QAM Modulation, Demodulation, Detection, and Eye Diagrams

Use 4-QAM baseband modulation to send 20 bits (bits 10010 01010 on I and bits 11101 01001 on Q) at an overall transmission rate of 2 bits per millisecond using three pulse shapes given below. Use a carrier whose frequency is 10kHz.

Plot the following signal in time and frequency domain for each pulse shape:

1. Pulse/baseband modulated inputs (2 plots – 1 for I and 1 for Q/domain)
2. Transmitted up-converted 4-QAM signal (1 plot/domain)
3. Filtered down-converted output (2 plots – 1 for I and 1 for Q/domain)

Eye diagrams should be plotted for the two waveforms (I and Q) taken just before detection blocks.

Need to build three systems based on the following three pulse shapes

• Square wave
• Raised Cosine with r=.5
• Raised Cosine with r=1

Answer 1

[Arthi Sathyamurthi]

Since this seems like a homework assignment, if you can provide the code you've written to solve the problem and ask a specific question about where you're facing difficulty, we may be able to provide some guidance.But on a high level overview, to completely simulate QAM modulation and demodulation use qammod and qamdemod functions and further to generate eyediagram use the eyediagram function. Further to develop a system using raised cosine use raised-cosine-filtering function