<< Chapter < Page Chapter >> Page >
Gives details about the A/D and D/A converters used in our DMT project.

Why, you might ask, did we implement our system by using a sampled analog waveform as the input rather than an arbitrary bit stream? First, it allowed us to actaully see and hear the errors introduced by a noisy channel, rather than just having a tally of the bit errors. Second, we found it motivational to have a visible goal (i.e. the input waveform) to shoot for as we watched our results improved with every version of our code. Finally, it gave us more experience coding and lets us put these nifty plots in this module, which helps constrast the encoded time-domain plots seen in other subsystems with a real speech signal.

Analog-to-digital (a/d)

The A/D converter in our system takes in a MATLAB vector corresponding to a sampled analog signal and converts it to a bit stream. This is a two step process: quantization and bit assignment. In quantization , the amplitude axis of the input signal is broken up into 2^B levels and each sample is rounded to the nearest level. Each level is assigned a B -bit binary number, so the length Q input vector of samples is mapped to a length BQ bitstream. Below are figures of the input and quantized input waveforms.

Input sampled waveform

The input waveform used was the'Handel'sound file built into MATLAB

Quantized input waveform

Quantized version of'Handel'

Digital-to-analog (d/a)

The D/A converter in our system performs the inverse operation of the A/D converter: it takes in a MATLAB bitsream and converts it to sampled analog signal. Here, it is only a one step process: since we performed B -bit A/D conversion, we assign each block of B bits the original associated quantization level. There is an implicit error induced in D/A conversion due to quantization: since we originally rounded the sampled points to the nearest level, the information regarding their exact values is lost. This is called quantization error . However, with a speech waveform, a 4-bit (16 quantization level) approximation of the signal sounds reasonably close to the real thing. To actually see how well our output signal matched up with our input, we compared it with a quantized version of the input waveform.

Other sources for information about A/D conversion: Amplitude Quantization

Our related MATLAB functions: a2d.m , d2a.m

Home | Previous: Implementation | Next: Serial/Parallel, Parallel/Serial

Questions & Answers

what is mutation
Janga Reply
what is a cell
Sifune Reply
how is urine form
Sifune
what is antagonism?
mahase Reply
classification of plants, gymnosperm features.
Linsy Reply
what is the features of gymnosperm
Linsy
how many types of solid did we have
Samuel Reply
what is an ionic bond
Samuel
What is Atoms
Daprince Reply
what is fallopian tube
Merolyn
what is bladder
Merolyn
what's bulbourethral gland
Eduek Reply
urine is formed in the nephron of the renal medulla in the kidney. It starts from filtration, then selective reabsorption and finally secretion
onuoha Reply
State the evolution relation and relevance between endoplasmic reticulum and cytoskeleton as it relates to cell.
Jeremiah
what is heart
Konadu Reply
how is urine formed in human
Konadu
how is urine formed in human
Rahma
what is the diference between a cavity and a canal
Pelagie Reply
what is the causative agent of malaria
Diamond
malaria is caused by an insect called mosquito.
Naomi
Malaria is cause by female anopheles mosquito
Isaac
Malaria is caused by plasmodium Female anopheles mosquitoe is d carrier
Olalekan
a canal is more needed in a root but a cavity is a bad effect
Commander
what are pathogens
Don Reply
In biology, a pathogen (Greek: πάθος pathos "suffering", "passion" and -γενής -genēs "producer of") in the oldest and broadest sense, is anything that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term pathogen came into use in the 1880s.[1][2
Zainab
A virus
Commander
Definition of respiration
Muhsin Reply
respiration is the process in which we breath in oxygen and breath out carbon dioxide
Achor
how are lungs work
Commander
where does digestion begins
Achiri Reply
in the mouth
EZEKIEL
what are the functions of follicle stimulating harmones?
Rashima Reply
stimulates the follicle to release the mature ovum into the oviduct
Davonte
what are the functions of Endocrine and pituitary gland
Chinaza
endocrine secrete hormone and regulate body process
Achor
while pituitary gland is an example of endocrine system and it's found in the Brain
Achor
what's biology?
Egbodo Reply
Biology is the study of living organisms, divided into many specialized field that cover their morphology, physiology,anatomy, behaviour,origin and distribution.
Lisah
biology is the study of life.
Alfreda
Biology is the study of how living organisms live and survive in a specific environment
Sifune
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Ece 301 projects fall 2003. OpenStax CNX. Jan 22, 2004 Download for free at http://cnx.org/content/col10223/1.5
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Ece 301 projects fall 2003' conversation and receive update notifications?

Ask