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izzat amir

on 21 January 2013

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Statement of Problem
Conclusions OUTLINE Ultra Wideband Antenna

Ultra-wideband (UWB) commonly refers to
signals or systems that either have a large
relative or absolute bandwidth.

Large channel capacity,
low transmit power
High data rates

Suitable for WPAN
Positioning and Tracking System
Radar and Imaging Applications Micro-Strip Antenna Advantages:

Ease of manufacturing
It has a very low fabrication cost.
Microstrip patch antennas are efficient radiators.
Easy in integration with microwave integration circuits. Proposing a micro-strip patch antenna with Negative Bow-Tie and Half-Disc design to exhibit the parametres of UWB Application in terms of Bandwidth, Return Loss and Voltage Standing Wave Ratio (VSWR) STATEMENT OF PROBLEM 1)To design an antenna of low power output at a frequency range of 3.1 until 10.6 GHz, with no signal distortion that can impair narrow band transmission.

2)To analyze the Negative Bow-Tie and Half-Disc Patch Antenna in order to achieve near unity VSWR.

3)To compare and analyze the performance of the antenna between simulation and measurement. DESIGN 1 NEGATIVE BOW-TIE ANTENNA DESIGN REVIEW METHODS & OPTIMIZATION USED IN THE DESIGN CONTINUED.. DESIGN 2 HALF DISC PATCH ANTENNA Three methods of optimization:

->Slot Patch.

->Partial Grounding.

->Slot Ground OPTIMIZATIONS *At first, I constructed full-circle patch, however the result was not good.
*The minimum return loss did not even reach -10 dB . Slot Patch *After optimizing the patch by making slot at the full circle patch, the result was far better in terms of bandwidth and the return loss. #Made optimizations with 5 different dimensions.

#The best was at b=2mm measured from the top.

#The bandwidth increased from 1.22 GHz to 5.7 GHz which was an impressive improvement.

#The return loss was still the same as before partial grounding which was 13.555 dB. Partial Grounding >>Made optimizations with 11 different dimensions.
>>The best was at b=2.2 mm measured from the top.
>>The bandwidth of the antenna increased from 5.7 GHz to 6.05 GHz.
>>Plus, the return loss has decreased too from -13.555 dB to -22 dB. Slot Ground FABRICATED DESIGN Summary of the Simulation and Measured Fabrication:
- Substrate : RT/Duroid 5870 (E=2.33)

Test :
-Rohde & Schwan ZVA 40 Vector Network Analyzer (VNA ) 10 MHz- 40 MHz COMPARISON BETWEEN FABRICATED & SIMULATED DESIGN The bow-tie antenna have become attractive candidate in the communication system due to the size of the conventional rectangular patch - T. Phairat & T. Chancha,2011)

Bow-tie antenna has been introduces as its characteristic that exhibits good impedance matching and maintain gain flatness over the whole UWB freq. range - Kim, Woo et al,2011) The simulated bandwidth value of the Negative Bow-Tie Patch Antenna is the best which is 6.12 GHz.

However, in the measured bandwidth value, the Half-Disc Patch Antenna shows the best result which is 6.0393 GHz.

Meanwhile, the Return Loss value for the Negative Bow-Tie Patch Antenna is the best for both simulated and measured which are -32.47 dB and -25.234 dB respectively. The best values for both simulated and measured VSWR are for Negative Bow-Tie Patch Antenna which is 1.0517 and 1.1233 respectively. CONCLUSION To design a microstrip patch antenna for low power output at a frequency range of (3.1 – 10.6) GHz, with no signal distortion, and a spectral mask that does not impair narrow band transmission --- ACCOMPLISHED!
To analyze and compare the performance of some antennas by simulation and measurements --- ACCOMPLISHED!
To analyze the Half Disc Patch Antenna in order to achieve near unity VSWR --- ACCOMPLISHED!

Plus, by using lower r has improved the measured result since it is more robust to external interruption.

As for me, I used Rogers RT/duroid 5880TM substrate with dielectric constant r = 2.2 and height of the substrate is h =0.794 mm. Meanwhile, my partner used s RT/duroid 5870TM substrate with dielectric constant r = 2.33 and height of the substrate is h =0.787 mm. THANK YOU FOR LISTENING SMA-CONNECTOR At the 4.9 GHz, the return loss value is -22 dB for simulation and –18.52 dB for measurement by using VNA.

At the simulation part by using CST, the antenna operates from 4.1468 to 9.9087 GHz and measurement by using VNA operates from 4.5607 to 10.6 GHz for S11 less than -10 dB. This bandwidth are satisfies the UWB as defined by FCC.

From the simulation, the bandwidth at 4.8 GHz is 120 %. Then, the bandwidth is increased to 125.8 % in the measurement. RETURN LOSS AND BANDWIDTH Voltage standing wave ratio (VSWR) is measure of how much power is delivered to an antenna.
A low VSWR means the antenna is well-matched because the perfect matching is when VSWR is equal to 1 where there is no reflection and return loss.
For the simulation, the value of the VSWR is 1.1839 and 1.3077 for measurement. Voltage Standing Wave Ratio (VSWR) Comparison with Partner’s Design
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