Analysis of a 1kbps Backscatter Receiver with up to -80dBm Tag-to-tag Receive Sensitivity

Abstract

Merging developments in RFID and wireless sensor networks have increased the interest in using backscatter radio for tag-to-tag communication. Low power consumption is a major concern, often limiting the choice to incoherent receivers such as diode envelope detectors. Link budget calculations require receiver sensitivity specifications, however accurate characterizations are scarce. In this work, we show that the receiver sensitivity is strongly related to the exciter incident power. Full-range analysis of a zero-bias diode detector shows a decreasing noise factor at higher incident powers, which leads to improved sensitivity. On the other side, at strong incident powers, the phase noise of the exciter interferes with the received signal, setting an lower bound to the sensitivity of the backscatter receiver. This work proposes a semi-passive RFID tag capable of 1kbps to 10kbps data rates in the 434MHz band using off the shelf components. The tag has a low power consumption of 85μW during receive, 45μW during transmit and less than 4μW in sleep. The receiver sensitivity at 1kbps shows a 25dB variation as a function of exciter incident power between -50 to 10dBm, while a peak sensitivity of around -80dBm is measured at an incident power of -25dBm.