GNU Radio Manual and C++ API Reference  3.10.9.1
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gr::digital::symbol_sync_cc Class Referenceabstract

Symbol Synchronizer block with complex input, complex output. More...

#include <gnuradio/digital/symbol_sync_cc.h>

Public Types

typedef std::shared_ptr< symbol_sync_ccsptr
 
- Public Types inherited from gr::block
enum  work_return_t { WORK_CALLED_PRODUCE = -2 , WORK_DONE = -1 }
 Magic return values from general_work. More...
 
enum  tag_propagation_policy_t { TPP_DONT = 0 , TPP_ALL_TO_ALL = 1 , TPP_ONE_TO_ONE = 2 , TPP_CUSTOM = 3 }
 enum to represent different tag propagation policies. More...
 

Public Member Functions

virtual float loop_bandwidth () const =0
 Returns the normalized approximate loop bandwidth. More...
 
virtual float damping_factor () const =0
 Returns the loop damping factor. More...
 
virtual float ted_gain () const =0
 Returns the user provided expected gain of the Timing Error Detector. More...
 
virtual float alpha () const =0
 Returns the PI filter proportional gain, alpha. More...
 
virtual float beta () const =0
 Returns the PI filter integral gain, beta. More...
 
virtual float sps () const =0
 Returns the nominal clock period in samples per symbol. More...
 
virtual void set_loop_bandwidth (float omega_n_norm)=0
 Set the normalized approximate loop bandwidth. More...
 
virtual void set_damping_factor (float zeta)=0
 Set the loop damping factor. More...
 
virtual void set_ted_gain (float ted_gain)=0
 Set the expected gain of the Timing Error Detector. More...
 
virtual void set_alpha (float alpha)=0
 Set the PI filter proportional gain, alpha. More...
 
virtual void set_beta (float beta)=0
 Set the PI filter integral gain, beta. More...
 
virtual void set_sps (float sps)=0
 Set the nominal clock period in samples per symbol. More...
 
- Public Member Functions inherited from gr::block
 ~block () override
 
unsigned history () const
 
void set_history (unsigned history)
 
void declare_sample_delay (int which, unsigned delay)
 
void declare_sample_delay (unsigned delay)
 
unsigned sample_delay (int which) const
 
bool fixed_rate () const
 Return true if this block has a fixed input to output rate. More...
 
virtual void forecast (int noutput_items, gr_vector_int &ninput_items_required)
 Estimate input requirements given output request. More...
 
virtual int general_work (int noutput_items, gr_vector_int &ninput_items, gr_vector_const_void_star &input_items, gr_vector_void_star &output_items)
 compute output items from input items More...
 
virtual bool start ()
 Called to enable drivers, etc for i/o devices. More...
 
virtual bool stop ()
 Called to disable drivers, etc for i/o devices. More...
 
void set_output_multiple (int multiple)
 Constrain the noutput_items argument passed to forecast and general_work. More...
 
int output_multiple () const
 
bool output_multiple_set () const
 
void set_alignment (int multiple)
 Constrains buffers to work on a set item alignment (for SIMD) More...
 
int alignment () const
 
void set_unaligned (int na)
 
int unaligned () const
 
void set_is_unaligned (bool u)
 
bool is_unaligned () const
 
void consume (int which_input, int how_many_items)
 Tell the scheduler how_many_items of input stream which_input were consumed. More...
 
void consume_each (int how_many_items)
 Tell the scheduler how_many_items were consumed on each input stream. More...
 
void produce (int which_output, int how_many_items)
 Tell the scheduler how_many_items were produced on output stream which_output. More...
 
void set_relative_rate (double relative_rate)
 Set the approximate output rate / input rate. More...
 
void set_inverse_relative_rate (double inverse_relative_rate)
 Set the approximate output rate / input rate using its reciprocal. More...
 
void set_relative_rate (uint64_t interpolation, uint64_t decimation)
 Set the approximate output rate / input rate as an integer ratio. More...
 
double relative_rate () const
 return the approximate output rate / input rate More...
 
