PopoSDR

Warning

This code is still experimental and was only tested on very specific conditions.

C/C++ Based SDR library with multithreaded pipelined DSP blocks

Available Blocks:

Sources:

• Network Source (UDP or TCP | Server or Client) ✅

Sinks:

• Terminal Sink (F32 or CF32) ✅

Filters:

• FIR Filter (Decimating or Interpolating) ✅
• Polyphase FIR (Decimating or Interpolating) ✅ - "Faster" Polyphase implementation useful for resampling.
• FIR Taps Generator (Gaussian, Lowpass, Root Raised Cosine) ✅
• CIC Filter (Decimating or Interpolating) ⚠️

General:

• AGC (Automatic Gain Control) ✅
• FM Modulator ✅
• FM Demodulator (Differentiate & Delay) ⚠️
• Constellation Mapper (Converts Bits to Symbols) ✅
• Constellation Demapper (Converts Symbols to Bits) ✅

Synchronizers:

• Carrier Recovery (Decision-Directed, ML) ✅
• Timing PLL (Decision-Directed Timing Recovery) ⚠️

Utils:

• Wave File Writing (.wav) for debugging tests

Some blocks are [EXPERIMENTAL] and marked with the ⚠️ this means they have some strange behaivour in some cases or just haven't been tested enough.

Modems (STILL IN DEV)

• Afsk Modulator (BELL 202 Like 1200Bd FSK Modulator)

• Gmsk Modulator (GMSK 4800bd Modulator)

Little Build Guide:

You will need a C++ Compiler with support for C++17 or greater, CMake and Make or Ninja...

1 - Clone the repo and cd into it:

git clone https://github.com/Paulo-D2000/PopoSDR.git
cd PopoSDR

2 - Now create a build folder and run cmake inside:

mkdir build
cd build
cmake ..

3 - Then run make OR ninja:

make

ninja

4 - Try some examples :)

Examples (EXPERIMENTAL)

Simulation:

• AFSK Test ✅ - Generates AFSK Packets and demodulates them writing some debug Wave files.

• GMSK Test ✅ - Generates GMSK Packets with CCSDS Syncword and demodulates them printing the detected syncwords, also writes debugging Wave files.

• Main Test ⚠️ - This is just some general testing code, ignore it please.

Network sources:

• WFM Mono UDP ✅ - Reads S16-LE IQ samples at 1 MHz SampleRate from one local UDP client on port 1234 feeds them to one WFM (Wide FM Station) demodulates the Mono chanel and writes one 48KHz S16-LE audio stream on stdout.

• GMSK Rx ⚠️ - Reads S16-LE IQ samples at 1MHz SampleRate from one local TCP server on port 1234 feeds them to a 1200Bd GMSK BT=0.5 demodulator that searches for the 0x1ACFFC1D Syncword and prints their data to stderr. It also outputs one S16LE 4800Hz stream on stdout for debugging.

• QAM RX ⚠️ - Reads S16-LE IQ samples at 48KHz SampleRate from one local TCP and feeds them to the experimental 16-QAM Demodulator outputting the synchronized IQ symbols via stdout as one 6000Hz IQ S16-LE stream... This is still on the testing phase!

Info:

• S16-LE - 16 bit signed integer
• IQ - Quadrature signal, 2 channels, Real & Imaginary
• The TimingPLL Block has 2 variants, Real (F32) and Complex (CF32), the first one was inspired on DireWolf's AFSK PLL while the second one uses a Maximum Likelyhood (ML-TED) with a Polyphase FIR Bank Interpolator. The Interpolator can set to (MMSE) 'Minimum Mean Square Error' having 128 arms or to (PFB) 'Matched Polyphase FIR Bank' with a variable number of filter arms.

// TODO

• ✅ Upload code.
• ✅ Get a modem example working.
• ✅ Fix the modulator code to generate the GMSK waveform again - AFSK1200 right now...
• ✅ Split the lib and modem code
• ⬜ Refactor modulator code.
• ⬜ Make the demodulator class & cleanup main
• ⬜ Make a modem class.
• ✅ Move main code to examples
• ✅ Setup CMake to build the lib / modems / examples
• ⬜ Refactor the TimingPLL class.
• ⬜ Add one build guide.
• ⬜ Document some of the API.
• ⬜ Add more blocks.

// Future plans / Goals

• ✅ Implement AFSK modulator
• ✅ Implement one PSK modulator
• ⬜ Implement one Burst PSK demodulator (FFT-based)
• ✅ Implement one Decision directed synchronizer (a * conj(â))
• ⬜ Add SoapySDR ?
• ⬜ Add one Example with Real Harware + SDR Modem
• ⬜ Implement more advanced synchronizers
• ⬜ Complete GMSK modem
• ⬜ Complete FSK / AFSK modems
• ⬜ Complete M-PSK / QAM / APSK modems
• ⬜ Add OFDM ?
• ⬜ Add DSSS / CDMA ?