Experimental Evaluation of Load-modulating Channel Estimation for Tunable Reflectarray

This paper proposes a novel channel estimation method for a tunable reflectarray (RA) utilizing integrated variable loads. Besides load-modulating array elements, a small number of power-detecting ones are installed in the RA. The power-detecting elements observe the received signal strength (RSS) of the pilot signal from a transmitter (Tx), and channels between the Tx and load-modulating elements are estimated from the change in the RSS during load modulation. This offers a simpler hardware configuration of the RA with neither a local signal source nor an I/Q detector for channel estimation. Experiments confirmed a sufficiently high channel estimation accuracy by the proposed method when the pilot signal is incident within the beamwidth of the array element.