uint64_t relative_rate_i () const
 return the numerator, or interpolation rate, of the approximate output rate / input rate More...
 
uint64_t relative_rate_d () const
 return the denominator, or decimation rate, of the approximate output rate / input rate More...
 
mpq_class & mp_relative_rate ()
 return a reference to the multiple precision rational representation of the approximate output rate / input rate More...
 
virtual int fixed_rate_ninput_to_noutput (int ninput)
 Given ninput samples, return number of output samples that will be produced. N.B. this is only defined if fixed_rate returns true. Generally speaking, you don't need to override this. More...
 
virtual int fixed_rate_noutput_to_ninput (int noutput)
 Given noutput samples, return number of input samples required to produce noutput. N.B. this is only defined if fixed_rate returns true. Generally speaking, you don't need to override this. More...
 
uint64_t nitems_read (unsigned int which_input)
 Return the number of items read on input stream which_input. More...
 
uint64_t nitems_written (unsigned int which_output)
 Return the number of items written on output stream which_output. More...
 
tag_propagation_policy_t tag_propagation_policy ()
 Asks for the policy used by the scheduler to moved tags downstream. More...
 
void set_tag_propagation_policy (tag_propagation_policy_t p)
 Set the policy by the scheduler to determine how tags are moved downstream. More...
 
int min_noutput_items () const
 Return the minimum number of output items this block can produce during a call to work. More...
 
void set_min_noutput_items (int m)
 Set the minimum number of output items this block can produce during a call to work. More...
 
int max_noutput_items ()
 Return the maximum number of output items this block will handle during a call to work. More...
 
void set_max_noutput_items (int m)
 Set the maximum number of output items this block will handle during a call to work. More...
 
void unset_max_noutput_items ()
 Clear the switch for using the max_noutput_items value of this block. More...
 
bool is_set_max_noutput_items ()
 Ask the block if the flag is or is not set to use the internal value of max_noutput_items during a call to work. More...
 
void expand_minmax_buffer (int port)
 
long max_output_buffer (size_t i)
 Returns max buffer size on output port i. More...
 
void set_max_output_buffer (long max_output_buffer)
 Request limit on max buffer size on all output ports. More...
 
void set_max_output_buffer (int port, long max_output_buffer)
 Request limit on max buffer size on output port port. More...
 
long min_output_buffer (size_t i)
 Returns min buffer size on output port i. More...
 
void set_min_output_buffer (long min_output_buffer)
 Request limit on the minimum buffer size on all output ports. More...
 
void set_min_output_buffer (int port, long min_output_buffer)
 Request limit on min buffer size on output port port. More...
 
void set_blkd_input_timer_value (unsigned int timer_value_ms)
 DEPRECATED Configure the timer set when input is blocked port. More...
 
unsigned int blkd_input_timer_value ()
 DEPRECATED Returns timer value set when input is blocked. More...
 
void allocate_detail (int ninputs, int noutputs, const std::vector< int > &downstream_max_nitems_vec, const std::vector< uint64_t > &downstream_lcm_nitems_vec, const std::vector< uint32_t > &downstream_max_out_mult_vec)
 Allocate the block_detail and necessary output buffers for this block. More...
 
buffer_sptr replace_buffer (size_t src_port, size_t dst_port, block_sptr block_owner)
 Replace the block's buffer with a new one owned by the block_owner parameter. More...
 
float pc_noutput_items ()
 Gets instantaneous noutput_items performance counter. More...
 
float pc_noutput_items_avg ()
 Gets average noutput_items performance counter. More...
 
float pc_noutput_items_var ()
 Gets variance of noutput_items performance counter. More...
 
float pc_nproduced ()
 Gets instantaneous num items produced performance counter. More...
 
float pc_nproduced_avg ()
 Gets average num items produced performance counter. More...
 
float pc_nproduced_var ()
 Gets variance of num items produced performance counter. More...
 
float pc_input_buffers_full (int which)
 Gets instantaneous fullness of which input buffer. More...
 
