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# Issue with ideal multiplier in ahdlLib library in Cadence

Last post Wed, May 29 2013 8:41 PM by lahsivece. 2 replies.
 Started by lahsivece 29 May 2013 10:22 AM. Topic has 2 replies and 584 views
• #### Wed, May 29 2013 10:22 AM

• lahsivece
• Joined on Tue, Oct 2 2012
• Posts 27
• Points 420
Issue with ideal multiplier in ahdlLib library in Cadence
 Dear All,I am using multiplier (provided in ahdlLib library)  to simulate the behaviour of mixer. One of the inputs (RF input to the mixer) is a sinusoid withh 100mV amplitude and frequency f_rf. The other input (LO input to the mixer ) is a square pulse with V_High =1  and V_low = 0 wityh frequency f_LO. Multiplier gain is set to 1. I am using PSS analysis (shooting method , errpreset set to moderate) to analyze frequency tones at the multiplier output. Ideally I expect that multiplier will generate a  frequency tone at IF frequency , f_IF= f_RF - f_LO with the peak amplitude given by (2/pi)*  (V_RF =100mV) . Since I am using an ideal multiplier , I expect RF signal to be present at IF output of multiplier with exactly same ampliude (multiplier gain is set to 1 ). But , I am observing loss through multiplier . Observed RF amplitude at the RF frequency was supposed to be 100mV but is 60.6mV and I am observing same loss for IF frequency. To summarize : I am observing loss through ideal multiplier (gain is set to 1 ) when I try to use multiplier as a mixer . I am using PSS analysis shooting method to simulate the multiplier.  Please advise .With Best Regards,Vishal
• Post Points: 20
• #### Wed, May 29 2013 10:47 AM

Re: Issue with ideal multiplier in ahdlLib library in Cadence
 Vishal,Are you using vsource (or vsin) as inputs, or port? It behaves perfectly (with vsource) in my case - I actually get half the peak amplitude at each tone (I'm not sure why it it whould be 2/pi). It's a voltage-based system. Here's my netlist (easier than showing all the properties on the sources):// Generated for: spectre// Generated on: May 29 18:42:13 2013// Design library name: RFworkshop// Design cell name: checkmult// Design view name: schematicsimulator lang=spectreglobal 0include "model/rfModels.scs"include "gpdk446.v10/models/nmos1.scs" section=nominclude "gpdk446.v10/models/pmos1.scs" section=nominclude "models/npnStd.scs"include "SpectreModels/RFmodels.scs"// Library name: RFworkshop// Cell name: checkmult// View name: schematicI0 (lo rf _net0) multiplier gain=1V0 (lo 0) vsource type=sine freq=1G ampl=1 fundname="LO"V1 (rf 0) vsource type=sine freq=900M ampl=1 fundname="RF"R0 (_net0 0) resistor r=1KsimulatorOptions options reltol=1e-3 vabstol=1e-6 iabstol=1e-12 temp=27 \    tnom=27 scalem=1.0 scale=1.0 gmin=1e-12 rforce=1 maxnotes=5 maxwarns=5 \    digits=5 cols=80 pivrel=1e-3 sensfile="../psf/sens.output" \    checklimitdest=psf pss  pss  fund=100M  harms=20  errpreset=moderate  annotate=statusmodelParameter info what=models where=rawfileelement info what=inst where=rawfileoutputParameter info what=output where=rawfiledesignParamVals info what=parameters where=rawfileprimitives info what=primitives where=rawfilesubckts info what=subckts  where=rawfilesaveOptions options save=allpubahdl_include "/export/home/apps/IC615_isr/tools/dfII/samples/artist/ahdlLib/multiplier/veriloga/veriloga.va"And attached is the picture of my results.Andrew. RFpiccie.png
• Post Points: 20
• #### Wed, May 29 2013 8:41 PM

• lahsivece
• Joined on Tue, Oct 2 2012
• Posts 27
• Points 420
Re: Issue with ideal multiplier in ahdlLib library in Cadence
 Hi Andrew,Thanks for the quick reply. I am using voltage sources as input . With two sinusoids as input, I am getting correct output. I made two silly mistakes while using multiplier. First was with vpulse source. I assigned v_high=1.2 when I should have assigned v_high=1.  I was calculating gain as 2/pi when it should have been 1/pi ( upconverted and downconverted product). pi comes into picture when digital pulse is expanded into fourier series. Regards,Vishal
• Post Points: 5