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Nonlinear Monopolar Signal-Adaptive Residue Suppressor

IP.com Disclosure Number: IPCOM000102260D
Original Publication Date: 1990-Nov-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 3 page(s) / 117K

Publishing Venue

IBM

Related People

Chung, PW: AUTHOR [+6]

Abstract

This nonlinear filter is used to eliminate undesirable and relatively low amplitude residue signals which are coincident with higher amplitude additive disturbance signals in channels using MR sensors. These higher amplitude additive disturbance signals are intended to be passed by the nonlinear filter for later signal processing in the data channel, resulting in the eventual elimination of the disturbance from a data signal.

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Nonlinear Monopolar Signal-Adaptive Residue Suppressor

       This nonlinear filter is used to eliminate undesirable
and relatively low amplitude residue signals which are coincident
with higher amplitude additive disturbance signals in channels using
MR sensors.  These higher amplitude additive disturbance signals are
intended to be passed by the nonlinear filter for later signal
processing in the data channel, resulting in the eventual elimination
of the disturbance from a data signal.

      There are essentially three distinctive operating regions in
this filter.
   1.   When the signal (residue) magnitude is small, the filter
should have a low roll-off frequency to effectively attenuate the
residue signals at the filter output (low-pass filter).
   2.   In the presence of a rising edge of a large amplitude signal
(rising edge of the additive disturbance signal), the filter should
have a high roll-off frequency, acting as a unity gain stage,
producing an accurate replica of the rising edge at the output of the
filter.
   3.   In the presence of a falling edge of a large amplitude signal
(the falling edge of the additive disturbance signal), the filter
should have a feedback system which provides a sufficiently fast
fall- time constant to accurately reproduce the falling edge of the
large amplitude signal but still suppress the subsequent and
coincident low amplitude residue signal.

      The figure is a detailed schematic of the nonlinear adaptive
filter.  Transistors Q1 and Q2 are the input devices for a
transconductance stage.  Transistors Q3 and Q4 are current mirrors in
this stage to supply a differential output current ig .  Resistors R1
and R2 are used in conjunction with current source J1 to control the
transconductance and maximum output current.  Transistors Q5 and Q6
comprise the Darlington stage, while resistor R3 is a parallel
resistor controlling a preset threshold potential Vthreshold.
Capacitor C is connected to ground before buffer B0, which isolates
the filter from varying load impedances.  Transistors Q7 and Q8 are
the input devices to another transconductance stage.  Resistors R4
and R5 are degeneration resistors for these input devices.  Resistors
R6 and R7 control the gain of this stage while source J2 provides
bias current.  Transistors Q9 and Q10 provide a second stage of
additional gain with biasing source J3 and degeneration resistors R8
and R9.  Transistor Q9 provides current to resistor R10, which biases
transistor Q11 into conduction only when a discharge current is
required by the filter.

      As described befor...