MSc Yuan Yao

1. A charge transfer model for CMOS image sensors
   H. Liqiang; S. Yao; A.J.P. Theuwissen;
   IEEE Transactions on Electron Devices,
   Volume 63, Issue 1, pp. 32-41, 2016.

2. Front-end receiver electronics for a matrix transducer for 3-D transesophageal echocardiography
   Z. Yu; S. Blaak; Z. Y. Chang; J. Yao; J. G. Bosch; C. Prins; C. T. Lancee; N. de Jong; M. A. P. Pertijs; G. C. M. Meijer;
   IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control,
   Volume 59, Issue 7, pp. 1500‒1512, July 2012. DOI: 10.1109/tuffc.2012.2350
   
   Abstract: ...

   There is a clear clinical need for creating 3-D images of the heart. One promising technique is the use of transesophageal echocardiography (TEE). To enable 3-D TEE, we are developing a miniature ultrasound probe containing a matrix piezoelectric transducer with more than 2000 elements. Because a gastroscopic tube cannot accommodate the cables needed to connect all transducer elements directly to an imaging system, a major challenge is to locally reduce the number of channels, while maintaining a sufficient signal-to-noise ratio. This can be achieved by using front-end receiver electronics bonded to the transducers to provide appropriate signal conditioning in the tip of the probe. This paper presents the design of such electronics, realizing time-gain compensation (TGC) and micro-beamforming using simple, low-power circuits. Prototypes of TGC amplifiers and micro-beamforming cells have been fabricated in 0.35-μm CMOS technology. These prototype chips have been combined on a printed circuit board (PCB) to form an ultrasound-receiver system capable of reading and combining the signals of three transducer elements. Experimental results show that this design is a suitable candidate for 3-D TEE.

3. Design of a low power time-gain-compensation amplifier for a 2D piezoelectric ultrasound transducer
   J. Yao; Z. Yu; M. A. P. Pertijs; G. C. M. Meijer; C. T. Lancee; J. G. Bosch; N. de Jong;
   In Proc. IEEE International Ultrasonics Symposium (IUS),
   IEEE, pp. 841‒844, October 2010. DOI: 10.1109/ultsym.2010.5935775
   
   Abstract: ...

   In this paper, a programmable time-gain compensation amplifier dedicated to a 2D piezoelectric ultrasound transducer is presented. It uses an open-loop amplifier structure consisting of a voltage-to-current converter and a current-to-voltage converter. The circuit has been designed in a standard 0.35-μm CMOS process. Simulation and measurement results show that gains of 0dB, 12dB, 26dB and 40dB can be achieved for input signals centered at 6MHz with 80dB dynamic range (100μV to 1V). The measured gain errors at 6MHz are below 1dB for all gain settings. The amplifier consumes only 130μW when driving a 250fF load.

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