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Measuring LNA s-parameter on wafer using Agilent 8722es

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Jan 3, 2005
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LNA measurement

i'l design a common-gate LNA using CMOS technology. the input is matching to 50ohm and the output port will resonance at the desired frequency. I wish to measure the LNA s-parameter on wafer using Agilent network analyzer 8722es.

can i measure the s parameter without matching output port to 50ohm? is it the s parameter measured by matching output to 50ohm and without matching to 50ohm is same? how to convert it?

thanks a lot...

Re: LNA measurement

S parameters are the measure of the power flowing into or out from a circuit.
Can you explain more deeply what are you doing?


LNA measurement

You can convert S-parameters to any matching ports. See it in any common book like Electrical Engineering Handbook or **broken link removed**
But the measurement error will be depend on matching port impedance.

Re: LNA measurement

The main idea of measuring S parameters direct on wafer is to don’t have any matching circuit.

The matching circuit has to follow the S parameters that you measured (to obtain Gain, Noise Figure, Power, etc).

Finally you can measure the combined S parameters (LNA + matching) to publish in the datasheet.

Re: LNA measurement

i read many papers about LNA, most of the design don't match their output port to 50ohm.

How can i measure the voltage gain of my LNA if i just let the output port of LNA resonance at operating frequency(high impedence)?

is it the voltage gain equal to S21?

LNA measurement

sometimes, the output does not match to 50 ohms because stability issues. S21 is a power gain not voltage gain.

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