Figure

Demo

dulation

Electronics

Rac

k

Unit

m

ultipliers 

ho

w

ev

er 

w

ere

seen

to

w

ork

w

ell

enough

in

this

application

to

allo

w

the

direct to baseband

mo

de 

V

oltage

Con

trolled

Ampli er

The

demo

dulated

signals

are

sen

t

to

a

v

oltage con

trolled

ampli er

stage 

It

is

built

out

of

an

Analog

Devices

SSM    

quad 

matc

hed

v

oltage con

trolled

amplifer 

The

wip

er

of

a

  K

p

oten

tiometer

is

used

as

the

gain

con

trol

v

oltage 

The

SSM    

outputs

curren

t

and

requires

an

opamp

con gured

as

a

transimp

edence

ampli er

on

the

output

to

pro

duce

a

v

oltage 

A

Maxim

MAX   

is

used 

The

MAX   

is

a

single

supply

opamp

and

can

run

to

v

olts 

making

it

idea

for

in

terfacing

to

a

micro

con

troller 

The

V

CA

allo

ws

b

oth

I

and

Q

gains

to

b

e

sim

ultaneously

adjusted 

preserving

their

ratio 

whic

h

determines

range