operation of pin diode at very high frequency?

Answer 1

A pin diode is typically used as an RF switch. Normally diodes are made of P-N junctions. They only conduct in one direction of course but in reverse bias (off) mode they look like a capacitor and can pass high frequency signals quite easily. The P and N regions are separated by a very very thin depletion region with no mobile conductors (insulator) so the capacitance is high.

The P-I-N diode separates the P and N regions with an undoped intrinsic region (the I in P-I-N). When the diode is forward bias, it looks like a normal diode and can conduct either a DC signal or a very small ac signal riding on a dc signal. When the P-I-N diode is reverse biased, the same kind of capacitor forms as before BUT now there is a thicker depletion region formed because the intrinsic region becomes part of the insulator in the capacitor.

The net is, when a P-I-N diode is compared to a normal P-N diode, in the forward biased mode, it will conduct small a.c. just as well as a normal diode bit when it's reverse biased, it looks like a very high impedance (small capacitor). It makes a great solid state RF switch.

http://en.wikipedia.org/wiki/PIN_diode

Answer 2

In High Frequency RF circuits such as UHF Radios, pin diodes are used as filters as these devices are seen by the circuit as capacitors. They are generally configured to act as band pass filters for tuning out unwanted harmonics.....

I hope this is enough information.....

Answer 3

sorry need more info