Background
The development period of the antenna can be counted from the end of the 20 th century and the 50 th century, and with the continuous expansion of the application field of wireless communication and the gradual improvement of integrated circuits, people also put forward various requirements on the antenna, such as high gain/broadband/multiband in performance, simple/small volume/light weight in structure, easy manufacturing in process planarization and the like. The traditional antenna is fixed due to the component constitution, the concealment and the anti-interference performance are poor, the integration level is not high, the application in some fields is faded out slowly, and people begin to research high-quality antennas in order to meet the requirements of wireless communication. With the rapid development of information technology, the antenna is also developed to miniaturization, multi-frequency, high-performance, wide-frequency band and high integration with modern communication systems or detection systems. The microstrip antenna is a novel antenna, and has unique advantages, so that the microstrip antenna is widely concerned by researchers at home and abroad, such as small volume, low profile, light weight, easy processing and integration, easy conformality and the like. At present, with the deepening of the theoretical research and the expansion of the application of the microstrip antenna, the microstrip antenna technology has become widely permeated in a large number of wireless communication systems such as space technology, medicine, mobile communication, remote measurement, satellite and the like, and is researched in a plurality of subjects.
In recent decades, researchers have studied and continuously improved microstrip antennas, and numerous methods are brought to the design of microstrip antennas, for example, a multi-band technology usually adopts a stacking method, a multi-branch method (an L-shaped branch, an F-shaped branch, a G-shaped branch, and the like), and a slotting method; the broadband technical method comprises the following steps: the technologies of a loading parasitic patch method, a multi-slot method, a short circuit probe method and the like can effectively realize the miniaturization, broadband, multi-splicing and high-gain indexes of the antenna, thereby improving the communication quality of the system and meeting the requirements of practical application.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a monopole microstrip antenna with coplanar waveguide feed, which breaks through the defects of narrower frequency band, lower gain and the like and expands the range of the microstrip patch antenna applied in the frequency band.
The technical scheme adopted by the invention for solving the technical problems is as follows: the monopole microstrip antenna comprises a feeding part, wherein the feeding part adopts coplanar waveguide feeding, the coplanar waveguide comprises a dielectric substrate and a feeder line, a transmission conduction band unit is arranged in the center of the dielectric substrate, ground plate units are arranged on two sides of the transmission conduction band unit, a radiation unit is attached to the dielectric substrate and is a rectangular frame, an 1/4 circular unit is loaded on a first inner angle of the rectangular frame, a square ring unit is loaded on a second inner angle, 1/4 circular units are loaded on a third inner angle and a fourth inner angle, and one of two 1/4 circular units is connected with a resonance branch; the feeder line is located at the notch of the bottom edge of the rectangular frame and connected with the quasi-L-shaped unit.
The resonance branch comprises a horizontal branch, a first vertical branch, a second vertical branch and a third vertical branch, one end of the first vertical branch is connected with one of the two 1/4 circular units, the other end of the first vertical branch is connected with one end of the horizontal branch, the other end of the horizontal branch is connected with one end of the second vertical branch, and the other end of the second vertical branch is positioned below the horizontal branch; the horizontal branch is also connected with one end of a third vertical branch, and the other end of the third vertical branch is positioned above the horizontal branch; the distance from the third vertical branch to the first vertical branch is less than the distance from the third vertical branch to the second vertical branch.
The quasi-L-shaped unit comprises a vertical rectangular part, a horizontal rectangular part and a semicircular part, the feeder line is connected to the middle of the horizontal rectangular part, the vertical rectangular part is connected to the side face of the horizontal rectangular part, and the semicircular part is connected to the upper portion of the vertical rectangular part.
The width of the upper edge and the lower edge of the rectangular frame is 7mm, and the width of the left edge and the right edge of the rectangular frame is 6 mm.
The radius of the inner circle of the 1/4 circular ring unit is 6mm, and the width is 3 mm.
The interior limit length of quad ring unit is 5mm, and the width is 3 mm.
The radius of the 1/4 circular element is 12 mm.
The length of the first vertical branch is 18mm, the length of the second vertical branch is 11mm, the length of the third vertical branch is 4mm, and the length of the horizontal branch is 25 mm; the widths of the horizontal branch knot, the first vertical branch knot, the second vertical branch knot and the third vertical branch knot are all 3 mm.
The length of the horizontal rectangular part is 16.5mm, and the width of the horizontal rectangular part is 5.2 mm; the vertical rectangular part is 13.8mm in length and 9.5mm in width; the radius of the semi-circular portion is 4.75 mm.
The gap between the feeder line and the rectangular frame is 0.5mm, the length of the feeder line is 7.5mm, and the width of the feeder line is 3.2 mm.
Advantageous effects
Due to the adoption of the technical scheme, compared with the prior art, the invention has the following advantages and positive effects:
the antenna of the invention has the main advantages that: firstly, the antenna adopts coplanar waveguide feed to realize the requirements of miniaturization and broadband, the size of an antenna medium is 54mm multiplied by 54mm, and the achieved bandwidth range is 1.8-4.8 GHz; secondly, the bandwidth of the antenna is expanded through a multi-branch loading method and the like on the basis of a square ring patch, and the voltage standing wave ratio VSVR is consistent with the return loss bandwidth; thirdly, the whole antenna structure is very simple and is easy to integrate into various communication application systems.
Detailed Description
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.
