A b s t r a c t --W h e a t s t o n e bridge magnetic field sensors using Giant Magnetoresistive Ratio (GMR) m u l t i l a y e r s w e r e designed, f a b r i c a t e d , a n d evaluated. The GMR ranged from 10% to 20% with saturation fields of 60 Oe to 300 Oe. The multilater resistances decreased linearly with magnetic field and showed little hysteresis.I n one sensor configuration, a permanent magnet bias was placed between two pairs of magnetoresistors, each pair representing opposite legs of the bridge. This sensor gave a bipolar bridge output whose output range was approximately GMR times the bridge source voltage.The second sensor configuration used shielding on one resistor pair, and it gave a bridge output dependent on the magnetic field magnitude, but not polarity, and the output range was approximately one half GMR times the bridge source voltage.Field amplifications of 3 to 6 were accomplished by creating a gap in a low reluctance magnetic path, thus providing the full range of outputs with 1/3 to 1/6 of the intrinsic saturation fields of the GMR multilayers.

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The device to be described in this presentation is a miniaturized high power coaxial component performing within a single package the functions of circulation, power limiting, and preselection. Attention is principally directed to the limiting and preselection functions which are accomplished through the use of a crossed-strip gyromagnetic coupler which differs from those previously reported in that the second-order nonlinear process rather than the first-order process is the basis for its operation. This limiter has been tested independently at power levels as high as 8 kw and found to exhibit a flat leakage output less than 200 mw and a spike leakage energy of about 0.5 erg. The limiter is mechanically tunable over a frequency range greater than 10% in C band. At a fixed setting the 3 db bandwidth is about 20 Mc. The recovery time of the limiter is determined by the kickback of energy from the garnet spin system. Experimental values of this quantity will be presented. The duplexer-limiter package operates at peak powers up to 40 kw into a 2:1 antenna mismatch. Input VSWR at the transmitter port is less than 1.35. Insertion loss from the transmitter port to the antenna port is less than 0.7 db. Low power insertion loss from antenna port through the limiter to the receiver port is 1.0 db.