Anritsu MS2024B - 3-3 VNA Master Architecture

VNA Fundamentals 3-3 VNA Master Architecture
Vector Network Analyzer MG PN: 10580-00289 Rev. K 3-3
3-3 VNA Master Architecture
A VNA can have 1-port only, in which case it measures only reflection signals. A VNA can
have 2-ports, in which case it can measure both reflection and transmission. A 2-port VNA
can also have two different capabilities: 1-path 2-port, or full-reversing. The 1-path 2-port
design allows reflection measurements only at one of the two ports and allows transmission
measurements only in one direction. The MS20xxB VNA Master and the S412E LMR Master
are two-port, 1-path VNA instruments that allow S
11
and S
21
measurements with a single
connection. The MS20xxC VNA Master is a full-reversing VNA that allows reflection
measurements from both ports and allows transmission measurements in both directions
(S
11
, S
21
, S
22
, and S
12
measurements with a single connection).
The MS20xxB compact VNA Master and the S412E LMR Master have an architecture that
automatically measures two S-parameters (S
11
and S
21
) with a single connection. Three
receivers are used, so the forward sweep from Port 1 simultaneously yields S
11
and S
21.
The MS20xxC VNA Master has an architecture that automatically measures the four
S-parameters with a single connection. Three receivers are used, so the forward sweep from
Port 1 simultaneously yields S
11
and S
21
, and the reverse sweep from Port 2 simultaneously
yields S
22
and S
12
. Thus, measurement of the four S-parameters for a two-port DUT requires
only two sweeps, the forward and reverse transmission.
Figure 3-1 and Figure 3-2 show a general block diagram of the three-receiver architecture
that is used in the MS20xxC VNA Master and show how the S-parameters are related to the
signals that are being transmitted and received by the ports. From Figure 3-1, you can see
how S
11
and S
21
are generated by a forward sweep (signal directed from Port 1). Figure 3-2
shows how S
22
and S
12
are generated by a reverse sweep (signal directed from Port 2).
Figure 3-1. MS20xxC VNA Master Block Diagram During Forward Sweep
DUT
Port 1 Port 2
Source
Receiver
Port 1
Receiver
Port 2
Reference
Receiver
Switch
Bridge/
Coupler
Bridge/
Coupler
S
11
S
21