NASA NTRS · 19660051602
Insertion loss of room temperature magnetoelastic waves in yttrium iron garnet from 1.6 to 8.5 gc
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Gilbreath, W. P., Sumsion, H. T.. 1966-05-01. Solid-phase welding of metals under high vacuum.. https://ntrs.nasa.gov/citations/19660051602
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To limit the 4080-mc local oscillator signal power input to the beat oscillator modulator of the Telstar satellite communications repeater, a subsidiary absorption limiter was used which consisted of an optically polished sphere of single-crystal yttrium iron garnet (YIG), placed in a resonant transmission cavity between the amplified 4080-mc output of the traveling-wave tube and the BO modulator input. The limiter holds the output power nearly constant above a given input threshold; below this threshold the YIG is linear and introduces only a small loss. The threshold is determined, for a given sample at a given frequency, by the external magnetic bias field. Temperature compensation over the desired range was obtained by orienting the crystal with the dc magnetic field along a [100] or “hard” axis. The total weight of the limiter package, including the bias magnet and cavity, is 13 ounces.