الفهرس 
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Abstract
This thesis is concerned with the superconductors and their uses in the fields of communications. Materials are classified into four main categories insulators such as wood, semiconductors such as silicon, conductors such as copper and superconductors such as yttrium marium copper oxide YBCO.
A superconductor can conduct electricity without electrical resistance at temperatureees above absolute zero. the change from normal electrical conductivity to superconductivity occurs abruptly at a critical temperature.
A superconductor is also able to rxclude the surrounding magentic field, this known as meissner effect.
In this thesis the characteristics of th superconducting materials and its applications on mobile communication sysytems are described. The filters used in base stations in the mobile communication systems that will be fabricated using microstrip technology are also described. The microstrip technology ad the substrates used in the high temperature superconductors are discussed. A t the end of this thesis a design and implementation of bandpass filters used in certain frequencies for the mobile communication fabricated from superconducting materials has been discussed.
Filtering is an essential feature in wireless communications system. it allows the system to consider only the frequency bands which contains the desires singles, neglecting all others. While filters are present in both base stations and handsets, high tempertaure superconductors HTS filter system can currently be deployed within base stations. this limitation arises from the physical size and power requirements of the refrigeration system.
The use of mobile telecommnuications has been increased rapidly all over the world. To provide gigh quality communication services under heavy traffic conditions, mobile base stations require having highly selective filters in their receivers and transmitters. Applications for highly selective filters allows decrease in adjacent channel interface, reduction in power requirements of handsets and an increase of the coverage of a cell without increasing the antenna height. When base station receivers are of small size they can be mounted on the top of the towers minimizing cable losses.
HTS filters have several advantages; they have very low insertion loss, very high selectiveity and very small size small. The limitations for HTS filters that they have low power handling, high cost and work environment requiring cryostat to cool the device below the critical.
The general properties of superconducting filters are summarized as follows: The HTS filter differs from the conventional metallic planar filters in many respects the insertion loss can be 1.7 db smaller, nose figure 1.4 db lowerattenuation of out of band OBR 45 db HIGHER. The HTS filters are the result of high temperature superconducting thin films exhibiting a very low surface resistance. The surface of YBa, CU3O7-8 is approximately 400 at a frequency of 10GHZ and a temperature of 77k.