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This module introduces Direct Digital Synthesis with prepared code that transmits arbitrary input as an FM radio signal. The module then explains how to program the DDS hardware and concludes with a simple Frequency Shift Keying exercise.


Direct Digital Synthesis ( DDS ) is a method for generating a desired waveform (such as a sine wave)by using the technique described in below.

Direct digital synthesis (DDS) ( Couch )

Quantized samples of a desired waveform are stored in the memory of the microprocessor system. This desired waveform can then begenerated by "playing out" the stored words into the digital-to-analog converter. The frequency of this waveform isdetermined simply by how fast the stored words are read from memory, and is thus programmable. Likewise, the phase andamplitude of the generated waveform are programmable.

The DDS technique is replacing analog circuits in many applications. For example, it is used in higher-pricedcommunication receivers to generate local oscillator signals. It can also be used to generate sounds in electronic pipe organsand music synthesizers. Another application is its use by lab instrument manufacturers to generate output waveforms infunction generators and arbitrary waveform generators ( Couch ).

In this lab you will familiarize yourself with the capabilities of the Analog Devices AD9854 DDS. The DDS board is installedbetween the 6-channel card and the DSP card at some (not all) lab stations. You can tell which boxes have them by the way the6-channel card sits higher inside the metal box.

Frequency modulation (fm) radio exercise

To get your feet wet and see a demonstration of the DDS, perform the following exercise. Copy the files FM.asm (downloadable here ) and mod.asm from the v:\ece320\54x\dds\ directory. Assemble and run the frequency modulation (FM) program FM.asm . Next, plug an audio source into one of the two DSP inputchannels that you've been using all semester. If you have a CD on you, pop it into the computer and use that. If not, usea music web site on the Internet as your audio source. Connect the computer to the DSP by using a male-male audiocable and an audio-to-BNC converter box (little blue box), both of which are in the lab. The computer has three audiooutputs on the back; use the middle jack. Ask your TA if you can't find the cable and/or box or don't see how to make theconnection. Next, connect a dipole antenna to the output of the DDS (port \#1 on the back of the DDS board). A crude buteffective dipole antenna can be formed by connecting together a few BNC and banana cables in the shape of a T . There should be one or two of these concoctions in thelab. Once the connections are made, turn on the black receiver in the lab, and tune it to 104.9 MHz (wide band FM). Youshould be able to hear your audio source!

If your audio sounds distorted, it's most likely due to the volume of your audio source being too loud andgetting clipped by the DSP analog-to-digital converter.

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Ece 320 spring 2004. OpenStax CNX. Aug 24, 2004 Download for free at http://cnx.org/content/col10225/1.12
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