layne a. berge michael t. reich masud a. aziz benjamin d. braaten

Tuning a Dual-Band Bow-tie Slot Antenna with Parabolic Radiating

Slots for the 900 MHz and 2400 MHz Bands

Layne A. BergeMichael T. Reich

Masud A. AzizBenjamin D. Braaten

NORTH DAKOTA STATE UNIVERSITY

APPLIED ELECTROMAGNETICS LAB

Department of Electrical and Computer Engineering

North Dakota State UniversityFargo, ND, USA

• Introduction and background information

• Purpose of research

• Simulated and measured results

• Discussion

• Conclusion



Overview

IntroductionNORTH DAKOTA STATE UNIVERSITY


M. Miao, B. Ooi, and P. Kooi, “Broadband CPW-fed wide slot antenna,”Microwave and Optical Technology Letters, vol. 25, no. 3, pp. 206–211,2000.

•Planar, bow-tie, CPW fed, slot antenna

•Original design maintained broadband operation between 3 and 5 GHz

BackgroundNORTH DAKOTA STATE UNIVERSITY


•Planar antennas are simple to fabricate in-house

•CPW (coplanar waveguide) feed allows balanced excitation

•Bow-tie antenna design has a dipole like gain pattern

Purpose of ResearchNORTH DAKOTA STATE UNIVERSITY


•Create an antenna design using a lower permittivity substrate (original ɛr = 10.1)

•Dual-band operation at lower, consumer-band frequencies• 900 MHz• 2400 MHz

DesignNORTH DAKOTA STATE UNIVERSITY


H = 140 mmW = 240 mm, Bw = 100.2 mmBi = 8 mmBo = 70.3 mmg= 0.4 mmd = 4.6 mmS = 7.5 mm



•Rogers 4003C

•Ɛr = 3.55

•Thickness = 1.6 mm



•Parabolic curves emulate a Vivaldi antenna design

•Broadband

•Greater slot perimeter = longer path taken by currents J. Mandeep and M. Nicholas, “Design An

X-Band Vivaldi Antenna,” Microwaves & RF, vol. 47, no. 8, 2008.

Measurement and Simulation ResultsNORTH DAKOTA STATE UNIVERSITY


•Compared both Method of Moments and Finite-Element Method

•Good correlation between simulated and measured results

•Dual-band operation at 900 MHz and 2400 MHz



•Gain at 900 MHz in the y-z plane (left) and x-z plane (right)•Gain pattern similar to a dipole antenna•Simulated gain excursion caused by ideal assumptions (infinite substrate layer)



•Gain at 2400 MHz in the y-z plane (left) and x-z plane (right)•Gain pattern deviates from that of a dipole at high frequencies•Caused by too large of a slot (electrically large dipole antenna → favors side-lobes)



•Surface currents at 900 MHz (left) and 2400 MHz (right)•Too large of slot evident in “odd” surface currents in 2400 MHz plot (right)



•Field strength at 900 MHz in the y-z plane (left) and x-z plane (right)•Low cross-polarization in both plots•Correlates well with gain plots



•Field strength at 2400 MHz in the y-z plane (left) and x-z plane (right)•Non-negligible cross-polarization evident in each plot•Reinforces distorted gain patterns

Discussion• Deviation from simulated and measured gain

results at 900 MHz occurred because of ideal assumption by software (infinite substrate)

• Poor gain plots at 2400 MHz– Asymmetries partly caused by radiation losses

through the substrate– Main cause was found to be the slot width being near

1.5λ– Large slot results in prominent side lobes– Similar to results for electrically long dipole antennas



Discussion• Maintained large bandwidth at both operating

frequencies (Return Loss > 10 dB)– 602 MHz bandwidth at 900 MHz– 229 MHz bandwidth at 2400 MHz

• Used a lower permittivity substrate– Less loss

• Curved slot sides presented a longer path to currents than a comparable straight side



Conclusion• Created a dual-band bow-tie slot antenna

operating at 900 MHz and 2400 MHz• Used a lower permittivity substrate than

previous designs• Used curved slot sides in order to reduce size

of antenna• Gain pattern at 2400 MHz was distorted– Slot width too wide



Questions?



Thank you for listening!

layne a. berge michael t. reich masud a. aziz benjamin d. braaten

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