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Impedance setting for ports in Spectre

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Be aware, when using ports in Spectre simulations, a real and imaginary impedance can be defined in the properties menu for the device. When a reactance is specified, this imaginary part is valid only when running small signal analyses like sp, ac, and noise. The reactance will give erroneous results if pss, psp, and pnoise analyses are run. We are reporting this to Cadence as an action item.


Originally posted in cdnusers.org by jmedina
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  • I believe this to be an erroneous conclusion. A simple experiment can verify this. Use two ports, one port for a source (port1) and a second source for a load (port2). Give port1 and port2 a real impedance, say 50 ohms. Give port1 an imaginary impedance and give port2 the conjugate match of that impedance. If port1 has a source power of "Psource", maximum power should be transferred to port2 since they have a conjugate match. I have tried this using flexible balance and shooting in PSS and neither yields the correct answer. Cadence identifies only ac, sp, and noise as being supported analyses with port reactance since the release of MMSIM6.0_USR2.
     
    If you perform the same experiment using real port impedance and external L and C to create imaginary parts for the impedance, you do get expected results when the ports are congugately matched.


    Originally posted in cdnusers.org by jmedina
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  • I believe this to be an erroneous conclusion. A simple experiment can verify this. Use two ports, one port for a source (port1) and a second source for a load (port2). Give port1 and port2 a real impedance, say 50 ohms. Give port1 an imaginary impedance and give port2 the conjugate match of that impedance. If port1 has a source power of "Psource", maximum power should be transferred to port2 since they have a conjugate match. I have tried this using flexible balance and shooting in PSS and neither yields the correct answer. Cadence identifies only ac, sp, and noise as being supported analyses with port reactance since the release of MMSIM6.0_USR2.
     
    If you perform the same experiment using real port impedance and external L and C to create imaginary parts for the impedance, you do get expected results when the ports are congugately matched.


    Originally posted in cdnusers.org by jmedina
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