Gas sensor based on surface acoustic wave（SAW） technology is needed to be improved in the detection limit

the response time and the reduction of temperature and humidity sensitivity.A dual-port SAW resonator coated with hyperbranched polymer membrane is introduced.By the establishment of Van Dyke model

the impacts of the sensitive polymer membrane on Q-value and insertion loss of chemical agent sensor as well as on circuit impedance matching are analyzed.Meanwhile

research is done to find out the impact of the location of membrane coating on the device

and the experiment result shows that coating on the center grating between interdigital transducers（IDT） has relatively best effects.The design and features of hyperbranched polymer are also introduced.Experiments are done on the sensor.By exposed to Sarin agent of 5.0 mg/m3

a 315 MHz dual-port SAW resonator coated with hyperbranched polymer membrane is applied.Experiments show that the sensitivity of the sensor can be achieved 600 Hz/mg/m3

the response time is 50 s

and recovery time is about 60 s.