915 MHz SAW wireless passive sensor system performance

Over the last 13 years, our group has been developing passive, wireless SAW device technology and the system has been continually evolving, providing gains in all aspects of the technology. Initial system proof-of-concept moved from 250 MHz to the current 915 MHz, which is a good choice from device and antenna size, and wireless RF component availability. Range has increased from less than a meter, to over 25 meters, and current testing is moving towards 100 meters for a NASA application. Several successful custom transceivers were developed and delivered to NASA and the US government. From custom-made systems, current efforts use a software defined radio (SDR) Universal Software Radio Peripheral (USRP) transceiver approach as the interrogator-receiver. This commercially off the shelf (COTS) hardware greatly reduces development time and cost and ensures rapid future improvements. The advantageous and SDR approach will be discussed, which include RF parameter adaptability in center frequency and bandwidth. The current status of the SAW wireless temperature sensors sensitivity and range will be used as the performance parameter measure, since it is the most ubiquitous of all sensor applications.