I am Keisuke Kawahara, a Ph.D. student at Yokohama National University, Japan. My interests include integrated circuit design, silicon photonics, optical communication, microwave theory, and signal processing.
![Si Photonic Crystal Modulator](https://private-user-images.githubusercontent.com/37934321/363422008-197a75e0-2dc5-4175-83d3-11f1a744abf7.png?jwt=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.UO3XW0hIcQDxcfRJWTF05CNN6bhHwusZd2Pgx4YrPYE)
Achieving record low power consumption by optimizing the electrode impedance of a photonic crystal slow-light optical modulator. 📄Optica (Open Access) 📄OFC
![Analog Multiplexer (AMUX)](https://private-user-images.githubusercontent.com/37934321/261212844-0a788fc4-a56a-4eec-8b89-ca3c76d87f3c.jpg?jwt=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.Yj2LnmOLsoVUcw3zlh0-EXiP5wJphz-73LmTLsp60IU)
World's first demonstration of bandwidth tripling of digital-to-analog converters using an analog multiplexer. 📄IEEE T-MTT 📄IEEE RWS
![Active Balun](https://private-user-images.githubusercontent.com/37934321/261214116-9ee94376-df53-490d-bfb3-57a3276ce3f3.jpg?jwt=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJnaXRodWIuY29tIiwiYXVkIjoicmF3LmdpdGh1YnVzZXJjb250ZW50LmNvbSIsImtleSI6ImtleTUiLCJleHAiOjE3MzkzMDMyMzUsIm5iZiI6MTczOTMwMjkzNSwicGF0aCI6Ii8zNzkzNDMyMS8yNjEyMTQxMTYtOWVlOTQzNzYtZGY1My00OTBkLWJmYjMtNTdhMzI3NmNlM2YzLmpwZz9YLUFtei1BbGdvcml0aG09QVdTNC1ITUFDLVNIQTI1NiZYLUFtei1DcmVkZW50aWFsPUFLSUFWQ09EWUxTQTUzUFFLNFpBJTJGMjAyNTAyMTElMkZ1cy1lYXN0LTElMkZzMyUyRmF3czRfcmVxdWVzdCZYLUFtei1EYXRlPTIwMjUwMjExVDE5NDIxNVomWC1BbXotRXhwaXJlcz0zMDAmWC1BbXotU2lnbmF0dXJlPTc3M2MxNDQ0ZDkyMmQwZmViYzU4ZWE0YjJiNjY2ZDE2ZWE4ZTAzZWZhZjJiMGVkYWZhM2VmNWM2N2YzY2E5YTImWC1BbXotU2lnbmVkSGVhZGVycz1ob3N0In0.VU57ve7uIRMr2LSr-vSQBe9xVtHOqdQDuexLM8L44xc)
Active feedback technique simultaneously enables imbalance correction and bandwidth extension. 📄IEEE TCAS-I 📄IEEE MWSCAS
![Differential Distributed Amplifier](https://private-user-images.githubusercontent.com/37934321/261214517-aa5208c0-3d57-4b71-93ee-fc7e6e1efe1f.jpg?jwt=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.3wS48nJYZKp8-N1vFbjRFOJ6-YEM6U_98htE-YW2VpY)
Coupled inductors halve the chip footprint of a differential distributed amplifier. 📄IEICE TREL (Open Access) 📄IEEE ISCAS
![CMOS Temperature Sensor](https://private-user-images.githubusercontent.com/37934321/261533123-48220bc9-70ce-4559-a445-4366c4f87275.png?jwt=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.Jb48D9NuAOr7shOhaRvXuknL_SxRSsDYI2q9uo66dG8)
The trimless temperature sensor is based on an open-source design rule and is freely reusable. GitHub Repository
![CMOS Operational Amplifier](https://private-user-images.githubusercontent.com/37934321/261536324-bac48c37-9dc6-4ac8-a65d-e2768d07fd89.png?jwt=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.L0zHfk5NKlQEjsHxf2IgNz5fXjiOzvRXsVO8PaOzzqk)
The class-AB CMOS operational amplifier consumes only 7.7 µA and provides a slew rate of 1 V/µs with a 1-nF load. Slides for 2021 and 2020