Wavetek 132 Spezifikationen PDF herunterladen (Seite 73)

As

before,

the

Wavetek

132

is

the

message

signal.

Set

up

the

Wavetek

132

to

produce

a

1

V

pp,

1kHz

square

wave,

with

the

attenuation

set

to

-20

dB.

The

Wavetek

186

is

the

carrier

signal.

Set

the

attenuation

to

-20dB

and

change

the

frequency

to

10

kHz.

b)

Demonstrate

the

fundamental

characteristic

of

an

FM

wave,

the

frequency

deviation

(maximum

departure

from

the

carrier

frequency)

is

directly

proportional

to

the

amplitude

of

the

modulating

wave.

Q:

What

is

the

time

domain

representation

of

this

wave?

View

the

spectrum

of

the

FM

wave.

Adjust

the

attenuation

on

the

132

until

the

carrier

is

nulled.

Print

the

oscilloscope

and

spectrum

analyzer

displays.

Q:

In

the

time

domain,

find

positive

frequency

deviation

(f")

and

the

negative

frequency

deviation

(

f")

using

the

crosshairs

of

the

oscilloscope.

What

is

the

peak

frequency

deviation?

What

is

the

modulation

index

(ß)?

Measure

2Af

on

the

spectrum

analyzer

for

this

value

of

ß?

Q:

Using

Carsons

rule,

what

is

the

bandwidth

for

this

signal?

Q:

Switch

the

message

signal

to

a

sine

wave.

Q:

What

is

the

frequency

representation

of

the

FM

sine

wave?

Q:

Measure

f,

f

and

2Af.

What

is

the

frequency

deviation,

ß

and

the

bandwidth?

We

will

demodulate

a

FM

signal

in

laboratory

5.

Lab

3

Page

8

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