DOI : 10.17577/IJERTV4IS070514
- Open Access
- Total Downloads : 545
- Authors : Sheng Peng, Hongxing Zheng
- Paper ID : IJERTV4IS070514
- Volume & Issue : Volume 04, Issue 07 (July 2015)
- Published (First Online): 31-07-2015
- ISSN (Online) : 2278-0181
- Publisher Name : IJERT
- License:
This work is licensed under a Creative Commons Attribution 4.0 International License
Design of Coplanar-Waveguide-Feed Antenna
Sheng Peng
Department of Electronic Engineering Tianjin University of Technology and Education
Tianjin, China
Hongxing Zheng
Department of Electronic Engineering Tianjin University of Technology and Education
Tianjin, China
AbstractDesign of dual-band and ultra-wide band (UWB) with band-notched antennas have been discussed in this paper. These antennas are fed by coplanar waveguide. Structure of dual-band antenna has been proposed with corner-free rectangle and isosceles trapezoid; it can work efficiency in 2.32GHz ~ 2.57GHz and 5.2GHz ~ 5.8GHz. The planar UWB antenna has a band-notched characteristic for the interference between the UWB applications and WLAN, which can be used to reject the frequency 5.1GHz ~ 5.9 GHz by inserting a thin slot on the radiation element. The results in simulation and measurement showed that both of them have wonderful impedance bandwidth and radiation efficiency that it is a kind of good performance, easy integration antenna with practical value.
KeywordsCPW; UWB antenna; band-notched characteristic; planar antenna
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INTRODUCTION
Printed antennas have attracted much attention due to the
-
ANTENNA DESIGN
-
Principle of coplanar waveguide feed
As shown in Figure 1, the coplanar waveguide composed of dielectric substrate and three conduction band. Three metal etching conduction bands are in the same side of the dielectric substrate. The signal is in the between of the two ground part on the one side of the dielectric substrate, the other side is nothing. Coplanar waveguide structure generally adopts the high dielectric constant substrate, and the wavelength is less than 0 inside the waveguide, therefore the electromagnetic field is concentrated in the medium and the air interface. Alternating electromagnetic field generated between the metal conduction bands and the ground conduction band, can produce longitudinal and transverse alternating electromagnetic field. For traditional metal waveguide, only TE and TM mode are transmuted. Coplanar waveguide is used as transmission line to conduction TEM wave, as constraint conditions:
advantages of wide bandwidth and ease to integrate with monolithic microwave integrated circuits [1]-[7]. Coplanar waveguide is a kind of planar transmission line structure [8]- [16], whose ground and radiation patch are on the same layer of medium plate. Various types of coplanar waveguide feed antenna have been reported to achieve the goal of multiband, broad band and miniaturization [17] – [23]. In [24], [25], the antenna fed by coplanar waveguide, can obtain good impedance matching between the radiation patch and feeder, and can realize 52% impedance bandwidth, by adjusting the distance between microstrip patch and ground plate, but it is a
d 0
in the formula, d = 2wf+s0
.
/(40 1/ 2 )
single working frequency band, can not meet the requirement of current WLAN. In [26], the antenna has been proposed with symmetrical double trapezoid microstrip structure, which have advantage of uniplanar geometry and easier to fabricate than the design fed by microstrip line, however, the working frequency just in 5.6GHz ~ 11.3 GHz.
This paper presented two kinds of antenna fed by coplanar waveguide, which has very wide impedance bandwidth and good omnidirectional radiation characteristics. Combining these two kinds of antenna, it can basically meet the requirements of various kinds of commonly used frequencies. The ultra-wideband antenna has a very wide bandwidth and wide application, while it has so many WLAN frequency of
Fig. 1. the structure of coplanar waveguide
-
Design of dual-band antenna
The Dual-band antenna contains two resonant paths, one of then corresponding to the length (w1) of corner-free rectangle at the top of the radiation patch, which makes the antenna working at high frequencies, another one corresponding to the high (w4) of isosceles trapezoid at the bottom of the radiation patch, which makes the antenna working in low frequency band. By adjusting w1 and w4, the expected work frequency can be easily obtained in antenna. The valuables w1 and w4 are referred to as formula .
signals used in the space, therefore the ultra-wideband antenna have a notch in the 5.1 GHz ~ 5.1 GHz frequency to avoid the interference of the WLAN. To make up the shortfall, the dual-
w1,4
c
fl ,h e
band antenna specially be designed for the application of WLAN. Both of the dual-band and ultra-wideband antennas could integrate with RF/microwave circuits easily, enabling a miniature hybrid or monolithic microwave integrated circuit.
