SatRFE Simple radio frontend for custom processing - Receives samples from SDR device and extracts sub-band and finally sends IQ samples in float pairs via ZeroMQ

In current version the frame is (SymbolRate x Oversample ratio) wide. This is the DEMODULATOR_SAMPLERATE constant

For example :

• Symbol Rate is 9600 , Oversample Ratio = 4
• we have a sampling rate of 38400 Hz
• DEMODULATOR_SAMPLERATE = 38400

To avoid RX Dc at center and enable energy detction (power based or autocorrelation), we shift the subband of interest by FRAME_OFFSET_LOW Hz + DEMODULATOR_SAMPLERATE/2

    example : Offset set at 10 000 Hz 
    sub-band is centered at (FRAME_OFFSET_LOW Hz + DEMODULATOR_SAMPLERATE/2)       
    =10 000 + 38400/2
    = 29200 Hz

Finally: if frequency of interst is f0 : - receiver is tuned to f0 -> we have a DC residual - we extract a subwindow (using Overalp/save channelizer) of (SymbolRate x Oversample ratio) Hz - This subband is not centered at f0, but at f0 - FFAME_OFFSET_LOW Hz + DEMODULATOR_SAMPLERATE/2

  example : 
    - you want to extract signal Symbol Rate is 9600 , Oversample Ratio = 4, centered at f = 436.500 MHz
    - DEMODULATOR_SAMPLERATE = 38400
    - (FRAME_OFFSET_LOW Hz + DEMODULATOR_SAMPLERATE/2)= 29200 Hz
    - Rx is tuned to f = 436.500 MHz - 29200 Hz ;
    - Channelizer (ddc) is centerd at +(FRAME_OFFSET_LOW Hz + DEMODULATOR_SAMPLERATE/2) = 29200
    - Received bandwidth is DEMODULATOR_SAMPLERATE = 38400

Required Qt Modules :

qt5-default libqt5svg5-dev

Required librairies :

• libusb-1.0-0-dev
• libgps-dev (connects to gpsd to retrieve time, otherwise on fail uses system time)
• libfftw3-dev
• libczmq-dev

### clone the repository, then from the folder :

• generate makefile : qmake

• compile make

• run ./picsatRF

  Current version only supports RTLSDR (FunCube to come)

Configuration

on startup looks for existing (or creates a new one) configuration file called picsatrfe.conf in program dir example

[Radio] RX_FREQUENCY=436.4708

[WebServer] port=8001

Webserver for remote control

Unless http port is set to 0 in config file, starts a http server listening by default on port 8001

supported requests are so far :

• http://<< ip >>:<< port >>/start
• http://<< ip >>:<< port >>/stop
• http://<< ip >>:<< port >>/status : returns a description of the current status (ongoing, not finished)
• http://<< ip >>:<< port >>/tune/ tunes to desired freq for example : * http://<< ip >>:<< port >>/tune/438.256 to receive 438.256000 MHz