Browse Prior Art Database

Tunable Pulsed Microwave Generator

IP.com Disclosure Number: IPCOM000109083D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 2 page(s) / 73K

Publishing Venue

IBM

Related People

Freeman, MR: AUTHOR [+2]

Abstract

Disclosed is a compact, tunable source of microwaves that operates at room temperature. The device consists of a parallel strip coplanar transmission line structure on a semi-insulating semiconductor substrate and a ferromagnetic or ferrimagnetic film (for example, yttrium iron garnet (YIG)) as shown in Fig. 1. A DC magnetic field is applied in the plane of the film. The transmission line is connected to a DC bias source. A subpicosecond dye laser pulse is used to short the end of the biased transmission line through the photoconductivity of the semiconducting substrate. This generates a fast rise time current pulse which propagates down the transmission line causing a pulsed magnetic field perpendicular to the plane of the YIG film.

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Tunable Pulsed Microwave Generator

       Disclosed is a compact, tunable source of microwaves that
operates at room temperature.  The device consists of a parallel
strip coplanar transmission line structure on a semi-insulating
semiconductor substrate and a ferromagnetic or ferrimagnetic film
(for example, yttrium iron garnet (YIG)) as shown in Fig. 1.  A DC
magnetic field is applied in the plane of the film.  The transmission
line is connected to a DC bias source.  A subpicosecond dye laser
pulse is used to short the end of the biased transmission line
through the photoconductivity of the semiconducting substrate.  This
generates a fast rise time current pulse which propagates down the
transmission line causing a pulsed magnetic field perpendicular to
the plane of the YIG film. The spins in the YIG are tilted out of
the plane by this perpendicular magnetic field and begin to precess
about the inplane applied field direction.  The spins precess at a
resonance frequency which depends on the applied DC field. The
precessing spins radiate at the resonance frequency which is
typically in the GHz range.  The microwave oscillations damp out
after a time of a few hundred picoseconds to as much as tens of
nanoseconds in  a low damping material like YIG.

      The dependence of the resonance frequency on applied magnetic
field is shown in Fig. 2.  In a zero applied field, the spins
resonate in the demagnetizing field of the sample created by its
planar shape.  T...