ELEC 241 Lab
The Receiver
The receiver consists of
three parts.
The first is the amplifier and filter on the
Antenna Interface,
the second is a Labview program to demodulate
the received signal,
and
the third is the earphone amplifier.
Two of these are already built, which leaves the Labview program.
From
our work in
the Design section of this Lab,
it appears that the receiver is only slightly more complex
that the transmitter.
In fact, we could use the transmitter VI as a receiver,
but it would sound pretty bad without the filters.
The Receiver VI
If you would like to practice your Labview programming skills,
you can make a copy of the transmitter VI and modify it as follows:
-
Remove the adder (which computes
between the A/D
output and the multiplier input
-
Replace it with a bandpass filter: bring up the
Functions
palette, select
Analysis,
then click on
Filter.
In the
Configure Filter
dialog, select
Bandpass
for the filter type and choose appropriate values for the other
parameters.
-
Similarly, insert a lowpass filter between the multiplier output
and the D/A input.
-
Change the A/D input channel to
ach4
and the D/A output channel to
ao1.
If you're fed up with Labview programming,
or don't have the time to get a receiver VI working,
a prefabricated receiver VI (with some additional bells
and whistles) is available.
You can load it from the Start menu by following the path
Programs ->ELEC 241 ->Radio Receiver.
The Earphone Driver.
We can reuse the earphone the earphone driver amplifier
from Experiment 6.2:
If yours is the worse for wear (or has been disassembled)
rebuild it now.
Connections.
Connect the receiver output of the
antenna interface
to the input
of the Receiver VI (ach4 on pin 46 of the interface connector).
Connect the demodulated output of the Receiver VI
(dac1 on pin 52) to the input
of the earphone driver.
Testing.
Set the function generator to produce a 2 mV
174 kHz sine wave. (To get such a small amplitude,
pull out the amplitude knob and rotate all the way
counter clockwise.)
Connect the function generator output to the J4-1
on the Antenna Interface module.
Start the Receiver VI. You should observe a 1 kHz
output from the receiver.