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how to understand analoglib/port in RF simulation
Aug 30^th, 2011, 6:39am

hi, everyone
when using analoglib/port in SpectreRF, I have some questions:
1. In trasmition line theory their is reflection where impedance is not matched. does circuit simulator consider reflection when connect port to circuit.
2. when simulate output power does this port can model the real test equipment such as spectrum analyzer.

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RFICDUDE

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Re: how to understand analoglib/port in RF simulation
Reply #1 - Aug 30^th, 2011, 5:25pm

1. Yes, the reflection coefficient at the port is considered in the simulation and results.

2. I am not 100% sure of your question. The PORT element is just a source with a defined source impedance. It is the various analysis types that produce results that can be made to correspond to equivalent results measured on test equipment. Large signal analysis like transient, PSS, envelope transient, harmonic balance, etc. are all capable of generating frequency domain spectrum results. The PORT element works with any of the large signal analysis, but you have to define the type of excitation being used (sine, pulse, piece-wise, sample points from a file).

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jeffrey-peng

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Re: how to understand analoglib/port in RF simulation
Reply #2 - Sep 1^st, 2011, 9:33am

RFICDUDE wrote on Aug 30^th, 2011, 5:25pm:

1. Yes, the reflection coefficient at the port is considered in the simulation and results.

2. I am not 100% sure of your question. The PORT element is just a source with a defined source impedance. It is the various analysis types that produce results that can be made to correspond to equivalent results measured on test equipment. Large signal analysis like transient, PSS, envelope transient, harmonic balance, etc. are all capable of generating frequency domain spectrum results. The PORT element works with any of the large signal analysis, but you have to define the type of excitation being used (sine, pulse, piece-wise, sample points from a file).

Thank RFICDUDE's reply
In question 2, I mean when the port is used as a load, and set as DC=0, it seems the circuit simulator trade this port as a simple resistor. I am not sure, a simple resistor can represent the real situation?

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RFICDUDE

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Re: how to understand analoglib/port in RF simulation
Reply #3 - Sep 1^st, 2011, 5:37pm

A spectrum analyzer does measure the power delivered to a 50 ohm load. The internal load is broadband resistive 50ohms, but I am not sure what the input amplifier configuration is.

A network analyzer is also broadband 50ohms, but the calibration takes into account the test cables and internal errors within some specified uncertainty.

So, the port load is representative of the ideal measurement case neglecting the practical imperfections, limitation, uncertainty and fixture issues of a "real" measurement.

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