Adaptive digital non-linearity compensation on a silicon microphone
A linearized system includes a nonlinear system configured for receiving an input signal; a digital nonlinear compensation component having an input coupled to an output of the nonlinear system, and having an output for generating an output signal; a low pass filter having an input coupled to the output of the digital nonlinear compensation component; a first summer having a first input configured for receiving a digital reference value and a second input coupled to an output of the low pass filter; and an error minimization component having an input coupled to an output of the first summer, and an output coupled to the digital nonlinear compensation component.
1 . An apparatus comprising:
a nonlinear system configured for receiving an input signal;
a digital nonlinear compensation component having an input coupled to an output of the nonlinear system, and having an output for generating an output signal;
a low pass filter having an input coupled to the output of the digital nonlinear compensation component;
a first summer having a first input configured for receiving a digital reference value and a second input coupled to an output of the low pass filter; and
an error minimization component having an input coupled to an output of the first summer, and an output coupled to the digital nonlinear compensation component.
2 . The apparatus of claim 1 , wherein the digital nonlinear compensation component comprises a second order transfer function.
3 . The apparatus of claim 2 , wherein the second order transfer function comprises an adapted second order coefficient.
4 . The apparatus of claim 1 , wherein the digital reference value comprises a logic zero value.
5 . The apparatus of claim 1 , wherein the error minimization component comprises:
a step size generator having an input configured for receiving an error signal from the first summer;
a second summer having a first input coupled to an output of the step size generator; and
an integrator having an input coupled to an output of the second summer and an output coupled to a second input of the second summer, wherein the output of the integrator is configured for generating an adapted coefficient.
6 . The apparatus of claim 5 , wherein the step size generator is configured for generating a constant step size.
7 . The apparatus of claim 5 , wherein the step size generator is configured for generating a step size comprising a function of the error signal.
8 . The apparatus of claim 1 , wherein the nonlinear system comprises a digital microphone.
9 . An apparatus comprising:
a nonlinear system configured for receiving an input signal;
a first low pass filter having an input coupled to an output of the nonlinear system;
a first summer having a first input coupled to an output of the first low pass filter, and having a second input coupled to the output of the nonlinear system;
a digital nonlinear compensation component having an input coupled to an output of the first summer, and having an output for generating an output signal;
a second low pass filter having an input coupled to the output of the digital nonlinear compensation component;
a second summer having a first input coupled to the output of the first low pass filter, and having a second input coupled to an output of the second low pass filter; and
an error minimization component having an input coupled to an output of the second summer, and an output coupled to the digital nonlinear compensation component.
10 . The apparatus of claim 9 , wherein the digital nonlinear compensation component comprises a second order transfer function.
11 . The apparatus of claim 10 , wherein the second order transfer function comprises an adapted second order coefficient.
12 . The apparatus of claim 9 , wherein the error minimization component comprises:
a step size generator having an input configured for receiving an error signal from the second summer;
a third summer having a first input coupled to an output of the step size generator; and
an integrator having an input coupled to an output of the third summer, and having an output coupled to a second input of the third summer, wherein the output of the integrator is configured for generating an adapted coefficient.
13 . The apparatus of claim 12 , wherein the step size generator is configured for generating a constant step size.
14 . The apparatus of claim 12 , wherein the step size generator is configured for generating a step size comprising a function of the error signal.
15 . The apparatus of claim 9 , wherein the nonlinear system comprises a digital microphone.