Introduction of PIN Diode Switches
PIN Diode Switches uses the PIN tube to present the impedance characteristic of approximately on or off under the DC positive and reverse bias voltages, and realizes the conversion of the control microwave signal channel.
Reflection and Absorption
The reflective switch is used to isolate the input microwave signal by reflecting the input microwave signal back when the PIN diode is turned on, so the standing wave in the "on" state is better, but the standing wave in the "off" state is very poor; The absorption switch adopts the load to absorb the reflected signal when the PIN diode is turned on, thereby improving the standing wave of the port, so the standing wave in the "on" and "off" states is better. Generally, reflective switches can withstand more power than absorptive switches. From the point of view of engineering application, although its price is slightly higher, we recommend choosing an absorbing switch, so it can reduce the inter-stage traction of the system in the off state.
Insertion Loss and Isolation
The PIN tube actually has a certain value of reactance and loss resistance, so the attenuation of the switch is not zero when it is turned on, which is called forward insertion loss, and the attenuation of the switch is not infinite when it is turned off, which is called isolation. The two are the main indicators to measure the quality of the switch. Generally, it is hoped that the insertion loss of the switch is small and the isolation degree is large.
Due to the storage effect of the charge, a process is required for the PIN tube to change from the off state to the on state and from the on state to the off state, and the time required for this process is the switching time.
Withstand Power (Power Capacity)
The maximum input power that the microwave switch can withstand under given operating conditions. It is related to PIN tube power capacity, circuit type (series or parallel), working state (continuous wave or pulse) and heat dissipation conditions.
Direct leakage of modulated video pulses on the RF main line. When the modulation speed of the video pulses is high and the carrier frequency is low, the RF energy of the leaked video may be aliased with the modulated carrier and cannot be filtered out by a high-pass filter, resulting in bit errors , so the smaller the video leak, the better.
PIN diodes are also non-linear, so they will generate harmonics. In broadband applications of PIN switches, harmonics may fall within the operating frequency band and cause interference.
Way to Control
The switch is controlled by TTL signal, "1" off, "0" on or "1" on and "0" off. Compatible with ECL.
The connector is mainly SMA-50K, or detachable. The detachable switch is a microstrip pin-type interface after removing the connector seat, which can be easily assembled with the circuit. At this time, attention should be paid to the signal crosstalk in space, so as not to reduce the isolation of the system.