Tianjia Sun

Tsinghua University, Peping, Beijing, China

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Publications (17)3.78 Total impact

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    ABSTRACT: This letter proposes a new wireless power transfer mechanism named the directly-strong-coupling.It adopts only two resonators and it achieves strong-coupling performances. Asymmetric sizes of antennas are designed to reduce the receiver's size for indoor applications. The mechanism remains a power efficiency of 35.6% over a distance of 1 m. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:250–253, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27315
    Microwave and Optical Technology Letters 02/2013; 55(2). · 0.59 Impact Factor
  • Tianjia Sun, Xiang Xie, Zhihua Wang
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    ABSTRACT: In recent years, significant efforts have been made to develop the implantable applications. The increasing functions, performances, and operating time push up the power requirement of the implantable medical microsystems. This has led to the interest in the wireless power transfer (WPT) as a promise way to provide more energy. However, the WPT suffers from some problems including unsatisfied power efficiency, limited transfer distance, unpredictable reliability, thermal issues and other problems. Therefore, this paper investigate in-depth the design challenges of the wireless power transfer for medical microsystems. Both the design concerns at the primary and secondary sides are introduced in-depth. At last, this paper looks in the future and summaries several possible future challenges.
    Wireless Symposium (IWS), 2013 IEEE International; 01/2013
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    ABSTRACT: This paper proposes a new wireless power transfer (WPT) system for the endoscopic capsule. In the system, a group of vertically segmented primary coils around the human body are adopted as the transmitting coils. According to the position of the endoscopic capsule, one of the transmitting coils is intelligently selected to transfer the power with the highest efficiency. This paper also presents a coil selection and control algorithm for the unique WPT system. Compared with the conventional design, the calculated transmission efficiencies of the new solution at the best and worst points of the body are enhanced by 53.5% and 138% respectively. And the average efficiency of the proposed solution is about 3.8%.
    Circuits and Systems (ISCAS), 2013 IEEE International Symposium on; 01/2013
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    ABSTRACT: This paper presents a wireless power transfer system for a motion-free capsule endoscopy inspection. Conventionally, a wireless power transmitter in a specifically designed jacket has to be connected to a strong power source with a long cable. To avoid the power cable and allow patients to walk freely in a room, this paper proposes a two-hop wireless power transfer system. First, power is transferred from a floor to a power relay in the patient's jacket via strong coupling. Next, power is delivered from the power relay to the capsule via loose coupling. Besides making patients much more conformable, the proposed techniques eliminate the sources of reliability issues arisen from the moving cable and connectors. In the capsule, it is critical to enhance the power conversion efficiency. This paper develops a switch-mode rectifier (rectifying efficiency of 93.6%) and a power combination circuit (enhances combining efficiency by 18%). Thanks to the two-hop transfer mechanism and the novel circuit techniques, this system is able to transfer an average power of 24 mW and a peak power of 90 mW from the floor to a 13 mm × 27 mm capsule over a distance of 1 m with the maximum dc-to-dc power efficiency of 3.04%.
    IEEE transactions on bio-medical engineering 06/2012; 59(11):3247-54. · 2.15 Impact Factor
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    ABSTRACT: In order to reduce the miss rate of the wireless capsule endoscopy and help physicians to read endoscopic images in an easier manner, this paper proposes a Micro-Ball endoscopy system which is equipped with six cameras. This work develops key techniques to miniaturize the size and lower the power consumption of the Micro-Ball. The Micro-Ball is activated by a wireless power supply unit with a rectifying efficiency of 93.6%. An effective image post-processing method for deriving 2D representation of the digestive tract wall is also presented. The Micro-Ball integrates a low-power attitude sensing unit to provide information for image registration and Micro-Ball control. These designs assure that the Micro-Ball has small size (diameter less than 15mm), can work for more than 15 hours, at an image resolution of 480×480 and an image frame rate of 2fps, when powered by 1.55V@60mAh battery. The effectiveness of the Micro-Ball system has been verified by an FPGA demonstration system.
    Biomedical Circuits and Systems Conference (BioCAS), 2012 IEEE; 01/2012
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    ABSTRACT: Proposed is a two-stage image compression method for wireless capsule endoscopy images to provide high compression rate and high image quality. The first stage, implemented inside the wireless capsule, contains a very low complexity integer transform followed by an optimised quantisation and Huffman encoding. The second stage is a simple post-processing for high subjective visual quality of the reconstructed image, which is applied outside the capsule. The compression method can provide not only high compression rate (86%) and high image quality (39.2%dB), but also low computation complexity.
    Electronics Letters 01/2012; 48(25):1588-1589. · 1.04 Impact Factor
