Reduced Link Correlation Using Multiple Antennas

High-frequency backscatter radio systems operate in the backscatter channel, a channel whose envelope probability density function (PDF) and bit-error-rate (BER) performance are strongly affected by the relationship between small-scale fading in the reader-to-tag and tag-to-reader propagation links – i.e., link correlation. This paper shows that backscatter radio systems using co-located reader transmitter and receiver antennas and a single RF transponder antenna can have the highest link correlation which results in the worst communication performance. It is shown that using separate reader antennas and multiple RF transponder antennas will decrease the detrimental effects of link correlation. Results show that if the correlation of the envelopes of the reader-to-tag and tag-to-reader propagation links is below approximately 0.6, near maximum backscatter communication performance can be achieved.