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RF switches
RF and microwave switches are used to route signals between different measuring instruments and test objects. This means that the signal path is altered depending on the type of application in order to carry out several different measurements, without disconnecting the components of the measurement setup.
What categories of switches are there?
Depending on the type of circuit, RF switches are divided into two categories:
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solid-state switches and
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electromechanical (EM) relays (electro-mechanical switches).
Solid-state switches compared to electromechanical (EM) relays
Solid-state switches are based on semiconductor devices (pin-diodes or FETs). Switching is achieved by altering the bias conditions of the component, whilst EM relays utilise electromagnetic induction to actuate a mechanical switch.
Pictured here: P9400 solid-state pin-diode transfer switch by Keysight
With solid-state switches, one can distinguish between pin-diodes and FETs. Switches based on pin-diodes are used at higher frequencies (typically 100MHz up to >50GHz) for ultra-fast switching. Switches based on FET technology are generally used for slightly lower frequencies, with a moderate switching speed (typically DC up to >20GHz).
FET switches are characterised by very good isolation at lower frequencies, whilst pin-diode switches offer good isolation in the high-frequency range.
Compared to solid-state switches, EM relays have relatively low insertion loss with higher power handling capacity, whilst solid-state switches offer high speed and a long service life.
How do you configure RF switches correctly?
When selecting an RF switch, in addition to the number and arrangement of the ports – for example, SPDT, SP4T or SP6T – the response of the unselected signal paths is crucial.
Terminated or absorptive RF switches typically terminate unused ports internally with 50 Ω. This reduces reflections and potential resonances, and connected signal sources see a defined impedance even when the switch is inactive.
In the case of unterminated or reflective switches, however, the deactivated ports are not matched to 50 Ω and reflect a large proportion of the incoming RF power. Depending on the test setup and application, this can affect the measurement result or connected components.
The appropriate switch configuration must therefore be tailored to the measurement task, number of ports, impedance, power and desired reflection response.
Customised switching matrices
Together with our parent company LXinstruments, we also offer to build a customised switching matrix tailored to your specific requirements and preferences.
We can draw on a wide variety of switch types from different manufacturers.
We are experts in radio frequency technology: Talk to us.
We look forward to discussing your individual requirements in person.
We look forward to hearing from you.
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