GNU Radio 3.6.2 C++ API
dc_blocker_ff.h
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1 /* -*- c++ -*- */
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22 
23 #ifndef INCLUDED_FILTER_DC_BLOCKER_FF_H
24 #define INCLUDED_FILTER_DC_BLOCKER_FF_H
25 
26 #include <filter/api.h>
27 #include <gr_sync_block.h>
28 
29 namespace gr {
30  namespace filter {
31 
32  class FILTER_API dc_blocker_ff : virtual public gr_sync_block
33  {
34  public:
35 
36  // gr::filter::dc_blocker_ff::sptr
38 
39  /*!
40  * \class dc_blocker_ff
41  * \brief a computationally efficient controllable DC blocker
42  *
43  * \ingroup filter_blk
44  *
45  * This block implements a computationally efficient DC blocker that produces
46  * a tighter notch filter around DC for a smaller group delay than an
47  * equivalent FIR filter or using a single pole IIR filter (though the IIR
48  * filter is computationally cheaper).
49  *
50  * The block defaults to using a delay line of length 32 and the long form
51  * of the filter. Optionally, the delay line length can be changed to alter
52  * the width of the DC notch (longer lines will decrease the width).
53  *
54  * The long form of the filter produces a nearly flat response outside of
55  * the notch but at the cost of a group delay of 2D-2.
56  *
57  * The short form of the filter does not have as flat a response in the
58  * passband but has a group delay of only D-1 and is cheaper to compute.
59  *
60  * The theory behind this block can be found in the paper:
61  *
62  * <B><EM>R. Yates, "DC Blocker Algorithms," IEEE Signal Processing Magazine,
63  * Mar. 2008, pp 132-134.</EM></B>
64  *
65  * \param D (int) the length of the delay line
66  * \param long_form (bool) whether to use long (true, default) or short form
67  */
68  static sptr make(int D, bool long_form=true);
69 
70  virtual int group_delay() = 0;
71  };
72 
73  } /* namespace filter */
74 } /* namespace gr */
75 
76 #endif /* INCLUDED_FILTER_DC_BLOCKER_FF_H */