A new signal processing method for wireless interrogation of a passive SAW sensor with multiple reflectors, utilizing the signal interference during overlap of the sensor's response bursts is introduced. Within this time interval, the amplitude or the phase, respectively, is measured. By varying the frequency of the relatively long interrogation bursts, destructive interferences (notches) are searched. So the measurand influencing the sensor or its identification information can be gained. The principle yields high resolution using a low cost interrogating system. The principle, the hardware effort and experimental results for temperature measurements are presented.