| 摘要 |
PROBLEM TO BE SOLVED: To obtain an electric field sensor, whose sensitivity can be enhanced in a band from low frequency up to high frequency by a method, wherein an antenna which receives applied electric field for being input to a sensor head is constituted of a pair of solenoid coils. SOLUTION: Radiant light from a light source is incident on a sensor head through an optical fiber 5. The sensor head changes the intensity of incident light according to the electric field strength of a space in which an antenna is installed, and the incident light is radiated to be detected by a photodetector. In this electric-field sensor, the antenna is constituted of a solenoid coil 2 and a solenoid coil 2 which are placed symmetrically on both side faces of a package 1, in which the sensor head is housed. Thereby, the solenoid coils 2 and the sensor head are connected to constituted a resonance circuit. The resonance frequency depends on the diameter and the pitch of the solenoid coils 2 for enhancing reception sensitivity. For example, in a high-frequency region of 1 MHz to 2 GHz, the sensitivity of the electric field sensor is enhanced, as compared with the case of a very small dipole antenna. Since the pitch of the solenoid coils 2 can be changed freely, the pitch can be set so as to be matched to the measuring frequency band.
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