Rise time: Port turning on equals 10 percent of the RF signal to 90 percent of the RF signal.įall time: Port turning off equals 90 percent of the RF signal to 10 percent of the RF signal. Port turning off equals 50 percent TTL control to 10 percent of the RF signal. Switching speed: Port turning on equals 50 percent transistor-transistor logic (TTL) control to 90 percent of the RF signal. Hot switch: The switch changes states while a signal is still being applied to the switch. Normally open (NO) switch: With no power applied, the common port isn’t connected to any of the output ports.Ĭold switch: No signal is applied to the switch while the switch is changing states. In a 1P2T switch, this is the “NC” port.įailsafe, absorptive switch: With no power applied, the common port is connected to a specified output port and all other ports are internally terminated with the specified impedance. Self-terminating switch: Another term for absorptive switch.įailsafe switch: With no power applied, the common port is connected to a specified output port.
The impedance is 50 Ω or 75 Ω, depending on model.
Reflective switch: Switch ports are high impedance (open) when turned off.Ībsorptive switch: Switch ports are internally terminated with an impedance when turned off. Here are definitions for some common terms: Source: JFW Industries RF Switch Glossary of Terms Both are single-pole, double-throw reflective switches, but there are significant differences in performance that may determine the best fit for a particular application.įigure 2: Solid-state and EM RF switches with similar functionality have significant performance differences. On the other hand, solid-state switches have lower isolation (40-80 dB), lower power levels and higher harmonic distortion than their EM counterparts.įigure 2 compares the specifications for a solid-state and an EM RF switch. Solid-state switches have no mechanical wear, so the insertion loss repeatability is excellent. They have fast switching speed (a few microseconds), high reliability (MTBF 250,000 hours typically) and can pass frequencies from 0.5 MHz to 18 GHz depending on model. Solid-state RF switches use semiconductor technology to switch the signals between input and output. They do exhibit mechanical wear that limits their lifetime to 1 million operations typically. RF switches can pass signals over an extremely wide frequency range, from DC up to 40 GHz, depending on model. They can change states in 10 milliseconds (ms) typically. As a mechanical technology, EM RF switches are relatively slow. EM RF switches have low insertion loss when closed and high port-to-port isolation when open, so they can transmit high-power, high-frequency signals 200 W at 1 GHz, for example. Two RF switch technologies are commonly available, each with different performance characteristics.Įlectromechanical (EM) RF switches route the signal between input and output using a relay: an electrically-controlled mechanical switch. Adding RF switches at key points allows the designer to automate the test flow, increasing throughput in high-volume production environments. RF switches are used extensively in radio-frequency and microwave test systems to route signals between instruments and devices under test (DUT) and change routing without having to connect or disconnect equipment. Figure 1: Two 1P8T 50? RF switches: solid-state (l) and electro-mechanical (r).
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