ELEC 470, Spring 2004
Prof. Rich Kozick

Homework 7


Date Assigned: Friday, March 5, 2004
Date Due: Thursday, March 11 and Tuesday, March 23, 2004

  1. Reading: Please continue studying Chapter 4 of the Lathi text on amplitude modulation, Sections 4.1 - 4.9.

  2. Special Topic Reports: Recall from the course syllabus the "special topic reports" that students will investigate individually or in pairs and present to the class. Some possible topics for special topic reports are available at
    http://www.eg.bucknell.edu/~kozick/elec47004/proj_ideas.html

    If you have not done so already, please send me an email note with potential topics and the name of your partner (if any).

  3. Problems: Please solve the following problems in the Lathi text and submit your solutions on the date specified. Appendix D.6 contains trigonometric identities that you might find useful.

    Due on March 11:

    All students: Problem 4.4-1.

    The following questions relate to the Simulink programs am_env.mdl, am_env_filt.mdl, dsb_coh.mdl, costas_init.m, and costas_demo.mdl, which are available from the course home page under Demonstrations and Class Notes. Instructions for running the programs are given on the Web page.

    1. In the AM demo am_env.mdl, what are the considerations in choosing the value of the "slider gain"?
    2. In the DSB-SC demo dsb_coh.mdl, investigate the effect of a phase shift between the transmitter and receiver oscillator. Relate your observations to the analysis in problem 4.4-1.
    3. In the DSB-SC demo dsb_coh.mdl, investigate the effects of a frequency error between the transmitter and receiver oscillator. Relate your observations to the analysis in problem 4.4-1.

    Due on March 23:

    All students: Problems 4.5-1 (part a only) and 4.5-2 (part a only).
    Graduate students: Problem 4.5-5.

  4. Graduate Students: (extra credit for undergraduates!)

    Develop a Simulink program that modulates two separate messages m1(t) and m2(t) onto a single carrier frequency using quadrature amplitude modulation (QAM) as described in Section 4.4 of the Lathi text. For example, you might make m1(t) and m2(t) sine waves with different frequencies. Demonstrate the effects of frequency and phase errors on the demodulated signals, and explain your results analytically based on problem 4.4-1.

    I will ask each graduate student to demonstrate their programs to the class on Tuesday, March 23.

Thank you.