Research On Radio Frequency Signal Human Body Penetration Characteristics And Key Chip Design Of WCE Receiver

The development of wireless technology has brought about revolutionary changes in many aspects of modern life,especially after its application in the medical field,making medical devices gradually develop in the direction of intelligence and portability.The popularity of wireless capsule endoscopy is a typical representative.However,there are still many deficiencies in this portable device,such as the resolution of the captured pictures,the standby problem caused by the battery capacity,and the positioning accuracy of tracking the lesion,which are urgently to be resolved.This paper mainly studies the penetration characteristics of wireless RF signals in human tissues and the design of WCE RF receiver chips.The specific work involved in this article is as follows:1.This paper analyzes the research status of wireless capsule endoscopies at home and abroad,focuses on current research hotspots,and elaborates future development trends.At the same time,the ultra-wideband wireless receiver is introduced to lay a solid theoretical foundation for the subsequent design.2.This paper introduces the theoretical research on the effects of electromagnetic waves on human tissues,including the research status of electromagnetic waves on biological tissues and the research on electromagnetic characteristics of biological tissues.The research methods of radio frequency signal human tissue penetration characteristics are reviewed.The specific path loss characteristics of signal propagation and the calculation method for evaluating the specific absorption rate of the safety of the wireless transmission system are described.Three methods for studying the penetration characteristics of human tissue are analyzed,and the advantages and disadvantages of each method and the future direction of development are explained.3.The main amplifier and demodulator of WCE receiver are analyzed and designed.Innovated in the pulse width adjustment circuit unit of the demodulator.The main reason is to add a MOS switch to the pulse width adjustment circuit.This MOS switch is controlled by the input signal,the gate of the MOS transistor is connected to the input signal,the drain is connected to the output of the delay circuit,and the source is connected to the ground.When the input signal comes to a high level,the MOS transistor is turned on,the switch is turned on,and the output level of the delay circuit is immediately pulled to a low level;when the input signal comes to a low level,the MOS transistor is turned off,and the switch is closed,The delay circuit works and the output signal is delayed.Using this MOS transistor,the output pulse is stabilized,so that the overall circuit realizes a more stable pulse width adjustment function.4.TSMC 0.18 um CMOS process is used to simulate the design of the designed receiver circuit.The analog power supply and the digital power supply are used.The power supply voltage is 1.8V and the carrier frequency is 4GHz.The layout design is completed.During the post-simulation,the maximum gain of the main amplifier is 26.58 d B.The demodulator can work normally when the input signal amplitude is 3m V ～ 125 m V.Finally,the PCB test board required for testing the chips is designed.