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C++/octave code for analyzing signals on VLF,LF,MF,HF
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README.md

signal-analysis

C++/octave code for analyzing signals on VLF,LF,MF,HF


Prerequisites

Installation

Contents

FSK bit stream extraction

m/analyze_fsk.m

LFSR detection

m/lfsr_test.m

PLL

m/pll_init.m initialization of PLL state to be used together with src/pll_cc.cc

Viterbi decoder (rate 1/2 constraint length k=N)

include/viterbi2.hpp using add-compare-select butterfly operations without preprocessor macros but is within 15% of the KA9Q implementation.

include/viterbi2_simple.hpp a more simple implementation which is slower than the one above but may be more suited for SIMD

STANAG 4285 decoder

Implementation along the STANAG 4285 specification

include/s4285_frame_detector.hpp synch sequence detection and doppler and carrier offset estimation

include/s4285_channel_estimator.hpp adaptive LMS filter with decision feedback for channel estimation and equalization

include/s4285_bitstream_decoder.hpp deinterleaver and viterbi decoder with soft symbol input

src/s4285_cc.cc octave interface

Currently the 600,1200,2400 baud modes with long interleaver are supported. The 2400 baud mode is untested since I did not find any signal on air using this mode

T-207 test

m/T207_test.m detects the presence of T-207 checksums in a given bit stream

USB to IQ mode conversion

m/r2ct.m converts a given wav file recorded with USB mode into a new wav file in IQ mode where the signal of interest is shifted to 0Hz

MSK demodulator

m/demo_msk.m demodulated MSK signals and extracts the bit streams

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