Evaluation of an electric field sensor with very small elements using a mach-zehnder interferometer>.

There is a great demand for electric field sensors with bandwidth wider than 1 GHz in order to evaluate electromagnetic fields near wireless equipment and to investigate EMC test equipment. An electric field sensor using an optical modulator is suitable for this purpose because it has a wide bandwidth and is compact. This paper describes an electric field sensor with a 10-mm-long element fabricated by depositing a nichrome layer on a glass substrate. First, based on the equivalent circuit of an electric field sensor, the frequency characteristic of the sensor was analyzed by the moment method and the relationship between the element length and frequency characteristic was clarified. Then, the characteristics of a fabricated sensor were analyzed. It was found that the sensor sensitivity was constant within ±4 dB at frequencies up to 4 GHz. The measured frequency characteristic of the sensor was close to the analytical result obtained by taking into account the dielectric constant of the material in which the sensor is mounted. It was also found that the sensor sensitivity was 16 mV/m, about 100 times higher than that of conventional sensors with a similar size element. The directionality of this sensor was equivalent to that of a tunable dipole antenna and the spatial resolution was comparable with the element length. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80(12): 69–78, 1997 [ABSTRACT FROM AUTHOR]