Can u tell me the functioning of this circuit...

I have come across this circuit and it was titled INPUT MATCHING NETWORK for the design of transistor ampplifier.i am not sure of the correct use of the components.can any one figure it out for me.
thank you.

this is basically a radio freqency matching circuit.

figure is taken from ADS I guess ( a radio frequency circuit simulation and design program). and these components are transmission lines. they are probably used to match the impedance seen to port1 ( probably 50ohms) to S11 parameter of the transistor. vertical lines are shorted stubs , used as inductance or capacitance etc...

you need to know some rf theory and design practises to be able to understand what these components do.

hope this helps

Hi,

The vertical micro strips are shorted stubs, quite normal to design matching network. You can see it for example if you do some tries using the smith chart utility, also inside ADS (Tools tab).

The horizontal is probably a 50 ohms line.

Apart from that, difficult to say more. It depends on the frequency and permittivity of the PCB together with the type of matching done at transistor s input (optimum NF, optimum Gain, Optimum linearity)

Hope this helps.

Cheers

This could also be some simple bandpass filter. At passband, the shorted stubs form a high-impedant load on the 50-ohm line at one freq. At it's second harmonic this becomes a short effectively blocking the signal from flowing through. But because both stubs and interconnecting line have different length this is not to straightforward.

Yet it's very easy to verify: Just take a simulator to check what this circuit does.