Complete link budget for forward and backward link in a RFID system are given with constituent parts. Backward link signal levels with current improvements requires separate TX and RX antenna bistatic configuration to overcome reader threshold. To further elaborate on link budgets, reflection coefficient and power equations are obtained from a RFID front-end model with circuit theory and shown on a passive RFID system. It is demonstrated that both forward and backward links have limitations on the range depending upon tag power dissipation, antennas in use and type of modulation. To make two distances equal, parameters are found from two way link equations. Then, ASK and BPSK modulations are compared on communication distance for given average backscatter difference power, minimum SNR to targeted BER on the reader by the equations obtained on the circuit model and MATLAB simulations.
RFID, RFID link budget, reflection coefficient, transmitted power, reflected power, ASK and BPSK bac
Safe wireless link and long battery life are indispensable feature for a portable and outdoor used device with build-in sensors. For this purpose, duty cycling, ultra-low power electronics design, dynamic power management, wireless network architecture and medium access control concepts in the design are explained in detailed. In this work, an ultra-low power wireless sensor network is designed with 4cmx4cm size and light weight nodes sending once every three minutes 115.2 kbps 5 byte package that have up to 131.25 year battery life time in theory with 3V (2x1.5V) 1000mAh battery. 868 and 915 MHz programmable 115.2 kbps ISM band FSK RF transceiver with a low power wake-up scheme is utilized for low cost unlicensed-used wireless sensor networks designed with Back Inverted F Antennas with 100m communication range for outdoor applications and 25m for indoor applications. Sensor node requires 0.5 uA, 2.5 mA, 0.8 uA, 14.6 mA and 25mA during sleep, measurement, sniff, receive and transmit mode respectively @ 868 MHz with 3V battery. The sensors has temperature compensation feature with -40-85 °C working range.
Low power transceiver, sensor networks, ISM band FSK RF module, wireless sensor node, Active RFID, l