelength; the impedance values ​​of the second microstrip line, the fourth microstrip line and the fifth microstrip line are linearly gradient, and the impedance values ​​at both ends are 50Ω and 100Ω respectively; in the second microstrip line and the fourth microstrip line, the impedance value of the near-port end is 100Ω, and in the fifth microstrip line, the impedance value of the near-port end is 50Ω; the impedance values ​​of the first microstrip line and the third microstrip line are both 50Ω;

[0009] A metal plate layer of equal size is arranged on the lower surface of the dielectric substrate, and the area corresponding to the annular radiation patch is set as a hollow area; the hollow area is a circle with a preset proportion of area cut off by the chord, and the circumscribed point of the annular radiation patch and the chord is the only intersection of the annular radiation patch and the circle; the preset proportion is less than one half.

[0010] In the technical solution provided by the utility model, the hollow area of ​​the annular radiation patch and the metal plate layer can ensure that the antenna has good broadband characteristics and gain effects, and the structure is simple and the processing difficulty is low; the power feeding network adopts a continuous gradient line structure, and the length is much longer than the microstrip line of the working wavelength, which can greatly reduce the input loss. Specifically, the annular radiation patch has good symmetry and gradient, which conforms to the characteristics of non-frequency-variable antennas, and can ensure the stability of the input impedance of the antenna within a wide frequency band to reflect good broadband characteristics; the structure of the hollow area of ​​the metal plate layer can couple the current at the edge of the radiation patch to improve the antenna's radiation pattern. At the same time, the metal plate layer in the non-hollow area is grounded, which can effectively suppress the radiation of the annular radiation patch to the surrounding area, so that the antenna radiation energy is concentrated in the normal direction perpendicular to the antenna plane, so that the antenna gain is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a top view of the ultra-wideband planar antenna in the utility model.

[0012] Figure 2 It is a bottom view of the ultra-wideband planar antenna in the utility model.

[0013] Figure 3The simulation results are as follows: return loss (S11) and VSWR (Voltage Standing Wave Ratio) of the ultra-wideband planar antenna in the utility model.

[0014] Figure 4 These are the simulation results of the gain and radiation efficiency of the ultra-wideband planar antenna in the present invention.

[0015] Figure 5 These are the xoz plane radiation patterns corresponding to the ultra-wideband planar antenna in the utility model at 3 GHz, 5 GHz and 7 GHz respectively.

[0016] Figure 6 These are the yoz plane radiation patterns corresponding to the ultra-wideband planar antenna in the utility model at 3 GHz, 5 GHz and 7 GHz respectively.

[0017] The symbols in the figure are as follows: annular radiation patch - 1; dielectric substrate - 2; power division feeding network - 3; first microstrip line - 4; second microstrip line - 5; third microstrip line - 6; fourth microstrip line - 7; fifth microstrip line - 8; metal plate layer - 9; hollow area - 10; ground plate - 11. DETAILED DESCRIPTION

[0018] There are two main views on the definition of ultra-wideband antennas: one is that the U.S. Defense Advanced Research Projects Agency (DARPA) calls antennas with a relative bandwidth exceeding 25% ultra-wideband antennas; the other is that the U.S. Federal Communications Commission (FCC) set the lower limit of ultra-wideband relative bandwidth in the civilian field at 20% in 2002.

[0019] Relative bandwidth BW m The calculation formula is as follows:

[0020]

[0021] In the formula, f H and f L They are the highest and lowest frequencies within the working bandwidth respectively.

[0022] The antennas provided by the prior art have the following main technical problems: the operating frequency is too high to be used in current mainstream communication equipment; the structure is complex, the processing is difficult and the processing cost is high; additional external lumped components are required, which makes the processing more complex; the metal patch pattern is relatively complex and the design is difficult.

[0023] Based on the above technical problems, the utility model provides a planar antenna with a simple structure, low processing difficulty and a wide-band antenna.