float pc_input_buffers_full_avg (int which)
 Gets average fullness of which input buffer. More...
 
float pc_input_buffers_full_var (int which)
 Gets variance of fullness of which input buffer. More...
 
std::vector< float > pc_input_buffers_full ()
 Gets instantaneous fullness of all input buffers. More...
 
std::vector< float > pc_input_buffers_full_avg ()
 Gets average fullness of all input buffers. More...
 
std::vector< float > pc_input_buffers_full_var ()
 Gets variance of fullness of all input buffers. More...
 
float pc_output_buffers_full (int which)
 Gets instantaneous fullness of which output buffer. More...
 
float pc_output_buffers_full_avg (int which)
 Gets average fullness of which output buffer. More...
 
float pc_output_buffers_full_var (int which)
 Gets variance of fullness of which output buffer. More...
 
std::vector< float > pc_output_buffers_full ()
 Gets instantaneous fullness of all output buffers. More...
 
std::vector< float > pc_output_buffers_full_avg ()
 Gets average fullness of all output buffers. More...
 
std::vector< float > pc_output_buffers_full_var ()
 Gets variance of fullness of all output buffers. More...
 
float pc_work_time ()
 Gets instantaneous clock cycles spent in work. More...
 
float pc_work_time_avg ()
 Gets average clock cycles spent in work. More...
 
float pc_work_time_var ()
 Gets average clock cycles spent in work. More...
 
float pc_work_time_total ()
 Gets total clock cycles spent in work. More...
 
float pc_throughput_avg ()
 Gets average throughput. More...
 
void reset_perf_counters ()
 Resets the performance counters. More...
 
void setup_pc_rpc ()
 Sets up export of perf. counters to ControlPort. Only called by the scheduler. More...
 
bool is_pc_rpc_set () const
 Checks if this block is already exporting perf. counters to ControlPort. More...
 
void no_pc_rpc ()
 If the block calls this in its constructor, it's perf. counters will not be exported. More...
 
void set_processor_affinity (const std::vector< int > &mask) override
 Set the thread's affinity to processor core n. More...
 
void unset_processor_affinity () override
 Remove processor affinity to a specific core. More...
 
std::vector< int > processor_affinity () override
 Get the current processor affinity. More...
 
int active_thread_priority ()
 Get the current thread priority in use. More...
 
int thread_priority ()
 Get the current thread priority stored. More...
 
int set_thread_priority (int priority)
 Set the current thread priority. More...
 
bool update_rate () const
 
void system_handler (pmt::pmt_t msg)
 the system message handler More...
 
void set_log_level (const std::string &level) override
 Set the logger's output level. More...
 
std::string log_level () override
 Get the logger's output level. More...
 
bool finished ()
 returns true when execution has completed due to a message connection More...
 
block_detail_sptr detail () const
 
void set_detail (block_detail_sptr detail)
 
void notify_msg_neighbors ()
 Tell msg neighbors we are finished. More...
 
void clear_finished ()
 Make sure we don't think we are finished. More...
 
std::string identifier () const
 
- Public Member Functions inherited from gr::basic_block
pmt::pmt_t message_subscribers (pmt::pmt_t port)
 
 ~basic_block () override
 
long unique_id () const
 
long symbolic_id () const
 
std::string name () const
 
std::string symbol_name () const
 
std::string identifier () const
 
gr::io_signature::sptr input_signature () const
 
gr::io_signature::sptr output_signature () const
 
basic_block_sptr to_basic_block ()
 
bool alias_set () const
 
std::string alias () const
 
pmt::pmt_t alias_pmt () const
 
void set_block_alias (std::string name)
 
void message_port_register_in (pmt::pmt_t port_id)
 
void message_port_register_out (pmt::pmt_t port_id)
 
void message_port_pub (pmt::pmt_t port_id, pmt::pmt_t msg)
 
void message_port_sub (pmt::pmt_t port_id, pmt::pmt_t target)
 
void message_port_unsub (pmt::pmt_t port_id, pmt::pmt_t target)
 
virtual bool message_port_is_hier (pmt::pmt_t port_id)
 
virtual bool message_port_is_hier_in (pmt::pmt_t port_id)
 
virtual bool message_port_is_hier_out (pmt::pmt_t port_id)
 
pmt::pmt_t message_ports_in ()
 Get input message port names. More...
 
