A New Balun for Antenna Measurement using Photonic Sensor

We have developed a new type of balun (photonic balun) for measuring characteristics of receiving antennas operated in balanced mode below about 2 GHz. The photonic balun consists of a photonic sensor with resistors in an aluminium box whose size is 2 cm times 2 cm times 4 cm. The common-mode rejection ratio is below -30 dB and Sdd of the differential mode is less than 0.2 below 1 GHz. From the pattern measurements of horizontal and vertical polarizations, the superiority of the photonic balun to conventional baluns are shown.