diff options
Diffstat (limited to 'gr-digital')
| -rw-r--r-- | gr-digital/lib/digital_mpsk_receiver_cc.h | 121 |
1 files changed, 70 insertions, 51 deletions
diff --git a/gr-digital/lib/digital_mpsk_receiver_cc.h b/gr-digital/lib/digital_mpsk_receiver_cc.h index bcb06e17c..d27967ad5 100644 --- a/gr-digital/lib/digital_mpsk_receiver_cc.h +++ b/gr-digital/lib/digital_mpsk_receiver_cc.h @@ -42,31 +42,38 @@ digital_make_mpsk_receiver_cc (unsigned int M, float theta, float omega, float gain_omega, float omega_rel); /*! - * \brief This block takes care of receiving M-PSK modulated signals through phase, frequency, and symbol - * synchronization. + * \brief This block takes care of receiving M-PSK modulated signals + * through phase, frequency, and symbol synchronization. * \ingroup sync_blk * \ingroup demod_blk * - * This block takes care of receiving M-PSK modulated signals through phase, frequency, and symbol - * synchronization. It performs carrier frequency and phase locking as well as symbol timing recovery. - * It works with (D)BPSK, (D)QPSK, and (D)8PSK as tested currently. It should also work for OQPSK and - * PI/4 DQPSK. + * This block takes care of receiving M-PSK modulated signals through + * phase, frequency, and symbol synchronization. It performs carrier + * frequency and phase locking as well as symbol timing recovery. It + * works with (D)BPSK, (D)QPSK, and (D)8PSK as tested currently. It + * should also work for OQPSK and PI/4 DQPSK. * - * The phase and frequency synchronization are based on a Costas loop that finds the error of the incoming - * signal point compared to its nearest constellation point. The frequency and phase of the NCO are - * updated according to this error. There are optimized phase error detectors for BPSK and QPSK, but 8PSK - * is done using a brute-force computation of the constellation points to find the minimum. + * The phase and frequency synchronization are based on a Costas loop + * that finds the error of the incoming signal point compared to its + * nearest constellation point. The frequency and phase of the NCO are + * updated according to this error. There are optimized phase error + * detectors for BPSK and QPSK, but 8PSK is done using a brute-force + * computation of the constellation points to find the minimum. * - * The symbol synchronization is done using a modified Mueller and Muller circuit from the paper: + * The symbol synchronization is done using a modified Mueller and + * Muller circuit from the paper: * - * G. R. Danesfahani, T.G. Jeans, "Optimisation of modified Mueller and Muller - * algorithm," Electronics Letters, Vol. 31, no. 13, 22 June 1995, pp. 1032 - 1033. + * G. R. Danesfahani, T.G. Jeans, "Optimisation of modified Mueller + * and Muller algorithm," Electronics Letters, Vol. 31, no. 13, 22 + * June 1995, pp. 1032 - 1033. * - * This circuit interpolates the downconverted sample (using the NCO developed by the Costas loop) - * every mu samples, then it finds the sampling error based on this and the past symbols and the decision - * made on the samples. Like the phase error detector, there are optimized decision algorithms for BPSK - * and QPKS, but 8PSK uses another brute force computation against all possible symbols. The modifications - * to the M&M used here reduce self-noise. + * This circuit interpolates the downconverted sample (using the NCO + * developed by the Costas loop) every mu samples, then it finds the + * sampling error based on this and the past symbols and the decision + * made on the samples. Like the phase error detector, there are + * optimized decision algorithms for BPSK and QPKS, but 8PSK uses + * another brute force computation against all possible symbols. The + * modifications to the M&M used here reduce self-noise. * */ @@ -140,8 +147,8 @@ class digital_mpsk_receiver_cc : public gr_block protected: - - /*! + + /*! * \brief Constructor to synchronize incoming M-PSK symbols * * \param M modulation order of the M-PSK modulation @@ -171,54 +178,61 @@ protected: void phase_error_tracking(gr_complex sample); -/*! + /*! * \brief Phase error detector for MPSK modulations. * * \param sample the I&Q sample from which to determine the phase error * - * This function determines the phase error for any MPSK signal by creating a set of PSK constellation points - * and doing a brute-force search to see which point minimizes the Euclidean distance. This point is then used - * to derotate the sample to the real-axis and a atan (using the fast approximation function) to determine the - * phase difference between the incoming sample and the real constellation point + * This function determines the phase error for any MPSK signal by + * creating a set of PSK constellation points and doing a + * brute-force search to see which point minimizes the Euclidean + * distance. This point