An optically controlled phase shifter for antenna array beam steering

A novel optically activated phase shifter using an organic semi-conducting polymer has been developed for antenna beam steering. A blend of poly(3-hexylthiophene) (P3HT, 95%) and [6,6]-Phenyl C61 butyric acid methyl ester (PCBM, 5%) was used as a photosensitive agent to control the main beam of a prototype two-patch antenna subjected to differential illumination. The array was fabricated on FR-4 substrate, with P3HT/PCBM spray coated onto the patches to analyse the effect of illumination on the far-field response of the antenna. Return loss (S
₁₁
) measurements of the antenna verified impedance matching throughout the resonant frequency shift during illumination (45mW to 1.4W over an area of 9.62cm
²
). The far-field results showed 8° and 22° shifts on either side of bore-sight under differential illumination conditions. Change in light intensity between the left-illuminated and right-illuminated regions of P3HT/PCBM is the key factor behind the change in permittivity of the organic region, leading to the beam steering.