Broad-Band Remote-Sensing Magnetometer

A broad-band remote-sensing magnetometer system has been developed for measuring fast-rising pulsed magnetic fields. Broad frequency response is achieved by frequency modulating a 1.5-GHz microwave carrier for transmission from the sensor to a remotely located receiver. The primary field probe is a ferrite-loaded coil, which produces a current proportional to the magnetic-field intensity. This current is used to frequency modulate a YIG-tuned transistor oscillator in the sensor. A traveling-wave amplifier in the receiver provides carrier amplification and amplitude limiting because it is operated in saturation mode. A new type of FM discriminator, which offers multiple-octave bandwidth potential, converts the frequency-modulated carrier to an amplitude-modulated carrier. The signal is finally detected and amplified for oscilloscope display. While the present system achieves a 50-MHz bandwidth, the system concept should be capable of extension to several times this bandwidth.