| With the improvement of modern semiconductor technology,products in the biomedical field are becoming more and more humanized to catch people’s ultimate health demand.As an increasingly high incidence of gastrointestinal diseases,researchers have been working on its painless and non-invasive detection methods.Wireless Capsule endoscopy(WCE)has been used in clinical testing as a better method.Its size and detection efficiency have always restricted the wide application of this technology.Integrated circuit technology is breaking through this bottleneck.While improving its functions,it is also very important to provide enough energy for the operation of the internal circuit of the capsule.RF Energy is widely distributed in the environment,the traditional energy collection circuit is to collect the existing power density and reach the hot spot.This paper mainly analyzes and designs the restriction of radio frequency energy on the human body and the corresponding energy receiving circuit.The works are as follows:1.Based on the existing electromagnetic model of human body,the radiation and path loss of different signal frequency bands passing through human body are analyzed,and the appropriate frequency band is selected considering the effect of receiving antenna.Thus,the link budget analysis is carried out to provide theoretical basis and index requirements for circuit design.2.In order to achieve a higher PCE and output voltage for the overall circuit under a wide input power range,this article optimizes the RF-DC circuit,and designs a rectifier with reconfigurable performance through the series-parallel conversion of two-stage rectifiers.The simulation shows that in the input power range of-23.7dBm～-6.7dBm and the load is300KΩ,the maximum output voltage can reach 2.71 V,and the PCE can reach more than 20%in the range close to 14 dBm,and the maximum can reach 28%.3.A set of RF energy receiving system is constructed,which is composed of matching module,reconfigurable RF-DC circuit,LDO circuit and energy storage module,and finally carried out overall simulation.The LDO circuit includes a high-performance voltage reference with a high PSRR to achieve a stable LDO output of 1.8 V and low ripple.4.The advantages of multi-pulse Time Hopping Ultra Wideband(TH-UWB)signal are analyzed.An OOK modulated transmitter is designed,taped and tested.Finally,the results are analyzed. |
