Electromagnetic Transmit Array With Optical Control for Beamforming

This proof-of-concept communication demonstrates the feasibility of using a slide projector to steer the beam of a transmit array by adding solar cells and varactor diodes to each unit cell. By irradiating each solar cell with the light of different intensities from a slide projector, the measured phase of the wave transmitted by the $4\times4$ transmit array shifts within 92° at 4.26 GHz, while the variation in magnitude is measured within 4 dB. Different light configurations are identified via a searching algorithm to achieve peak/null beamforming in a particular direction. The beam of the prototypical $4\times4$ transmit array can be shifted by ±24° in terms of the peaks and −30° to 36° in terms of nulls. The concept of adding light modulation to the transmit array with a slide projector can provide update rates of tens of milliseconds with control of brightness and color distributed over a large area of the array.