Fig. 4: Measurement results.
From: Wireless active feedback loop for backscattering communication
a, b Visualization of the signal in the closed loop. Presence of oscillation (a). No oscillation (b). c–f. Characterization of read distance d as a function of signal amplitude for a closed loop (with 4 GHz RF filter and QH800 antenna for signal recovery) by a metal plate (c), by a rectangular resonant loop (d), by a dipole patch (e). f Same as (e) but using a −20 dB coupler to pick up the signal.
