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.
- April 2016 – March 2020: Bachelor of Electrical Engineering, Tokyo University of Science, Noda, Chiba, Japan
- April 2020 – March 2022: Master of Electrical Engineering, Tokyo University of Science, Noda, Chiba, Japan
- April 2022 – present: Ph.D. in Progress, Yokohama National University, Yokohama, Kanagawa, Japan
![Analog Multiplexer (AMUX)](https://private-user-images.githubusercontent.com/37934321/261212844-0a788fc4-a56a-4eec-8b89-ca3c76d87f3c.jpg?jwt=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.mKBQNLW0sjVxuzV7s9og8c9rg3TVoI0faAyzHEbzLqI)
The image-rejection analog multiplexer extends signal bandwidth by three times through a combination of digital signal processing and analog multiplication. (K. Kawahara et al., IEEE Trans. Microw. Theory Tech., vol. 71, no. 1, pp. 22–34, Jan. 2023.)
![Active Balun](https://private-user-images.githubusercontent.com/37934321/261214116-9ee94376-df53-490d-bfb3-57a3276ce3f3.jpg?jwt=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.efDxP0QHoo5ZGQ1WwRPxyl87xaRgc8cHptSpsTGnXlU)
The active balun converts single-ended signals to differential signals. A small chip area and low imbalance characteristics over a wide bandwidth were demonstrated. (K. Kawahara et al., IEEE Trans. Circuits Syst. I: Regul. Pap., vol. 70, no. 6, pp. 2317–2330, Jun. 2023.)
![Differential Distributed Amplifier](https://private-user-images.githubusercontent.com/37934321/261214517-aa5208c0-3d57-4b71-93ee-fc7e6e1efe1f.jpg?jwt=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.gZjOe6xp2Ev39tvjHr9s7EF762O9HaMu_WylfFGjvp8)
The distributed amplifier operates over a wide bandwidth ranging from DC to tens of gigahertz. The use of coupling inductors halves the area of differential distributed amplifiers. (K. Kawahara et al., IEICE Trans. Electron., vol. E106.C, no. 11, pp. 669–676, Nov. 2023.)
![CMOS Temperature Sensor](https://private-user-images.githubusercontent.com/37934321/261533123-48220bc9-70ce-4559-a445-4366c4f87275.png?jwt=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJnaXRodWIuY29tIiwiYXVkIjoicmF3LmdpdGh1YnVzZXJjb250ZW50LmNvbSIsImtleSI6ImtleTUiLCJleHAiOjE3MjE5MTI4NzYsIm5iZiI6MTcyMTkxMjU3NiwicGF0aCI6Ii8zNzkzNDMyMS8yNjE1MzMxMjMtNDgyMjBiYzktNzBjZS00NTU5LWE0NDUtNDM2NmM0Zjg3Mjc1LnBuZz9YLUFtei1BbGdvcml0aG09QVdTNC1ITUFDLVNIQTI1NiZYLUFtei1DcmVkZW50aWFsPUFLSUFWQ09EWUxTQTUzUFFLNFpBJTJGMjAyNDA3MjUlMkZ1cy1lYXN0LTElMkZzMyUyRmF3czRfcmVxdWVzdCZYLUFtei1EYXRlPTIwMjQwNzI1VDEzMDI1NlomWC1BbXotRXhwaXJlcz0zMDAmWC1BbXotU2lnbmF0dXJlPTlkZWI0OGVjNGZkNGJjNzFjNWE4ODY5MzQyNDUwOTg4NDdjNWNkMzU0MDkyZmNkZDRmYjNiOTE0ZmI3MjllYjEmWC1BbXotU2lnbmVkSGVhZGVycz1ob3N0JmFjdG9yX2lkPTAma2V5X2lkPTAmcmVwb19pZD0wIn0.zWb_o9l2uHL3jF9vHcxAFfZUjQ9b0JNVbV90FkzmIgU)
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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.AOp_SWNi0dCLeaM5KQ7zGZFvc6Zhfk4jdGgiTk_op6s)
The class-AB CMOS operational amplifier consumes only 7.7 µA and has a slew rate of 1 V/µs for a 1-nF load. (Slides for 2021 and 2020.)