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About ports

analogy

Lets say that you have a two port network.If the output port isn't matched to 50 Ohms, is it still safe to use output port resistance as 50 Ohms and get ZM2 ?


Secondly , if the output isn't matched, what should be the port resistance ?

Thanks.

Parents

  • That's not unexpected. The output referred compression point is telling you the output power (which is the power developed in the load port) when that output power drops by NdB from the expected linear output power (as the input power is increased). If the output of the circuit was low enough impedance and the voltage across the port not affected by the load, you would expect the output power to change significantly. If it is dependent upon the load, then it's different still. Even if you're measuring input-referred compression point, this could vary.

    What you need to measure depends on the spec of what the circuit will be driving.

    For an on-chip circuit, commonly the output will actually be a voltage-based circuit, so maybe you should be measuring voltage compression rather than power compression? If using the "xdb" analysis (compression analysis) capabilities of the hb analysis that have been introduced in the last couple of releases of MMSIM (since MMSIM13.1 if my memory is correct), this can do both voltage and power compression (it's a checkbox on the hb choose analysis form). If using the older swept based approach and direct plot form approach, you may need to do a transformation to convert the output. You may find this solution (written by me a number of years ago) useful if using an older version: 

    Regards,

    Andrew.

Reply

  • That's not unexpected. The output referred compression point is telling you the output power (which is the power developed in the load port) when that output power drops by NdB from the expected linear output power (as the input power is increased). If the output of the circuit was low enough impedance and the voltage across the port not affected by the load, you would expect the output power to change significantly. If it is dependent upon the load, then it's different still. Even if you're measuring input-referred compression point, this could vary.

    What you need to measure depends on the spec of what the circuit will be driving.

    For an on-chip circuit, commonly the output will actually be a voltage-based circuit, so maybe you should be measuring voltage compression rather than power compression? If using the "xdb" analysis (compression analysis) capabilities of the hb analysis that have been introduced in the last couple of releases of MMSIM (since MMSIM13.1 if my memory is correct), this can do both voltage and power compression (it's a checkbox on the hb choose analysis form). If using the older swept based approach and direct plot form approach, you may need to do a transformation to convert the output. You may find this solution (written by me a number of years ago) useful if using an older version: 

    Regards,

    Andrew.

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