diff options
Diffstat (limited to 'gr-fft/include/gnuradio/fft/window.h')
| -rw-r--r-- | gr-fft/include/gnuradio/fft/window.h | 42 |
1 files changed, 32 insertions, 10 deletions
diff --git a/gr-fft/include/gnuradio/fft/window.h b/gr-fft/include/gnuradio/fft/window.h index 4a7fb44ff9..92f62c64cb 100644 --- a/gr-fft/include/gnuradio/fft/window.h +++ b/gr-fft/include/gnuradio/fft/window.h @@ -35,19 +35,41 @@ namespace gr { public: enum win_type { - WIN_NONE = -1, //!< don't use a window - WIN_HAMMING = 0, //!< Hamming window; max attenuation 53 dB - WIN_HANN = 1, //!< Hann window; max attenuation 44 dB - WIN_BLACKMAN = 2, //!< Blackman window; max attenuation 74 dB - WIN_RECTANGULAR = 3, //!< Basic rectangular window - WIN_KAISER = 4, //!< Kaiser window; max attenuation a function of beta, google it - WIN_BLACKMAN_hARRIS = 5, //!< Blackman-harris window - WIN_BLACKMAN_HARRIS = 5, //!< alias to WIN_BLACKMAN_hARRIS for capitalization consistency - WIN_BARTLETT = 6, //!< Barlett (triangular) window - WIN_FLATTOP = 7, //!< flat top window; useful in FFTs + WIN_HAMMING = 0, //!< Hamming window; max attenuation 53 dB + WIN_HANN = 1, //!< Hann window; max attenuation 44 dB + WIN_BLACKMAN = 2, //!< Blackman window; max attenuation 74 dB + WIN_RECTANGULAR = 3, //!< Basic rectangular window; max attenuation 21 dB + WIN_KAISER = 4, //!< Kaiser window; max attenuation see window::max_attenuation + WIN_BLACKMAN_hARRIS = 5, //!< Blackman-harris window; max attenuation 92 dB + WIN_BLACKMAN_HARRIS = 5, //!< alias to WIN_BLACKMAN_hARRIS for capitalization consistency + WIN_BARTLETT = 6, //!< Barlett (triangular) window; max attenuation 26 dB + WIN_FLATTOP = 7, //!< flat top window; useful in FFTs; max attenuation 93 dB }; /*! + * \brief Given a window::win_type, this tells you the maximum + * attenuation you can expect. + * + * \details + * For most windows, this is a set value. For the Kaiser window, + * the attenuation is based on the value of beta. The actual + * relationship is a piece-wise exponential relationship to + * calculate beta from the desired attenuation and can be found + * on page 542 of Oppenheim and Schafer (Discrete-Time Signal + * Processing, 3rd edition). To simplify this function to solve + * for A given beta, we use a linear form that is exact for + * attenuation >= 50 dB. + * + * For an attenuation of 50 dB, beta = 4.55. + * + * For an attenuation of 70 dB, beta = 6.76. + * + * \param type The window::win_type enumeration of the window type. + * \param beta Beta value only used for the Kaiser window. + */ + static double max_attenuation(win_type type, double beta=6.76); + + /*! * \brief Helper function to build cosine-based windows. 3-coefficient version. */ static std::vector<float> coswindow(int ntaps, float c0, float c1, float c2); |