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From: Jerry Avins on 8 Jun 2010 09:53
On 6/8/2010 5:59 AM, John wrote:


> First of all, a fixed point number is not necessarily an integer. It
> is, as the name implies, a number with a fixed decimal point and
> constant resolution, as opposed to floating point. Fixed point numbers
> are often specified using "Q" notation as discussed here:
>
> http://en.wikipedia.org/wiki/Q_%28number_format%29
>
> Conversion from float to fixed does not result in an integer. You
> might consider whether a Q3.12 format is useful in your situation.

Also see http://en.wikipedia.org/wiki/Fixed-point_arithmetic and Randy
Yates' excellent treatment www.digitalsignallabs.com/fp.pdf

Jerry
--
Engineering is the art of making what you want from things you can get.
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From: Avier on 9 Jun 2010 13:40



i f you are working in matlab envornment,,,,,,,then i can help

From: m26k9 on 10 Jun 2010 21:25
Thank you very much John, Jerry and Avier.

The floating to fixed point conversion in the SHARC dsp I am using converts
the floating point to an "two's complement fixed-point integer".

Somehow a scaling is performed such the the integer part of the
constellation ends up at the MSB's of the fixed-point converted result.
Which is what I am quite confused about.

Thank you again.
From: Jerry Avins on 10 Jun 2010 23:05
On 6/10/2010 9:25 PM, m26k9 wrote:
> Thank you very much John, Jerry and Avier.
>
> The floating to fixed point conversion in the SHARC dsp I am using converts
> the floating point to an "two's complement fixed-point integer".
>
> Somehow a scaling is performed such the the integer part of the
> constellation ends up at the MSB's of the fixed-point converted result.
> Which is what I am quite confused about.
>
> Thank you again.

The integer part? What other part is there?

Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
From: m26k9 on 10 Jun 2010 23:59
Thank you Jerry.

What I meant was the constellation value as the integer part. The rest is
the noise. So in the fixed-point converted result, a certain number of
MSB's contain the constellation value, like 1,3,5 and the rest of the bits
are the noise part.

Somehow a scaling is done so that the constellation value ends up at the
MSB's when fixed-point converted.

Cheers.
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