Microwave properties

Hong KH (1974) Microwave Properties of Liquids and Solids Using a Resonant Microwave Cavity as a Probe, Ph.D. dissertation, University of North Texas, Texas, USA. 

Solid food materials have dielectric properties dependent upon their composition. In many instances, particularly when developing microwavable food products, it is necessary to know the effective bulk microwave properties of the product, crushed, as is, or when agglomerated together. Typical examples are peas, beans, com, pasta, flour... 

This article give an overview about the microwave properties of insulating and superconducting oxide dielectrics. In addition, microwave measurement techniques for bulk and thin film oxides will be reviewed. 

Basic relations defining microwave properties of dielectrics and normal/superconducting metals... 

For the physical description of the microwave properties of dielectric materials and metals we consider Maxwell s equations in the absence of localized charges ... 

Microwave properties of dielectric single crystals, ceramics and thin films... 

Apart from ybco, thin films with reasonable microwave properties have been prepared from the thallium-based compounds Tl2Ba2CaCu208 (Tc 105 K) and Tl2Ba2Ca2Cu30io (Tc 115 K) [10], hts films with reasonable and qualified microwave properties nowadays can be grown on wafers up to more than 4 in diameter, the most common size are 2 and 3 for microwave applications. A very important step was the preparation of double-sided coating, which have turned out to be essential for planar microwave devices, where the metal ground plane needs to be superconducting in order to achieve high quality factors. 

Table 5.1 Microwave properties of the most important microwave dielectrics (SC= bulk single crystals , bc = bulk ceramics , tf = thin films , r/ = temperature coefficient of resonant frequency . The materials marked with are tuneable dielectrics.

The microwave properties of oxide based dielectric bulk material, thin film nonlinear dielectric materials and oxide high temperature superconducting materials were reviewed in this article. In addition, the most important microwave measurement techniques have been discussed. Important future directions of related material research aiming towards further integration both on chip and subsystem level, increase of performance and cost reduction are ... 

Kirihara, S., Miyamoto, Y, and Kajiyama, K., Pabrication of ceramic-polymer photonic crystals by stereolithography and their microwave properties, J. Am. Ceram. Soc., 85, 1369, 2002. 

C. L. Huang, Y. B. Chen, Microwave properties of B203-doped Nd(Mgi/2Tii/2)03-CaTi03 dielectric resonators at microwave frequency, Mater. Lett. 60 (2) (2006) 198-202. 

The intrinsic conductivity of conjugated polymers leads, in the field of their microwave properties (e.g. 

The following section describes the bibliographic synthesis of work done in the field of microwave properties of conducting polymers more as an aid to understanding rather than from the RAM material applications point of view. 

Some physical effects such as moisture absorption [49], temperature [50], protonation level [50], electron localization (polyorthotoluidine) [5la,b], polyaniline [52], crystallinity [53], elongation [54a,b,55] on microwave properties of polyaniline have been found through characterisation with the perturbation cavity method [56], Other methods have been employed and compared with the former one, such as microwave impedance bridge in the X-band (8.2-12.4 GHz) [57] or APC 7 standard (130 MHz-18 GHz) [47] with good agreement. 

Polypyrrole or polyaniline loaded fabrics have been studied as microwave absorbers either in the form of pure fabric or composites [84,80-92]. The application involves their use either under the form of multilayer absorbers [86], camouflage nets [93], or absorber with continuous variation of conductivity inside the plane [94] (edge cards for use in low observable technologies). An example of microwave properties which can be achieved with this type of material is given in Figure 8.6. 

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