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Altera_Forum's avatar
Altera_Forum
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11 years ago

Computing Argument of a Complex Number

Hi,

I have a complex input, both I & Q are 16 bit wide signed integers, and I want to compute its argument.

I have read several solutions, CORDIC, LUT based ATAN, and Altera ATAN function.

The latter seems to consume a huge amount of resources, and it's using floating point to the best of my knowledge... I've eliminated this one.

My questions are:

1) Should I convert to fixed point arithmetic?

2) What is the best (and fastest in terms of implementation) solution to use?

5 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    11 years ago

    Puts are always the quickest. The values can either be loaded from a file or computed in the hdl itself. It will have the lowest latency too. But depending on the accuracy requirements it can eat a lot of ram. Fixed point will always be better than floating because of its integer based arithmatic.

  • Altera_Forum's avatar
    Altera_Forum
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    11 years ago

    Please excuse my ignorance, but... what is "puts"? Or do you mean LUTs?

    I've just read the documentation of this core:

    http://opencores.org/project,cordic

    It does exactly what I want, converting rectangular to polar... seems like I tend to use it. What do you think?
  • Altera_Forum's avatar
    Altera_Forum
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    11 years ago

    I meant puts. I was playing from my phone and got autocorrected.

    I'd it does what you want, go for it. Don't expect much support for anything from open cores though.
  • Altera_Forum's avatar
    Altera_Forum
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    11 years ago

    Would you please explain more what do you mean by "puts"?

    CORDIC is giving good results, but it takes several clock cycles to compute.