1. Field of the Invention
This invention relates generally to apparatus for sensing electromagnetic radiation and more particularly to a search-coil antenna for detecting magnetic fields.
2. Description of the Prior Art
A search-coil is a device that measures fluctuating magnetic fields and comprises a magnetic antenna and associated electronics therefor. When used on sounding rockets or on spacecraft, search-coils are typically mounted on a boom in order to escape the electronic noise generated by other scientific instruments and/or subsystems in the immediate vicinity.
As a general rule, scientific instrumentation should impact mass constraints as little as possible; however, boom-mounted instruments in particular must be lightweight to survive deployment under high stress conditions when used in connection with spacecraft. This weight constraint can limit both the size of the sensor and its placement on the boom. Both factors translate into severe constraints on the capability of the instrument to measure weak electromagnetic fields encountered, for example, in space.
For this type of task, the known prior art typically comprises relatively heavy ferrite-loaded loop type antennas shown and described, for example, in the section entitled "Loop Antennas" by G. S. Smith, which appears in Antenna Engineering Handbook, edited by R. C. Johnson et al, McGraw-Hill, Inc., New York, 1961.