I am working on a pattern reconfigurable antenna where i need to use PIN diode as a switch to achieve pattern reconfigurable antenna. But I am confused about the fact that if i use PIN diode in the parasitic element of a yagi how would it work? Because diode only let current flow in one direction but we know in the parasitic element of a yagi antenna we get ac current which changes direction? So how will it work? I am also confused about biasing the diode? can anyone please share a biasing schematic for PIN in antenna?
By saying AC, do you mean the RF signal? If so, then the PIN diode direction wouldn't matter, because it will appear as a conductor for the RF signal.
You can check some publications on reconfigurable antennas to see how to bias the diode. It is just a simple series of DC supply (such as a battery or batteries), a resistor and the PIN diode, but you will need to insert an inductance in the series with it to block the RF signal from the DC supply.
At least that what I know.
PIN diode to be used in the path of RF signal input and it is to be connected such that its cathode is towards RF input and Anode is towards antenna. During ON period, diode is made ON by applying forward biasing and during OFF period diode is to be reversed bias. Ideally, during forward bias, diode resistance is zero and RF reach to antenna through diode and during reverse bias (OFF) period, diode will block RF reaching to antenna.
Additionally, you need to use blocking capacitors to avoid DC reaching to antenna or source as well as blocking inductor to avoid RF flow to DC supply
Take care in DC Switching design circuit.The DC blocking to RF and RF blocking to DC plays an important role .
I agree with Mr. Elangovan Sundaram that biasing should be done to PIN diode to make it ON of OFF , but if you are working with patch antennas you should be careful. RF and DC circuit should not interfere.
see the snap shot
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