New technique for measuring electromagnetic fields

A new light modulated array technique for measuring electromagnetic fields is described. The array element used is a dipole made using a photodiode. A modulated laser scanning system is used to scan the array. When the photodiode element is illuminated by the modulated laser beam, the self-impedance of the dipole is itself modulated, and the secondary wave is detected by a remote receiver. Because the array is isolated and of small scatter cross-section, the disturbance to the measured field is minimised. An example measurement at 8.5 GHz is described. The results indicate that the technique provides a rapid method of imaging electromagnetic fields. The limitations of this approach are also discussed.