pmt::pmt_t message_ports_out ()
 Get output message port names. More...
 
void _post (pmt::pmt_t which_port, pmt::pmt_t msg)
 
bool empty_p (pmt::pmt_t which_port)
 is the queue empty? More...
 
bool empty_p ()
 
bool empty_handled_p (pmt::pmt_t which_port)
 are all msg ports with handlers empty? More...
 
bool empty_handled_p ()
 
size_t nmsgs (pmt::pmt_t which_port)
 How many messages in the queue? More...
 
void insert_tail (pmt::pmt_t which_port, pmt::pmt_t msg)
 
pmt::pmt_t delete_head_nowait (pmt::pmt_t which_port)
 
msg_queue_t::iterator get_iterator (pmt::pmt_t which_port)
 
void erase_msg (pmt::pmt_t which_port, msg_queue_t::iterator it)
 
virtual bool has_msg_port (pmt::pmt_t which_port)
 
const msg_queue_map_t & get_msg_map (void) const
 
virtual void setup_rpc ()
 Set up the RPC registered variables. More...
 
bool is_rpc_set ()
 Ask if this block has been registered to the RPC. More...
 
void rpc_set ()
 When the block is registered with the RPC, set this. More...
 
virtual bool check_topology (int ninputs, int noutputs)
 Confirm that ninputs and noutputs is an acceptable combination. More...
 
template<typename T >
void set_msg_handler (pmt::pmt_t which_port, T msg_handler)
 Set the callback that is fired when messages are available. More...
 
- Public Member Functions inherited from gr::msg_accepter
 msg_accepter ()
 
 ~msg_accepter () override
 
void post (pmt::pmt_t which_port, pmt::pmt_t msg) override
 send msg to msg_accepter on port which_port More...
 
- Public Member Functions inherited from gr::messages::msg_accepter
 msg_accepter ()
 

Static Public Member Functions

static sptr make (enum ted_type detector_type, float sps, float loop_bw, float damping_factor=1.0f, float ted_gain=1.0f, float max_deviation=1.5f, int osps=1, constellation_sptr slicer=constellation_sptr(), ir_type interp_type=IR_MMSE_8TAP, int n_filters=128, const std::vector< float > &taps=std::vector< float >())
 

Additional Inherited Members

- Protected Types inherited from gr::basic_block
enum  vcolor { WHITE , GREY , BLACK }
 
- Protected Member Functions inherited from gr::block
 block (void)
 
 block (const std::string &name, gr::io_signature::sptr input_signature, gr::io_signature::sptr output_signature)
 
void set_fixed_rate (bool fixed_rate)
 
void add_item_tag (unsigned int which_output, uint64_t abs_offset, const pmt::pmt_t &key, const pmt::pmt_t &value, const pmt::pmt_t &srcid=pmt::PMT_F)
 Adds a new tag onto the given output buffer. More...
 
void add_item_tag (unsigned int which_output, const tag_t &tag)
 Adds a new tag onto the given output buffer. More...
 
void remove_item_tag (unsigned int which_input, uint64_t abs_offset, const pmt::pmt_t &key, const pmt::pmt_t &value, const pmt::pmt_t &srcid=pmt::PMT_F)
 DEPRECATED. Will be removed in 3.8. More...
 
void remove_item_tag (unsigned int which_input, const tag_t &tag)
 DEPRECATED. Will be removed in 3.8. More...
 
void get_tags_in_range (std::vector< tag_t > &v, unsigned int which_input, uint64_t abs_start, uint64_t abs_end)
 Given a [start,end), returns a vector of all tags in the range. More...
 
