3 * Copyright 2004 Free Software Foundation, Inc.
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23 #ifndef INCLUDED_GR_IIR_FILTER_FFD_H
24 #define INCLUDED_GR_IIR_FILTER_FFD_H
26 #include <gr_sync_block.h>
30 class gr_iir_filter_ffd;
31 typedef boost::shared_ptr<gr_iir_filter_ffd> gr_iir_filter_ffd_sptr;
32 gr_iir_filter_ffd_sptr
33 gr_make_iir_filter_ffd (const std::vector<double> &fftaps,
34 const std::vector<double> &fbtaps) throw (std::invalid_argument);
37 * \brief IIR filter with float input, float output and double taps
40 * This filter uses the Direct Form I implementation, where
41 * \p fftaps contains the feed-forward taps, and \p fbtaps the feedback ones.
43 * \p fftaps and \p fbtaps must have equal numbers of taps
45 * The input and output satisfy a difference equation of the form
48 y[n] - \sum_{k=1}^{N} a_k y[n-k] = \sum_{k=0}^{M} b_k x[n-k]
51 * with the corresponding rational system function
54 H(z) = \frac{\sum_{k=0}^{M} b_k z^{-k}}{1 - \sum_{k=1}^{N} a_k z^{-k}}
57 * Note that some texts define the system function with a + in the denominator.
58 * If you're using that convention, you'll need to negate the feedback taps.
60 class gr_iir_filter_ffd : public gr_sync_block
63 friend gr_iir_filter_ffd_sptr
64 gr_make_iir_filter_ffd (const std::vector<double> &fftaps,
65 const std::vector<double> &fbtaps) throw (std::invalid_argument);
67 gri_iir<float,float,double> d_iir;
68 std::vector<double> d_new_fftaps;
69 std::vector<double> d_new_fbtaps;
73 * Construct an IIR filter with the given taps
75 gr_iir_filter_ffd (const std::vector<double> &fftaps,
76 const std::vector<double> &fbtaps) throw (std::invalid_argument);
79 ~gr_iir_filter_ffd ();
81 void set_taps (const std::vector<double> &fftaps,
82 const std::vector<double> &fbtaps) throw (std::invalid_argument);
84 int work (int noutput_items,
85 gr_vector_const_void_star &input_items,
86 gr_vector_void_star &output_items);