Catherine A. Allen

Leaky-waves in a metamaterial-based two-dimensional structure for a conical beam antenna application

A two-dimensional periodic mushroom structure is proposed as a leaky-wave antenna with a conical beam. To the authors knowledge, this is the first 2D leaky wave antenna demonstrated experimentally. The structure can be modelled as a composite right/left-handed (CRLH) transmission line and exhibits both backward and forward leakage. The radiation patterns for the antenna are shown and demonstrated a scanning range of 15/spl deg/-33/spl deg/ in the backward region and 27/spl deg/-63/spl deg/ in the forward region.

Design of microstrip resonators using balanced and unbalanced composite right/left-handed transmission lines

Balanced and unbalanced composite right/left-handed transmission lines are used in the design of resonators. The balanced resonator is designed by changing the nonlinear phase response in order to control the spacing between modes and the Q factor. Two balanced ring resonators are measured and one demonstrates increased mode spacing/decreased Q factor and the other demonstrates decreased mode spacing/increased loaded Q factor. The unbalanced resonator is designed by changing the nonlinear phase response and magnitude response. A measured unbalanced ring resonator shows increased mode spacing with a reasonable Q factor. A microstrip line resonator is measured to demonstrate higher frequency capabilities.

Design of ring resonator mode spacing and bandwidth using the phase response of composite right/left handed transmission lines

The adjustable phase response of composite right/left-handed transmission lines is used in the design of two ring resonators. The first design demonstrates the increase of higher order modes beyond the third harmonic of the fundamental frequency. The second design demonstrates the decrease of the bandwidth to about half that of a conventional microstrip ring resonator.

2-D Frequency-Controlled Beam-Steering by a Leaky/Guided-Wave Transmission Line Array

A composite right/left-handed transmission line is used in an array for two-dimensional beam scanning. This type of transmission line, acts as a guided-wave or leaky-wave structure depending on frequency. This dual utility allows for a simple and inexpensive array that can be scanned independently in two planes. The fabricated array demonstrates a scanning range that is as great as -42deg to 21deg in one plane and -21deg to 15deg in the orthogonal plane

A two-dimensional edge excited metamaterial-based leaky wave antenna

A two-dimensional structure is proposed as an edge-excited leaky-wave antenna. The structure can be modeled as a composite right/left-handed (CRLH) transmission line consisting of lumped elements and RH transmission lines. The radiation patterns for the antenna are shown and demonstrate a scanning range of -24/spl deg/ to 0/spl deg/ in the backward region and 0/spl deg/ to 47/spl deg/ in the forward region.

Fixed Frequency and Tunable Metamaterial-Based Ring Resonators with Narrowly Spaced Resonances

Metamaterial-based composite right/left-handed transmission lines are used in the design of fixed frequency and tunable ring resonators. Under specific design conditions, the first two resonant modes can be narrowly spaced. A simple passive band-pass filter is demonstrated at 2.92 GHz with a bandwidth of about 9% using this concept. This type of design is also used as a tunable resonator and a tuning range of 30% is demonstrated.

Unusual propagation characteristics in CRLH structures

A purely LH material (V.G. Veselago, Soviet Physics Uspekhi. vol. 10, no. 4, pp. 509-514. 1968) cannot exist physically because it would violate Einsteins relativity: in such a hypothetical material, the group velocity would be unbounded and would become larger than the speed of light at high frequencies. In fact, natural right-handed (RH) series-L/shunt-C parasitics are always present and become dominant at high frequencies, limiting group velocity to that associated with the RH contributions only. Therefore a practical LH material is in effect a composite right/left-handed material (CRLH), already described in previous publications (C. Caloz and I. Itoh, IEEE Trans. Antennas Propagat.; A. Sanada et al, IEEE Microwave Wireless Comp. Lett.), and applied to several novel components and antennas. However, unique CRLH effects never occurring in conventional periodic structures, such as non-zero group velocity associated with infinite wavelength and guided wavelength increasing with frequency in the LH frequency range have never been analyzed in detail thus far. This is the object of the present contribution, where these effects are demonstrated for the different cases of homogeneous, ideal-lumped and real physical CRLH TLs. For simplicity, the discussion is restricted to lossless TLs without loss of generality.

Practical applications of metamaterial-based structures in microwave systems

In this paper, metamaterial-based transmission lines will be discussed, with a focus placed on how these structures can be utilized in microwave systems. The different devices necessary for a basic dual-band receiver will be discussed and it will be shown how these dual-band components can be realized using metamaterial-based structure. Also, two different types of two-dimensional beam scanning systems will be introduced that utilize both one and two dimensional metamaterial-based structures.