Organizational Unit:
Undergraduate Research Opportunities Program
Undergraduate Research Opportunities Program
2012
,
Hassig, Santiago
Passive Radio Frequency Identification (RFID) tags are powered by energy-harvesting
charge pumps through AC-to-DC rectification of the wireless RF signal: typically
a pulse-interval encoded (PIE) continuous-waveform (CW). These charge pumps are
comprised of capacitors and diodes, the latter being the leading barrier of passive tag
operation. Specifically, the pump diode turn-on voltage is responsible for limited tag
sensitivity, read range, and reliability. The Power Optimized Waveform (POW) is a
new, non-invasive transmission signal that improves RFID tag sensitivity by providing
higher peak voltages without exceeding Federal Communications Commission
(FCC) output power regulations. Two POWs that are tested are the 1-POW, comprised
of two sinusoids centered about a carrier signal frequency, and the Square
POW, the product of a carrier signal and a voltage modulating square wave. A Dickson
charge pump was used to measure the power gain of POW versus CW. Spectral
efficiency and charge pump efficiency were calculated at different transmit powers
and POW frequency spacing. Positive gain was achieved at low transmit powers (< ~4
dBm), and higher frequency spacing, making POW preferable over CW in low power
applications.