Summary

International Symposium on Antennas and Propagation

2010

Session Number:3TC4

Session:

Number:3TC4-5

A Leaky-Wave Antenna Using a Composite Right/Left Handed Transmission Line

Tommy Wong,  Chi Hou Chan,  Quan Xue,  

pp.-

Publication Date:2010/11/23

Online ISSN:2188-5079

DOI:10.34385/proc.52.3TC4-5

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Summary:
A leaky-wave (LW) antenna is basically a wave-guiding structure which possesses a mechanism that permits it to leak power along its length. There are two different basic types of LW antennas, depending on whether the geometry of the guiding structures is uniform or is periodically modulated along its length [1]-[3]. The uniform LW antenna is uniform or has a small, smooth and continuous taper along the length of the guiding structure. It radiates into the forward quadrant and can scan, in principle, from broadside to end-fire, with the beam nearer to end-fire at higher frequencies. In practice, broadside radiation is not possible as the propagation constant, β, is always greater than zero. Periodic modulation of the guiding structure is introduced in the periodic LW antenna in which the propagation constant can be represented in the form of a Floquet expansion and thus it is constituted by the superposition of an infinite number of space harmonics [1]. Both forward and backward radiations can be achieved while broadside radiation is also not possible. Basically, any open composite right/left handed (CRLH) transmission line (TL) can operate as LW antenna since its dispersion curve always penetrates into the radiation region [1], [4]-[5]. When it is under the balanced condition, the transition from the left-handed to right-handed bands is seamless. This transition is characterized by the frequency ωo where β is equal to zero at which broadside radiation is made possible [1], [6]-[7]. Another distinctive advantage of the CRLH LW antenna over conventional LW antenna is that it can operate at fundamental mode. In this paper, we propose a new CRLH TL. The unit cell is constituted of a short-circuit stub shunt inductor and a pair of metallic walls serving as a series capacitor. The metallic wall is conveniently fabricated using the plated through hole technology [8]-[9]. Based on this unit-cell design, a 30-element CRLH LW antenna is fabricated and tested. The measured radiation patterns illustrated that the main beam of the antenna is effectively scanned by varying the operating frequency. The scanning range is from -80o at 4.7 GHz to +75o at 7.3 GHz and the peak gain is about 11.5 dBi at 6.5 GHz.