[0024] The technical solution proposed by the utility model will be further explained below in combination with the accompanying drawings and embodiments. The planar antenna specifically comprises: a dielectric substrate 2, a power division feeding network 3 and a metal plate layer 9;

[0025] The dielectric substrate 2 is rectangular, and four equal-sized circular radiation patches 1 are equidistantly arranged on its upper surface parallel to the long sides;

[0026] A power division feeding network 3 is arranged on the upper surface of a dielectric substrate 2, and includes a first microstrip line 4, a second microstrip line 5, a third microstrip line 6, a fourth microstrip line 7 and a fifth microstrip line 8; one end of the first microstrip line 4 is connected to a port located on a long side of the dielectric substrate 2, and the other end is connected to one end of two left-right symmetrical second microstrip lines 5, the other end of each second microstrip line 5 is connected to one end of a third microstrip line 6, the other end of each third microstrip line 6 is connected to one end of two left-right symmetrical fourth microstrip lines 7, the other end of each fourth microstrip line 7 is connected to one end of a fifth microstrip line 8, and the other end of each fifth microstrip line 8 is radially connected to a circular ring-shaped radiation patch 1; the first microstrip line 4, the third microstrip line 6 and the fifth microstrip line 8 are all perpendicular to the long side of the dielectric substrate, and the second microstrip line 5 and the fourth microstrip line 7 are all parallel to the long side of the dielectric substrate;

[0027] The lengths of all microstrip lines are much longer than the working wavelength; the impedance values ​​of the second microstrip line 5, the fourth microstrip line 7 and the fifth microstrip line 8 are linearly gradient, and the impedance values ​​at both ends are 50Ω and 100Ω respectively; in the second microstrip line 5 and the fourth microstrip line 7, the impedance value of the near-port end is 100Ω, and in the fifth microstrip line 8, the impedance value of the near-port end is 50Ω; the impedance values ​​of the first microstrip line 4 and the third microstrip line 6 are both 50Ω;

[0028] The metal plate layer 9 of equal size is arranged on the lower surface of the dielectric substrate 2, and the area corresponding to the annular radiation patch 1 is set as a hollow area 10; the hollow area 10 is a circle with a preset proportion of area cut off by a chord, and the circumscribed point of the annular radiation patch 1 and the chord is the only intersection of the annular radiation patch 1 and the circle; the preset proportion is less than one half.

[0029] The thickness and dielectric constant of the dielectric substrate 2 and the width of each microstrip line should meet certain conditions.

[0030] When h>W m When the microstrip line width W m Calculated according to the following formula:

[0031]

[0032] When h≤Wm When , the microstrip line width W is calculated according to the following formula:

[0033]

[0034] Among them, ε r is the dielectric constant of the dielectric substrate 2, ε re is the effective relative dielectric constant of the microstrip line, h is the thickness of the dielectric substrate 2, and Z0 is the preset impedance value of the microstrip line.

[0035] It should be noted that the preset impedance of the first microstrip line 4 is flexibly set according to actual needs. In actual manufacturing, the width of the first microstrip line 4 is obtained according to the dielectric constant and preset impedance of the microstrip line, the thickness of the dielectric substrate 2 and the dielectric constant of the dielectric substrate 2. Therefore, in a specific actual case, the effective relative dielectric constants of all microstrip lines are equal, but the impedance values ​​of the second microstrip line 5, the fourth microstrip line 7 and the fifth microstrip line 8 are linearly gradient, so their widths are also different and need to be calculated based on the above relationship.

[0036] The annular radiation patch 1 has good symmetry and gradient, and this structure is very consistent with the characteristics of non-frequency-variable antennas. Therefore, it can be ensured that the input impedance of the antenna remains stable within a wide frequency band, so that it has good broadband characteristics. For the one-to-four power-dividing feeding network 3 of the ultra-wideband antenna, the transmission characteristics of its structure need to change less with frequency within a wider frequency band. In the actual antenna array feeding network, due to the need for power distribution, the feeding network has a discontinuous branch structure. This discontinuous structure will cause energy reflection, which will cause the transmission characteristics of the feeding network to change significantly when the frequency changes. To avoid the above problems, the feeding network adopts a multi-section impedance transformer, and by increasing the number of sections of the impedance transformer, the characteristic impedance step change between two adjacent sections of the impedance transformer is very small. When the number of impedance transformers increases infinitely, the one-to-four power-dividing feeding network 3 constitutes a continuous gradient line structure. As long as the length of the gradient line is much longer than the working wavelength, its input loss will become very small, thereby satisfying the ultra-wideband characteristics. The ground plane 11 on the back of the antenna is a metal plate layer 9, in which the hollow area 10 is cut out to form a fan-shaped structure, which can couple the current at the edge of the radiation patch to improve the antenna's directivity. At the same time, since the other parts of the metal plate layer 9 are grounded, the radiation of the annular radiation patch 1 to the surrounding area can be effectively suppressed, so that the antenna radiation energy is concentrated in the normal direction perpendicular to the antenna plane, thereby increasing the gain of the antenna.