The structure of dual-band antenna is shown in Figure 2, the radiation part and ground plane were etched on coplanar sides of the FR-4 (r = 4.4 and h = 1.6mm). The width of the antenna (W1) is 26mm, and the length of the antenna (L1) is
35mm. The antenna fed with coplanar waveguide, makes the antenna working frequency band has a good impedance matching by adjust the width of the feeder (wf) and the gap (s0).
Fig. 2. configuration of dual-band antenna
It is found that the impedance bandwidth of the proposed design can be improved by adjusting the bottom side of trapezoidal. As show in figure 3, the center of high frequency shift up as the increase of s0, while the center of low frequency be stay, Adjust the value of w1, the change of reflection coefficient S11 of antenna is shown in Figure 4. The Figure 4 shows that the changing of w1 affects on S11 a lot. With increasing of w1, the center of high frequency shift to the right, but it has less impact on the low frequency band. The figure 5 shows that l1 has a certain influence on both frequency bands, it can improving the bandwidth of the high frequency band with the increase of l1. The corner-free rectangle patch make antenna works at 2.32GHz ~ 2.57GHz frequency band. Changing the long side w4 of rectangular, it can be known by Figure 6 that w4 mainly affects the center part of the low frequency band, and the center part of the low frequency shift to the left with the increase of w4. When w4 = 21.5 mm, the antenna gets the optimal resonance at 2.32GHz ~ 2.57GHz frequency band.
0
-10
S (dB)
11
s =0.6
0
-10
S (dB)
11
-20
-30
0
S (dB)
11
-10
-20
-30
0
-10
S (dB)
11
-20
-30
-40
w =4
1
1
w =6
1
w =8
2 3 4 5 6
Freq(GHz)
Fig. 4. S11 for different length of w1
1
l =6
1
l =7
1
l =8
2 3 4 5 6
Freq(GHz)
Fig. 5. S11 for different length of l1
4
w =19.5
4
w =21.5
4
w =23.5
2 3 4 5 6
-20
0
0
s =1.0
0
s =1.4
Fig. 6. S11
Freq(GHz)
for different length of w4
-30
2 3 4 5 6
Freq(GHz)
Fig. 3. S11 for different length of s0
-
Design of Band-Notched UWB Antenna
The radiation patch of band-notched UWB antenna is composed of circular structure and semi-circular structures. Through adjusting the two center position and radius size to make antenna work in ultra wideband spectrum, at the same time, opening a slit in the middle of the patch to change the current distribution on antenna, which can realize band- notched feature on 5.1GHz ~ 5.9 GHz frequency band.
0
-5
-10
S (dB)
11
-15
-20
-25
-30
a=5.5
a=7 a=8.2
2 4 6 8 10 12
Freq(GHz)
Fig. 9. S11 for different length of a
0
b=11
Fig. 7. configuration of Band-Notched UWB antenna
-5 b=12.5
b=13
In order to get the prefect match, the distance of the coplanar waveguide (s02) must be adjusted to the appropriate value. As the figure 6 shows that when s02 = 0.2mm, the antenna gets the optimal resonance. The radiation patch consists of a semicircular and circular which overlap each other. To make the antenna works in ultra wide band by adjust the radius of circle (a) and the radius of semicircular (b). Figure 7 shows that with the increases of a, the reflection coefficient of 5.9GHz ~ 11.8GHz frequency band move down significantly. When a = 8.2mm, the antenna gets the optimal resonance. As show in Figure 8, the value of b also could be the important factors. Opening slit in the middle of the
-10
S (dB)
11
-15
-20
-25
2 4 6 8 10 12
Freq(GHz)
Fig. 10. S11 for different length of b
radiation patch can change the current distribution, at last achieving notch function. The band-notched are mainly affected by the length of gap m, as the increases of m in Figure 8, the band-notched obviously move to left. By adjusting the size of m to avoid the interference WLAN band, when m=15mm, the band-notched is in 5.1GHz~5.9GHz frequency band.
0
0
-5
-10
S (dB)
11
-15
02
s =0.4
-20
-5 s =0.3
m=14
02
-25
m=14.5
S (dB)
11
-10
-15
-20
-25
s =0.2
02 m=15
-30
2 4 6 8 10 12
Freq(GHz)
Fig. 11. S11 for different length of m
-
-
EXPERIMENTAL RESULTS AND DISCUSSION
By optimization of the antenna structure, the dimensions
2 4 6 8 10 12
Freq(GHz)
Fig. 8. S11 for different length of s02
of the dual-band antenna and band-notched UWB antenna are showed in Table 1 and Table 2. According to the optimization parameters, the actual processing of the two antennas are shown in Figure 8 and Figure 9. Using high-performance RF integration AV3629 vector network analyzer to measure reflection coefficient S11 and VSWR of antenna, the measured results coincide with the simulation results.
