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+/* -*- c++ -*- */
+/*
+ * Copyright 2010 Free Software Foundation, Inc.
+ *
+ * GNU Radio is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3, or (at your option)
+ * any later version.
+ *
+ * GNU Radio is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Radio; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+
+#ifndef INCLUDED_GR_CPM_H
+#define INCLUDED_GR_CPM_H
+
+#include <vector>
+
+class gr_cpm
+{
+ public:
+	enum cpm_type {
+	 LRC,
+	 LSRC,
+	 LREC,
+	 TFM,
+	 GAUSSIAN,
+	 GENERIC = 999
+	};
+
+    /*! \brief Return the taps for an interpolating FIR filter (gr_interp_fir_filter_fff).
+	 *
+	 * These taps represent the phase response \f$g(k)\f$ for use in a CPM modulator,
+	 * see also gr_cpmmod_bc.
+	 *
+	 * \param type The CPM type (Rectangular, Raised Cosine, Spectral Raised Cosine,
+	 *             Tamed FM or Gaussian).
+	 * \param samples_per_sym Samples per symbol.
+	 * \param L The length of the phase response in symbols.
+	 * \param 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 \a K = \p samples_per_sym x \p L.
+	 *         This can be used directly in an interpolating FIR filter such as
+	 *         gr_interp_fir_filter_fff with interpolation factor \p samples_per_sym.
+	 *
+	 * All phase responses are normalised s.t. \f$ \sum_{k=0}^{K-1} g(k) = 1\f$; this will cause
+	 * a maximum phase change of \f$ h \cdot \pi\f$ between two symbols, where \a 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
+     */
+	static std::vector<float>
+	phase_response(cpm_type type, unsigned samples_per_sym, unsigned L, double beta=0.3);
+};
+
+#endif /* INCLUDED_GR_CPM_H */
+