CP/PC364 Data Communications & Networks Laboratory

Amplitude Shift Keying

Overview

Amplitude Shift Keying is the process of using amplitude modulation with discrete (i.e. digital) inputs.

In contrast to the amplitude modulation lab we will be using a square wave for the control voltage to modify the signal. We will be using the XR-2206 chip exactly as in the AM lab to develop the carrier frequency as a sine wave.

Datasheet: XR2206 [Copyright 1972 EXAR Corporation. Datasheet June 1997]

Objectives

1. Develop a sinusoidal wave with minimum distortion
2. Examine amplitude modulation

Setup

Use the circuit from the AM lab for sine wave generation with minimum distortion.

Exercise - AM modulation

Square Wave

1. Using the frequency generator create the signal you will be sending.
   • Connect the frequency generator to the oscilloscope to see the waveform you are creating.
   • Modify the frequency to give a 10 Hz square wave.
   • Modify the amplitude and offset to get a wave with amplitude between -V_cc/2 and V_cc/2.
2. Connect the square wave to the dc bias input.
3. Connect the oscilloscope so that both the square wave from the frequency generator and the output of the XR-2206 chip are visible on the screen.
   • Print the waveforms (input and output together) and paste it in your lab notebook.