Ordinary diodes are composed of PN knots. A thin layer of low-doped intrinsic semiconductor layer is added between the P and N semiconductor materials, and the diode of this P-I-N-N-N-N-Node is a PIN diode. Because of the existence of an intrinsic layer, the PIN diode is widely used, from low-frequency to high frequency applications, mainly used in the RF field, used as RF switches and RF protection circuits, and also uses photodiodes (Photodiode) ). The PIN diode includes a PIN photodiode and a PIN switching diode. Be
The microwave switch exhibits approximately turning or disconnection characteristics under DC positive-reverse bias, and realizes control microwave signal channel conversion. The PIN diode is the same as the PN junction diode, but there is a fundamental difference in the microwave band. Since the total charge of the PIN Diode I is mainly generated by the bias current. Instead of generating a microwave current instantaneous value, it exhibits a linear resistance to the microwave signal. This resistance is determined by the DC offset, the positive offset resistance is small, close to the short circuit, the anti-polarization resistance is large, close to the open circuit. Therefore, the PIN diode does not produce nonlinear rectification, which is the fundamental difference between the general diode, so it is well suited for microwave control devices. Therefore, the PIN diode can be used as a variable impedance element. It is often applied to high frequency switches (ie microwave switches), phase shift, modulation, and limiting. Be
Working principle
Because the RF resistance of the PIN diode is related to the DC bias current, it can be used as a radio frequency switch and an attenuator. Scented RF Circuit: When the diode is biased, i.e., when the diode is zero nature or an anti-bias, not only the maximum operating frequency of the switch will be limited, and the lowest operating frequency will be limited, such as the PIN tube. Controlling the opening of DC or low frequency signals. The switch is affected by the cutoff frequency of the tube, there is an upper limit operating frequency. The frequency band of the required switch is as wide as possible because the frequency band of the signal source is getting wider and wider. Be
Characteristic
When the negative voltage (or zero bias) is loaded, the PIN tube is equivalent to capacitive + resistance; when the voltage is added, the PIN tube is equivalent to a small resistance. The reflection phase (reference phase) of the short-circuit ridge waveguide is the same as the reflection phase of the short-circuit waveguide control of the PIN Tube of the Power Pin Tube by changing the structural size and selecting the PIN diode parameter. The reflection phase of the short-circuit waveguide controlled by the PIN tube control of the negative voltage (or 0 bias) is also required to be opposite to the standard phase (-164 ° ~ + 164 °). Be
Consider parameters
1. Insertion loss: The switch is not zero when the switch is turned on, called insertion loss
2. Isolation: The switch is not infinite when the switch is disconnected, called isolation
3. Switching time: Due to the storage effect of the charge, the PIN management needs a process, and the time required for this process.
4. Belt power: under a given operating conditions, the maximum input power that the microwave switch can withstand
5. Voltage standing wave coefficient: only reflects port input, output match
6. Video Leakage
7. Harmonic: PIN diodes are also non-linear, thus generating harmonics, and PIN switches are in broadband applications, and harmonics may fall in use in the frequency band. Switch Classification: Reflective and absorption, the performance of the absorbent switch is excellent in reflective switches.
Reprinted from the virtual electronic information.
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