**6. Acknowledgment**

The author would like to thank his family for the support and understanding during the preparation of the manuscript. Also, the author would like to express his appreciation to the research assistants, staffs and students of the RF and Microwave Laboratory, the Sirindhorn International Thai-German Graduate School of Engineering, King Mongkut's University of Technology North Bangkok for their interest in RF and microwave topics as well as for their support.