[0037] Example 1

[0038] This embodiment provides an ultra-wideband planar antenna, including a dielectric substrate 2, four annular radiation patches 1 located above the dielectric substrate and a one-to-four power splitter feeding network 3 connected to the four annular radiation patches 1, and a ground plate 11 located below the dielectric substrate including a hollow area 10 and other parts of a metal plate layer 9.

[0039] like Figure 1 As shown, the metal layer located above the dielectric substrate 2 includes four annular radiation patches 1 and a one-to-four symmetrical power division feeding network 3 connected to the four annular radiation patches 1; the one-to-four power division feeding network 3 is a linear gradient structure, and the port adopts a 50ohm coaxial feeding interface.

[0040] like Figure 2 As shown, the grounding plate 11 located below the dielectric substrate 2 includes four fan-shaped hollow areas 10 and other parts of the metal plate layer 9, each hollow area 10 is respectively located below each annular radiation patch 1, and the horizontal straight line of each hollow area 10 is tangent to the outer diameter of the annular radiation patch 1.

[0041] The dielectric substrate 2 is located between the annular radiation patch 1 and the ground plane 11, and adopts Rogers 4350B with a dielectric constant of 3.66, with a width W of 60 mm, a length L of 240 mm, and a height of 0.762 mm. The four annular radiation patches 1 located above the dielectric substrate 2 have the same size, with an outer radius R1 = 8.5 mm, an inner radius R2 = 4 mm, and a distance D = 60 mm between adjacent annular radiation patches 1.

[0042] The first microstrip line 4 and the third microstrip line 6 are microstrip lines with an impedance value of 50 ohm, the length of the first microstrip line 4 is h1=13.93 mm, the length of the third microstrip line 6 is h3=8.93 mm, and the line widths of the first microstrip line 4 and the third microstrip line 6 are both 1.6 mm. The second microstrip line 5, the fourth microstrip line 7, and the fifth microstrip line 8 are linear gradient lines with impedance values ​​from 100 ohm to 50 ohm, the length of the second microstrip line 5 is h2=58.4 mm, the length of the fourth microstrip line 7 is h4=28.4 mm, and the length of the fifth microstrip line 8 is h5=6.45 mm; the second microstrip line 5, the fourth microstrip line 7, and the fifth microstrip line 8 have an impedance value of 100 ohm at one end and a line width of 0.35 mm, and an impedance value of 50 ohm at the other end and a line width of 1.6 mm. Port 1 is a signal input port, using a 50 ohm coaxial feeding interface.

[0043] The grounding plate 11 located below the dielectric substrate 2 includes a hollow area 10 and other parts of the metal plate layer 9. The grounding plate 11 is as large as the dielectric substrate 2, and the hollow area 10 is composed of four identical fan-shaped slots, with a slot radius Rx = 26 mm and a horizontal straight line length m = 41.67 mm.

[0044] The simulation results of return loss (S11) and VSWR of the utility model are as follows: Figure 3 As shown. It can be seen that the -10dB impedance bandwidth is 2.07GHz-9.91GHz, and its relative bandwidth is 130.6%. The voltage standing wave ratio (VSWR) at 2GHz-10GHz is <2, and the lowest is 1.23. Among them, the return loss refers to the ratio of the power reflected back by the RF input signal to the input signal power, which is measured in dB and is a negative number. The voltage standing wave ratio refers to the ratio of the voltage amplitude between the antinode voltage and the trough voltage of the transmission line, also known as the standing wave coefficient or standing wave ratio. When the standing wave ratio is equal to 1, it means that the impedance of the feeder and the antenna is completely matched. At this time, all the high-frequency energy is radiated by the antenna, and there is no energy reflection loss; when the standing wave ratio is infinite, it means full reflection, and no energy is radiated at all.

[0045] The simulation results of gain and radiation efficiency of the utility model are as follows: Figure 4 As shown. It can be seen that as the frequency (Freq) increases, the gain tends to increase, and the maximum gain is 13.85dBi. The maximum radiation efficiency is 91.8%, and the average radiation efficiency exceeds 87%. Among them, the gain refers to the ratio of the radiated power flux density of the antenna in a certain specified direction to the maximum radiated power flux density of the reference antenna at the same input power. If not otherwise specified, the antenna gain refers to the gain in the direction of maximum radiation; under the same conditions, the higher the gain, the better the directivity, and the longer the distance of radio wave propagation, that is, the coverage distance increases. Radiation efficiency refers to the ratio of the power radiated by the antenna (that is, the power that effectively converts the electromagnetic wave part) to the active power input to the antenna. It is a value that is always less than 1. Antenna efficiency is generally defined as the ratio of the radiated power of the antenna to the input power.

