摘要： This article focuses on the application of split ring resonator based sensor for follow up recovery of lower extremity trauma patients. The proposed sensor mainly monitors the changes of dielectric properties of lower limb tissues such as skin, fat, muscle and bone. As part of the characterization of microwave sensor, it is crucial to assess the signal penetration in in-vivo tissues. This work presents a new approach for investigating the penetration depth of Split Ring Resonator sensor in in-vivo context of the femoral area. The method is based on the measurement of skin, fat, and muscle tissue thicknesses from ultrasound images. The microwave reflectivity, S11 measurements are done in conjunction with ultrasound measurements on four volunteers to deduce the effective permittivity of the in-vivo tissues. The tissue thickness information derived from ultrasound measurements were used to create 3D simulation model in CST studio 2017. The measured S11 values are used to optimize the effective permittivity of that model. The penetration depths are calculated from the simulation of electric field distribution in the optimized model. The analysis on measured data shows that the thigh region contributes highest penetration depth up to 17.5mm. This result has higher significance in demonstrating the in-vitro penetration depth measurements and other tests which are going to be performed in the future.