**7. References**

248 Trends in Electromagnetism – From Fundamentals to Applications

Fig. 24 (b) shows the induction at the center of a block of material b1. Fig. 24 (c) and Fig. 24 (d) represent the torque exerted on the blocks and the force exerted on the block b1, respectively. Fig. 24 (e) represents the distribution of the magnetic induction for two

(°) (a) Geometry.

θ=0°

θ=45° (e) The distribution of the magnetic induction.

θ

θ(°)

θ(°)

Fig. 24. Magnetic characteristics of the rotating multiblock system.

The conventional gas compression refrigerators have been mainly used for refrigeration applications. Generally, such refrigerators are not power-efficient. In addition, gases used in these refrigerators causes harmful effects on the environments. This has led to the development of magnetic refrigeration technology. Over the last decade or so, magnetic refrigeration at room temperature has become the subject of considerable attention. This technology is based on the use of magnetocaloric effect: that is the response of a solid to an applied magnetic field which emerges as a change in its temperature. This technology is

positions 0 θ

(b) Induction (T)

(c) Torque (N.m)

(d) Forces (N)

**6. Conclusion** 

 = ° and 45 θ= ° .


**11** 

*Iran* 

**Coupled-Line Couplers Based** 

**(CRLH) Transmission Lines** 

Masoud Movahhedi and Rasool Keshavarz

**on the Composite Right/Left-Handed** 

*Electrical Engineering Department, Shahid Bahonar University of Kerman, Kerman,* 

Recently, the idea of complex materials in which both the permittivity and the permeability possess negative real values at certain frequencies has received considerable attention. In 1967, Veselago theoretically investigated plane-wave propagation in a material whose permittivity and permeability were assumed to be simultaneously negative (Veselago, 1968). For materials with negative permittivity and permeability, several names and terminologies have been suggested, such as "left-handed" media, media with "negative refractive index" (NIR), "backward-wave" (BW) media and "double-negative"(DNG) material (Caloz & Itoh, 2005). In this book chapter, materials with negative permittivity and permeability, and hence negative index of refraction, will be referred indistinctly as left-handed metamaterials

Metamaterials have found many applications in electromagnetic problems. For instance, numerous novel MTM-based microwave components have been proposed to control amplitudes, frequencies, and wave numbers of propagating and non-propagating electromagnetic modes (Caloz & Itoh, 2005). Advances in MTMs have also stimulated the development of new couplers with unique coupling mechanisms. Recently, coupled-line couplers (CLCs) using composite right/left-handed transmission lines (CRLH TLs), which are the special realization of transmission lines based on the metamaterial concept, with broad bandwidth and arbitrary loose/tight coupling levels have been developed. But usually these couplers occupy large length and also, because of using stubs in their structures, width of them would be large. For eliminating this drawback, we have proposed some new backward and forward coupled line couplers with high coupling levels, broad

Organization of this chapter is as follows. In Section 2 theory of CRLH TLs, interdigital capacitor and their equivalent circuit models and parameters, have been explained. Section 3, at first, reviews some conventional CRLH- based CLCs and in continues presents our proposed couplers. In this section, three CLCs based on the concepts of CRLH CLCs are presented; a symmetrical backward CLC (Section 3.3.1), an asymmetrical backward CLC

(LHMs) or metamaterials (MTMs) (Caloz & Itoh, 2005).

bandwidths and compact sizes, base on the CRLH TLs.

(Section 3.3.2) and a symmetrical forward CLC (Section 3.3.3).

**1. Introduction** 

