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Did you know I've got a l33t motherf---ing geek in the family? He's
finishing up his Masters and will get a Doctorate in EE. I've always
believed that if not for the efforts of a tiny percentage of the
population humanity would still be living in grass huts.
From my np brother:
"""
what the hell am I doing?
I thought I would write about what I study and research as it's a very
esoteric field but may be interesting to some of you. Or if it's not
interesting to you, at least you'll have something to say when someone
asks you what I do. I'll try to avoid the minutiae of the subject while
still giving you some tangible information.
I study Sigma-delta data converters. Sigma-delta is a specific type of
architecture that works well for 16 to 24-bit applications like audio.
A data converter is a specific type of integrated circuit (IC) that
converts analog signals to or from digital signals.
Analog signals are voltages or currents that represent "real-world"
signals. Two examples are:
(1) the current on a speaker wire that represents the desired acoustic
output of the speaker
(2) the voltage driving a transmitting radio antenna the represents the
desired electro-magnetic radiation
Digital signals are 1's and 0's that can be processed by a computer.
In short, analog signals are a necessary evil and digital signals offer
some attractive benefits (e.g. robust manipulation, compact storage,
accurate duplication). Data converters then exist at the boundary of
the real-world and the digital world.
For example, an analog-to-digital converter (ADC) can take the voltage
signal from a microphone on a cell phone and convert it to a digital
format so that it can be transmitted. Likewise, a digital-to-analog
converter (DAC) can take the digital signal the cell phone receives and
convert it into a current signal that can drive the speaker.
The big areas of research in this field are (1) lower power and (2)
migrating technologies. The desire for lower power is easy to
understand: lower power = more battery life in a portable device.
Analog circuits usually consume more power than digital circuits so good
research in this area can be lucrative.
Migrating technologies refers to the changing transistor dimensions.
This is what the terms 90nm, 65nm, 45nm (nm = nanometer) mean. Cost in
the IC business is proportional to area. So, there's a big push from
the "digital circuits people" for smaller transistors and newer
technologies. These smaller transistors make analog design very
difficult and new, innovative techniques are required at each technology
node to maintain the performance of the previous generation.
My research is looking at replacing some very complex analog circuits
inside a sigma-delta ADC with "digital-like" circuits that produce the
same function.
In my opinon, data converter design is one the most difficult aspects of
IC design. A good designer has to know analog circuits, digital
circuits, signal-processing, and sensors/transducers. And as long as
innovative designs are required, there will be good jobs for high
quality engineers.
End transmission.
"""
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Shay <sha### [at] none none> wrote:
> I've always
> believed that if not for the efforts of a tiny percentage of the
> population humanity would still be living in grass huts.
Agreed. It has always irritated me how some people belittle the "nerds"
who "don't have a life" and instead sit all day long in their dark
libraries and laboratories doing nerdy stuff. These people who belittle
the "nerds" say that they should get a life and that they are missing what
life is all about, wasting their life. These people who belittle them are
saying this while driving cool cars, watching television, playing game
consoles, talking to their cellphones, going to the doctor to be cured of
diseases which were lethal a couple of hundred years ago...
Without those "no-life nerds" we would still live in the grass huts.
Because of the different interests at least some people have, we can have
luxuries today.
Another thing which irritates me is the definition of "having a life"
these people have. Why is their definition more correct than other people's?
Don't you "have a life" when you are happy with what you are doing? Why
should someone be belittled as not "having a life" just because his
interests are different?
--
- Warp
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Warp wrote:
> Don't you "have a life" when you are happy with what you are doing?
Totally agreed with all of it, but especially this. How many of the
people telling you to "get a life" just can't wait to get off for the
weekend so they can have some fun?
--
Darren New / San Diego, CA, USA (PST)
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> Another thing which irritates me is the definition of "having a life"
> these people have. Why is their definition more correct than other
> people's?
> Don't you "have a life" when you are happy with what you are doing? Why
> should someone be belittled as not "having a life" just because his
> interests are different?
Agreed too Warp, my girlfriend says how she used to laugh at people like me
at school and tell them to "get a life", but now she admits that actually
it's the other way round. She still says to me sometimes about me and my
work colleagues pretending to do important stuff the whole time which really
isn't, until I remind her that things like mobile phones will not invent
themselves, and actually it takes a *HUGE* number of people to get a product
like that onto the market.
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Shay wrote:
> I study Sigma-delta data converters. Sigma-delta is a specific type of
> architecture that works well for 16 to 24-bit applications like audio. A
> data converter is a specific type of integrated circuit (IC) that
> converts analog signals to or from digital signals.
IIRC, this involves generating a pulse train from an analogue signal.
This train consists of negative and positive pulses in such a way that
if you average them together, you get the original signal. But actually
to make the converter, you send the pulses to a counter, which then
converts them into normal binary numbers.
(The pulse train itself has the desirable property that all the pulses
are "equal". In other words, unlike a binary signal that has a most
significant bit and a least significant bit, and you need to know which
bits those are, the pulse train doesn't require any such synchronisation.)
The DSP book I read had a whole chapter on A/D and D/A conversion.
Apparently A/D conversion actually works better if you deliberately add
a tiny amount of noise. (For the same reason that POV-Ray purposely adds
sampling jitter to the antialias pass.)
> The big areas of research in this field are (1) lower power and (2)
> migrating technologies.
Makes sense...
> In my opinon, data converter design is one the most difficult aspects of
> IC design. A good designer has to know analog circuits, digital
> circuits, signal-processing, and sensors/transducers. And as long as
> innovative designs are required, there will be good jobs for high
> quality engineers.
Heh. It's well beyond my field... ;-)
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Invisible wrote:
> IIRC, this involves generating a pulse train from an analogue signal.
> This train consists of negative and positive pulses in such a way that
> if you average them together, you get the original signal. But actually
> to make the converter, you send the pulses to a counter, which then
> converts them into normal binary numbers.
Sounds like PWM.
Fun stuff. A while back I was playing around with some DSP-type stuff.
What I found was interesting is that if you generate an ideal square
wave, them attempt to sweep it, you'll get audible artifacts, but if you
generate the square wave by adding sine waves at odd harmonics, and you
use a cycle of that generated wave to produce a sweep, it works nice and
smooth, as it should.
--
~Mike
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Mike Raiford wrote:
> Sounds like PWM.
Strictly, that's what D/A and A/D converters do. ;-)
> Fun stuff. A while back I was playing around with some DSP-type stuff.
> What I found was interesting is that if you generate an ideal square
> wave, them attempt to sweep it, you'll get audible artifacts, but if you
> generate the square wave by adding sine waves at odd harmonics, and you
> use a cycle of that generated wave to produce a sweep, it works nice and
> smooth, as it should.
Somebody doesn't understand the Nyquist limit, and sinc filtering,
methinks...
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Invisible wrote:
> Somebody doesn't understand the Nyquist limit, and sinc filtering,
> methinks...
I understand the Nyquist limit, but not sinc filtering.
--
~Mike
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>> Somebody doesn't understand the Nyquist limit, and sinc filtering,
>> methinks...
>
> I understand the Nyquist limit, but not sinc filtering.
OK, well suffice it to say that if you have an odd number of samples,
it's not possible to make half of them negative and half of them
positive. ;-)
If you manually sum sinewaves, it does the right thing automatically.
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Invisible wrote:
> OK, well suffice it to say that if you have an odd number of samples,
> it's not possible to make half of them negative and half of them
> positive. ;-)
>
> If you manually sum sinewaves, it does the right thing automatically.
Ahh, makes sense.
--
~Mike
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