Lab Handout
Analysis of an Over-Sampling DSP System

Implement and analyze a basic over-sampling DSP system that includes digital anti-aliasing and digital anti-imaging filters. The project is shown in block diagram form below:

The pseudo-analog signal is to emulate the following analog signal:

Notice that since the bandwidth of interest (W) is up to 500 Hz, the last 1 kHz sinusoid represents an unwanted signal component (noise.)

At various stages of the DSP system, generate frequency spectra of the signal, designated by S1, S2, S3, etc. Compare and contrast the spectra at these various stages by answering the questions posed below.

Procedure and Analysis

Use the analog MATLAB m-file (instructor provided) to construct s(t). Use the following specifications to construct the pseudo-analog signal

Length of the signal: 1000 ms
Sampling rate: 64 kHz

Create the over-sampled digital signal from the pseudo-analog signal using the instructor m-file sample. This is the “test signal” for further processing.

Design a digital low-pass filter of order 500 with a Blackman window and a cutoff frequency of 500 Hz at the over-sampling rate. Use this filter to process the test signal in the blocks labeled “low-pass filter.”

Process the test signal according to the block diagram above.

Conduct a spectrum analysis of the test signal at various stages of processing. Include in the report graphs of the spectra of the signal as follows (use the instructor m-file dtft_demof). [Note: depending on the speed of your computer the DTFT computations can take time; be patient.]

Spectrum Range – Hz No. of freq. points Fs S1 0 to 1200 4000 16000 S2 0 to 1200 4000 1000 S3 0 to 3500 8000 16000 S4 0 to 3500 8000 1000 S5 0 to 3500 8000 16000 S6 0 to 3500 8000 16000

Include in your report a discussion that addresses the following questions. (Concentrate on the presence or absence and position of frequency components in the…