Various investigations have been reported on metamaterials with near-zero permittivity and/or index of refraction (n) because of their useful applications such as: highly directive beams, compact resonators, zero phase delay lines, wave front transformers, transparent coating, and subwavelength tunneling.
The 2-D Metallic wire arrays are probably the simplest structures to realize an neff< 1 effective medium and can be analyzed using a simple plasma theory with reduced electron density. A simple design methodology for directive monopole antennas, which can be applied at any microwave frequencies, is introduced by embedding a monopole within a metallic wire array with neff < 1. Due to the symmetry in the wire-array / monopole system, there are four identical main beams. If a single main beam is desired, metal reflectors can be applied at the three boundaries of the wire arrays.
Directive monopole antenna model
n1 sin(θ1) = n2 sin(θ2)
n2 <1 = n1 -> θ1 < θ2
Fabricated Antenna Prototype
Measured Radiation Patterns With
· R. Zhou, H. Zhang, and H. Xin, "Metallic Wire Array as Low-effective Index of Refraction Medium for Directive Antenna Application," accepted, IEEE Trans. Antenn. Propag., vol.58, no.1, pp.79,87, Jan. 2010
· R. Zhou, H. Zhang, and H. Xin, "Experimental Demonstration of Narrow Beam Monopole Antenna Embedded in Low Effective Index of Refraction (n < 1) Metallic Wire Media," accepted, Microwave and Optical Technology Letter, 103 (9), 094324, April 2008
· R. Zhou, H. Zhang, and H. Xin, "Radiation Characteristics of Monopole Antenna Embedded in Low Effective Index of Refraction (n < 1) Wire Media,", URSI Symp., Jan. 2008
· H. Xin, and R. Zhou, "Low-Effective Index of Refraction Medium Using Metallic Wire Array", in IEEE AP-S Intl Symp. Dig., pp. 2530-2533, June 2007
Millimeter-Wave On-Chip Antenna
There is much interest in developing systems at high operating frequencies. For example, the wireless personal area network is moving to the 60 GHz ISM band for wide proportional bandwidth and free spectrum cost. Other applications include the 77-GHz vehicular radar and the military satellite communication system (MILSTAR) at 20 / 44 GHz. To meet the different requirements of these systems, various types of antennas have to be designed. Among them, the on-chip antennas become attractive due to its ease for integration and low-cost. To further improve the performance of the on-chip antenna, it is desired to shrink the size of the antenna. In this way, both the loss introduced by the antenna and the cost of the whole system can be reduced.
Inspired by the concept of metamaterials, we design a uni-planar, easy for integration and compact antenna for high-frequency applications (higher than 40 GHz). The measurement results are consistent with the simulations, showing good performance of the antenna.
Photo of the fabricated meta-material inspired CPW antenna
Incorporating active constituents with gain into metamaterials has been recognized as a promising technique for compensating losses. We have experimentally verified the feasibility of obtaining left-hand transmission line with gain at microwave frequency utilizing effective negative resistance. It is also observed that the measured phase constant is negative from 1.75 GHz to 2.75 GHz while the measured attenuation constant is also negative, indicating left-handedness with gain in that frequency range.
A balanced-type composite left/right-handed transmission line designs:
•L.-M. Si, T. Jiang, K. Chang, T.-C. Chen, X. Lv, L. Ran, and H. Xin, “Active microwave metamaterials incorporating ideal gain devices,” Materials, vol. 4, no. 1, pp. 73–83, Dec. 2010.
•T. Jiang, K. Chang, L.-M. Si, L. Ran, and H. Xin, “Active microwave negative-index metamaterial transmission line with gain,” Phys. Rev. Lett., vol. 107, no. 20, p. 205503, Nov. 2011.
•Kihun Chang, Tao Jiang, L. Ran, and Hao Xin, “Investigation of microwave negative refractive index (NRI) transmission lines incorporating tunnel diodes,” IEEE Antennas Wirel. Propag. Lett., vol. 11, pp. 671–674, 2012.
•D. Ye, K. Chang, L. Ran, and H. Xin “Volumetric microwave gain medium with negative refractive index,” under review.