Wavetek 132 Spezifikationen PDF herunterladen (Seite 16)

the

input,

the

output

of

the

envelope

detector

and

the

radio.

Transmission

of

the

signal

also

incorporates

the

use

of

the

HP8656B

signal

generator.

Using

the

summer

circuit

of

laboratory

1,

two

tones

are

added

to

produce

a

double

tone

signal.

The

AM

exercise

is

repeated

using

the

double

tone

signal.

FM

signals

are

generated

using

the

same

equipment

as

the

AM

signals.

For

sine

wave

and

square

wave

messages,

the

frequency

deviation,

bandwidth

and

modulation

indexes

are

measured

and

compared

with

theory.

Theoretical

Carson's

rule

calculations

are

compared

to

measurements

[Ref.

3].

E.

LABORATORY

4:

FREQUENCY-DIVISION

MULTIPLEXING

AND

TIME-

DIVISION

MULTIPLEXING

In

the

FDM

portion

of

this

lab,

two

signals

are

combined

and

the

HP8590B

spectrum

analyzer

is

introduced.

Two

message

signals,

both

at

10

kHz,

are

amplitude

modulated

onto

separate

carrier

frequencies.

These

signals

are

then

combined.

The

sidebands

are

located

and

measured

with

respect

to

their

center

frequencies.

The

combined

signals

are

then

amplitude

modulated

onto

a

carrier

frequency.

This

signal

is

then

analyzed.

The

result

demonstrates

that

two

messages

at

the

same

frequency

can

be

transmitted

on

one

carrier

and

recovered.

The

concepts

of

increased

signal

bandwidth,

crosstalk

and

frequency

spacing

are

also

demonstrated.

Theoretical

calculations

for

determining

the

signals

components

are

compared

to

measured

values.

The

TDM

circuit

is

constructed

using

four

integrated

circuit

chips

adapted

from

Ref.

[4].

See

Figure

2

of

Appendix

D.

A

square

wave

and

a

triangle

wave

are

produced

using

a

XR8038

precision

waveform

generator.

They

are

multiplexed

with

two

external

inputs,

a

DC

signal

and

a

square

wave,

using

a

CD4051B

analog

multiplexor.

The

output

waveform

is

a

combination

of

the

four

signals.

Each

signal

is

sampled

once

every

clock

pulse.

The

clock

frequency

of

7.5

kHz

is

provided

by

a

CD4029B

up/down

counter.

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