Analysis of Phase Noise Performance in Spatially Separated Backscatter Systems

Backscatter radio systems are generally considered to be suitable only for short range transmission limited by the two-way path losses and receiver sensitivity. Using a simple model of the receiver noise due to the leakage of the carrier signal into the receiver, we show that by spatially separating the transmit and receive antennas to increase isolation while sharing a single local oscillator such that the phase noise is correlated, a 6m antenna separation can achieve 10$,000\mathrm{m}^{2}$ area of coverage, 3 times greater than a monostatic system. This can be increased a further 10 times if a delay is introduced to the path of the LO-Rx to match the propagation delay to within 1ns. Such a system could be implemented with a distributed antenna system or dedicated LO cable channel between the Tx and Rx nodes.