orbdemod 0.1.0

ORBCOMM satellites downlink signal demodulator

Orbcomm_Demodulator

Orbcomm_Demodulator is a Python-based toolkit for demodulating ORBCOMM satellite downlink signals.
This project was originally developed to process raw voltage data captured by the 21CMA (21 Centimeter Array) radio telescope, and aims to provide a complete, standardized processing pipeline from raw samples to decoded ORBCOMM data packets.

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Core Pipeline Features

The demodulation chain includes:

• Digital Down Conversion (DDC) for raw high-rate samples.
• Symbol Timing Recovery using Gardner TED and Farrow interpolator.
• Carrier Phase Recovery via a 2nd-order Costas Loop.
• Differential Decoding and Frame Synchronization.
• Fletcher-16 Checksum with 1-bit Error Correction (ECC).

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Installation

You can install the package directly from GitHub using:

pip install git+https://github.com/JinYi1108/Orbcomm_Demodulator.git

For development and debugging, an editable installation is recommended:

git clone https://github.com/JinYi1108/Orbcomm_Demodulator.git
cd Orbcomm_Demodulator
pip install -e .

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Examples and Test Data

Example scripts are provided in the examples/ directory. Due to storage limits, large raw datasets are hosted on Zenodo.

1. Raw Voltage Data (21CMA)

• File: 20250415-1940-0.dat (approx. 8 GB)
• Source: Raw voltage data recorded by the 21CMA radio telescope.
• Download: Available on Zenodo (DOI: 10.5281/zenodo.18213739)

2. DDC Processed IQ Data (21CMA)

• File: raw_data/iq_data_0.dat
• Description: This is the IQ data generated from the raw 21CMA .dat file after Digital Down Conversion (DDC). It is provided for quick testing of the backend stages (STR, Costas, etc.).

3. Test Data (from ORBCOMM-receiver)

• File: raw_data/1552071892p6.dat
• Description: Derived from the original 1552071892p6.mat from Frank Bieberly's project. It has been downsampled and filtered to a baseband IQ format.

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Acknowledgements

This project is developed based on ORBCOMM-receiver project by Frank Bieberly (https://github.com/fbieberly/ORBCOMM-receiver).