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    ABSTRACT: Wireless endoscopic Micro-Ball system makes it possible to generate the map of gastrointestinal (GI) tract wall. This paper proposes a new method for the generation of small intestine map based on the attitude sensing system embedded in the endoscopic Micro-Ball. In this method, the captured images can be inversely projected on the interior wall of small intestine and then 2D representation of the inversely projected images can be created. The method reduces the complexity of 2D representation of small intestine map, because it removes the perspective distortion of the captured images. Moreover, the attitude information related to the images determines the location of the generated images in the small intestine map. The location information can reduce the amount of calculation when used in image registration of the endoscopic Micro-Ball images. Experimental results show the method is feasible and high efficient.
    Biomedical Circuits and Systems Conference (BioCAS), 2012 IEEE; 01/2012
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    ABSTRACT: A chipset, including one master chip and six same slave chips, is designed and implemented for the endoscopic Micro-Ball, which has six cameras to minimize the blind area while examining the human gastrointestinal (GI) tract. For lowering power consumption, a multi-level clock management for the whole chipset is implemented. A power and area efficient 4 × 4 JPEG image compressor with high image quality is integrated into the slave chip to reduce energy consumption and save FLASH memory space. The master chip and slave chip have been fabricated in 0.18 μm CMOS technology. The experimental results show that the designed chipset for Micro-Ball can support different image frame rates: from 1fps to 6fps with 480×480 image resolution. The power consumption of the chipset is 1.6mW@2fps. The power consumption of the Micro-Ball is estimated about 6mW@2fps. It can work for more than 15 hours, powered by a 1.55V@60mAh battery.
    Circuits and Systems (ISCAS), 2012 IEEE International Symposium on; 01/2012
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    ABSTRACT: This paper presents a wirelessly ultra-low-power system for equilibrium measurement in Total Hip Replacement (THR) surgery. The system consists two parts: the Contact Array Measurement System (CAMS) and the display part. The CAMS is designed to measure the contact distribution of the sensors array between the surface of the femoral head and the acetabulum of the template. The sensors array is designed on the surface of the femoral head and the data is transmitted wirelessly by a low power transceiver. The CAMS composes of a sensors array (31 sensors used in current system), an ultra-low-power microprocessor, and an ultra-low-power transceiver. The display part demonstrates the contact distribution in-vivo in 3D images. The two parts of the system communicate with each other on a RF link at the band of 400MHz. The signal conditioning circuits, the sub-threshold 8-bit microprocessor and the transceiver have been designed and fabricated in 0.18μm CMOS process. The tested results show that the solution of the signal conditioning circuits is 60.1μVpp (1.35g) with ±100mVpp input and the chip can operate under 1.2V to 3.6V voltage supply for single battery application with 116-160μA power consumption. The 3Mbps MSK transmitter consumes only 3.9mW in total. The system has been validated by experimental results. Some clinical experiments will be carried out in the future.
    New Circuits and Systems Conference (NEWCAS), 2012 IEEE 10th International; 01/2012
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    ABSTRACT: Nowadays the interpretation of the images acquired by wireless endoscopy system is a tedious job for doctors. A viable solution is to construct a map, which is a 2D representation of gastrointestinal (GI) tract, based on image registration to reduce the redundancy of images and improve the understandability of them. Nevertheless, the limited field of view makes it difficult for traditional wireless capsule endoscopy system to capture sufficient image information for a complete GI map. The work reported in this paper addresses the problem of the 2D representation of GI tract based on a new wireless Micro- Ball endoscopy system with multiple image sensors. This paper analyses the characteristics of images captured by Micro-Ball endoscopy system and proposes a determination method for registration of wireless endoscopic images based on phase correlation method (PCM). The performance of PCM and the proposed determination method is verified with experiments.
    International Symposium on Circuits and Systems (ISCAS 2011), May 15-19 2011, Rio de Janeiro, Brazil; 01/2011
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    ABSTRACT: The wireless endoscopic Micro-Ball is used to capture images of gastrointestinal (GI) tracts and save them into Flash memories. The batteries will be exhausted after the Micro-Ball is excreted from human body. So a new wireless power transmission (WPT) solution is proposed to deliver energy from an image reader to the Micro-Ball to fetch the stored images. In this solution, considering that the posture of the Micro-Ball is uncertain when it is placed into the image reader and the volume of the Micro-Ball is too small to contain multiple receiving coils, we employ multiple emitting coils in the image reader and one single receiving coil inside the Micro-Ball. Additionally, an adaptive control mechanism is proposed to select the optimum emitting coil with the highest power efficiency to transmit wireless power to the Micro-Ball placed inside the image reader. As a result, the Micro-Ball can work well in the image reader under all postures with highest power efficiency. The experimental results prove that the power delivering efficiency is in the range of 32% to 36%.
    International Symposium on Circuits and Systems (ISCAS 2011), May 15-19 2011, Rio de Janeiro, Brazil; 01/2011