void get_tags_in_range (std::vector< tag_t > &v, unsigned int which_input, uint64_t abs_start, uint64_t abs_end, const pmt::pmt_t &key)
 Given a [start,end), returns a vector of all tags in the range with a given key. More...
 
void get_tags_in_window (std::vector< tag_t > &v, unsigned int which_input, uint64_t rel_start, uint64_t rel_end)
 Gets all tags within the relative window of the current call to work. More...
 
void get_tags_in_window (std::vector< tag_t > &v, unsigned int which_input, uint64_t rel_start, uint64_t rel_end, const pmt::pmt_t &key)
 Operates like gr::block::get_tags_in_window with the ability to only return tags with the specified key. More...
 
void enable_update_rate (bool en)
 
buffer_sptr allocate_buffer (size_t port, int downstream_max_nitems, uint64_t downstream_lcm_nitems, uint32_t downstream_max_out_mult)
 Allocate a buffer for the given output port of this block. Note that the downstream max number of items must be passed in to this function for consideration. More...
 
- Protected Member Functions inherited from gr::basic_block
 basic_block (void)
 
 basic_block (const std::string &name, gr::io_signature::sptr input_signature, gr::io_signature::sptr output_signature)
 Protected constructor prevents instantiation by non-derived classes. More...
 
void set_input_signature (gr::io_signature::sptr iosig)
 may only be called during constructor More...
 
void set_output_signature (gr::io_signature::sptr iosig)
 may only be called during constructor More...
 
void set_color (vcolor color)
 Allow the flowgraph to set for sorting and partitioning. More...
 
vcolor color () const
 
virtual bool has_msg_handler (pmt::pmt_t which_port)
 Tests if there is a handler attached to port which_port. More...
 
virtual void dispatch_msg (pmt::pmt_t which_port, pmt::pmt_t msg)
 
template<typename Derived >
std::shared_ptr< Derived > shared_from_base ()
 This is meant to be called by derived classes (e.g. block) to get a shared pointer internally. This is needed because std::enable_shared_from_this doesn't seem to work with derived classes in an inheritance hierarchy. More...
 
- Protected Attributes inherited from gr::block
std::vector< long > d_max_output_buffer
 
std::vector< long > d_min_output_buffer
 
unsigned int d_blkd_input_timer_value = 250
 
gr::thread::mutex d_setlock
 
const pmt::pmt_t d_pmt_done
 
const pmt::pmt_t d_system_port
 
- Protected Attributes inherited from gr::basic_block
std::string d_name
 
gr::io_signature::sptr d_input_signature
 
gr::io_signature::sptr d_output_signature
 
long d_unique_id
 
long d_symbolic_id
 
std::string d_symbol_name
 
std::string d_symbol_alias
 
vcolor d_color
 
bool d_rpc_set
 
gr::logger_ptr d_logger
 
gr::logger_ptr d_debug_logger
 Default logger. More...
 
msg_queue_map_t msg_queue
 Verbose logger. More...
 
std::vector< rpcbasic_sptr > d_rpc_vars
 
pmt::pmt_t d_message_subscribers
 

Detailed Description

Symbol Synchronizer block with complex input, complex output.

This implements a discrete-time error-tracking synchronizer.

For this block to work properly, the input stream must meet the following requirements:

  1. if not using the PFB Matched Filter interpolator, and using a non-CPM timing error detector, the input pulses must have peaks (not flat), which usually can be implemented by using a matched filter before this block.
  2. for decision directed timing error detectors, the input pulses should nominally match the normalized slicer constellation, which is normalized to an average symbol magnitude of 1.0 over the entire constellation.

Member Typedef Documentation

◆ sptr

Member Function Documentation

◆ alpha()

virtual float gr::digital::symbol_sync_cc::alpha ( ) const
pure virtual

Returns the PI filter proportional gain, alpha.

See the documentation for set_alpha() for more details.

◆ beta()

virtual float gr::digital::symbol_sync_cc::beta ( ) const
pure virtual

Returns the PI filter integral gain, beta.

See the documentation for set_beta() for more details.

