2014 IEEE Asia-Pacific Conference on Applied Electromagnetics (APACE) 8 - 10 December, 2014 at Johor Bahru, Johor, Malaysia
A Novel 94-GHz Dipole Bow-tie Slot Antenna on Silicon for Imaging Applications Osama M. Haraz1,3, Mohamed Abdel-Rahman2, Saleh A. Alshebili2,3, Abdel-Razik Sebak3,4 Electrical Engineering Department1 Faculty of Engineering, Assiut University, Assiut, 71515 Egypt
[email protected]
KACST Technology Innovation Center in RFTONICS3 King Saud University, Riyadh, Saudi Arabia
[email protected],
[email protected]
Prince Sultan Advanced Technologies Research Institute2 College of Engineering, King Saud University Riyadh 11421, Saudi Arabia
[email protected]
Department of Electrical and Computer Engineering4 Concordia University, Montreal, Quebec H4G 2W1 Canada
[email protected] element is still below 3 dBi. It is desirable to increase the antenna gain for imaging applications [3].
Abstract—This paper presents a novel dipole bow-tie slot antenna on silicon substrate operating at 94-GHz for imaging applications. The proposed antenna consists of a differentially fed printed folded dipole cut away from the 0.2-μm aluminum above the 1.2-μm silicon dioxide (SiO2) layer built on the 380-μm thick silicon substrate. To increase the antenna impedance bandwidth, a bow-tie slot is added to the dipole slot antenna. The simulated results show that the proposed dipole bow-tie slot antenna exhibits a 5.3 GHz bandwidth starting from 90.1 GHz to 95.4 GHz with a fractional bandwidth (FBW) of about 5.7% while the dipole slot antenna has a bandwidth of 3.3 GHz starting from 92.1 GHz to 95.4 GHz with a FBW of about 3.5%. The proposed dipole bow-tie slot antenna also has a maximum realized gain of 9.7 dBi, which is better than that of the dipole slot antenna, and sidelobe levels of -9.5 dB in both principle planes compared to that of the dipole slot antenna. The proposed antenna is a good candidate for 94-GHz imaging applications.
In this paper, a novel diffrentially-fed dipole bow-tie slot antenna is introduced. The reason for utilizing bow-tie slots in conjunction with the dipole slot antenna is to enhance the antenna matching impedance bandwidth and gain. Simulation results show an impedance bandwidth of ~5.7% at a center frequency of 94 GHz (92.1 GHz–95.4 GHz), and a maximum achieved normalized gain of 9.7 dBi at 94 GHz and a total theoretical radiation efficiency ~97% with uni-directional radiation patterns.
W3
Keywords—dipole antenna; bow-tie antenna; millimeter-waves; imaging applications; silicon.
I.
W1 L3
INTRODUCTION
Millimeter–wave (MMW) antenna technologies are widely utilized in short distance high-data-rate wireless communication systems and in different recent applications such as imaging applications [1]. Coplanar waveguide (CPW) technology has been explored for designing antennas with omnidirectional radiation pattern characteristics that can potentially applied in short-range communication applications and indoor imaging systems [2]. CPW microstrip patch antenna configurations were recently proposed at MMW frequencies. CPW microstrip patch antennas are simple structures that can be easily fabricated in single element and array configurations for higher gains. In addition, CPW microstrip patch antennas can be easily integrated with monolithic microwave integrated circuits (MMICs) yielding compact low profile, high gain and high directivity configurations. However, the maximum achieved gain reported from a CPW microstrip patch antenna
L
L1 W2 L2 W (a)
Silicon substrate
H
(b) Fig. 1. Geometrical configuration of the conventional dipole slot antenna, (a) top view, and (b) side view.
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II.
TABLE II.
ANTENNA GEOMETRY AND DESIGN
A. Dipole Slot Antenna Fig. 1 shows the geometry of a conventional dipole slot antenna cut away from 0.2-μm aluminum layer. The metallic layer is located above the 380-μm thick silicon substrate. A 1.2-μm thick layer of silicon dioxide (SiO2) is added between the silicon substrate and the aluminum metallic layer as an insulating dielectric layer. A 50-Ω differentially fed port is used to feed the dipole slot antenna. The optimized geometrical parameters are calculated using Computer Simulation technology (CST) Microwave Studio full-wave Electromagnetic simulation program [4]. The parameters of the conventional dipole antenna operating at 94-GHz are summarized in Table I.
TABLE I. Parameter Value
Parameter Value Parameter Value
L1
2230
315
495
380
L1
2160
215
Dipole Antenna Parameters L2 L3 H W1 = W2 = W3 759
596
380
Rx
Bow-Tie Antenna Parameters Ry x y
350
610
60°
0
163.2
280
RESULTS
All simulations have been carried out using CST Microwave Studio that is based on Finite Integration Technique (FIT), which is equivalent to finite difference time domain (FDTD) method. The antenna performances for the proposed dipole bow tie slot antenna including reflection coefficient |S11|, maximum realized gain, and radiation patterns have been calculated and presented in this section. The performance of the conventional dipole slot antenna have been also calculated and presented here for comparison purposes.
Dipole Antenna Parameters L2 L3 H W1 = W2 = W3 718
L=W
III.