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    ABSTRACT: This paper proposes an omnidirectional wireless power receiving IC for implanted biomedical applications. The IC consists of new power receiving circuits (switch-mode CMOS Rectifier) and new power combination circuits (Skipping Booster). By predicting the coming of the current zero-cross-point (ZCP), the proposed CMOS rectifier switches current with more precise timing. By skipping the rectification in some certain periods, the proposed Skipping Booster combines energy from all rectifiers together. Thanks to the two new circuits, the wireless power receiving IC could receive omnidirectional wireless power with a peak efficiency of 93.6%, which is higher than the conventional results (30%∼80%). It has been verified with a prototype of a batteryless endoscopic capsule.
    01/2011;
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    ABSTRACT: While the wireless endoscopic capsule examining human's large gastrointestinal (GI) cavity, such as stomach and large intestine, many interested spots are omitted by only one or two cameras due to its limited field of view. This paper proposes the new system architecture of the Micro-Ball for medical endoscopy application. Six cameras are embedded in the Micro-Ball for multiple fields of view, which can reduce endoscopic miss rate greatly. Based on this system architecture, a new working mode is proposed. The captured image data are saved in the Flash memory instead of being transmitted outside human body wirelessly. Only less than 6mJ is consumed when the Micro-Ball captures a frame of 480×480 image and writes the image data into the Flash memory. The endoscopic Micro-Ball can work in human's GI tract for 10 hours when the image frame rate is 2 fps. The Micro-Ball endoscopy system is verified on the FPGA-based demonstration system.
    Engineering in Medicine and Biology Society (EMBC), 2010 Annual International Conference of the IEEE; 10/2010
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    ABSTRACT: This paper investigates the design and optimization of a wireless power transmission link targeting Micro-Ball Endoscopy applications. A novel asymmetric resonant coupling structure is proposed to deliver power to an endoscopic Micro-Ball system for image read-out after it is excreted. Such a technology enables many key medical applications with stringent requirements for small system volume and high power delivery efficiency. A prototyping power transmission sub-system of the Micro-Ball system was implemented. It consists of primary coil, middle resonant coil, and cube-like full-direction secondary receiving coils. Our experimental results proved that 200mW of power can be successfully delivered. Such a wireless power transmission capability could satisfy the requirements of the Micro-Ball based endoscopy application. The transmission efficiency is in the range of 41% (worst working condition) to 53% (best working condition). Comparing to conventional structures, Asymmetric Resonant Coupling Structure improves power efficiency by 13%.
    Engineering in Medicine and Biology Society (EMBC), 2010 Annual International Conference of the IEEE; 10/2010
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    ABSTRACT: Now it is a tedious work for clinicians to interpret the images acquired by wireless endoscopy system, and a viable solution is to construct a map, which is the two- dimensional representation of gastrointestinal (GI) tract, to reduce the redundancy of images and improve the understandability of them. But it is difficult for traditional wireless endoscopy system to realize image capture with wide field of view and so it is difficult to generate the map of GI tract. A wireless Micro-Ball endoscopy system makes the full view image capture possible. Then image registration is a key technology for constructing the map. This paper discusses and analyzes two key problems on image registration in detail for Micro-Ball endoscopy system. A two-threshold criterion is proposed for determining the possibility of valid registration between two images, and a MSE approach is also given out to appropriately decide the registration direction in the final step of registration process.
    01/2010;
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    ABSTRACT: This paper proposes a new Wireless-Powered Micro-Ball Endoscopy system, in which wireless power is emitted from an emitter array embedded in a floor and resonantly relayed by a passive wireless power jacket on patients. Comparing to other wireless powering endoscopy systems, both the patients' freedom of movement and the power efficiency are improved. To enhance the power efficiency, an End-Fire Helix Emitter is proposed, which is a fundamentally novel structure used for generating near field alternative magnetic field with high efficiency. This paper also proposes a Load-Adaptive power converter circuit to keep optimal power efficiency by matching the varied load impedance. A prototyping design is fabricated. At the frequency of 24.05MHz, the power efficiency of transmission from floor to wireless jacket is 44.6%, and the overall energy efficiency from floor to Endoscopic Micro-Ball is 2.5% at best.
    01/2010;
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    ABSTRACT: While wireless endoscopic capsule examining human's large gastrointestinal (GI) cavity, such as stomach and large intestine, it is possible that many interested spots are omitted by the one or two cameras due to its limited field of view. This paper proposes a new globularity capsule endoscopy system with multi-camera. Through analyzing the multi-camera system's optical characteristic and power consumption of the endoscopic capsule system, this paper proposes the spatial physical structure and the electronic architecture of the globularity capsule without blind area. Its diameter can be less than 15mm. The capsule can work in human's GI tract for 8 hours when the image frame rate is 4fps.
    Biomedical Circuits and Systems Conference, 2009. BioCAS 2009. IEEE; 12/2009

Publication Stats

25 Citations
3.78 Total Impact Points

Institutions

  • 2009–2013
    • Tsinghua University
      • • Institute of Microelectronics
      • • Department of Electronic Engineering
      • • Institute of Microelectron
      Peping, Beijing, China