Step by step sequence of how the receiver was created.
The following section describes, in sequence, how the image was received and reconstructed.
Recording the signal
The receiver records the transmitted signal through the use of Matlab’s audio recorder object.
Removing the delay
The recorded signal is convolved with a time reversed version of the chirp signal appended to the transmitted signal. Since the chirp signal is unlikely to be similar to any other signal in the received waveform, the spike in the aforementioned calculation will be where the BPSK modulated signal begins in time in the recorded signal.
Demodulating the bpsk signal
In order to decode the BPSK analog waveform into bits, the dot product of each analog sine wave representing a bit in the recorded message is taken with sin(2 Pi fc t)and -sin(2 Pi fc t). If the dot product withsin(2 Pi fc t) is bigger, a 0 is chosen; otherwise, a 1 is chosen.
Decoding the bits
After reconstructing a coded bit string from the analog waveform, the 7-4 Hamming encoded bits are decoded using Matlab’s built in decode function.
Reconstructing the image
Finally, the decoded bit string is converted into the original image using the opposite process that the transmitter used to create a string of bits from an image.
