diff options
| -rw-r--r-- | host/utils/usrp_cal_utils.hpp | 40 |
1 files changed, 31 insertions, 9 deletions
diff --git a/host/utils/usrp_cal_utils.hpp b/host/utils/usrp_cal_utils.hpp index 1b9df9d03..3750be9cb 100644 --- a/host/utils/usrp_cal_utils.hpp +++ b/host/utils/usrp_cal_utils.hpp @@ -263,15 +263,15 @@ static uhd::usrp::multi_usrp::sptr setup_usrp_for_cal( **********************************************************************/ UHD_INLINE void set_optimal_rx_gain(uhd::usrp::multi_usrp::sptr usrp, uhd::rx_streamer::sptr rx_stream, - double wave_freq = 0.0) + double wave_freq = 0.0, + double gain_step = 3.0) { - const double gain_step = 3.0; - const double gain_compression_threshold = gain_step * 0.5; - const double actual_rx_rate = usrp->get_rx_rate(); - const double actual_tx_freq = usrp->get_tx_freq(); - const double actual_rx_freq = usrp->get_rx_freq(); - const double bb_tone_freq = actual_tx_freq - actual_rx_freq + wave_freq; - const size_t nsamps = size_t(actual_rx_rate / default_fft_bin_size); + const double gain_step_threshold = gain_step * 0.5; + const double actual_rx_rate = usrp->get_rx_rate(); + const double actual_tx_freq = usrp->get_tx_freq(); + const double actual_rx_freq = usrp->get_rx_freq(); + const double bb_tone_freq = actual_tx_freq - actual_rx_freq + wave_freq; + const size_t nsamps = size_t(actual_rx_rate / default_fft_bin_size); std::vector<samp_type> buff(nsamps); uhd::gain_range_t rx_gain_range = usrp->get_rx_gain_range(); @@ -290,6 +290,10 @@ UHD_INLINE void set_optimal_rx_gain(uhd::usrp::multi_usrp::sptr usrp, // this by looking for the gain setting where the increase // in the tone is less than the gain step by more than the // gain compression threshold (curr - prev < gain - threshold). + // This routine starts searching at the bottom of the gain range + // rather than the top in order to minimize the chances of + // exposing frontend components to a dangerous amount of power + // from the incoming signal. // Initialize prev_dbrms value usrp->set_rx_gain(rx_gain); @@ -297,6 +301,24 @@ UHD_INLINE void set_optimal_rx_gain(uhd::usrp::multi_usrp::sptr usrp, prev_dbrms = compute_tone_dbrms(buff, bb_tone_freq / actual_rx_rate); rx_gain += gain_step; + // First, get the signal above the noise floor + while (rx_gain <= rx_gain_range.stop()) { + usrp->set_rx_gain(rx_gain); + capture_samples(usrp, rx_stream, buff, nsamps); + curr_dbrms = compute_tone_dbrms(buff, bb_tone_freq / actual_rx_rate); + delta = curr_dbrms - prev_dbrms; + + // Check that the signal power is not already high + if (curr_dbrms >= 0) + break; + // Check that the signal power has increased as the gain increases + if (delta >= gain_step - gain_step_threshold) + break; + + prev_dbrms = curr_dbrms; + rx_gain += gain_step; + } + // Find RX gain where signal begins to clip while (rx_gain <= rx_gain_range.stop()) { usrp->set_rx_gain(rx_gain); @@ -305,7 +327,7 @@ UHD_INLINE void set_optimal_rx_gain(uhd::usrp::multi_usrp::sptr usrp, delta = curr_dbrms - prev_dbrms; // check if the gain is compressed beyone the threshold - if (delta < gain_step - gain_compression_threshold) + if (delta < gain_step - gain_step_threshold) break; // if so, we are done prev_dbrms = curr_dbrms; |