3. Ultra Wide Band (UWB) is an emerging technology for short range wireless
communication.
Its features are:
1. High data rates (upto 500 Mbps).
2. Low power (microwatt range) and Low cost.
3. Fading robustness
4. Short range (within 10m)
5. More secure with the help of PN (pseudo random noise) codes and is hence
protected from jamming.
6. Various multiple access techniques like TH- UWB and DS- UWB as well as
various modulation techniques such as PPM, PAM, BPSK and OOK.
A February 14, 2002 Report and Order by the FCC authorised the unlicensed use
of UWB in the range of 3.1- 10.6 GHz for commercial applications.
The EIRP for UWB emitters operating in the UWB is -41.3 dBm/MHz.
It provides interference with existing frequency bands of communication like,
WiMAX, WLAN, C-Band, and X-Band satellite communication
Introduction to UWB Technology
4. Electromagnetic Band Gap (EBG) is a Frequency Selective Surface (FSS)
and is a kind of metamaterial with electrical properties.
EBG structures are utilised by a variety of optical and microwave devices
as filters for unwanted signals.
EBG structures offer an efficient suppression of the interferences by
inducing a wide Omni- directional stop band in the operating frequency
range (Filtering characteristics).
EBG structures present very high impedance for vertical and horizontal
modes at certain frequencies. These structures can be analysed as resonant
circuits, in which the capacitance is provided by the proximity of the metal
plates and the inductance is related to the thickness of the structure.
Introduction about EBG structures
5. YOUR SITE HERE
CONCEPT OF EBG
METALLIC
PATCH
METAL
VIA DIELECTRIC
SUBSTRATE
GROUND PLANE
ELECTRIC FIELD LINE DISTRIBUTION
6. EBG- Structures
YOUR SITE HERE
Proposed EBG
Structure
Planar EBG and its equivalent circuit
Mushroom EBG
7. PROPOSED ANTENNA
The ultra-wideband systems are very sensitive to electromagnetic interferences with existing
narrowband wireless communication systems such as WiMAX and WLAN.
It is necessary to design antennas with multiband filtering characteristics to avoid
interferences with applications working in this band.
To solve the above problems different methods have already been proposed and presented
to design UWB with band notched characteristics
For example-
Different types of slots on the radiating patch or on the ground plane
Split-ring resonators
Tuning stubs
Meandering
Folded strips
Resonated cells on CPW
Miniaturization in feed line
Right- Angled EBG structure etched on patch/ground plane(Proposed)
The proposed antenna covers the band of 3- 12.24 GHz and has dimensions of 30*30 mm2
.
8. Right- Angled EBG structure and its Equivalent circuit
YOUR SITE HERE
• Equivalent circuit of proposed EBG can be presented as given above.
• There is a series resonant circuit, due to via presents an inductance, and a
capacitance due to the metal proximity
• A tank circuit is there due to the gap capacitance between feed line and EBG, an
inductance presented by the corner type discontinuous EBG structure.
• It can be visualised as plate. This plate presents very high impedance for the
modes at certain frequencies.
• EBG has frequency selective nature, so it can be used as a filter.
9. Proposed Antenna
Top View of Proposed antenna
Back View of Proposed antenna
Fabricated Prototype antenna-
Top View
10. Dimensions Summary of Proposed Antenna
Variables W L R R1 R2 g S
Size(mm) 30 30 8.3 5.8 5 5.5 0.6
Variables Lf Wf Wg Lg Wg1 Lg1
Size(mm) 11.8 2.8 30 11 5 4
11. Simulation of Proposed microstrip patch antenna is done with the Ansoft HFSS 13
software.
In this simulation analysis we try to optimize different performance parameters of the
antenna such as Return loss, VSWR, group delay, radiation pattern etc.
HFSS is a high-performance full-wave electromagnetic field simulator. It is based on
popular FEM method.
Fabricated prototype antenna is printed on the FR-4 substrate with thickness of 1.6
mm, dielectric constant Ɛr = 4.4 and loss tangent of 0.02.
Initially, a primary antenna (a circular antenna) which provides the UWB band is
designed.
To create a notched characteristics for WiMAX applications, we have cut a CSRR slot
on circular patch.
Second band notched characteristic for WLAN applications has been achieved by
drawing an RA- EBG through via near the right side of the feed line.
A micro- strip feed line of 2.8 mm width has been used to achieve 50Ω characteristic
impedance.
Simulation of Right- Angled EBG Antenna
12. Analysis of Different Parameters
• Initially, a primary antenna (a circular
patch antenna) which provides the
UWB band as VSWR is shown in the
figure.
