Specifications

13
Noise-parameter measurements in minutes rather than days
Noise figure measurement methods
Y-FACTOR: The most prevalent method for measuring noise figure is the Y-factor technique.
It relies on a noise source connected to the input of the device under test (DUT). When the
noise source is turned off, it presents a room temperature (cold) source termination. When
the noise source is turned on, it creates excess noise, equivalent to a hot source termination.
Under these two conditions, noise power is measured at the output of the DUT, and the scalar
gain and noise figure of the amplifier is calculated. The Y-factor method is used by Agilent’s
NFA Series and by spectrum analyzers with preamplifiers and a noise figure personality option.
COLD SOURCE:
An alternate method for measuring noise figure is the cold source or
direct noise technique. With this method, only one noise power measurement is made at the
output of the DUT, with the input of the amplifier terminated with a room temperature source
impedance. The cold source technique requires an independent measurement of the
amplifier’s gain. This technique is well suited for vector network analyzers (VNAs) because
VNAs can measure gain (S21) extremely accurately by utilizing vector error correction.
The other advantage of the cold source method is that both S-parameter and noise figure
measurements can be made with a single connection to the DUT.
Setting up and making noise-parameter measurements is simple and fast using a PNA-X
and a Maury Microwave automated tuner. Maury’s latest software dramatically improves
both the speed and accuracy of noise-parameter measurements, making them a practical
option for all RF engineers.
Noise
receiver
DUT
Noise
receiver
DUT