关键词 > ECE4163/ECE6183
ECE 4163 / ECE 6183 DSP Lab Complex Amplitude Modulation: Exercises
发布时间:2022-10-28
Hello, dear friend, you can consult us at any time if you have any questions, add WeChat: daixieit
Complex Amplitude Modulation: Exercises
DSP Lab (ECE 4163 / ECE 6183)
2019
In a previous lab we used amplitude modulation (AM) to affect a speech signal. This method computes the output signal as
y(t) = x(t) cos(2πf1 t). (1)
This AM method can lead the spectrum of the signal x to overlap itself. To shift a speech signal to a higher frequency without causing spectral overlapping as in Figure 1, we can use complex AM. This method is shown in the Matlab demo programs.
1 Exercises
1. Using an input wave file of your choice, use Matlab to implement complex AM (like in the Matlab demo file).
2. Use Python to obtain the same output signal as in Matlab using the same input wave file as in the preceding part. Your Python output should be the same as your Matlab output.
3. Real-time complex AM. Implement real-time complex AM in Python with PyAudio. Your pro- SUBMIT
gram should take the microphone signal as input and produce an output audio signal (on speakers or headphones). Compare the sound with real-valued AM in equation (1) which was implemented earlier in the course. To avoid feedback issues and to hear the signals clearly, it is recommended to use headphones or earbuds to compare the audio of the two methods.
x(t) [SIGNAL]
0.6
0.4
0.2
0
−0.2
−0.4
−0.6
−0.8
50
40
30
20
10
−2000 −1500 −1000 −500 0 500 1000 1500 2000
Frequency (Hz)
==
y(t) = real[g(t)] [OUTPUT SIGNAL]
0.3
0.2
0.1
0
−0.1
−0.2
−0.3
−0.4
25
20
15
10
5
−2000 −1500 −1000 −500 0 500 1000 1500 2000
Frequency (Hz)
Figure 1: Complex AM