# ECE 3500 – Introduction to Signals and Systems – Labs

**Project: Cardiac Pacemaker Communication System – FSK Transceiver**

ECE 3500 Course Website

Digital Lab Equipment Documentation and Tutorials

This is a five week long experiment about frequency and amplitude modulation. Using electronic components, students build a frequency shift keying (FSK) circuit. Both modulator and demodulator modules are constructed and tested. The carrier frequencies used here are 1 kHz and 5 kHz, for representation of logical 0 and 1, respectively. We have purposefully chosen these low frequencies to allow straightforward prototyping in the laboratory using bread boards. The concepts from this experiment are expanded in the EM class where students build the FSK system in the MHz range.

## Lab 1 – Fourier Transform and Signal Analysis

Objectives

- To experiment with synthesizing and analyzing musical notes
- To become familiar with Fourier/spectral analysis of signals
- To become familiar with some signal processing capabilities of MATLAB

ProcedureThis assignment consists of three parts. In the first part, you will become familiar with Fourier analysis in MATLAB. In the second part, you will verify the correctness of the signal you generated by comparing the Fourier transform of the first eight notes in the "music" signal and making sure that the dominant frequency components in each note correspond to the fundamental frequency and any harmonic frequencies you have included. In the third part, you will attempt to identify a short piece of music that you download from the class homepage. To verify the accuracy of identification, you will synthesize the same music according to the identified music and compare the results with the original piece.

Lab Documents:

- Pre-Lab Assignment
- Lab Assignment
- MATLAB file: beethove.m

## Lab 2 – Design of a Digital Communication System

OrganizationThis lab is split into three parts:

- Implementation of the FSK Generator
- Implementing the DSBSC amplitude modulator and demodulator.
- Implementation of the decision circuitry to recover the digital signal from the demodulated signal and combining all the above circuits and testing the complete communication system.

Lab Documents

- Lab Assignment
- Supplementary documentation
- MATLAB files: TX.m, FSKmod.m, spec_analysis.m

Helpful Documents

## Lab 3 – Design and Simulation of a BPSK System

ObjectivesIn this experiment, you will familiarize yourself with another type of modulation which is called binary phase-shift keying (BPSK). BPSK is a double side band suppressed carrier modulation scheme for binary signals. In BPSK, an information bit b controls the phase of a carrier cos(ωct). For example, one may choose to transmit cos(ωct) if the information bit is 1, and cos(ωct+π)=−cos(ωct) if the information bit is 0. In this experiment, we also examine the fact that the receiver is unaware of the exact frequency and phase of the carrier used by the transmitter; and thus a method of carrier phase and frequency recovery is introduced and examined.

Lab Documents

- Lab Assignment
- MATLAB files: text2bin.m, bin2text.m, TestPLL.m, testtext.mat