# I'm struggling to find a way to filter the ECG signal and make modulation for the other signals

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Yousef Ahmed2022-10-24

Implement using MATLAB all of the modulation and demodulation techniques are given :
1. Amplitude modulation and demodulation
2. Frequency modulation and demodulation
The message signal used in all modulation techniques given in 1 and 2 are:
• Sinusoidal m(t) with amplitude Am=1 VP and fm is 100Hz while the carrier amplitude is Ac=2 VP with frequency fc=40 kHz
• Sinusoidal m(t) with amplitude Am=2 VP and fm is 100Hz while the carrier amplitude is Ac=2 VP with frequency fc=40 kHz
• ECG signal (attached) the carrier amplitude is Ac=2 VP with frequency fc=40 kHz
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William Rose 2022-11-23
What is VP?

### 回答（1 个）

William Rose 2022-11-23
@Yousef Ahmed, please make an attempt. Then others will assist.
For all of these, the carrier wave is fc=40 kHz. Therefore it makes sense to use a sampling rate (fs) that is five or (preferably) ten times faster than fc. That way each cycle of the carrier will have enough samples to represent it well.
Here is a start for the first case.
fc=4e4; % carrier frequency (Hz)
fs=10*fc; % sampling rate (Hz)
t=0:1/fs:1; % time vector, duration 1 sec
fm=100; % freq. of m(t) (Hz)
m=VP*sin(2*pi*fm*t); % m(t)
m is the signal you will use to modulate the carrier. You should get back a signal very similar to m when you do the demodulation. The second case will be similar, but the amplitude of m will be 2*VP. In the third case, m will be the EKG signal. In the third case, you will need a 10 second long time vector to match the EKG duration, and you will need to deal with the fact that the EKG is sampled at 1 kHz.
You work on the rest. Good luck!

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