Anritsu MS2024B - 11-4 How the VVM Function Works

11-4 How the VVM Function Works Vector Voltmeter, Option 15
11-4 PN: 10580-00289 Rev. K Vector Network Analyzer MG
11-4 How the VVM Function Works
1. Insertion technique (2-port). One technique uses the Vector Network Analyzer in a
straightforward manner with its 2-port setup. By characterizing the insertion phase
delay of a signal by measuring S
21
or S
12
through the cable, the operator can determine
the phase shift of the component or cable from input connector to output connector. The
Vector Network Analyzer Option 15 display presents those S
21
or S
12
data as insertion
loss in dB and insertion phase in degrees.
2. Reflection technique (1-port). The second technique (using the Vector Network
Analyzer) measures the S
11
or S
22
reflected signal on a component or cable, and
depends upon the procedure in which the far end of the cable is deliberately
mismatched, either shorted or left open-circuited. This reflects virtually 100% of the
input signal, and the phase delay of the measured reflected signal is therefore equal to
twice the one-way phase of the cable. Likewise, the cable attenuation is twice the
one-way loss. This technique is especially useful for situations in which you must
manually create multiple phase matched cables. This would be done by carefully
snipping small amounts of cable with a diagonal cutters, perhaps 1/8th inch at a time,
and re-measuring the effect on the 2-way phase.
Note
The MS20xxC VNA Master features a fully-reversing architecture, which allows for
measurements (on Port 1 and Port 2) of all four S-parameters without
reconnecting the DUT. With Option 15 VVM, you can make a Return measurement
type (amplitude and phase) on either Port 1 (S
11
) or Port 2 (S
22
). Similarly, you
can make an Insertion measurement type (amplitude and phase) either with Port 1
transmitting (S
21
) or with Port 2 transmitting (S
12
). You select the Port using the
Cal Port soft key under the CW menu. When making Return measurements, you
can connect two cables (one to each port) and then toggle the Cal Port setting to
look at the Return results of both cables without having to disconnect and
reconnect.