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<title>CMSIS-DSP: Signal Convergence Example</title>
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<div class="title">Signal Convergence Example<div class="ingroups"><a class="el" href="group__groupExamples.html">Examples</a></div></div> </div>
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<dl class="section user"><dt>Description:</dt><dd></dd></dl>
<dl class="section user"><dt></dt><dd>Demonstrates the ability of an adaptive filter to "learn" the transfer function of a FIR lowpass filter using the Normalized LMS Filter, Finite Impulse Response (FIR) Filter, and Basic Math Functions.</dd></dl>
<dl class="section user"><dt>Algorithm:</dt><dd></dd></dl>
<dl class="section user"><dt></dt><dd>The figure below illustrates the signal flow in this example. Uniformly distributed white noise is passed through an FIR lowpass filter. The output of the FIR filter serves as the reference input of the adaptive filter (normalized LMS filter). The white noise is input to the adaptive filter. The adaptive filter learns the transfer function of the FIR filter. The filter outputs two signals: (1) the output of the internal adaptive FIR filter, and (2) the error signal which is the difference between the adaptive filter and the reference output of the FIR filter. Over time as the adaptive filter learns the transfer function of the FIR filter, the first output approaches the reference output of the FIR filter, and the error signal approaches zero. </dd></dl>
<dl class="section user"><dt></dt><dd>The adaptive filter converges properly even if the input signal has a large dynamic range (i.e., varies from small to large values). The coefficients of the adaptive filter are initially zero, and then converge over 1536 samples. The internal function <a class="el" href="arm__signal__converge__example__f32_8c.html#a8f521e839d4fad24a4f12a18dfeae5d4">test_signal_converge()</a> implements the stopping condition. The function checks if all of the values of the error signal have a magnitude below a threshold DELTA.</dd></dl>
<dl class="section user"><dt>Block Diagram:</dt><dd></dd></dl>
<dl class="section user"><dt></dt><dd><div class="image">
<img src="SignalFlow.gif" alt="SignalFlow.gif"/>
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</dd></dl>
<dl class="section user"><dt>Variables Description:</dt><dd></dd></dl>
<dl class="section user"><dt></dt><dd><ul>
<li><code>testInput_f32</code> points to the input data </li>
<li><code>firStateF32</code> points to FIR state buffer </li>
<li><code>lmsStateF32</code> points to Normalised Least mean square FIR filter state buffer </li>
<li><code>FIRCoeff_f32</code> points to coefficient buffer </li>
<li><code>lmsNormCoeff_f32</code> points to Normalised Least mean square FIR filter coefficient buffer </li>
<li><code>wire1</code>, wir2, wire3 temporary buffers </li>
<li><code>errOutput</code>, err_signal temporary error buffers</li>
</ul>
</dd></dl>
<dl class="section user"><dt>CMSIS DSP Software Library Functions Used:</dt><dd></dd></dl>
<dl class="section user"><dt></dt><dd><ul>
<li><a class="el" href="group__LMS__NORM.html#gac7ccbaea863882056eee815456464670" title="Initialization function for floating-point normalized LMS filter. ">arm_lms_norm_init_f32()</a></li>
<li><a class="el" href="group__FIR.html#ga5afaa7b8e6735bbc19e582aa9755b0e1" title="Initialization function for the floating-point FIR filter. ">arm_fir_init_f32()</a></li>
<li><a class="el" href="group__FIR.html#ga0cf008f650a75f5e2cf82d10691b64d9" title="Processing function for the floating-point FIR filter. ">arm_fir_f32()</a></li>
<li><a class="el" href="group__LMS__NORM.html#ga72b3755ed1cf97622851cbbeff83c69e" title="Processing function for floating-point normalized LMS filter. ">arm_lms_norm_f32()</a></li>
<li><a class="el" href="group__BasicScale.html#ga5e769c8e22da173674c6abca7291e713" title="Multiplies a floating-point vector by a scalar. ">arm_scale_f32()</a></li>
<li><a class="el" href="group__BasicAbs.html#ga0e8fc7df3033cdbe9cda8a766a46e6d9" title="Floating-point vector absolute value. ">arm_abs_f32()</a></li>
<li><a class="el" href="group__BasicSub.html#ga76b8b2aec34269c6de0b090cab00fb33" title="Floating-point vector subtraction. ">arm_sub_f32()</a></li>
<li><a class="el" href="group__Min.html#ga514e2c920c432e1a3df2cb03f01d2797" title="Minimum value of a floating-point vector. ">arm_min_f32()</a></li>
<li><a class="el" href="group__copy.html#gaa6dfe9554ca61eb3d1eee498396bce88" title="Copies the elements of a floating-point vector. ">arm_copy_f32()</a></li>
</ul>
</dd></dl>
<p><b> Refer </b> <a class="el" href="arm_signal_converge_example_f32_8c-example.html">arm_signal_converge_example_f32.c</a> </p>
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