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Design >> RF Design >> Pss amplitude?
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Message started by Newbie on Sep 13^th, 2005, 12:39am

Title: Pss amplitude?
Post by Newbie on Sep 13^th, 2005, 12:39am

Hi all,

Running pss simulation, noticed that amplitude(dbm) of port plays a big part on simulated results. From spectre user guide, suggested value is -10 dbm. How do i determine what is the correct value?

Thanks.

Title: Re: Pss amplitude?
Post by Ken Kundert on Sep 13^th, 2005, 8:40am

The port is generally used to produce the input signal for the circuit, so the amplitude should be set to match the input amplitude expected for the circuit.

-Ken

Title: Re: Pss amplitude?
Post by Eugene on Sep 13^th, 2005, 9:09am

It is important to note that the dBm specified as a port property is available power, not necessarily the power actually delivered to the load. The port delivers the specified dBm only to a matched resistive load. If a port delivers x Volts across a matched load, the open circuit Voltage is 2x Volts. And that is as it should be. Even so, this point causes a lot of confusion. I recently attended an EldoRF workshop where the speaker adamantly and incorrectly described the behavior of Spectre's port primitive.

Title: Re: Pss amplitude?
Post by Ken Kundert on Sep 13^th, 2005, 8:48pm

It does seem to cause a lot of confusion. And each RF simulator vendor seems to provide the port functionality in a somewhat different way. Even Agilent, which I find odd as I patterned the behavior of the port after signal generators produced by Agilent and Tektronix.

-Ken

Title: Re: Pss amplitude?
Post by newbie on Sep 13^th, 2005, 11:34pm

ok thanx guys.. one other thing... what is the difference between the noise figure from sp analysis and the noise figure from psnoise analysis.
From sp analysis noise figure is in range of 2db, but for pnoise the noise figure is in range of hundreds?

???

thanks

Title: Re: Pss amplitude?
Post by Ken Kundert on Sep 14^th, 2005, 9:08am

PNoise can compute noise figure in frequency translation circuits such as mixers, whereas sp (and noise) are limited to linear time-invariant circuits, such as simple amplifiers and filters.

If the noise figure from the PNoise analysis is hundreds of dB, then you have probably have configured the analysis improperly. Have you set refsideband correctly?

-Ken

Title: Re: Pss amplitude?
Post by byang on Sep 14^th, 2005, 9:28am

You can also try PSP. PSP is an extension of SP by using PSS result as operating point.

You may have more clue by comparing the results.

Baolin