Microwave diode circuits are classical ones that originate from receiver coherers and are mainly used in mixers and other devices. They still remain widely used today in communication technologies extending into the sub-millimeter wave range, as well as in practical wireless power transmission systems. Their value has been kept in this technical region.

Since joining Mitsubishi Electric in 1983, the awardee has conducted research and development on microwave circuits and equipment for radio systems. Furthermore, since joining the Kanazawa Institute of Technology in 2009, he has engaged in the research and development of rectennas for wireless power transfer systems.

While conducting this research in the late 1980s, he found that IC-integrated diode pairs exhibited excellent characteristic matching and could drastically suppress even-order mixing products. He demonstrated that this could benefit transceivers performing direct frequency conversion (DC) between radio frequencies and baseband. He developed an MMIC for a 40 GHz band DC transmitter used in terrestrial communications, and this remains one of the significant topologies for millimeter-wave mixers. He then applied this technology to an X-band mobile satellite communication DC transceiver. Furthermore, it was applied to the world's first DC receiver for third-generation mobile phones, which was field-tested and proven to work as a mobile phone. This work earned the 2002 The Promotion Award for Electrical Science and Technology (Ohm Technology Award). His group was the first in the world to formulate output power and third-order distortion for this even-harmonic mixer and conventional fundamental diode mixers, demonstrating the ultimate performance achievable as a transmit mixer [5].

For wireless power transfer systems, his group proposed a rectenna with a Diode on Antenna (DoA) topology, which connects the antenna directly to the rectifying diode in order to suppress circuit losses. This realizes the circuit function within the antenna, thereby reducing circuit losses. This achieved rectification efficiencies of 92.7% and 83.7% at 1 W and 10 W input power, respectively, in the 5.7 GHz band [7, 8], earning the 2022 Electronics Society Award from the IEICE. Furthermore, a rectenna IC operating in the 24 GHz band, integrating both the antenna and the rectifier on a ~1 mm² GaAs chip, achieved the world's highest rectification efficiency of 72.7% at an input power of 1 W [9]. This work won the Best Paper Award at the IEEE WPTCE conference in 2025. Additionally, he has theoretically clarified the limiting performance of these diode rectifiers [10, 11].

As described above, his contributions extend beyond IC integration of microwave/millimeter-wave diode circuits and their application in wireless systems, encompassing significant academic contributions.

He also served as General Chair for TJMW2014 and VJMW2015, as well as Chair of the Wireless Power Transfer Research Committee and the URSI-C National Committee. Within IEEE MTT-S, he was an elected ADCOM member from 2006–08, 2010 and 2012–14, promoting collaboration with the microwave research committees in the Asia-Pacific region. In recognition of these contributions, he received the N. Walter Cox Award in 2014, was elected an IEEE Fellow in 2017 and became an IEEE Life Fellow in 2026.

As outlined above, the awardee has achieved globally significant results in the IC integration and application of microwave and millimeter-wave diode circuits. His accomplishments are substantial, and his contributions to the academic community make him a highly deserving recipient of this Society's Achievement Award.

References

1. K. Itoh, A. Iida, Y. Sasaki and S. Urasaki, "A 40 GHz band monolithic even harmonic mixer with an antiparallel diode pair," 1991 IEEE MTT-S Int. Microw. Symp. Digest, pp. 879-882, 1991.
2. H. Ikematsu, K. Tajima, K. Kawakami, K. Itoh, Y. Isota and O. Ishisa,” Distortion characteristics of an even harmonic type direct conversion receiver for CDMA satellite communications,” IEICE Trans. Electron, vol. E82-C, no.5, pp.699-707, 1999.
3. K. Itoh, T. Yamaguchi, T. Katsura, K. Sadahiro, T. Ikushima, R. Hayashi, F. Ishizu, E. Taniguchi, T. Nishino, M. Shimozawa, N. Suematsu, T. Takagi and O. Ishida, "Integrated even harmonic type direct conversion receiver for W-CDMA mobile terminals," 2002 IEEE MTT-S Int. Microw. Symp. Digest, pp. 9-12, 2002.
4. T. Nojima, Y. Yamao, T. Takano, K. Ito, S. Narahashi, ”RF circuits for mobile communication systems,” pp.191-241, The Institute of Electronics, Information and Communication Engineers, 2007.
5. J. Hashimoto, K. Itoh, M. Shimozawa and K. Mizuno, "Fundamental limitations on the output power and the third-order distortion of balanced mixers and even harmonic mixers," IEEE Trans. Microw. Theory Techn., vol. 64, no. 9, pp. 2853-2862, 2016.
6. K. Itoh, N. Sakai, K. Noguchi, “Highly efficient high-power rectenna with the diode on antenna (DoA) topology,” IEICE Trans. Electron, vol. E105-C, no. 10, pp. 483 - 491, Oct. 2022.
7. N. Sakai, K. Noguchi and K. Itoh, "A 5.8-GHz band highly efficient 1-W rectenna with short-stub-connected high-impedance dipole antenna," IEEE Trans. Microw. Theory Techn., vol. 69, no. 7, pp. 3558-3566, 2021.
8. N. Sakai, N. Furutani, K. Uchiyama, Y. Hirose, F. Komatsu and K. Itoh, "5.8 GHz band 10 W rectenna with GaAs E-pHEMT gated anode diode on the aluminum nitride antenna for thermal dispersion," 2023 IEEE/MTT-S Int. Microw. Symp. Digest, pp. 1003-1005, 2023.
9. K. Itoh, R. Sato, Y. Hirose, N. Sakai, M. Tsuru and K. Noguchi, "A 24 GHz band highly efficient GaAs 1 W rectenna MMIC electromagnetically coupled with an external AlN antenna for thermal dispersion," Proc. 2025 IEEE Wireless Power Techn. Conf. and Expo (WPTCE), pp. 1-4, 2025.
10. K. Kikkawa, T. Saen, N. Sakai and K. Itoh, A 2.4-GHz 10-W class bridge rectifier and its efficiency analysis with the behavioral model,” IEEE Trans. Microw. Theory Techn., vol. 70, no. 3, pp. 1994-2001, 2022.
11. Y. Hirose, N. Kakutani, F. Komatsu, N. Sakai, M. Tsuru and K. Itoh, "K-Band high-power rectification with GaAs E-pHEMT gated anode diodes," IEEE J. Microw., vol. 6, no. 1, pp. 204-214, 2026.