Wireless passive surface acoustic wave（ SAW） sensor can be operated in very harsh environment to monitor change of temperature

strain

torque and other factors. The resonant frequency of SAW sensor can be obtained by group delay characteristics of wireless measuring sensor. However

unexpected environmental reflection problem will occur in wireless measurement in some complex environments

which results in measured group delay curve becomes distorted and it is difficult to extract resonant frequency of SAW sensor. Measurement system is set up by measuring the group delay characteristics of the SAW sensor

and time domain windowing technique has been applied to correct the measurement results. The results show that influence of environmental reflection on group delay can be effectively suppressed by using time domain windowing technique

which is important to improve the signal noise ratio in practical application of passive wireless SAW sensor.