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22 #ifndef _GR_SINGLE_POLE_IIR_H_
23 #define _GR_SINGLE_POLE_IIR_H_
26 #include <gr_complex.h>
28 * \brief class template for single pole IIR filter
30 template<class o_type, class i_type, class tap_type>
31 class gr_single_pole_iir {
34 * \brief construct new single pole IIR with given alpha
36 * computes y(i) = (1-alpha) * y(i-1) + alpha * x(i)
38 gr_single_pole_iir (tap_type alpha = 1.0)
45 * \brief compute a single output value.
46 * \returns the filtered input value.
48 o_type filter (const i_type input);
51 * \brief compute an array of N output values.
52 * \p input must have n valid entries.
54 void filterN (o_type output[], const i_type input[], unsigned long n);
57 * \brief install \p alpha as the current taps.
59 void set_taps (tap_type alpha)
61 if (alpha < 0 || alpha > 1)
62 throw std::out_of_range ("Alpha must be in [0, 1]\n");
65 d_one_minus_alpha = 1.0 - alpha;
68 //! reset state to zero
74 tap_type prev_output () { return d_prev_output; }
78 tap_type d_one_minus_alpha;
79 tap_type d_prev_output;
84 // general case. We may want to specialize this
86 template<class o_type, class i_type, class tap_type>
88 gr_single_pole_iir<o_type, i_type, tap_type>::filter (const i_type input)
92 output = d_alpha * input + d_one_minus_alpha * d_prev_output;
93 d_prev_output = output;
95 return (o_type) output;
99 template<class o_type, class i_type, class tap_type>
101 gr_single_pole_iir<o_type, i_type, tap_type>::filterN (o_type output[],
102 const i_type input[],
105 for (unsigned i = 0; i < n; i++)
106 output[i] = filter (input[i]);
111 // Specialized case for gr_complex output and double taps
112 // We need to have a gr_complexd type for the calculations and prev_output variable (in stead of double)
114 template<class i_type>
115 class gr_single_pole_iir<gr_complex, i_type, double> {
118 * \brief construct new single pole IIR with given alpha
120 * computes y(i) = (1-alpha) * y(i-1) + alpha * x(i)
122 gr_single_pole_iir (double alpha = 1.0)
129 * \brief compute a single output value.
130 * \returns the filtered input value.
132 gr_complex filter (const i_type input);
135 * \brief compute an array of N output values.
136 * \p input must have n valid entries.
138 void filterN (gr_complex output[], const i_type input[], unsigned long n);
141 * \brief install \p alpha as the current taps.
143 void set_taps (double alpha)
145 if (alpha < 0 || alpha > 1)
146 throw std::out_of_range ("Alpha must be in [0, 1]\n");
149 d_one_minus_alpha = 1.0 - alpha;
152 //! reset state to zero
158 gr_complexd prev_output () { return d_prev_output; }
162 double d_one_minus_alpha;
163 gr_complexd d_prev_output;
166 template< class i_type>
168 gr_single_pole_iir<gr_complex, i_type, double>::filter (const i_type input)
172 output = d_alpha * (gr_complexd)input + d_one_minus_alpha * d_prev_output;
173 d_prev_output = output;
175 return (gr_complex) output;
178 //Do we need to specialize this, although it is the same as the general case?
180 template<class i_type>
182 gr_single_pole_iir<gr_complex, i_type, double>::filterN (gr_complex output[],
183 const i_type input[],
186 for (unsigned i = 0; i < n; i++)
187 output[i] = filter (input[i]);
190 #endif /* _GR_SINGLE_POLE_IIR_H_ */