Basic RF circuit design - trace impedance or pi-network??

[roogadget]

Michael Ossmann - RF Circuit Design




I am designing an RF antenna at the moment.

My source impedance and output impedance (antenna) are both 50 ohm.

I have calculated the microstrip impedance to about 50 ohms.
Is that all that is required?

What about the use of Pi-networks? L-networks..etc??

I feel like I'm missing something here.

cheers

[Benta]

If the output impedance of your TX amp, the antenna and the microstrip are all 50 ohms, then yes, that's all for impedance matching. But usually you also want to filter out harmonics of the transmitted signal, depending on modulation type. This might be integrated in the TX amp already, can't say.

[roogadget]

What do you mean by "filter out harmonics", like EMI??

[David Hess]

Benta means that the L or T matching network can also operate as a low pass filter to remove harmonic distortion from the amplifier which is commonly required to meet regulatory requirements.  So even if matching is not required, a low pass filter likely is.