Thailand-Japan MicroWave 2013
60 GHz Antenna-on-Chip (AoC) using Asymmetric Artificial Magnetic Conductor (AMC) on 0.18 m CMOS technology Adel Barakat†+ Ahmed Allam† Hala Elsadek* Mohamed El-Sayed† H. Jia‡ and Ramesh K. Pokharel‡ †School of ECCE, Egypt-Japan University of Science and Technology New Borg Al-Arab, Alexandria, Egypt ‡Center of Japan-Egypt Corporation, Kyushu University
Motooka 744, Nishi-ku, Fukuoka, 819-0395 Japan
*Microstrip Circuits Department, Electronics Research Institute Dokki, Cairo, Egypt E-mail:
+
[email protected]
Abstract This paper presents a 60 GHz Antenna-on-Chip (AoC) designed using 0.18µm CMOS process. AoC performance is enhanced using asymmetric Artificial Magnetic Conductor (AMC). As asymmetric AMC shields AoC from the lossy CMOS substrate, gain and efficiency of 0.8dBi and 49%, respectively, are achieved. Asymmetric AMC has similar properties to the conventional Perfect Electric Conductor (PEC) allowing for reduced feeding circuit loss than symmetric AMCs. The asymmetric AMC saves about 2dB/mm at 60GHz of insertion loss than symmetric AMC. Keyword 60 GHz, CMOS, Antenna-on-Chip (AoC), Artificial Magnetic Conductor (AMC)
1. I NTRODUCTION The 60 GHz band is known by its unlicensed wide bandwidth of 7 GHz (from 57 to 64 GHz) which allows for data rates of several gigabytes, surpassin g current technologies. AoC is a promising technology that guarantees single chip integration of the antenna, radio frequency circuits and digital circuits allowing for System-on-Chip (SoC), hence, promising low cost and power saving devices. However, the CMOS substrate inherited losses due to its high permittivity and low resistivity causes performance degradation [1]. Design methodologies such as micromachining [2] and proton implantation [3] are used to improve the AoC performance. Nevertheless, these techniques reduce system level integration and increase the overall cost.
AMC cells’ number in the direction of current flow and decreasing them in the perpendicular direction. In this paper, an asymmetric R-AMC is proposed to guarantee enhanced radiation characteristics when combined with AoC as will discussed in the following sections. High Frequency Structure Simulator, HFSS®, is used for simulations. The paper sections are as follows: section 2 presents the design of R-AMC unit cell. While, section 3 shows the use of AMC as ground plane. Finally, section 4 describes the design of AoC with asymmetric R-AMC comparing it with previously reported designs symmetric R-AMC.
y x (a) 3D View (b) Top View Fig. 1. Asymmetric R-AMC Unit Cell Electromagnetic shielding using AMCs [1] is another probable methodology used to enhance AoC performance. A shield plane of AMCs is inserted between the AoC and the lossy CMOS substrate so as to minimize losses. The AMC plane can be characterized by a reflection coefficient of +1 at its center frequency thus the reflected wave can constructively enhance the total EM-field. In [1], rectangular (R)-AMC is presented with the use of optimization methodology introduced by [4] to reduce the design size and to enhance performance. In [4] AoC efficiency can be enhanced by increasing
Fig. 2. Asymmetric R-AMC Phase Response 2. A SYMMETRIC AMC D ESIGN An asymmetric R-AMC unit cell is shown in Fig. 1. The phase response shown in Fig. 2 differs according to the polarization of the incident wave. The asymmetric R-AMC shows AMC properties for Y-polarized signal from 56 GHz to 64 GHz. AMC properties are used to ensure high efficiency of AoC. For the X-polarized signal, it shows PEC reflection properties.
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Thailand - Japan Micro Wave 2013
with other components such as power amplifier. Both AoCs are matched for 60GHz band as shown in Fig. 6.
Unit cell Asymmetric
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Fig. 7. Simulated Gain of triangular AoC s
Radiation performance comparison of both AoCs is shown in Fig. 7 and Fig. 8 . The AoC with asymmetric AMC has better gain and efficiency than AoC with symmetric AMC at the bandwidth of interest. The reduced insertion loss appears as an increase of efficiency as HFSS® computes efficiency as the ratio between the power radiated from and the power at the input of its feeding circuit. 60
(a) Symmetric AMC (b) Asymmetric AMC Fig. 5. Top view of Triangular AoCs 4. A O C DESIGN WITH ASYMMETRIC AMC 0
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Fig. 6. Simulated S11 of triangular AoCs
Triangular AoC presented in [1] is re-simulated using a feeding circuit output as shown in Fig. 5 for both symmetric and asymmetric AMCs. This output position is selected in order to allow for integratio n
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Fig. 4. S21 of ML with AMC ground plans A 50Ω-microstrip line (ML) with symmetric and asymmetric AMCs as ground plane is shown in Fig. 4. The ML has length and width of 860μm and 12μm, respectively for both cases. Asymmetric AMC shows approximately 2dB/mm lower insertion loss at 60GHz than the symmetric one as shown in Fig. 4. This guarantees AoC of better loss performance in case of using asymmetric AMC. The reason for increased loss in case of symmetric AMC is that it is not optimized for ML.
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Fig. 8. Simulated Efficiency of triangular AoC s
References [1]A. Barakat, A. Allam, R. K. Pokharel, H. Elsadek, M. El-Sayed, and K. Yoshida, “Compact Size High gain AoC Using Rectangular AMC in CMOS for 60 GHz Millimeter Wave Applications,” IEEE IMS2013 Digest, Seattle, USA, June, 2013. [2]J. G. Kim, H. S. Lee, H. Lee, J. B. Yoon, and S. Hong, “60-GHz CPW-FED post-supported patch antenna using micromachining technology,” IEEE Microwave Wireless Component Letters, vol. 15, no. 10, pp. 635 – 637, October, 2005. [3]K. T. Chan, A. Chin, Y. P. Chen, Y. D. Lin, T. S. Duh, and W. J. Lin, “Integrated antennas on Si, proton-implanted Si and Si-on-quartz,” in IEDM Tech. Dig., Washington, DC, USA, pp. 40.6.1 – 40.6.4, December, 2001. [4]A. Barakat, A. Allam, R. K. Pokharel, H. Elsadek, M. El-Sayed, and K. Yoshida, “Performance Optimization of a 60 GHz Antenna-on-Chip over an Artificial Magnetic Conductor,” IEEE Proceedings of JEC-ECC, Alexandria, Egypt, pp. 118 – 121, March, 2012.