0
-5
S (dB)
11
-10
-15
-20
Measure Simulate
Fig. 12. photograph of dual-band antenna
-25
2 3 4 5 6
Freq(GHz)
Fig. 14. comparison between measured and simulated S11 for the proposed antenna
4.0
3.5
VSWR
3.0
2.5
2.0
1.5
1.0
Measure Simulate
Fig. 13. photograph of band-notched UWB antenna
TABLE I. PARAMETERS OF THE DUAL-BAND ANTENNA (MM)
2 3 4 5 6
Freq(GHz)
Fig. 15. comparison between measured and simulated VSWR for the proposed antenna
W1
L1
wf1
w11
w2
w3
w4
30
30
2.91
6
26
4
20.9
l01
l1
l2
s01
s2
h
14.6
7
6
1
1
1.6
As shown in Figure 12, the radiation patterns were measured at frequencies of the three working frequency bands. H-plane patterns are round, which can send and receive signals in all directions. E-plane patterns similar to dumbbell shape, which shows that the antenna has good omnidirectional radiation characteristics.
TABLE II. PARAMETERS OF BAND-NOTCHED UWB ANTENNA (MM)
0
-6
-12
150
120
90 60 E H
30
W2
L2
wf2
w12
a
b
m
28
26
1.5
3
8.2
12.2
15
n
L02
s02
h
0.2
10.3
0.2
1.6
-18 180 0
-12
As shown in Figure 10, the S11 parameter of dual-band antenna in 2.32GHz ~ 2.57GHz and 5.15GHz ~ 5.80GHz two bands are less than -10dB and the minimum values of S11 of the center frequency are below -20dB, which reached good transmission characteristics outwardly. As shown in Figure 11, the antenna VSWR is less than 1.5 in the above band.
-6 210
0
240
270
-
2.4GHz
300
330
0
-10
150
120
90 60 E H
8
6
VSWR
30
4
Simulate Measure
-20 180
-10
210
0
240
270
300
0
330
2
0
2 4 6 8 10 12
Freq(GHz)
Fig. 18. comparison between measured and simulated VSWR for the
0
-10
-20
150
-
5.2GHz
90
120
proposed antenna
60
E The radiation patterns were measured at frequencies of 4,
H 7, 8, 9 and 10GHz in the principal E-plane and H-plane. For
brevity, the radiation patterns are shown in Figure 17. The H
30 plane pattern of antenna is performance for amplitude omni-
directional in the 4 GHZ band. When the frequency is greater than 7 GHz, the direction graph edge no longer keep the
-20
-10
180
210
0
330
maximum value and have small sag. The E plane pattern of antenna is an approximation of "8" glyph, which cross polarization amplitude is less than -20 dB in the whole band. The results show that the antenna satisfies the radiation condition in the whole work band.
0
240 300
270
-
5.8GHz
0
-10
150
120
90 60 E H
30
Fig. 16. radiation patterns of dual-band antenna at required frequencies.
As shown in Figure 15 and Figure 16the impedance bandwidth is 9.1GHz within the frequency band of 2.7GHz- 11.8GHz, and the antenna has obvious band-notched characteristics in the frequency 5.1GHz-5.9GHz band which can effectively prevent the interference of WLAN.
0 Simulate
-20
-30
-20
-10
0
180
210
240 300
270
0
330
-5
S (dB)
11
-10
-15
-20
Measure
0
-10
-20
-30
150
120
-
4GHz
90
60 E
H
30
-25
-30
2 4 6 8 10 12
Freq(GHz)
Fig. 17. comparison between measured and simulated S11 for the proposed antenna
-30
-20
-10
0
180
210
240 300
270
-
7GHz
0
330
0
-10
150
120
90 60 E H
30
-
-
CONCLUSION
The radiation patterns were measured at frequencies of 4, 7, 8, 9 and 10GHz in the principal E-plane and H-plane. For brevity, the radiation patterns are shown in Figure 17. The H plane pattern of antenna is performance for amplitude omni-
-20
180
-20
directional in the 4 GHZ band. When the frequency is greater
0 than 7 GHz, the direction graph edge no longer keep the
maximum value and have small sag. The E plane pattern of
-10
0
210
240 300
270
-
8GHz
90
330
E
antenna is an approximation of "8" glyph, which cross polarization amplitude is less than -20 dB in the whole band. The results show that the antenna satisfies the radiation condiion in the whole work band.
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