Research On Medical Wireless Surface Acoustic Wave Sensing System

The acoustic wave sensors are widely used in many applications, such as environmental monitoring, chemical treatment and biological analysis, etc., because of their high sensitivity, repeatability, and low-cost. The thesis addresses the Android based a portable acoustic wave medical diagnostic system taking advantages of acoustic wave sensors and Bluetooth technology. The proposed system has low cost, high flexibility and a compact structure with the characteristics of mobile medical product design. System control and reporting are performed by this personal digital assistant.Firstly, the circuit design methods of surface acoustic wave sensor are summarized.The sensor signal processing technology based on the way of dual channel mixing detection is studied for the SAW sensor of center frequency 249MHz. Preprocessing module, measuring module and communication module of the system are designed. The two oscillation loop of reference and detecting channel, mixing circuit, filtering circuit, TTL shaping circuit are included to the preprocessing part, and the module for frequency measurement is designed based on FPGA, which completed the function of measuring the output signal frequency accurately. The wireless data transmission module is built by the Bluetooth communication technology. On this basis, the PCB board is completed, and the performance of the circuit is tested.Then, the implementation method of software module for the medical wireless surface acoustic wave sensor system is studied based on the Android system development platform in the thesis. The Java API of Bluetooth wireless communication technology is mainly studied. The APP interface of medical wireless sensor system is designed and related functional modules with Java programming language is completed.Finally, the surface of the SAW sensor is coated with Parylene C by using coating apparatus PDS2010 to facilitate the further experiment. The stability is tested at room temperature and constant temperature respectively and the function of the system is verified. The whole sensing system combines technologies of radio frequency (RF) circuit, microcontroller and Bluetooth programming. To conclude, the wireless SAW sensor system is suitable for real-time monitoring due to its characteristics of high sensitivity and good stability etc.