How Does The Noise Figure Measurement Work; Noise Source; Y-Factor Measurement - Keysight Technologies N9040B UXA Manual

Introduction to Noise Figure

How does the Noise Figure Measurement Work?

How does the Noise Figure Measurement Work?
The noise figure measurement is usually made on 2-port devices to see the
decrease of the signal-to-noise ratio as the signal goes through the DUT. The
N9069C Noise Figure Measurement Application uses the Y-factor method to
calculate the noise figure. This section briefly explains how a complete Y-factor
measurement is made. You can refer to Application Note 57-2: Noise Figure
Measurement Accuracy - The Y-Factor Method for more detailed information.
The test system can be seen as a two-stage system as shown in the following
figure. The DUT is stage 1 and the instrument connected to the DUT is stage 2.
The noise figure of the DUT can be calculated using the following equation.
Equation 1-1
This equation is the basis for the noise figure measurement. The noise figure
and gain of the DUT are measured in the process.
Figure 1-1 Noise Figure Measurement Using a Two-Stage System

Noise Source

The Y-factor method uses a noise source to provide stimulus to the DUT input.
The noise source has two known levels of noise with a pre-calibrated Excess
Noise Ratio (ENR). The noise from the noise source is broadband.
Equation 1-2
ON
T
s
states.

Y-factor Measurement

The complete Y-factor measurement of the DUT noise figure and gain consists
of two steps, calibration and measurement, as shown in
analyzer measures the noise power corresponding to the noise source On and
noise source Off in certain bandwidth at different frequencies. A total of four
measurements are taken in the process.
10
F F [ ( F 1 ) G ⁄
= – –
1 12 2
ON OFF
ENR ( T T ) T ⁄
= –
s s
OFF
and are the noise temperatures of the noise source in its ON and OFF
T
s
is the reference temperature of 290 K.
T
0
]
1
0
N9069C Noise Figure Measurement Guide
Figure 1-2. The