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# PSS Analysis's reliability-Difference between time domain response in PSS and Tran analysis

Last post Thu, Apr 12 2012 10:51 AM by Tawna. 1 replies.
 Started by Imank 12 Apr 2012 10:41 AM. Topic has 1 replies and 2298 views
• #### Thu, Apr 12 2012 10:41 AM

• Imank
• Joined on Sun, Oct 30 2011
• Posts 1
• Points 20
PSS Analysis's reliability-Difference between time domain response in PSS and Tran analysis
 I'm designing a wide band matching network to drive an antenna.The output pulse at the output of pulse generator is delivered to one N1PORT as the antenna model thet refered to a S1P file with value from 1GHz to 8GHz. I want to use this interface between antenna(S1P port with n1port component) and pulse generator(transmitter) I did PSS and Transient analysis to plot output signal. Here are the defined parameters in both simulations: 1-PSS:fundamental tone in 40MHz and I'm going to calculate harmonics to 10GHz cause I want to see output PSD to 10GHz so I defined 250 as number of harmonics. 2-Transient: As input pulse is a unipolar 40MHz pulse rate with 1.2V amplitude, I set the transient time equal to 200ns to reach steady state condition (However, I think my circuit has no transient state). After simulation, I plotted transient response of output at the positive port of N1PORT both in Tran and PSS simulation. ( to put matching circuit between them I grounded one input of 1-port network and directly connected another input to  matching circuit's output). But  the results are completely different, so: a) I wonder to know which one is reliable based on using 1-Port instance, PSS or Tran analysis? (I think Transient is the most reliable analysis but as I have s1p  file, I'm not sure!!) b) I want to Plot PSD(Power Spectral Density) of output signal, I used direct plot form to plot PSS>---Function: Power>--Modifier:dBm. I'm not sure that is it true or wrong? Indeed, dBmP is PSD of output? How can I plot output's PSD in 1Hz or 1MHz scale?  Thanks in Advance.
• Post Points: 20
• #### Thu, Apr 12 2012 10:51 AM

• Tawna
• Joined on Fri, Jul 11 2008
• Snohomish, WA
• Posts 209
• Points 5,565
RE: PSS Analysis's reliability-Difference between time domain response in PSS and Tran analysis
 Hi Iman, If your s-parameter data starts at 1G (at the lowest point), that is going to be a problem. And it is not surprising at all that your results aren't accurate. You need data down to dc (or close to it.) Please read this blog posting: http://www.cadence.com/Community/blogs/rf/archive/2011/03/23/my-favorite-nport-settings.aspx?postID=1260942 If you need further help, please file a Service Request as I mentioned in my previous note. best regards, Tawna Best regards, Tawna Wilsey Staff Support AE, Global Customer Support Cadence Design Systems, Inc.
• Post Points: 5