gr-fft: added tukey window generation

2 files changed, 33 insertions, 0 deletions

diff --git a/gr-fft/include/gnuradio/fft/window.h b/gr-fft/include/gnuradio/fft/window.h
index 8daeacaf9..6b4411393 100644
--- a/gr-fft/include/gnuradio/fft/window.h
+++ b/gr-fft/include/gnuradio/fft/window.h
@@ -288,6 +288,16 @@ public:
     static std::vector<float> riemann(int ntaps);
 
     /*!
+     * \brief Build a Tukey window.
+     *
+     * \param ntaps Number of coefficients in the window.
+     * \param alpha Shaping parameter for the Tukey window, an
+     *        alpha of zero is equivalent to a rectangular
+     *        window, an alpha of 1 is equivalent to Hann.
+     */
+    static std::vector<float> tukey(int ntaps, float alpha);
+
+    /*!
      * \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 8638d3738..8b0a07f43 100644
--- a/gr-fft/lib/window.cc
+++ b/gr-fft/lib/window.cc
@@ -316,6 +316,29 @@ std::vector<float> window::riemann(int ntaps)
     return taps;
 }
 
+std::vector<float> window::tukey(int ntaps, float a)
+{
+    if ((a < 0) || (a > 1))
+        throw std::out_of_range("window::tukey: alpha must be between 0 and 1");
+
+    float N = static_cast<float>(ntaps - 1);
+
+    float aN = a * N;
+    float p1 = aN / 2.0;
+    float mid = midn(ntaps);
+    std::vector<float> taps(ntaps);
+    for (int i = 0; i < mid; i++) {
+        if (abs(i) < p1) {
+            taps[i] = 0.5 * (1.0 - cos((2 * GR_M_PI * i) / (aN)));
+            taps[ntaps - 1 - i] = taps[i];
+        } else {
+            taps[i] = 1.0;
+            taps[ntaps - i - 1] = 1.0;
+        }
+    }
+    return taps;
+}
+
 std::vector<float> window::build(win_type type, int ntaps, double beta)
 {
     switch (type) {