Question

In Lab 2, you learned

- various plotting techniques

- how to create an exponentially faded version

of a given sinusoidal signal.

In this assignment, you will be working with two sinusoidal

signals. The higher-frequency signal

c(t) = cos(2*pi*F*t) (where F is in Hertz)

will be referred to as "carrier"; while the lower-frequency

signal

v(t) = 1.5 + cos(2*pi*f*t + q) (f in Hz, again)

will be referred to as "envelope". Note that the envelope has

a positive offset of 1.5 units.

In amplitude modulation (AM), the envelope multiplies the carrier

and the resulting product signal

x(t) = v(t)*c(t)

is the AM signal.

_________________________________________________________________

Your code should generate three signal vectors. Plot them in a

SINGLE figure consisting of THREE subplots (3 rows, 1 column).

The SUBPLOT function should be used. EACH subplot should have

labels on the horizontal and vertical axes, and also the

appropriate title:

CARRIER, AM SIGNAL 1 and AM SIGNAL 2

(i) Suppose that F = 200 Hz (above). Create a time vector td

that contains 800 samples of c(t), spanning 50 periods.

td should have the form

td = 0 : d : 50*T-d

where T is the period of c(t) and d is to be determined.

(ii) Let c be the vector of values c(t), where t ranges over

td (of part (i)). Plot c against td (first plot,

"CARRIER").

(iii) Determine f and q such that the envelope v(t) completes

exactly four periods while c(t) completes (exactly) 50

periods; and v(0) = 2.5 (maximum possible value).

Plot x(t) = v(t)*c(t) for this case, where t ranges

over td from part (i). Label this plot as "AM SIGNAL 1".

(iv) Determine f and q such that the envelope v(t) completes

exactly 7.5 periods while c(t) completes (exactly) 50

periods; and v(0) = 0.5 (minimum possible value).

Plot x(t) = v(t)*c(t) for this case also, where t again

ranges over td. Label this plot as "AM SIGNAL 2"

Answer 1