Optical feeding antenna with wide bandwidth for evaluation of radiated emission test sites above 1 GHz

As a way to improve optical feeding antennas with a wide bandwidth above 1 GHz for evaluation of radiated emission test sites, we developed a tears drop type antenna composed of biconical type antenna elements and a sphere that utilizes a uni-traveling-carrier photodiode (UTC-PD) as a photo detector instead of the usual PIN photo diode. The radiated electric field was measured and compared with values calculated from the finite integration (FI) method. A numerical simulation revealed that the calculated frequency characteristics and directivities of the electric field radiated from the tears drop type antenna agreed very well with the measured values. In addition, the measured frequency characteristics of the electric field radiated from the antenna were almost flat within 9 dB in the frequency range from 1 GHz to 6 GHz, and the measured electric field levels were from 97 dBμV/m to 106 dBμV/m. The radiation directivities in the θ direction almost complied with those specified by CISPR16-1-4 Ed.2. Our examinations showed that the tears drop type antenna is superior to a biconical type antenna.