Switching Considerations; Connector Integrity; Voltage Standing Wave Ratio; Path Isolation - Keithley S46 Instruction Manual

S46/S46T Microwave Switch System Instruction Manual

Switching considerations

Signals switched by the S46/S46T may be subject to various effects that can seriously
affect their integrity. The following paragraphs discuss these effects and ways to minimize
them.
CAUTION

Connector integrity

As is the case with any high-resistance device, the integrity of connectors can be damaged
if they are not handled properly. If connector insulation becomes contaminated, the
insulation resistance will be substantially reduced, affecting high-impedance measurement
paths. Refer to
Oils and salts from the skin can contaminate connector insulators, reducing their
resistance. Also, contaminants present in the air can be deposited on the insulator surface.
To avoid these problems, never touch the connector insulating material. In addition, use
the relay only in clean, dry environments to avoid contamination.

Voltage standing wave ratio

The Voltage Standing Wave Ratio (VSWR) is a measurement of mismatch in a cable,
waveguide, or antenna system. The measurement is shown as ratio to 1, e.g., a VSWR of
1.2 is actually the ratio of 1.2:1. Refer to the specifications located in
S46T VSWR information.

Path isolation

The path isolation is the equivalent impedance between any two test paths in a
measurement system. Ideally, the path isolation should be infinite, but the actual
resistance and distributed capacitance of cables and connectors results in less than infinite
path isolation values for these devices.
Path isolation resistance forms a signal path that is in parallel with the equivalent
resistance of the DUT. For low-to-medium device resistance values, path isolation
resistance is seldom a consideration; however, it can seriously degrade measurement
accuracy when testing high-impedance devices. The voltage measured across such a
device, for example, can be substantially attenuated by the voltage divider action of the
device source resistance and path isolation resistance. Also, leakage currents can be
generated through these resistances by voltage sources in the system. Refer to the
specifications located in
Do not close more than one RF path per multiport switch.
Degradation of RF performance will result and the switch may be
damaged.
Section 4 for cleaning information.
Appendix A for S46/S46T isolation information.
Connections
Appendix A for S46/
S46-901-01 Rev. C / January 2006
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