Hello everyone. I am a college student currently using ADS for my term project. The objective is to design a microwave LNA with certain specs. I am currently trying to match the input for max available gain. I used the gain and noise circles to pick my point.

The point corresponds to 18.5 + j 22.75 (non-normalized). My terminations are all 50 Ohm. Since I am new to ADS, I started doing this the only way I know: I build a new schematic with two 50 Ohms terminations. In between, I have placed an L network of microstrip lines with Z0 = 50. Their lines are to be adjusted such that Zin becomes 18.5 + j 22.75.

I used the smith chart utility to map from 50 to that impedance and used linecalc (with my substrate model) to calculate the lengths of my line length and open stub. But when I place these values in the network and simulate to find Zin, I do not get 18.5 + j 22.75.

I hope this is clear enough. I attached my files for your viewing.

The point corresponds to 18.5 + j 22.75 (non-normalized). My terminations are all 50 Ohm. Since I am new to ADS, I started doing this the only way I know: I build a new schematic with two 50 Ohms terminations. In between, I have placed an L network of microstrip lines with Z0 = 50. Their lines are to be adjusted such that Zin becomes 18.5 + j 22.75.

I used the smith chart utility to map from 50 to that impedance and used linecalc (with my substrate model) to calculate the lengths of my line length and open stub. But when I place these values in the network and simulate to find Zin, I do not get 18.5 + j 22.75.

I hope this is clear enough. I attached my files for your viewing.

## Attachments

My specs are: Gain > 15 dB, NF < 1.2 dB at 2.45 GHz

I have performed the input matching, then conjugate matched the output. But the final matched circuit always has a NF that is much higher than what the point I selected (on the gain/noise circles) corresponded to.

For example, in the updated attached file, my selected point had a 0.3 NF, yet in after matching, I get a NF of about 1.

Can you please help me here?

## Attachments

To match Z0 to Zs (Zs optained from Gain/Noise circles) I basically create a new schematic, with two 50 Ohms terminations, and a MLIN L matching network. I use Zin tool from s parameter palette and set it to Zin1 = Zin(S11,portZ1). Then I tune such that Zin reads Zs. Finally I place the obtained line lengths into my final schematic as the input matching network.

Am I doing this correctly?

Also, your input matching network may have insertion loss which will degrade the noise figure even though you may be generating the desired optimal source impedance.

You will want to add an output matching network to improve the gain.

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