how to measure the noise up to 1.6ghz use the HP 8970A

1.6 ghz network analyzer

I have two independent blocks: a LNA at 1.9GHz, a mixer(containing a amplifier and a RF filter).
I measure the LNA+mixer with HP 8970A using mode 1.4, mode 1.4 needs to input IF range and fixed LO freq.

from the Friis formula:Ftotal=F1+(F2-1)/Ga1,
F2 means the NF of mixer, Ftotal means the NF of LNA+mixer. F1 is the NF of LNA which is unknown and want to be measured.
I can get F2 and Ftotal using mode 1.4 of HP 8970A. Now the problem is how to get Ga1, Ga1 is the available Gain of the LNA. Generally speaking, we can't measure Ga1 directly, but it can be calculated from its formula.In the formula, S parameter can be measured from the VNA, but there is a "source reflection coefficient", what does it mean? how to measure it?

Thx!

hp 8970b e27

littlemmx said:

When i measure amplifier with the noise figure meter 8970,i found the Gain was less than others instrument,such as Vector Network measure system,Spectrum Analyzer,etc.
why?

Click to expand...

How much lower ?

The Noise Figure Metere makes scalar measurements, as well as the spectrum analyzer; therefore, there would be some differences with the VNA results if the LNA is not well matched.

hp8970a error codes

htforever said:

I have two independent blocks: a LNA at 1.9GHz, a mixer(containing a amplifier and a RF filter).
I measure the LNA+mixer with HP 8970A using mode 1.4, mode 1.4 needs to input IF range and fixed LO freq.

from the Friis formula:Ftotal=F1+(F2-1)/Ga1,
F2 means the NF of mixer, Ftotal means the NF of LNA+mixer. F1 is the NF of LNA which is unknown and want to be measured.
I can get F2 and Ftotal using mode 1.4 of HP 8970A. Now the problem is how to get Ga1, Ga1 is the available Gain of the LNA.

Click to expand...

Rigth ! F2 is the (linear) noise factor of your down converting block !

F1 is the LNA unknown noise factor and Ftot is the LNA+mixer noise factor.

You may obtain the Gins (insertion gain ) of the LNA directly from the NFM by rationing the measured power with the LNA in place with the measured power without the LNA .

htforever said:

Generally speaking, we can't measure Ga1 directly, but it can be calculated from its formula.In the formula, S parameter can be measured from the VNA, but there is a "source reflection coefficient", what does it mean? how to measure it?
Thx!

Click to expand...

The source reflection coefficient is that of the noise source.

But pay attention ! The noise source has two different states and two different reflection coefficients.

Try using the Gins, available directly from the NFM.

But in the Friis formula, Ftotal=F1+(F2-1)/Ga1,
The Ga1 means the available Gain of the LNA, but not the insertion gain(Gi).

In order to calculate the F1,I need to know Ga1, How can I get available Gain of the LNA(Ga1)?

There is a formula to calculate Ga1, in the formula we need to know S11,S12,S21,S22 and
the source reflection coefficient of the noise source while hot. How can I get the source reflection coefficient of the noise source while hot?

Thx!

htforever said:

But in the Friis formula, Ftotal=F1+(F2-1)/Ga1,
The Ga1 means the available Gain of the LNA, but not the insertion gain(Gi).

In order to calculate the F1,I need to know Ga1, How can I get available Gain of the LNA(Ga1)?

There is a formula to calculate Ga1, in the formula we need to know S11,S12,S21,S22 and
the source reflection coefficient of the noise source while hot. How can I get the source reflection coefficient of the noise source while hot?

Thx!

Click to expand...

Obviously Gav is not Gins.

But if the noise source, the LNA and the Noise Figure Meter are well matched --> Gav is more or less equal to Gins.
To measure the reflection coefficient of the noise source you need a vector network analyzer (use the special function 9.2 to set in the hot state the noise source).

Hi,
I am measuring the NF of a monolithic mixer at 900MHz and IF frequency of 200MHz, the objective is to measure the SSB NF, after calibration with the noise source only i inserted RF BP filter centered around the 900MHz before the mixer RF port and an IF filter of center frequency 177MHz at the output of the mixer, then i entered the values of loss compensation tables for the RF filter before the DUT and the IF filter after the DUT, the NFA type i am using is HP N8973A, now to my surprise i found gain very large 26dB while expected 5.5dB( from spectrum analyzer) and NF of -8dB!!!. When i disabled the RF filter loss compensation table and substituted it with a fixed value of 3dB( which is the filter IL at center frequecny 900HMz) the results are reasonable and close to expected (G=5.4dB and NF=13.8dB). I tried another thing, i deleted all the values of the RF filter loss comp. table that lie in the stop band of the filter and i find the results getting more reasonable!!.
Does anyone has explanation?!

I have another question to ask: what's the difference between uncorrected NF and corrected Gain&NF?

SF 9.2 means Noise Source On(uncorrected), why don't use SF 9.4 Noise Source On(corrected)?

Ftotal(the NF of LNA+mixer) and F2(the NF of mixer) can be measured using HP 8970A with mode 1.4, but mode 1.4 consist of two kinds of NF,uncorrected NF and corrected NF,which one is the Ture Ftotal and F2?

Thanks very much!

htforever said:

I have another question to ask: what's the difference between uncorrected NF and corrected Gain&NF?

Click to expand...

The uncorrected NF is the NF of the DUT plus the noise figure of the instrumentation (Noise figure measurement system) you use to perform the measurement (your Ftotal).
The corrected noise figure is just the DUT noise figure (your F1).

htforever said:

SF 9.2 means Noise Source On(uncorrected), why don't use SF 9.4 Noise Source On(corrected)?

Click to expand...

It's the same. You use this special function to switch (steady state) on the noise source, then you perform the measurement through a VNA

htforever said:

Ftotal(the NF of LNA+mixer) and F2(the NF of mixer) can be measured using HP 8970A with mode 1.4, but mode 1.4 consist of two kinds of NF,uncorrected NF and corrected NF,which one is the Ture Ftotal and F2?
Thanks very much!

Click to expand...

The uncorrected noise figure with the DUT in place is Ftotal, the uncorrected noise figure without the DUT is your F2.

if i don't have system LO,i use Signal Generator as the mixer's LO,will it effect the NF of the amp?

littlemmx said:

if i don't have system LO,i use Signal Generator as the mixer's LO,will it effect the NF of the amp?

Click to expand...

What do you mean?

using hp8971c
1.5 mod