OPTIMIZED GEOMETRICAL PARAMETERS OF CONVENTIONAL DIPOLE SLOT ANTENNA (UNITS IN ) L=W
OPTIMIZED GEOMETRICAL PARAMETERS OF PROPOSED DIPOLE BOW-TIE SLOT ANTENNA (UNITS IN )
A. Reflection Coefficients S11 Fig. 3 shows the simulated reflection coefficient |S11| versus frequency of the proposed dipole bow-tie slot antenna compared to the conventional dipole slot antenna. It can be seen from results that the achieved matching impedance bandwidth is 5.3 GHz starting from 90.1 GHz to 95.4 GHz with a fractional bandwidth (FBW) of about 5.7%. Meanwhile, the dipole slot antenna has a bandwidth of 3.3 GHz starting from 92.1 GHz to 95.4 GHz with a FBW of about 3.5%. This is due to the existence of the two bow-tie shaped slots in conjunction with the dipole slot arms.
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B. Proposed Dipole Bow-tie Slot Antenna The geometrical configuration of the proposed dipole bowtie slot antenna is presented in Fig. 2. The two arms of bow-tie slots are cut away from the aluminum layer on each side of the dipole slot. Adding this broadband shape to the conventional dipole antenna will enhance the matching impedance bandwidth of the proposed antenna. The bow-tie slot has an elliptical-shaped sector of minor and major radii of Rx and Ry, respectively. The sector angle is while the sector is located at a distance x and y from the origin. The optimized parameters are obtained after applying optimization based on Genetic Algorithm (GA) technique on all antenna geometrical parameters (L, W, L1, L2, L3, W1, W2, W3, Rx, Ry, , x, and, y ) to achieve the maximum available bandwidth with maximum realized gain. The optimized parameters of the proposed dipole bow-tie slot antenna are summarized in Table II.
B. Maximum Realized Gain The Simulated maximum realized gain versus frequency of the proposed dipole bow-tie slot antenna is presented in Fig. 4. The gain curve for the conventional dipole slot antenna is also shown on the same curve for comparison purpose. Results show that the gain of the proposed antenna is higher than that of the conventional dipole antenna across the entire frequency band of interest.
Ry Rx
Fig. 3. Simulated reflection coeficients |S11| versus frequency of the proposed dipole bow-tie slot antenna compared to the conventional dipole slot antenna.
Fig. 2. Geometrical configuration of the proposed dipole bow-tie slot antenna.
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(a)
(b)
(c)
(d)
Fig. 4. Simulated maximum realized gain versus frequency of the proposed dipole bow-tie slot antenna compared to the conventional dipole slot antenna.
Fig. 7. Simulated 3D radition pattern of the proposed dipole bow-tie antenna at f equals (a) 90 GHz, (b) 92 GHz, (c) 94 GHz, and (d) 96 GHz.
The simulated radiation patterns in both xz-plane ( 0°) and yz-plane ( 90°) at f = 94 GHz of the proposed dipole bow-tie antenna compared to the conventional dipole antenna are calculated and illustrated in Fig. 5 and Fig. 6, respectively. Results show that the radiation patterns of the proposed antenna have better sidelobe levels especially in the xz-plane compared to the dipole antenna. The three-dimensional (3D) radiation patterns of the proposed antenna at different frequencies through the desired frequency range, i.e. 90, 92, 94, and 96 GHz are shown in Fig. 7. It can be noticed that the proposed antenna exhibits a stable radiation pattern across the desired frequency band.
Fig. 5. Simulated radiation pattern in the xz-plane ( 0°) at f = 94 GHz of the proposed dipole bow-tie slot antenna compared to the conventional dipole slot antenna.
IV.
CONCLUSIONS
A novel dipole bow-tie slot antenna on silicon substrate operating at 94-GHz for imaging applications was introduced. The proposed antenna was built on a 380-μm thick silicon substrate. A 1.2-μm silicon dioxide (SiO2) layer was used as an insulating dielectric material between the silicon substrate and the aluminum metallic layer. To increase the antenna impedance bandwidth, a bow-tie slot was added to the dipole slot antenna. Results show that the proposed antenna exhibits a FBW of 5.7% (90.1-95.4 GHz) compared to 3.5% (92.1 - 95.4 GHz) for the dipole slot antenna. The proposed antenna had shown better maximum realized gain and sidelobe levels compared to that of the dipole slot antenna. The proposed antenna is considered a good candidate for 94-GHz imaging applications. ACKNOWLEDGMENT
Fig. 6. Simulated radition pattern in the yz-plane ( 90°) at f = 94 GHz of the proposed dipole bow-tie slot antenna compared to the conventional dipole slot antenna.
This work was supported by King Abdul-Aziz City for Science and Technology (KACST) Technology Innovation
C. Radiation Patterns
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Center in radiofrequency and photonics (RFTONICS) in the esociety hosted at King Saud University. REFERENCE [1]
[2]
[3]
[4]
Tang, A., Zhiwei Xu, Gu, Q.J., Yi-Cheng Wu, Chang, M.C.F., "A 144 GHz 2.5mW multi-stage regenerative receiver for mm-Wave imaging in 65nm CMOS", IEEE Radio Frequency Integrated Circuits Symposium (RFIC), On page(s): 1 - 4, Volume: Issue: , 5-7, 2011. T. H. Anh, M. Han, Y.-H. Baek, S.-J. Lee, H. N. Van, J.-H. Kim, Y.-S. Chae, H.-C. Park, J.-K. Rhee, J.-H. Jung and Y.-W. Park, “Coplanar waveguide (CPW)-FED circular slot antenna for W-band and imaging system applications,” Vol. 53, No. 10, October 2011. Z. Briqech, O. M. Haraz, and A.-R. Sebak, “CPW-Fed Yagi Array with Dielectric Resonator Antenna For W-Band And Imaging System Applications”, IEEE AP-S International Symposium on Antennas and Propagation and 2011 USNC/URSI National Radio Science Meeting in Chicago, Illinois, USA, July 8- 14, 2012. CST Microwave Studio, version2012B.02, CST Microwave Studio, Wellesley Hills, MA, 2012.
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