◆ damping_factor()

virtual float gr::digital::symbol_sync_cc::damping_factor ( ) const
pure virtual

Returns the loop damping factor.

See the documentation for set_damping_factor() for more details.

Note that if set_alpha() or set_beta() were called to directly set gains, the value returned by this method will be inaccurate/stale.

◆ loop_bandwidth()

virtual float gr::digital::symbol_sync_cc::loop_bandwidth ( ) const
pure virtual

Returns the normalized approximate loop bandwidth.

See the documentation for set_loop_bandwidth() for more details.

Note that if set_alpha() or set_beta() were called to directly set gains, the value returned by this method will be inaccurate/stale.

◆ make()

static sptr gr::digital::symbol_sync_cc::make ( enum ted_type  detector_type,
float  sps,
float  loop_bw,
float  damping_factor = 1.0f,
float  ted_gain = 1.0f,
float  max_deviation = 1.5f,
int  osps = 1,
constellation_sptr  slicer = constellation_sptr(),
ir_type  interp_type = IR_MMSE_8TAP,
int  n_filters = 128,
const std::vector< float > &  taps = std::vector< float >() 
)
static

Make a Symbol Synchronizer block.

This implements a discrete-time error-tracking synchronizer.

For this block to work properly, the input stream must meet the following requirements:

  1. if not using the PFB Matched Filter interpolator, and using a non-CPM timing error detector, the input pulses must have peaks (not flat), which usually can be implemented by using a matched filter before this block.
  2. for decision directed timing error detectors, the input pulses should nominally match the normalized slicer constellation, which is normalized to an average symbol magnitude of 1.0 over the entire constellation.
Parameters
detector_typeThe enumerated type of timing error detector to use. See enum ted_type for a list of possible types.
spsUser specified nominal clock period in samples per symbol.
loop_bwApproximate normalized loop bandwidth of the symbol clock tracking loop. It should nominally be close to 0, but greater than 0. If unsure, start with a number around 2*pi*0.040, and experiment to find the value that works best for your situation.
damping_factorDamping factor of the symbol clock tracking loop. Damping < 1.0f is an under-damped loop. Damping = 1.0f/sqrt(2.0f) is a maximally flat loop response. Damping = 1.0f is a critically-damped loop. Damping > 1.0f is an over-damped loop.
ted_gainExpected gain of the timing error detector, given the TED in use and the anticipated input amplitude, pulse shape, and Es/No. This value is the slope of the TED's S-curve at timing offset tau = 0. This value is normally computed by the user analytically or by simulation in a tool outside of GNURadio. This value must be correct for the loop filter gains to be computed properly from the desired input loop bandwidth and damping factor.
max_deviationMaximum absolute deviation of the average clock period estimate from the user specified nominal clock period in samples per symbol.
ospsThe number of output samples per symbol (default=1).
slicerA constellation obj shared pointer that will be used by decision directed timing error detectors to make decisions. I.e. the timing error detector will use this constellation as a slicer, if the particular algorithm needs sliced symbols.
interp_typeThe enumerated type of interpolating resampler to use. See the interpolating resampler type enum for a list of possible types.
n_filtersThe number of arms in the polyphase filterbank of the interpolating resampler, if using an interpolating resampler that uses a PFB.
tapsThe prototype filter for the polyphase filterbank of the interpolating resampler, if using an interpolating resampler that uses a PFB.

◆ set_alpha()

virtual void gr::digital::symbol_sync_cc::set_alpha ( float  alpha)
pure virtual

Set the PI filter proportional gain, alpha.

Sets the PI filter proportional gain, alpha. This gain directly multiplies the clock phase/timing error term in the PI filter when advancing the loop. It most directly affects the instantaneous clock period estimate, T_inst, and instantaneous clock phase estimate, tau.

This value would normally be adjusted by setting the loop bandwidth and damping factor. However, it can be set here directly if desired.

Setting this parameter directly is probably only feasible if the user is directly observing the estimates of average clock period and instantaneous clock period over time in response to an impulsive change in the input stream (i.e. watching the loop transient behavior at the start of a data burst).

