question archive Digital Communications Prac 2 Demodulating AM recorded signal: A standard AM modulated signal is generated in Matlab and transmitted (low power transmission) over the air using an SDR USRP X310
Digital Communications Prac 2 Demodulating AM recorded signal: A standard AM modulated signal is generated in Matlab and transmitted (low power transmission) over the air using an SDR USRP X310
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Digital Communications Prac 2
Demodulating AM recorded signal:
A standard AM modulated signal is generated in Matlab and transmitted (low power transmission) over the air using an SDR USRP X310. The signal is then recorded using an RTL-SDR for 20 seconds. The sampling frequency of the recorded signal is 240kHz. To load the signal into the Matlab, use load('AMRecordedSamples.mat'). Make sure that the recorded signal file is in the working directory of the Matlab.
The students are required to
i) design a non-coherent AM demodulator in Matlab (see lecture notes for non-coherent AM demodulator) and run the demodulator on the recorded signal. Play the demodulated signal in Matlab using the “sound” command. Before playing the signal, remember you need to resample the demodulated signal to the sample rate which the sound card on your computer can process. Most sound cards work with 48KHz. For resampling you can use the Matlab command “resample”. If your demodulator is working correctly, you will listen to a message in the recorded signal.
ii) Write a one-page report on how you design your demodulator. Your report should answer these questions: i) did you listen to the message in the recorded signal? ii) Is the message clear or noisy? If the message is noisy, can we reduce the noise by passing it through the low pass filter in Matlab?
