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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.

Introduction

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

find the 15th term of the geometric sequince whose first is 18 and last term of 387
Jerwin Reply
I know this work
salma
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
virgelyn Reply
hmm well what is the answer
Abhi
how do they get the third part x = (32)5/4
kinnecy Reply
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
hmm
Abhi
is it a question of log
Abhi
🤔.
Abhi
I rally confuse this number And equations too I need exactly help
salma
But this is not salma it's Faiza live in lousvile Ky I garbage this so I am going collage with JCTC that the of the collage thank you my friends
salma
Commplementary angles
Idrissa Reply
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
hii
Uday
hi
salma
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele 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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