Agilent Technologies 346A Manual do Utilizador descarregar pdf (Página 3)

Measurement techniques

In order to select the right instrument for your noise ﬁ gure needs, it is important

to have a basic understanding of how noise ﬁ gure measurements are made as

well as their associated measurement uncertainties. Noise ﬁ gure measurement

uncertainty depends not only on the test equipment, but is also a function of the

characteristics of the device under test (DUT)—for example, S-parameters and

noise parameters.

There are two main methods in use today to measure noise ﬁ gure. The most

prevalent method is called the Y-factor or hot/cold-source technique. The

Y-factor method uses a noise source placed at the input of the DUT, providing

two levels of input noise. This method yields noise ﬁ gure and scalar gain of

the DUT, and is used with both spectrum and noise ﬁ gure analyzer solutions.

The Y-factor technique is easy to use, and it provides good measurement

accuracy, especially when the noise source has a good source match and

can be connected directly to the DUT.

The other method used is called the cold-source or direct-noise method. Instead

of using a noise source at the DUT’s input, only a known termination (usually

50 ohms) is needed. However, the cold-source method requires an independent

measurement of the DUT’s gain. This method works well with vector network

analyzers, since vector error correction can be used to get very accurate

gain (S

) measurements. When using the PNA-X, the combination of vector

error correction and the PNA-X’s unique source-correction method provides

the highest noise ﬁ gure measurement accuracy in the industry. The other

advantage of the cold-source method is that both S-parameter and noise ﬁ gure

measurements can be made with a single connection to the DUT. During system

calibration, a noise source is required.

Find out more www.agilent.com/ﬁ nd/nf

The two main methods of

measuring noise ﬁ gure are:

• Y-factor

• Cold-source

To ﬁ nd out more about these

methods see Application Note

57-1, Fundamentals of RF

and Microwave Noise Figure

Measurements, literature

number 5952-8255E.

1 2 3 4 5 6 7 8 ... 21 22

Sem comentários

Agilent Technologies 346A Manual do Utilizador Página 3