is then used to derotate the sample to the + * real-axis and a atan (using the fast approximation function) to + * determine the phase difference between the incoming sample and + * the real constellation point * * This should be cleaned up and made more efficient. * * \returns the approximated phase error. - */ + */ float phase_error_detector_generic(gr_complex sample) const; // generic for M but more costly - /*! + /*! * \brief Phase error detector for BPSK modulation. * * \param sample the I&Q sample from which to determine the phase error * - * This function determines the phase error using a simple BPSK phase error detector by multiplying the real - * and imaginary (the error signal) components together. As the imaginary part goes to 0, so does this error. + * This function determines the phase error using a simple BPSK + * phase error detector by multiplying the real and imaginary (the + * error signal) components together. As the imaginary part goes to + * 0, so does this error. * * \returns the approximated phase error. - */ + */ float phase_error_detector_bpsk(gr_complex sample) const; // optimized for BPSK - /*! + /*! * \brief Phase error detector for QPSK modulation. * * \param sample the I&Q sample from which to determine the phase error * - * This function determines the phase error using the limiter approach in a standard 4th order Costas loop + * This function determines the phase error using the limiter + * approach in a standard 4th order Costas loop * * \returns the approximated phase error. - */ + */ float phase_error_detector_qpsk(gr_complex sample) const; - /*! + /*! * \brief Decision maker for a generic MPSK constellation. * * \param sample the baseband I&Q sample from which to make the decision * - * This decision maker is a generic implementation that does a brute-force search - * for the constellation point that minimizes the error between it and the incoming signal. + * This decision maker is a generic implementation that does a + * brute-force search for the constellation point that minimizes the + * error between it and the incoming signal. * * \returns the index to d_constellation that minimizes the error/ */ @@ -230,24 +244,27 @@ protected: * * \param sample the baseband I&Q sample from which to make the decision * - * This decision maker is a simple slicer function that makes a decision on the symbol based on its - * placement on the real axis of greater than 0 or less than 0; the quadrature component is always 0. + * This decision maker is a simple slicer function that makes a + * decision on the symbol based on its placement on the real axis of + * greater than 0 or less than 0; the quadrature component is always + * 0. * * \returns the index to d_constellation that minimizes the error/ - */ + */ unsigned int decision_bpsk(gr_complex sample) const; - /*! + /*! * \brief Decision maker for QPSK constellation. * * \param sample the baseband I&Q sample from which to make the decision * - * This decision maker is a simple slicer function that makes a decision on the symbol based on its - * placement versus both axes and returns which quadrant the symbol is in. + * This decision maker is a simple slicer function that makes a + * decision on the symbol based on its placement versus both axes + * and returns which quadrant the symbol is in. * * \returns the index to d_constellation that minimizes the error/ - */ + */ unsigned int decision_qpsk(gr_complex sample) const; private: @@ -260,16 +277,17 @@ protected: float d_freq, d_max_freq, d_min_freq; float d_phase; -/*! + /*! * \brief Decision maker function pointer * * \param sample the baseband I&Q sample from which to make the decision * - * This is a function pointer that is set in the constructor to point to the proper decision function - * for the specified constellation order. + * This is a function pointer that is set in the constructor to + * point to the proper decision function for the specified + * constellation order. * * \return index into d_constellation point that is the closest to the recieved sample - */ + */ unsigned int (digital_mpsk_receiver_cc::*d_decision)(gr_complex sample) const; // pointer to decision function @@ -282,14 +300,15 @@ protected: gr_complex d_p_2T, d_p_1T, d_p_0T; gr_complex d_c_2T, d_c_1T, d_c_0T; - /*! + /*! * \brief Phase error detector function pointer * * \param sample the I&Q sample from which to determine the phase error * - * This is a function pointer that is set in the constructor to point to the proper phase error detector - * function for the specified constellation order. - */ + * This is a function pointer that is set in the constructor to + * point to the proper phase error detector function for the + * specified constellation order. + */ float (digital_mpsk_receiver_cc::*d_phase_error_detector)(gr_complex sample) const; |