This dissertation presents the most recent advances in microwave metamaterials (MTMs) based on the C&barbelow;omposite R&barbelow;ight/L&barbelow;eft-H&barbelow;anded (CRLH) transmission line (TL) concept. The CRLH TL based MTMs are non-resonant structures which are constituted of periodic repetition of series capacitors and shunt inductors with a unit cell's size much smaller than the guided wavelength and have favorable broadband and low-loss properties for microwave applications. In addition, planar CRLH TL-based MTMs permit a low-cost fabrication using printed circuit board (PCB) technology and a high level of integration with other microwave components and systems.;Metamaterial-based coupled-line couplers were shown to exhibit an extraordinary coupling level compared with conventional coupled-line couplers. However, the even/odd-mode analysis which was used to analyze MTM couplers provides little insight into the coupling mechanism. To this end, the coupled-mode theory is extended and applied to couplers consisting of the general CRLH TLs to provide a phenomenological explanation of the complex coupling behavior. The theory was simplified for a quasi transverse electromagnetic (quasi-TEM) case to provide further insight into the coupling mechanism. Importantly, the coupling equation indicates a distinct advantage of CRLH TL couplers, which have a maximum coupling depending on its coupling length. Three examples corresponding to three different coupling topologies were demonstrated and the developed theory accurately predicts the coupling level and coupling frequency range.;Impulse regime guided-wave application. The study of coupled-mode theory in the time domain reveals an interesting derivative relation between input and coupled ports of conventional coupled-line couplers operating under an impulse regime. The conventional coupled-line couplers can be considered as a special case of CRLH TL coupled-line couplers where the left-handed elements are infinite. It is shown that a first-order time derivation of an impulse signal of duration DeltaT can be accurately obtained at the coupled port of a coupler operating at a center frequency f 0 and satisfying the condition 4DeltaTf0 1. As a symmetric, four-port device, a coupled-line coupler can simultaneously provide coupling between two pairs of input/coupled ports. Combining with a proper time delay circuit, these properties lead to a first- and second-order time derivative circuit using only a single coupled-line coupler. A broadside coupler is fabricated in a multi-layer PCB technology, which shows the operating principle and the feasibility of this concept for other arbitrary impulse regime signals.;Radiated-wave application. It is well known that open CRLH TL structures support a fast-wave and therefore can operate as a leaky-wave antenna (LWA). Being conveniently printed on planar commercial substrate, CRLH TL LWAs provide a frequency-scanning directive beam in full space but suffer from a low radiation efficiency due to its finite lengths. For this reason, two novel power-recycling concepts were proposed to significantly enhance the radiation efficiency of LWA and its 2D array. The first cross-recycling concept which is suitable for 2D LWA arrays, recycles the non-radiated power between array elements until most of the input power has leaked out. Therefore, it effectively increases the total radiated power for a given input power. In addition, it is shown that an increasing in the number of array elements directly enhances both directivity and radiation efficiency of the cross-recycling 2D LWA array. The measured result of a 2D LWA array of 5 elements indicates an increase of 160% in radiation efficiency. (Abstract shortened by UMI.);This work contributes to the development of novel CRLH TL components, antennas and systems in three specific classes of application: harmonic regime guidedwave, impulse regime guided-wave and radiated-wave. In the first class, a wideband bandpass filter, an infinite wavelength series power divider and enhanced coupled-line coupler are developed and verified experimentally. The second class consists of a time differentiator component and a pulse position modulation transmitter system. In the third class, two novel power-recycling concepts to systematically enhance the radiation efficiency of Leaky-Wave Antennas (LWAs) are presented, verified numerically using electromagnetic simulation and demonstrated experimentally.
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