gr::analog::cpm Class Reference

Return the taps for an interpolating FIR filter (gr::filter::interp_fir_filter_fff). More...

#include <gnuradio/analog/cpm.h>

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::filter::interp_fir_filter_fff). More...

Detailed Description

Return the taps for an interpolating FIR filter (gr::filter::interp_fir_filter_fff).

Member Enumeration Documentation

cpm_type

enum gr::analog::cpm::cpm_type

Enumerator
LRC
LSRC
LREC
TFM
GAUSSIAN
GENERIC

Member Function Documentation

phase_response()

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::filter::interp_fir_filter_fff).

These taps represent the phase response \(g(k)\) 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. \( \sum_{k=0}^{K-1} g(k) = 1\); this will cause a maximum phase change of \( h \cdot \pi\) 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