Parameters
alphaPI filter proportional gain

◆ set_beta()

virtual void gr::digital::symbol_sync_cc::set_beta ( float  beta)
pure virtual

Set the PI filter integral gain, beta.

Sets the PI filter integral gain, beta. This gain is used when integrating the clock phase/timing error term in the PI filter when advancing the loop. It most directly affects the average clock period estimate, T_avg.

This value would normally be adjusted by setting the loop bandwidth and damping factor. However, it can be set here directly if desired.

Setting this parameter directly is probably only feasible if the user is directly observing the estimates of average clock period and instantaneous clock period over time in response to an impulsive change in the input stream (i.e. watching the loop transient behavior at the start of a data burst).

Parameters
betaPI filter integral gain

◆ set_damping_factor()

virtual void gr::digital::symbol_sync_cc::set_damping_factor ( float  zeta)
pure virtual

Set the loop damping factor.

Set the damping factor of the loop. Damping in the range (0.0, 1.0) yields an under-damped loop. Damping in the range (1.0, Inf) yields an over-damped loop. Damping equal to 1.0 yields a crtically-damped loop. Damping equal to 1.0/sqrt(2.0) yields a maximally flat loop filter response.

Damping factor of the 2nd order loop transfer function. When a new damping factor is set, the gains, alpha and beta, of the loop are automatically recalculated.

Parameters
zetaloop damping factor

◆ set_loop_bandwidth()

virtual void gr::digital::symbol_sync_cc::set_loop_bandwidth ( float  omega_n_norm)
pure virtual

Set the normalized approximate loop bandwidth.

Set the normalized approximate loop bandwidth. Useful values are usually close to 0.0, e.g. 2*pi*0.045.

It should be a small positive number, corresponding to the normalized natural radian frequency of the loop as digital low-pass filter that is filtering the clock phase/timing error.

Technically this parameter corresponds to the natural radian frequency of the 2nd order loop transfer function (scaled by Fs), which is the radius of the pole locations in the s-plane of an underdamped analog 2nd order system.

The input parameter corresponds to omega_n_norm in the following relation:

omega_n_norm = omega_n*T = 2*pi*f_n*T = 2*pi*f_n_norm

where T is the period of the clock being estimated by this clock tracking loop, and omega_n is the natural radian frequency of the 2nd order loop transfer function.

When a new loop bandwidth is set, the gains, alpha and beta, of the loop are automatically recalculated.

Parameters
omega_n_normnormalized approximate loop bandwidth

◆ set_sps()

virtual void gr::digital::symbol_sync_cc::set_sps ( float  sps)
pure virtual

Set the nominal clock period in samples per symbol.

Sets the nominal clock period, resetting some of the tracking loop variables to adjust to the new clock period.

Parameters
spsUser specified nominal clock period in samples per symbol.

◆ set_ted_gain()

virtual void gr::digital::symbol_sync_cc::set_ted_gain ( float  ted_gain)
pure virtual

Set the expected gain of the Timing Error Detector.

Sets the expected gain of the timing error detector, given the TED in use and the anticipated input amplitude, pulse shape, and Es/No. This value is the slope of the TED's S-curve at timing offset tau = 0. This value is normally computed by the user analytically or by simulation in a tool outside of GNURadio. This value must be correct for the loop filter gains to be computed properly from the desired input loop bandwidth and damping factor.

When a new ted_gain is set, the gains, alpha and beta, of the loop are automatically recalculated.

Parameters
ted_gainexpected gain of the timing error detector

◆ sps()

virtual float gr::digital::symbol_sync_cc::sps ( ) const
pure virtual

Returns the nominal clock period in samples per symbol.

See the doecumentation for set_sps() for more details.

◆ ted_gain()

virtual float gr::digital::symbol_sync_cc::ted_gain ( ) const
pure virtual

Returns the user provided expected gain of the Timing Error Detector.

See the documentation for set_ted_gain() for more details.


The documentation for this class was generated from the following file: