Weak current College】 【RF microwave switch technical parameters】.

Microwave radio frequency of the switch parameter description
Note: consolidation of information is the basic product selection parameters, specific works are not for details, see the related bibliography.

PIN diode switch
Microwave switches use PIN tube in DC positive and negative bias renders the approximate conduction and switching of impedance characteristics for control transform microwave signal channel.
PIN diode current-voltage characteristics of DC and pn junction diode is the same, but in the microwave band there are essential differences. Because the PIN diode I layer the total charge is mainly produced by the bias current, not by the microwave current instantaneous values, so its microwave signal only renders a linear resistance. This resistance determined by the DC bias, bias when resistance is small, close to the circuit, the resistance against bias, when close to the circuit breaker. So PIN diode for microwave signal does not produce non-linear function is rectifier and the essential difference between General diodes, suitable for microwave control devices.
Main parameter description
Insertion loss and isolation
PIN tube actually exist certain values of the reactor and loss resistance, so the switch breakover attenuation is not zero, as is the insertion loss, switch disconnects the attenuation is not infinite, as isolation. When the two key indicators to measure switch, generally want low insertion loss and isolation.

Switching time
As a result of charge storage effect, PIN tube from the globe into on-State, as well as from the on-State into the closing state requires a process, this process needs time to become a switch time.

"Opening delay" to control the impulse of 90 per cent into the managed microwave pulse envelope of 10 per cent of the time needed;
"Switch opening time" as the controlled microwave pulse envelope from 10% to 90% of the time, has become the "rise";
The "off delay" to control the impulse of 10 per cent to controlled microwave pulse amplitude 90% of the time needed;
The "switch-off time" as the controlled microwave pulse envelope from 90% to 10% of the time, has become "the falling edge."
General "opening delay" and the "off delay" depending on the drive circuit, and the "rise" and "falling edge" depends on the PIN and the choice of the bias circuit.

Withstand the power
In the given operating conditions, microwave switch can withstand the maximum input power. And PIN tube power capacity, circuit type (series or parallel), working status (CW or pulsed) to thermal conditions. General failure mechanism in two ways: voltage pulse power breakdown, is common; CW thermal burn, is common.

Voltage standing-wave coefficient
Voltage standing-wave coefficient only reflect port input and output match. Port voltage standing-wave coefficient minimum, switch of loss not necessarily minimal; however difference loss minimal switching its voltage standing-wave coefficient certainly small.

Harmonic
PIN diode with nonlinear, which generates harmonics, when applied to a wider forum, harmonic may fall into the band to filter out, so to give attention to.

Structure description
Reflection and absorption-type switch:
Reflective switches through PIN diode breakover input of microwave signals reflected back up to the quarantine function, so in the "open" State standing wave relationship is good, but in the "off" State standing wave is very bad; absorption-type switch is used to absorb the load PIN diode breakover reflection signal, thus improving the VSWR, hence its "open" and "off" State of standing waves are relatively good. Typically, reflective switches take power than the absorption-type switch, but the price is relatively cheap. While the absorption-type switch can decrease in off-state of the system of stage traction.