[0046] The radiation patterns of the xoz surface of the utility model at 3GHz, 5GHz and 7GHz are as follows: Figure 5 As shown, the yoz surface radiation patterns corresponding to 3GHz, 5GHz, and 7GHz are as follows Figure 6 As shown. It can be seen that the half-power beam width of the xoz plane gradually narrows with the increase of frequency, and the half-power beam width of the yoz plane remains basically stable. In other words, the utility model maintains stable radiation characteristics within the working frequency band. Among them, radiation pattern: The antenna radiation pattern refers to the graph of the relative field strength (normalized modulus) of the radiation field changing with direction at a certain distance from the antenna. It is a graphical description method of the antenna radiation characteristics.

[0047] In summary, in the technical solution provided by the utility model, the hollow areas of the annular radiation patch 1 and the grounding plate 11 can ensure that the antenna has good broadband characteristics and gain effects, and the structure is simple and the processing difficulty is low; the power feeding network adopts a continuous gradient line structure, and the length is much longer than the microstrip line of the working wavelength, which can greatly reduce the input loss. Specifically, the annular radiation patch has good symmetry and gradient, which conforms to the characteristics of non-frequency-variable antennas, and can ensure the stability of the input impedance of the antenna within a wide frequency band to reflect good broadband characteristics; the structure of the power division feeding network has ultra-wideband characteristics, which can ensure the ultra-wideband characteristics of the antenna; the structure of the hollow area of ​​the grounding plate 11 can couple the current at the edge of the radiation patch to improve the antenna's radiation pattern. At the same time, the metal plate layer in the non-hollow area is grounded, which can effectively suppress the radiation of the annular radiation patch to the surrounding area, so that the antenna radiation energy is concentrated in the normal direction perpendicular to the antenna plane, so that the antenna gain is increased.

[0048] Furthermore, in the preferred solution, the width of each microstrip line is determined based on the properties of the dielectric substrate and the microstrip line through a relationship, which can further ensure that the antenna has good broadband characteristics and gain effects in different practical application environments.

[0049] 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 scope of protection.

Claims

1. An ultra-wideband planar antenna, characterized in that: It comprises a dielectric substrate (2), a power division and feeding network (3) and a metal plate layer (9); The dielectric substrate (2) is rectangular, and four circular radiation patches (1) of equal size are arranged on its upper surface parallel to the long sides and at equal distances; A power division feeding network (3) is arranged on the upper surface of a dielectric substrate (2), and comprises a first microstrip line (4), a second microstrip line (5), a third microstrip line (6), a fourth microstrip line (7) and a fifth microstrip line (8); one end of the first microstrip line (4) is connected to a port located on a long side of the dielectric substrate (2), and the other end is connected to one end of two left-right symmetrical second microstrip lines (5); the other end of each second microstrip line (5) is connected to one end of a third microstrip line (6); the other end of each third microstrip line (6) is connected to one end of two left-right symmetrical fourth microstrip lines (7); the other end of each fourth microstrip line (7) is connected to one end of a fifth microstrip line (8); and the other end of each fifth microstrip line (8) is radially connected to a circular ring-shaped radiation patch (1); the first microstrip line (4), the third microstrip line (6) and the fifth microstrip line (8) are all perpendicular to the long side of the dielectric substrate, and the second microstrip line (5) and the fourth microstrip line (7) are all parallel to the long side of the dielectric substrate; The length of all microstrip lines is much larger than the operating wavelength; The impedance values ​​of the second microstrip line (5), the fourth microstrip line (7) and the fifth microstrip line (8) are all linearly gradient, and the impedance values ​​at both ends are 50Ω and 100Ω respectively; in the second microstrip line (5) and the fourth microstrip line (7), the impedance value at the near-port end is 100Ω, and in the fifth microstrip line (8), the impedance value at the near-port end is 50Ω; the impedance values ​​of the first microstrip line (4) and the third microstrip line (6) are both 50Ω; Metal plate layers (9) of equal size are arranged on the lower surface of the dielectric substrate (2), and the areas corresponding to the annular radiation patches (1) are all set as hollow areas (10); the hollow areas (10) are circles whose area is cut off by a chord with a preset proportion, and the tangent point of the annular radiation patch (1) and the chord is the only intersection point between the annular radiation patch (1) and the circle; the preset proportion is less than one-half.

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