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# Noise simulation in Complex filter

Last post Mon, Apr 5 2010 8:28 AM by Megh. 2 replies.
 Started by Megh 31 Mar 2010 04:03 PM. Topic has 2 replies and 2205 views
• #### Wed, Mar 31 2010 4:03 PM

• Megh
• Joined on Tue, Mar 30 2010
• Posts 2
• Points 25
Noise simulation in Complex filter
 Cadence recommends following way to do the noise simulation in Complex filters: -According to principle of superposition noise can be calculated as follows:1. Calculate output noise (V**2/Hz) when only portI is active:- at Iout: Ioutn_I(f);- at Qout: Qoutn_I(f).2. Now calculate output noise (V**2/Hz) when only portQ is active:- at Iout: Ioutn_Q(f);- at Qout: Qoutn_Qf).Now you can calculate the total otput noise (V**2/Hz) at both outputs:Ioutn(f) = Ioutn_I(f) + Ioutn_Q(f);Qoutn(f) = Qoutn_I(f) + Qoutn_Q(f);______________________________________________________________________________The complex BPF is made of 2 LPFs. Both of them have gain = 0dB. Also Gain is 0dB for complex out to complex input. Now I see that input referred noise is double that of output referred noise even though gain is 0dB .  I don't know why this is happening. Please help.ThanksMegh
• Post Points: 20
• #### Sat, Apr 3 2010 4:47 AM

• Tawna
• Joined on Fri, Jul 11 2008
• Snohomish, WA
• Posts 212
• Points 5,625
Re: Noise simulation in Complex filter
 Hi Megh,You don't say what type of noise analysis you are running.... Is this ac noise, spectreRF pnoise, etc. ?    For a summary of existing noise documentation, you may want to take a look at:  Summary of existing documentation on various RF related noise analyseshttp://support.cadence.com/wps/mypoc/cos?uri=deeplinkmin:ViewSolution;solutionNumber=11585972 (I suspect that you may be referring to COS Solution  11162588 .   You may want to consider filing a Service Request so that a Support AE can assist you in greater detail.)best regards,Tawna   Best regards, Tawna Wilsey Staff Support AE, Global Customer Support Cadence Design Systems, Inc.
• Post Points: 20
• #### Mon, Apr 5 2010 8:28 AM

• Megh
• Joined on Tue, Mar 30 2010
• Posts 2
• Points 25
Re: Noise simulation in Complex filter
 Hello Tawna,Thanks for replying. I am performing AC Noise analysis.Please let me know what do you think on the stated problem.I will file an SR on this.ThanksMeghraj
• Post Points: 5