Keysight Technologies N5221A

5-2 Keysight N5221A/22A Service Guide
Theory of Operation
Network Analyzer System Operation
5-
Network Analyzer System Operation
The PNA network analyzer generates two (2-port models) or four (4-port
models) phase-locked incident signals and an LO signal from the internal
synthesized source. By means of signal separation, the incident signals are
divided into reference signals and test signals.
The reference signals are applied to the receiver group, while the test signals
are applied to the device under test (DUT) and then to the receiver group. The
LO signal is applied directly to the receiver group where it is mixed with the test
and reference signals to produce IF signals for each of the eight receivers (A–D,
R1–R4) for 4-port models or four receivers (A, B, R1, R2) for 2-port models.
These IF signals are downconverted and then sampled and digitally processed.
Figure 5-1 is a simplified block diagram of the 4-port network analyzer system
and Figure 5-2 is a simplified block diagram of the 2-port network analyzer
system.
Figure 5-1 4-Port System Simplified Block Diagram