Design Of FBAR Sensor Read-out Circuit

The FBAR sensors have a wide range of applications for its high sensitivity, high operating frequency and low power loss, but FBAR sensor read-out circuit was rarely reported; In order to find suitable FBAR sensor read-out circuit, the six-port reflectometer is used as FBAR sensor read-out circuits in this paper.The reflection coefficient vs frequency curve of the FBAR can be measured by six-port reflectometer, the resonant frequency shift of FBAR can reflect the external physical changes, which is obtained by the reflection coefficient vs frequency curve. Take FBAR accelerometer for example, which the resonant frequency is 2.700 GHz was reported, and the operating bandwidth is 2.690 ~ 2.710 GHz. To verify the six-port reflectometer can be used as the FBAR sensor read-out circuit, the microstrip six-port reflectometer is designed, which the operating bandwidth is 2.650 ~ 2.740 GHz in this paper.In order to verify that the good process robustness of the microstrip six-port reflectometer for FBAR accelerometer read-out circuit, the process error of the designed microstrip six-port reflectometer is analyzed, which the operating bandwidth is 2.650 ~ 2.740 GHz; The analysis results show that the operating bandwidth of microstrip six-port reflectometer is still larger than the operating bandwidth required for FBAR accelerometer, when the metal conductor width of microstrip is changed 50 ?m, the thickness of metal conductors is changed 5 ?m, the substrate thickness is changed 5 ?m; However, when dielectric constant of the substrate is changed 0.1, the microstrip six-port reflectometer cannot be used for the FBAR accelerometer of 2.690 ~ 2.710 GHz.Using the six-port reflectometer to measure the reflection coefficient of the FBAR, the six-port reflectometer must be calibrated. To improve precision and efficiency of six-port reflectometer calibration, the best calibration method presented by Hoer is analyzed in this paper; The analysis results show that only 8 of the 11 system parameters can be obtained at the first time, when the Hoer method is used, the remaining 3 system parameters will be obtained at the second step; The 11 system parameters can be obtained at the first time, when the calibration formula in Hoer method is changed, the time required for calibration is shortened.In order to further verify that the six-port reflectometer for FBAR sensor read-out circuit, and make design of FBAR sensors becoming more accurate and simple; The resonant frequency of FBAR sensor can be obtained directly by the model of the minimum system of FBAR sensor is established in the ADS software.Finally, the microstrip six-port network is measured by using the vector network analyzer, the microstrip six-port reflectometer consist of microstrip six-port network and detector. The reflection coefficient of a matched load was measured by using microstrip six-port reflectometer, and the results were compared with results of the vector network Analyzer, close agreement, which verified the microstrip six-port reflectometer can be used as FBAR sensor read-out circuit.