Keysight Technologies N5247B, Service Manual

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Keysight N5247B Service Guide 5-65
Theory of Operation
Noise Measurement Group Operation (Option 029)
Noise Measurement Group Operation (Option 029)
The noise measurement group measures the noise figure up to 50 GHz. Refer
to Figure 5-21 on page 5-67 and the detailed block diagrams at the end of
Chapter 4 .
In this section the following assemblies are described:
— A56 Test Port 1 Option 029 Switch
— A64 Test Port 1 Option 029 Tuner
— A57 Test Port 2 Option 029 Switch
— A59 Noise Downconverter
— A9 Noise Receiver Board
A56 Test Port 1 Option 029 Switch
The A56 bypass switch is placed in the Port 1 source path, allowing the source
signal to be switched between normal test mode configuration and internal
noise tuner configuration.
A64 Test Port 1 Option 029 Tuner
The A64 internal tuner is placed in the Port 1 source path together with the
Port 1 switch. The internal tuner is used to vary the Port 1 transmission line
impedance during a noise figure calibration. This enables the source port to be
fully vector corrected during subsequent noise figure measurements.
A57 Test Port 2 Option 029 Switch
The A57 bypass switch is placed in the Port 2 source path, allowing switching
between normal test mode configuration and noise figure measurement mode.
When the PNA-X is switched into noise figure measurement mode, the switch
allows both the source incident signal and the noise incident signal from the
DUT to simultaneously pass through to the A59 Noise Downconverter.
A59 Noise Downconverter
The A59 noise downconverter contains an input Low Noise Amplifier (LNA), an
RF Filter Bank, an LO Filter Bank, and a mixer. For 6 – 50 GHz signals, the LNA
provides the necessary gain to enable measurements on low noise and low
gain devices. The signals are routed through the RF Filter Bank where the noise
signal is filtered for third harmonic conversion rejection. The noise signals are
mixed with the LO synthesized signal to produce IF noise signals before being
sent to the A9 Noise Receiver board. For frequencies between 10 MHz – 6 GHz,
the noise signals bypass the A59 noise downconverter, going to the A9 noise
receiver board, where the signals are amplified, filtered, and mixed with the LO
synthesized signal to produce the IF noise signals.