In this paper, we study a Wireless Passive Sensor Network (WPSN) that employs binary coded differential delay line surface acoustic wave (SAW) devices to monitor temperature in a harsh conditioned environment. The sensors are individually addressed by different reflector patterns. The number of sensors in the system is related to the coded reflectors pattern length which itself is limited by the size constraint of sensors. We propose a new sectorized system model for the WPSN by utilizing a phased circular antenna array to increase the number of sensors in the system that yields higher sensing spatial accuracy. Moreover, the sensing accuracy is further improved by a new two-step detection procedure that purifies the response signal and removes the interference of undesired sensors.