synchronizers_blk

# Synchronizers

gr::analog::pll_carriertracking_cc
gr::analog::pll_freqdet_cf
gr::analog::pll_refout_cc
gr::digital::clock_recovery_mm_cc
gr::digital::clock_recovery_mm_ff
gr::digital::costas_loop_cc
gr::digital::fll_band_edge_cc
gr::digital::msk_timing_recovery_cc
gr::digital::ofdm_chanest_vcvc
gr::digital::ofdm_sync_sc_cfb
gr::digital::pfb_clock_sync_ccf
gr::digital::pfb_clock_sync_fff
gr::digital::pn_correlator_cc
gr::digital::symbol_sync_cc
gr::digital::symbol_sync_ff
tm_type
gr::digital::tm_type
THRESHOLD_DYNAMIC
THRESHOLD_ABSOLUTE

Correlate stream with a pre-defined sequence and estimate peak.

Input:

- Stream of complex samples.

Output:

- Output stream that just passes the input complex samples

- tag 'phase_est': estimate of phase offset

- tag 'time_est': estimate of symbol timing offset

- tag 'corr_est': the correlation value of the estimates

- tag 'amp_est': 1 over the estimated amplitude

- tag 'corr_start': the start sample of the correlation and the value

- Optional 2nd output stream providing the advanced correlator output

This block is designed to search for a sync word by correlation and uses the results of the correlation to get a time and phase offset estimate. These estimates are passed downstream as stream tags for use by follow-on synchronization blocks.

The sync word is provided as a set of symbols after being filtered by a baseband matched filter.

The phase_est tag can be used by downstream blocks to adjust their phase estimator/correction loops, and is currently implemented by the gr::digital::costas_loop_cc block.

The time_est tag can be used to adjust the sampling timing estimate of any downstream synchronization blocks and is currently implemented by the gr::digital::pfb_clock_sync_ccf block.

The caller must provide a "time_est" and "phase_est" tag marking delay from the start of the correlated signal segment, in order to mark the proper point in the sync word for downstream synchronization blocks. Generally this block cannot know where the actual sync word symbols are located relative to "corr_start", given that some modulations have pulses with intentional ISI. The user should manually examine the primary output and the "corr_start" tag position to determine the required tag delay settings for the particular modulation, sync word, and downstream blocks used.

For a discussion of the properties of complex correlations, with respect to signal processing, see: Marple, Jr., S. L., "Estimating Group Delay and Phase Delay via Discrete-Time 'Analytic' Cross-Correlation, IEEE_Transcations on_Signal_Processing, Volume 47, No. 9, September 1999