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Method for Generating Shouldering Distortion on a High-Frequency Sinewave

IP.com Disclosure Number: IPCOM000039678D
Original Publication Date: 1987-Jul-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Myers, W: AUTHOR

Abstract

The circuit described generates a controlled amount of odd-order "shouldering" distortion, or distortion consisting of odd-order harmonics and fundamental all in phase at their peaks (sometimes referred to as "cosine sum" distortion), on a high-frequency sinusoidal waveform, to duplicate the type of distortion seen on surface analysis testing waveforms for magnetic data storage disks and heads. The desired results are achieved with a simple non-linear network followed by a differentiation circuit (a 6 dB/octave high-pass filter). The non-linear network symmetrically clips the input signal, which then has all frequency components shifted 90 degrees by a high-pass filter, creating the proper phase relationship between the fundamental and harmonics. Referring to Fig.

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Method for Generating Shouldering Distortion on a High-Frequency Sinewave

The circuit described generates a controlled amount of odd-order "shouldering" distortion, or distortion consisting of odd-order harmonics and fundamental all in phase at their peaks (sometimes referred to as "cosine sum" distortion), on a high-frequency sinusoidal waveform, to duplicate the type of distortion seen on surface analysis testing waveforms for magnetic data storage disks and heads. The desired results are achieved with a simple non-linear network followed by a differentiation circuit (a 6 dB/octave high-pass filter). The non-linear network symmetrically clips the input signal, which then has all frequency components shifted 90 degrees by a high-pass filter, creating the proper phase relationship between the fundamental and harmonics. Referring to Fig. 1, the Input Signal comes from a low-impedance source and is AC coupled and then passed through resistance R1 so that the non-linear load formed by diodes D1 and D2 will have a finite impedance to work against. Resistance R2 allows "softening" of the clipping to control the level of high-order harmonics; the lower the value, the more higher-order harmonics are generated, while a higher value of resistance R2 will give fewer high-order harmonics. Resistance R1 can easily be replaced by several resistors of different value, switched by a diode-switching arrangement, to allow selection of

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different distortion characte...