The embodiment of the invention relates to a monopole microstrip antenna fed by coplanar waveguide, which comprises a feeding part, wherein the feeding part adopts coplanar waveguide feeding, the coplanar waveguide comprises a dielectric substrate and a feeder line, a transmission conduction band unit is arranged in the center of the dielectric substrate, grounding plate units are arranged on two sides of the transmission conduction band unit, and the back surface of the dielectric substrate is not provided with a metal floor. A radiation unit is pasted on the medium substrate and is a rectangular frame 1, 1/4 circular units 2 are loaded on a first inner angle of the rectangular frame 1, a square ring unit 3 is loaded on a second inner angle, 1/4 circular units 4 are loaded on a third inner angle and a fourth inner angle, and one of the two 1/4 circular units 4 is connected with the resonant branch; the feeder line 6 is located at a notch of the bottom side of the rectangular frame 1 and connected to the pseudo-L-shaped unit.
The resonance branch comprises a horizontal branch 51, a first vertical branch 52, a second vertical branch 53 and a third vertical branch 54, one end of the first vertical branch 52 is connected with one of the two 1/4 round units, the other end of the first vertical branch is connected with one end of the horizontal branch 51, the other end of the horizontal branch 51 is connected with one end of the second vertical branch 53, and the other end of the second vertical branch 53 is positioned below the horizontal branch 51; the horizontal branch 51 is also connected with one end of a third vertical branch 54, and the other end of the third vertical branch 54 is positioned above the horizontal branch 51; the distance from the third vertical branch 54 to the first vertical branch 52 is smaller than the distance to the second vertical branch 53. The loading of the resonant branch can change the surface current of the antenna radiation patch so as to prolong the effective path of the current, expand the bandwidth and ensure that the voltage standing wave ratio VSVR is consistent with the return loss bandwidth.
The quasi-L-shaped unit includes a vertical rectangular portion 71, a horizontal rectangular portion 72, and a semicircular portion 73, the feeder 6 is connected at a middle position of the horizontal rectangular portion 72, the vertical rectangular portion 71 is connected to a side of the horizontal rectangular portion 72, and the semicircular portion 73 is connected to an upper portion of the vertical rectangular portion 71. The impedance bandwidth of the antenna can be further increased by loading the pseudo-L-shaped element on the feed line.
The antenna structure of the embodiment mainly comprises a dielectric layer, a quasi-L-shaped unit, a square ring unit, a resonance branch node and a feeder line, wherein the radiation units are printed on a Tastic TLT (tm) with the thickness of 1mm, the size of the radiation units is 54mm multiplied by 54mm, and the relative dielectric constant of the radiation units isr2.25, loss tangent tan 0.0006, without a metal ground plate on the lower surface of the dielectric substrate. The size calculation in antenna design is derived from the analysis and calculation of a monopole microstrip antenna by means of a dipole, the monopole microstrip antenna usually operates in a quarter-wavelength mode, and the corresponding free-space wavelength and the wavelength in a medium can be calculated by the formula lambda ═ c/f. The specific dimensional parameters of the antenna are shown in table 1.
Antenna size parameter
|
Parameter value (mm)
|
Antenna size parameter
|
Parameter value (mm)
|
G
|
54
|
a
|
5
|
L1 |
5.2
|
W1 |
1.5
|
L2 |
16.5
|
W2 |
5.2
|
L3 |
13.8
|
W3 |
9.5
|
L4 |
18
|
W4 |
25
|
L5 |
4
|
W5 |
3
|
L6 |
11
|
W6 |
3
|
L7 |
7
|
W7 |
8.47
|
b
|
3
|
W8 |
6
|
R1 |
12
|
R2 |
4.75
|
R3 |
6
|
g
|
0.5
|
Wf |
3.2
|
h
|
1 |
TABLE 1 antenna parameter table
Because the antenna works in free space, in order to enable the designed antenna working parameters to be closer to reality, after the antenna structure model is established, when HFSS13.0 is used for analyzing the antenna performance parameters, the boundary condition of the antenna needs to be set as an ideal conductor boundary, the distance between the radiation boundary surface (namely an air cavity surface) and a radiator needs to be not less than lambda/4, the bottom surface of the antenna model dielectric substrate needs to be set as an ideal boundary, the input port of the antenna is set as waveguide port excitation, the microstrip feeder is positioned at the center of the port, the antenna is set as a fast frequency sweeping type, and the performance of the antenna in a 1-5GHz frequency band is analyzed and calculated.
The antenna of the present invention achieves good performance criteria with a return loss parameter (S11) of 91% (3GHz, 1.8-4.8GHz) as shown in fig. 2. FIG. 3 shows the variation of the voltage standing wave ratio of the antenna with frequency, and it can be seen from FIG. 3 that VSVR <2dB in the frequency band of 1.8-4.8GHz, which meets the technical index. Fig. 4 shows the gain of the antenna, and it can be seen from fig. 4 that the gain of the antenna is substantially above 2.7dB and can reach 4.5dB at most in this frequency band.
In general, each characteristic parameter of an antenna is a function of frequency, and the antenna may have the best characteristics at the center frequency. The return loss S11 and the Gain are two important parameters for the antenna performance, wherein the theoretical requirement is that S11< -10dB and the Gain is more than 2.5dB in the same bandwidth to indicate that the antenna has practical application value. The frequency band range of the antenna is 1.8-4.8GHz, the relative working bandwidth is 91%, the voltage standing wave ratio VSVR of the antenna is consistent with the return loss bandwidth, the input impedance matching of the antenna is good, the gain extreme value is 4.5dB, and the frequency band of Bluetooth and WiMAX working is covered, so that the designed antenna structure can be applied to a wireless communication system working in the frequency band. The invention fully exerts the characteristics of small volume, low profile, easy integration and the like of the microstrip patch antenna, breaks through the defects of narrower frequency band, lower gain and the like, and expands the range of the microstrip patch antenna applied in the frequency band.