1. Research Institute of Electrical Communication Tohoku University Sendai 980-8577 Japan
2. Institute of Ultra High Frequency Semiconductor Electronics of RAS Moscow 117105 Russia
3. Department of Computer Science and Engineering University of Aizu Aizu-Wakamatsu 965-8580 Japan
4. Department of Electrical Engineering University at Buffalo SUNY Buffalo NY 14260 USA
5. Department of Electrical, Computer, and Systems Engineering Rensselaer Polytechnic Institute Troy NY 12180 USA