fft: added gaussian window

and updated the docs for gaussian and tukey windows

2 files changed, 31 insertions, 0 deletions

diff --git a/gr-fft/include/gnuradio/fft/window.h b/gr-fft/include/gnuradio/fft/window.h
index 9fc15c123..8cc6a5d9b 100644
--- a/gr-fft/include/gnuradio/fft/window.h
+++ b/gr-fft/include/gnuradio/fft/window.h
@@ -300,6 +300,10 @@ public:
 
     /*!
      * \brief Build a Tukey window.
+     * <pre>
+     * Bloomfield, P. Fourier Analysis of Time Series: An Introduction. New York:
+     * Wiley-Interscience, 2000, pp 69 (eqn 6.9)
+     * </pre>
      *
      * \param ntaps Number of coefficients in the window.
      * \param alpha Shaping parameter for the Tukey window, an
@@ -309,6 +313,17 @@ public:
     static std::vector<float> tukey(int ntaps, float alpha);
 
     /*!
+     * \brief Build a Gaussian window using the equation
+     * <pre>
+     * exp(-(1/2) * (n/sigma)^2)
+     * </pre>
+     *
+     * \param ntaps Number of coefficients in the window.
+     * \param sigma Standard deviation of gaussian distribution.
+     */
+    static std::vector<float> gaussian(int ntaps, float sigma);
+
+    /*!
      * \brief Build a window using gr::fft::win_type to index the
      * type of window desired.
      *
diff --git a/gr-fft/lib/window.cc b/gr-fft/lib/window.cc
index 8b0a07f43..430b435bd 100644
--- a/gr-fft/lib/window.cc
+++ b/gr-fft/lib/window.cc
@@ -339,6 +339,22 @@ std::vector<float> window::tukey(int ntaps, float a)
     return taps;
 }
 
+std::vector<float> window::gaussian(int ntaps, float sigma)
+{
+    if (sigma <= 0)
+        throw std::out_of_range("window::gaussian: sigma must be > 0");
+
+    float a = 2 * sigma * sigma;
+    double m1 = midm1(ntaps);
+    std::vector<float> taps(ntaps);
+    for (int i = 0; i < midn(ntaps); i++) {
+        float N = (i - m1);
+        taps[i] = exp(-(N * N / a));
+        taps[ntaps - 1 - i] = taps[i];
+    }
+    return taps;
+}
+
 std::vector<float> window::build(win_type type, int ntaps, double beta)
 {
     switch (type) {