This paper presents the prediction and measurement of the phase response from awireless surface acoustic wave (SAW) device for temperature sensingapplications. This wireless sensor consists of two or more arrays of an interdigitaltransducer (IDT)and reflector pair with different IDT-reflector distances. Pulse modulatedsignals are transmitted from a remote reader system and their echoes arereturned with different time delays due to the different IDT-reflectordistances. Corresponding intermediate frequency signals are generated in a mixer and their phasedifferences are calibrated to temperature values. Using the coupled-mode theory ofSAWs, the phase characteristic relative to temperature was examined. The effectof the relative distances between the two reflector arrays is demonstrated. Theinfluence of the phase reversal location, which produces multiple temperaturevalues for a given phase difference, is also discussed and a simple solutionis illustrated. This sensor is coupled with a small planar antenna, which willbe well suited for applications that require passive and conformal sensors.