Phase-nonreciprocal ε-negative and CRLH metamaterials are analyzed using a new approach in which field analysis and transmission line model are combined. The examined one-dimensional nonreciprocal metamaterials are composed of a ferrite-embedded microstrip line periodically loaded with shunt stubs. In the present approach, the phase constant nonreciprocity is analytically estimated and formulated under the assumption of operating frequency far above the ferromagnetic resonant frequency. The present approach gives a good explanation to the phenomenon in terms of ferromagnetic properties of the ferrite and asymmetric geometry of the metamaterial structure, showing a good agreement with numerical simulations and experiment.

A new structure of a waveguide-type left-handed transmission line is proposed. It is composed of two rectangular waveguides with many stubs. One waveguide is put on another waveguide symmetrically. When one mode with odd electric field distribution is excited, the stubs work as open stubs and the mode propagates with very small loss. Guided regions of the left-handed mode and a right-handed mode are discussed using an approximate equivalent circuit. Tuning the structure parameters, the band gap between the two regions can be removed, and the wave propagates continuously from the left-handed frequency regions to the right-handed frequency region. The transmission line is applied to a leaky waveguide. It is confirmed experimentally that the beam angle of the radiation wave changes from the backward to the forward directions.

A dispersion diagram is useful in interpreting the characteristics of a periodic structure. In particular, the fast-wave region, where the wave is radiating, and the slow-wave region, where the wave is guided, can be determined from the dispersion diagram. An electronically-controlled composite right/left-handed (CRLH) transmission line (TL) was previously proposed and utilized as a leaky-wave (LW) antenna operating in the fast-wave region. However, since a guided-wave application operates in the slow-wave region, it is meaningful to study slow-wave effects of the proposed TL. In this paper, the dispersion diagram is used to investigate the slow-wave factor (SWF), which is necessary to understand the fast/slow-wave operations. Furthermore, the frequency characteristics are measured to find the cut-off frequencies in the LH and RH regions. Based on experimental results, it is observed at a fixed frequency, 2.6-GHz, that the phase of a proposed 6-cell structure can be changed by up to 280 in the LH slow-wave region.

A novel two-dimensional (2D) beam scanning antenna array using composite right/left-handed (CRLH) leaky-wave antennas (LWAs) is proposed. The antenna array consists of a set of CRLH LWAs and a Butler matrix (BM) feeding network. The direction of the beam can be scanned two-dimensionally in one plane by changing frequency and in the other plane by switching the input ports of the BM. A four-element antenna array in the microstrip line configuration operating at 10.5 GHz is designed with the assistance of full-wave simulations based on the method of moment (MoM) and the finite-element method (FEM). The antenna array is fabricated and radiation characteristics are measured. The wide range 2D beam scanning operation with the angle from -30 deg to +25 deg in one plane by sweeping frequency from 10.25 GHz to 10.7 GHz and with four discrete angles of -46 deg, -15 deg, +10 deg, and +35 deg in the other plane by switching the input port is achieved.

We propose here a composite right/left handed transmission line constructed by using conductor-backed coplanar strips. In this line, we can easily realize a shunt inductor without via because it has the electric-wall symmetry at the guide center. The left-handed nature is verified by both the finite difference time-domain (FDTD) and the equivalent-circuit calculations. Furthermore, we demonstrate the proposed line can easily satisfy the balanced condition for no band gap between the right-handed and the left-handed modes, and can be applied to a leaky-wave antenna, numerically and experimentally.

We present a design procedure of a leaky-wave antenna with low sidelobes based on the stub-loaded ridge-rectangular waveguide. As a typical example, we desig the antenna with the Taylor distribution of -30 dB sidelobes and fabricated it. The agreement between the measured and the numerical results validate the proposed antenna.

In this paper, we presented a beam adjustable antenna made up of a slit waveguide and a dielectric slab. In order to change the radiation main-beam angle, we changed the phase constant of the waveguide mode by inserting a dielectric slab for perturbing its field distribution. The direction of radiation main-beam can be steered by dynamically changing the position of the dielectric slab. For the theoretical analysis, the dispersion relation, including the phase and attenuation constants, was determined by solving the transverse resonance equation. An agreement between the theoretical and experimental radiation pattern verifies the beam-steering mechanism. Up to 23beam-steering angle can be achieved using this approach.

We have presented a new analytical method for the stub-loaded ridge waveguide that is a candidate of leaky-wave antennas in the millimeter-wave region. This guide has many singular conductor edges, so that its accurate analysis is very difficult. The present method overcomes such difficulty by introducing the singular fields at the edges into the field expressions beforehand. Then we have investigated the dispersion characteristics for various structural parameters, to find a structure suitable to antenna applications. Finally, we have verified their behavioral feature experimentally.

A novel millimeter-wave planar leaky-wave antenna is described which consists of a dielectric slab loaded by metallic periodic strips. Several new techniques are discussed, such as an air-gapped dielectric waveguide to reduce conductor loss of the ground plane, a canceling array to suppress the reflections in the waveguide due to the metallic strips, a compact feed, and a simple polarizer. By applying these new techniques, we achieved an excellent antenna efficiency, exceeding 70% at 76 GHz band for both vertical and 45-degree inclined linear polarizations.