noise floding, aliasing and frequency conversion effects?

[flyinspace]

Hi,everyone:
In SpectreRF document, I read the function of PNOISE analysis just as:
"PNOISE analysis computes the total noise at the output, which includes contributions from the input source and the output load. The amount of the output noise that is attributable to each noise source in the circuit is also computed and output individually. The analysis includes the effects of noise folding, aliasing and frequency conversion effects. It is useful in computing input-referred noise, noise figure, the phase noise of oscillators, and the noise behaviour of mixers, switched-capacitor filters and similar circuits."
Who can explain "noise floding, aliasing and frequency conversion effects"? Please tell me where can obtain relative paper to research them!
Thanks

 

[flatulent]

Re: noise floding, aliasing and frequency conversion effects

One example of the aliasing might be the noise at the image frequency of a mixer getting into the IF along with that of the desired mixing product. This is why in a high quality, high price, multiple conversion receiver the mixers after an IF amplifier chain is preceded by another band pass filter to keep the noise from the IF amplifiers at the mixer's image frequency out of the next stage of the signal path.

I have never heard of the flooding term.

 

[brmadhukar]

Re: noise floding, aliasing and frequency conversion effects

Hi,

Here is an example for ease of understanding.

RF = 1575.42 MHz ( GPS)

LO1 = 1550.9MHz

IF1 = RF - LO1 = 25.42MHz

The image will be at LO1 - IF1 = 1525.48MHz.
Any frequency component at the RF in this range shall be also presnt at 25.42MHz. This the image noise.

LO2 = 16.325291MHz (say)

IF2 = IF1 - LO2 = 8.192MHz

If the bandwith is 2MHz, any frequency of sampling below 6MHz will produce overlap of spectra ( -ve and positive) and this icalled folding / aliasing.

Refer Lyons.

BRMAdhukar

 

[flyinspace]

hi,BRMAdhukar
Thank you!
What's your meaning of "Refer Lyons"? papers?
And can you explain frequency conversion effects?
Best Regrads
flyinspac

 

[brmadhukar]

Re: noise floding, aliasing and frequency conversion effects

Hi,
"Understanding DSP" by Richard Lyons explains to you all about the sampling/folding/aliasing.

Frequency conversion effects: I shall try to communicate what I understand.

Any mixer normally does not produce only the sum and difference frequencies of the inputs. It also produces their harmonics and this may be explained as the nonlinear output of the mixer. These harmonics may fall in band with the signal at some other stage and cause interference.

BRM

 

[flyinspace]

Hi, brmadhukar
<Understanding Digital Signal Processing>
Author:Richard Lyons
Do you know where is the E-version to download?
I am very interested in the detailed content.
Thanks
Best Regards