| Wireless capsule endoscope started the epoch of gastrointestinal inspection. It is possible to inspect the whole small intestine by endoscope image. It is painless and does not make patient feel disconfortable. The inspection is very convenience. However, some tech-necks still exist, such as orientation, moving mechanism and energy sources. These problems limit the application of wireless capsule endoscope. Aiming at the technical problems of energy transmission and anti-interference, this dissertation analyzed the research status of wireless capsule endoscope, concluded and compared wireless endoscope products and prototype designs, and designed the wireless capsule endoscope on-demand. This paper especially paid attention to the reseach of high-efficency and low-frequency electromagnetic induction link, anti-interference technology in radio-frequency communication, and antenna of wireless capsule endoscope. It mainly includes the following distinctive research work and conclusions:1. A wireless capsule endoscope on-demand was designed by adopting the mode of cooperation between programmable logic device and micro control unit. This design has been awarded with invention patent. This capsule is digital and double-direction. In order to get high data rate, it transmits image data with radio-frequency. And it transmits control command with low-frequency electromagnetic induction link to reduce the consumption power. The programmable logic device and the radio-frequency transmitter in wireless capule endoscope are to collect and send image data. And the micro control unit is to receive control command and set relative parameters. It is much more effectively and compactly to transmit the image data with this method. At the same time, it can predigest the design of the control device and make the system scheme more rational. The wireless capsule endoscope added managing and controlling ability. It can modify parameters instantly and on-demand by controlling.2. A new rectifier called the composite rectifier was designed by researching the character of inductive voltage in the three-dimension receiver of the wireless capsule endoscope. The wave of each inductive voltage of the three-dimension receiver is identical. The only difference among the three inductive voltages is magnitude and initial phase. Initial phase only concludes in-phase and out-of-phase. If using the half-wave rectifier and full-wave rectifier for synthesis, it will effect energy transmitting efficency and control data receiving. The composite recitifier is helpful to improve system sensitivity. It can overcome the direction limit of the electromagnetic induction link, eliminate the blind spot and enhance the efficiency of energy transmitting. This design can provide a perfect flat for control command and energy transmitting in wireless capsule endoscope.3. A new anti-interference was designed by analyzing the channel characters of different application in same frequency. This way can provide new research thought for solving the interference of the low-power and portable device in wireless transmitting. It involves many merits as follows: By error controlling and changing channel, it can enhance the anti-interference ability of wireless endoscope system and ensure data communication. By sending control command via low-frequency electromagnetic induction link, it can reduce the time of error processing. Once confirming data packet is lost or wrong, it will send request for retransmitting command, and reduced needless data sending and consumption power. Channel changing and error controlling is dealt with out-body device, and would not add the complexity of in-body device.4. A new antenna was designed for the wireless capsule endoscope by researching the miniature technology and the factors effecting antenna capability. This kind of antenna is composed of the spiral structure of Archimedes, dielectric substrate and shorting pin. It includes merits as little size, broad-band, high efficiency, and not be effected by tissues around it. The diameter of this antenna is not more than 8.3mm. The center frequency is 2.44GHz. When the voltage standing wave ratio is not more than 2, the range of the frequency is 2.3～2.63GHz. The minimum return loss is -23.7dB. This antenna is made by PCB. The consistency of this antenna is great. So the antenna can be completely integrated into the wireless endoscope capsule.This dissertation researched the wireless capsule endoscope in structure, parameter control, electromagnetic induction link, anti-interference and antenna. It not only reduced the complexity of wireless endoscope capsule, decreased consumption power, enhanced parameter control, but also reduced data transmitting error ratio, improved image quality, and enlarged the wireless energy transmitting. It settled the theory and practice foundation for latter research on wireless capsule endoscope.
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