Measurement system and antenna therefor

A radiation measurement system includes a dipole antenna (4,18) for radiating an EM field in response to an electrical signal generated by an opto-electrical converter (12). The opto-electrical converter (12) is provided with an optical signal representing the EM field to be emitted. Optical signals avoid disturbance of the EM field by a coaxial cable required to feed the antenna. In order to obtain an ideal dipole antenna with well known radiation properties, an inner conductor (16) is used to couple the signal from the opto-electrical converter (12) to both halves (4,18) of a hollow dipole antenna. FIG.