• To create a notched characteristics for
WiMAX applications, a CSRR slot is
cut on the circular patch, whose
VSWR result is shown here.
• The VSWR due to the EBG has been
shown which has been achieved by
drawing an RA- EBG through via
near the right side of feed line.
• VSWR of proposed antenna
(combined with both CSRR and
EBG) have been presented in dark
line in the figure. VSWR of proposed antenna
13. Analysis of Different Parameters
With the help of Anritsu Vector Network Analyzer, we have
analyze different parameters of designed antenna like return
loss, VSWR, group delay and Unechoic chamber for radiation
pattern.
The Proposed antenna covers UWB band with VSWR < 2 with
Dual notched characteristics.
VSWR v/s Frequency Return loss S11 v/s Frequency
14. Parametric Variations and results
YOUR SITE HERE
Variation in CSRR Length through varying
Gap “g”
variation in Wg1 of EBG
Effect of gap variation between feed line and EBG
Variation in Lg1 of EBG
15. The antenna displays good omni- directional radiation patterns in the H- plane and dipole- like
radiation patterns in the E- plane.
Measured and Simulated, Normalized E & H
Field Patterns
a) E- field at 3.1 GHz
b) H- field at 3.1 GHz
c) E- Field at 4.5 GHz d) H- Field at 4.5 GHz
16. Group Delay measurement has been performed on two identical antennas face to face.
Measured Group Delay of proposed antenna shows variation which is less than 1 ns for un- notched band that
deteriorate phase linearity, while for notched band it is highly exceeded to 4 ns for WiMAX band and
approximately 2 ns for WLAN band.
The Group Delay verifies that the proposed antenna exhibits phase linearity for UWB band except notched
band.
It also claims that proposed antenna has omni- directional radiation pattern.
Measured Group Delay v/s Frequency
Plot
17. Gain & Efficiency Vs Frequency
Peak Gain is approximately zero for the WLAN band.
For WiMAX band peak realized gain is -5dB that means antenna could
not receive or radiate power properly so the radiation efficiency is very
low for WiMAX band i.e., approximately 10% only
18. VECTOR CURRENT DISTIRBUTION AT 3.5 GHz
YOUR SITE HERE
The stronger vector current distribution concentrated near the edges of the CSRR
slot is seen at the center frequency of first notched band (3.3- 3.6 GHz) i.e., at 3.5 GHz.
19. VECTOR CURRENT DISTRIBUTION AT 5.5 GHz
YOUR SITE HERE
The strongest vector current distribution is concentrated at the RA- EBG at the center
frequency of second notched band (5.1- 5.8 GHz) i.e., at 5.5 GHz.
20. VECTOR CURRENT DISTRIBUTION AT 6.5 GHz
YOUR SITE HERE
At the pass- band frequency of 6.5 GHz i.e., outside the notched band, the distribution
of the vector current is uniform as shown below.
21. VECTOR CURRENT DISTRIBUTION AT 7.5 GHz
YOUR SITE HERE
At the pass- band frequency of 7.5 GHz i.e., outside the notched band, the distribution
of the vector current is uniform as shown below.
22. Comparison of Proposed Antenna
Ref. No. Size (mm2)
Band
covered
(GHz)
EBG Type
[16] 38x40 3.1-10.6 M- EBG
[18] 35x39 3.1-10.6 Mushroom
[19] 30x35 3.1-10.2 Square
[21] 42x48.7 2-10.6 L- Shape
[22] 30x32 3-11 Mushroom
[23] 40x40 2-12 Mushroom
[24] 40x40 2-12 Mushroom
[25] 38x40 3-12 Mushroom
Proposed 30x30 3-12.24
Right Angled-
Shape
EBG STRUCTURE TYPE AND COVERED BAND
24. Conclusion
Proposed antenna covers UWB band and overcomes the interference
problems from WLAN and WiMAX applications.
CSRR and EBG structures have been successfully designed to produce
band- stop filtering characteristics.
Proposed antenna has simple structure and compact size of 30*30 mm2.
Results and analysis of this antenna indicates that EBG approach is better
than slot method or CSRR to produce band notch.
Proposed antenna is applicable in miniature devices, simple design and
compact size as added advantage.
25. Future Scope
To increase the number of notched band of proposed
Antenna, we can change the dimensions of the EBG.
We can increase the number of notch bands by
increasing the number of EBG Structures.
The size of the proposed antenna can be further
reduced.
26. Authors are thankful to Prof. Ananjan Basu and Prof. S.K.
Koul, (CARE) - IIT Delhi, New Delhi, INDIA for providing
the measuring facilities and useful discussions.
ACKNOWLEDGMENT
YOUR SITE HERE
27. References
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