This code is part of the assignment given for the course Digital Communication. We use a standard binary data as an input signal, (randomly generated 16bit array in code).
The dependencies required for the compilation in python3 are:
- Numpy
- Scipy
- Matplotlib
These can be installed using the command line / Terminal commands as :
pip install numpy pip install scipy pip install matplotlib After installing the dependencies, you can download this repository and continue to execute FSK.py using python3.
FSK.py is the core file for Frequency Shift Keying of a digital input datastream. It consists of namely 2 trivial functionsFSKgen(inpSig, fskFreq1, fskFreq2) and FSKdemod(FSKsig)which are used to modulate a FSK waveform and demodulate a digital bitstream from the generated FSK respectively.
The input arguments to the modulator are inpSig which is the 16bit input data to be modulated with 2 frequencies fskFreq1,fskFreq2 that becomes the carrier frequencies for bits 1&0 respectively. Since the output signal is a continous time signal, we sample the signals at a sampling rate for each symbol or bit, I have used a sampling rate of 100samples/bit. Thus for a 16bit sequence we obtain total of 1600samples.
We use 100samples of a standard sinewave of frequency fskFreq1 for bit1 and 100samples of standard sinewave of frequency fskFreq2 for bit0.
After iterating for every bit in the 16bit sequence, we obtain the FSK signal which has Frequency fskFreq1 if bit is 1 and fskFreq2 if bit is zero.
The output FSK for sequence [1101100011001000] is :
Upon doing Fourier transform of the FSK signal, we obtain 2 significant peaks at the 2 FSK frequencies used :
Passing the FSK signal to the function FSKdemod() gives the demodulated bit sequence by using a frequency detection technique(zero crossing) :
