gr::satellites::doppler_correction Class Reference

Performs Doppler correction using a frequency vs. time file. More...

#include <doppler_correction.h>

Inheritance diagram for gr::satellites::doppler_correction:

Public Types
typedef std::shared_ptr< doppler_correction >	sptr

Public Member Functions
virtual void	set_time (double t)=0
	Sets the current time.
virtual double	time ()=0
	Returns the current time.
virtual double	frequency ()=0
	Returns the current frequency in Hz.

Static Public Member Functions
static sptr	make (const std::string &filename, double samp_rate, double t0, const std::string &timesync_tag="")
	Build the Doppler Correction block.

Detailed Description

Performs Doppler correction using a frequency vs. time file.

The Doppler Correction block uses a text file listing frequency vs. time to perform Doppler correction on its input signal. The same block can be used for Doppler simulation by inverting the frequency values in the input file or by taking the complex conjugate of the output of the block.

The text file should contain lines with a timestamp and a frequency separated by a space. The timestamps are given in seconds, and typically consist of UNIX time. The t0 parameter in the block constructor gives the starting time, which is the timestamp corresponding to the first sample processed by the block. As long as the timestamps in the file and this timestamp are consistent, the block will work correctly. The frequencies are given in Hz.

The block can also use time tags such as those generated by the UHD Source block to update its internal timestamp. In this case the timestamps in the file should use UNIX seconds, since the UHD timestamps also use UNIX seconds. When using UHD time tags, the t0 parameter can be left as 0.

The Doppler correction block interpolates the frequency linearly between each pair of entries in the text file, and generates a correction with continuous phase.

An optional time synchronization tag functionality is provided, mainly intended for uplink Doppler correction of burst transmissions. When this tag is received, the Doppler correction block sets its internal time to the current UNIX time of the PC. Usually, the "packet_len" tag at the beginning of the burst is used as time synchronization tag.

Member Typedef Documentation

sptr

typedef std::shared_ptr<doppler_correction> gr::satellites::doppler_correction::sptr

Member Function Documentation

frequency()

virtual double gr::satellites::doppler_correction::frequency ( )

pure virtual

Returns the current frequency in Hz.

Implemented in gr::satellites::doppler_correction_impl.

make()

sptr gr::satellites::doppler_correction::make ( const std::string & filename, double samp_rate, double t0, const std::string & timesync_tag = "" )

static

Build the Doppler Correction block.

Parameters

filename	Path of the text file describing the Doppler data
samp_rate	Sample rate
t0	Timestamp corresponding to the first sample
timesync_tag	Tag used to trigger time synchronization to the current PC clock

set_time()

virtual void gr::satellites::doppler_correction::set_time ( double t )

pure virtual

Sets the current time.

Parameters

t	Tiemstamp corresponding to the current time.

Implemented in gr::satellites::doppler_correction_impl.

References t.

time()

virtual double gr::satellites::doppler_correction::time ( )

pure virtual

Returns the current time.

Implemented in gr::satellites::doppler_correction_impl.

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

• doppler_correction.h