NF of a receiver front end at standard blocker frequency
I designed a front end of wideband receiver.
I did pss/pnoise analysis to calculate total noise figure of receiver. The pac magnitude at the "small signal params" is 1 and phase is 0.
I can see noise figure plot without any problem.
But now i wanna to calculate the total noise figure of receiver at the presence of 80MHz blocker with 0dBm power.
What do I do in the port properties to give a 80MHz 0dBm blocker and what do I do to set the analysis in the analog environment window (what is the difference in the pss/pnoise)?
please help me
At the port properties there is a 'Display second sinusoid' tick where you can set the blocker. PSS is periodic steady state analysis, and pnoise is periodic noise which use the results, operating points of the PSS analysis to calculate the noise.
Thanks for your help. I set port properties, But set first sinusoid. Is it wrong?
My filters don't attenuate the 80 MHz 0-dBm blocker at the any nodes of receiver when I run tran analysis and I give 80 MHz 0-dBm. But when I see pac plot, signals at 80 MHz are rejected more than 13 dB.
My receiver has filtering characteristics at the any nodes of circuit. But there is no attenuated when I see time domain plots.
Can you help me?
The sencond sinusoid at the port properties good to check the IP3, which is necessary RX parameter for design. Furthermore if you want to run pnoise from pss to calculate NF at the presence of a blocker you will need the blocker next to your desired signal at the same time.
80MHz blocker what means in your terminology? Is it an actual 80MHz carrier frequency or a carrier which is 80MHz far from your receiver's center frequency?
Are you using mixer in the RX chain, and if so what is the intermediate frequency? Do you have direct, homodyne or heterodyne receiver?
I have never used pac analysis, the normal AC was enough for me to the endpoint of my LNA. If you don't have mixer transient has to be fast, and usually gives the right results.
I'm using N-path filters. So It's filter and mixer. Therefore I should do pss/pnoise analysis. My RX is direct conversion. So my LO is 2 GHz and I give a 0-dBm blocker. My RX is for GSM. So Blocker offset frequency is 20 MHz. But my PC don't have enough Ram to calculate that. So I give 80 MHz 0-dBm blocker and the blocker frequency will be 2.08 GHz.
Until today, my input port properties set to 2.08 GHz 0-dBm at source. Is it wrong? do I give blocker to second sinusoid?
I consider desire signal in 2 GHz and LO frequencu is 2 GHz too. But I think to find receiver NF at the presence of 0-dBm blocker, I should give Pac magnitude=1 and Pac phase=0 as desire frequency and give a second sinusoid with 0-dBm amplitude and 2.08 GHz frequency. Then I do pss/pnoise analysis and see NFdsb to find receiver NF at the presence of 0-dBm blocker. Is it true or is my method wrong?
With direct conversion fLO=2GHz, and fRF=2GHz, the downconverted signal is a DC voltage, and the amplitude will depend on the relative phase of LO and RF signal. You would test a lot of phase sets to find worst NF I think, so you wouldn't use second sinusoid then. fLO=2GHz and fRF=2.08GHz are good and don't use second sinusoid.
I am not sure the pac analysis can handle frequency conversion and/or N-path filtering. But I have never used it. As I mentioned, pss and tran always have to give the right results.