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Dynamic Analysis of Nonlinear Devices in the Presence of Noise

IP.com Disclosure Number: IPCOM000081248D
Original Publication Date: 1974-Apr-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 4 page(s) / 107K

Publishing Venue

IBM

Related People

Argyle, BE: AUTHOR [+2]

Abstract

The system described measures the dynamic behavior of a nonlinear device such as motion of magnetic bubble domain walls in magnetic materials where signals, especially from thin films, are buried in the noise.

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Dynamic Analysis of Nonlinear Devices in the Presence of Noise

The system described measures the dynamic behavior of a nonlinear device such as motion of magnetic bubble domain walls in magnetic materials where signals, especially from thin films, are buried in the noise.

The essential elements of the measuring system are illustrated in the block diagrams of Figs. 1 and 2. A nonlinear device to be measured may be characterized by a transfer (response) function as in Fig. 3. The reference output of a lock-in amplifier 12 provides a low-frequency modulation of the high- frequency sinusoidal drive 5, which is transmitted to the experiment 8 via radio- frequency (RF) amplifier 4, 7 and power splitter 6A. This modulated drive has the form

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where x(0) is the peak response corresponding to the peak drive h(0) at frequency omega(2) . The device response x(t) is converted to voltage V(x(t)) by a suitable transducer, not shown. For example, in characterizing the domain wall response of a bubble domain material, a photodetector used in conjunction with the Faraday effect will detect the domain wall motion x(t).

The signal voltage from the experiment is processed by a standard tracking receiver 6B whose elements are shown in Fig. 2. Included are a mixer 21, bandpass filter and intermediate frequency (IF) amplifier 22, log amplifier 23, and a detector 24. The local oscillator 19 producing f(z) -f(if) and a mixer 20 in conjunction with a tracking signal at a frequency f(2) +f(z) from source 5, provide a standard means for receiver tracking of f(z) by mixing f(2) +f(IF) with f(2) . Typically, f(IF) could be 0.1 MHz. The output voltage of the mixer 2I is given by V(mixer) = V(x) (t) ' V(osc) (f(2)+f(IF) which includes components at frequencies f(IF),f(1) f(IF) +f(1) , f(IF)-f(1) and others as well as harmonics and sidebands.

The bandpass filter 22, having full width at half maximum of a few kilocycles, selects the components at f(IF)+/- f(1) by rejecting the harmonics and sidebands and any residual fundamentals of f(2) It also removes most of the noise components which may be present at all frequencies, such as shot noise originating in a photodetector.

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A. Slope of Transfer Function dx/dh vs h (at fixed frequency) is accomplished by a ramp generator 1 driving gain of RF amplifier 4 an inverse log amplifier 10, the divider 14 and the XY recorder 1...