IQ multiplier

Hello,

I learned that when a signal is multiplied by an IQ signal, the signal can be down sampled by 2. So assume that I have a signal that samples at 100MS and I multiplied it by an IQ signal. Then I can down sample each I and Q to 50MS. How is it working? Do I need a filter before down sampling? Or can I down sample without any filtering? Any example design that show how I can do this preferably in FPGA?

Best regards

Reply to
ma
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A signal needs two samples taken in the time of the period of its highest frequency. They can either be assembles as one stream at the given rate or as two streams at half that rate, one I and one Q. In different words, one complex sample can replace two real-only samples.

What do you mean by "multiplied by an IQ signal? I don't understand the procedure you allude to.

Jerry

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Engineering is the art of making what you want from things you can get.
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Reply to
Jerry Avins

ma wrote: > Hello, >

A signal needs two samples taken in the time of the period of its highest frequency. They can either be assembles as one stream at the given rate or as two streams at half that rate, one I and one Q. In different words, one complex sample can replace two real-only samples.

What do you mean by "multiplied by an IQ signal"? I don't understand the procedure you allude to.

Jerry

--
Engineering is the art of making what you want from things you can get.
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Reply to
Jerry Avins

Thanks for your reply. I have a real signal that sampled at say 100MSPS. I want to create an IQ signal from it. I am multiplying it with I and Q signals. After this multiplication, I have two signals one I and one Q. As you explained, it is a complex representation of my signal. So I can have 50MSPS on each stream. How can I do downsampleing in this case? Should I filter the signal before downsampling or not? If I am not doing any filtering, is there any chance for aliasing in this case? Where can I read more about this subject?

Regards

Reply to
ma

Hey Jerry, an IQ multiplier refers to the machine built by the Krell. It was Dr. Mobius' undoing.

Clay

Reply to
Clay

...

Just goes to show what I know! I thought is was a Montessori thing. Flowers for Algernon, anyone?

Jerry

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Engineering is the art of making what you want from things you can get.
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Reply to
Jerry Avins

I think what the OP is alluding to when saying that s/he's "multiplying it with I and Q signals" is that the input signal's being mixed by a 50MHz quadrature oscillator.

Rick Lyons' excellent treatise on the subject is here:

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For me, this was one of those articles you read where the penny miraculously drops.

Cheers, Howard

Reply to
Howard Long

...

That was also my guess, but I wanted it from him for two reasons; to be sure, so we don't go round in circles using different assumptions, and also to see if he knew enough about the system he wants to understand to be able to fill in the blocks in his block diagram. It's OK to treat those blocks as magic boxes until you have to implement them. Then not.

Yes. Rick has the gift of clarity.

Jerry

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Engineering is the art of making what you want from things you can get.
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Reply to
Jerry Avins

(snipped)

Hi Clay,

Good God. Forbidden Planet. Possibly the single greatest science fiction movie *EVER* produced. (And that was BEFORE computer-generated graphics.)

Anyone who saw that movie, back then, was "touched" by its grandeur, its thrills, its romance, its hope for the future, its profound message of human evil and human goodness.

Ha ha. I should run out and rent the DVD of that movie tonight.

See Ya', [-Rick-] Clay, ... Copyright Form :-)

Reply to
Rick Lyons

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