gr::analog::cpm Class Reference

#include <cpm.h>

List of all members.

Public Types
enum	cpm_type {   LRC, LSRC, LREC, TFM,   GAUSSIAN, GENERIC = 999 }
Static Public Member Functions
static std::vector< float >	phase_response (cpm_type type, unsigned samples_per_sym, unsigned L, double beta=0.3)
	Return the taps for an interpolating FIR filter (gr_interp_fir_filter_fff).

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Member Enumeration Documentation

enum gr::analog::cpm::cpm_type

Enumerator:

LRC
LSRC
LREC
TFM
GAUSSIAN
GENERIC

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Member Function Documentation

static std::vector<float> gr::analog::cpm::phase_response	(	cpm_type	type,
		unsigned	samples_per_sym,
		unsigned	L,
		double	beta = 0.3
	)		[static]

Return the taps for an interpolating FIR filter (gr_interp_fir_filter_fff).

These taps represent the phase response for use in a CPM modulator, see also gr_cpmmod_bc.

Parameters:

type	The CPM type (Rectangular, Raised Cosine, Spectral Raised Cosine, Tamed FM or Gaussian).
samples_per_sym	Samples per symbol.
L	The length of the phase response in symbols.
beta	For Spectral Raised Cosine, this is the rolloff factor. For Gaussian phase responses, this the 3dB-time-bandwidth product. For all other cases, it is ignored.

Output: returns a vector of length K = samples_per_sym x L. This can be used directly in an interpolating FIR filter such as gr_interp_fir_filter_fff with interpolation factor samples_per_sym.

All phase responses are normalised s.t. ; this will cause a maximum phase change of between two symbols, where h is the modulation index.

The following phase responses can be generated:

• LREC: Rectangular phase response.
• LRC: Raised cosine phase response, looks like 1 - cos(x).
• LSRC: Spectral raised cosine. This requires a rolloff factor beta. The phase response is the Fourier transform of raised cosine function.
• TFM: Tamed frequency modulation. This scheme minimizes phase change for rapidly varying input symbols.
• GAUSSIAN: A Gaussian phase response. For a modulation index h = 1/2, this results in GMSK.

A short description of all these phase responses can be found in [1].

[1]: Anderson, Aulin and Sundberg; Digital Phase Modulation

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The documentation for this class was generated from the following file:

• cpm.h