Output Matching network of a 60GHz Class A PA

[Sam315]

Hello, Can anyone help me with the concept of how to do the output matching network of a class A PA. My S21 is 12dB and my S11 is matched at 60GHz. I have performed the load-pull simulation and found that the optimum load is like 11+j14. Now, what should be the next step to determine the output matching considering the optimum load? I have read in many papers that there should be conjugate matching in order to get the maximum efficiency but I am confused about how to do that conjugate matching in my design. If possible please help me.

--- Updated Aug 5, 2021 ---

Hello, Can anyone help me with the concept of how to do the output matching network of a class A PA. My S21 is 12dB and my S11 is matched at 60GHz. I have performed the load-pull simulation and found that the optimum load is like 11+j14. Now, what should be the next step to determine the output matching considering the optimum load? I have read in many papers that there should be conjugate matching in order to get the maximum efficiency but I am confused about how to do that conjugate matching in my design. If possible please help me.

A further approach that I have done is I used that optimum load and calculated capacitance and inductance according to that. But in the end, if I place it in the circuit connecting Vdd and the following inductor my gain reduces. I am so confused about where I am doing wrong!

 

[BradtheRad]

The goal of impedance matching is to maximize power going to the load. For your given Watts and frequency, there is a combination of volts and Amperes which achieves this. Ohm's law lets you calculate these particular values.

It's possible in some situations that you want lesser voltage instead of greater voltage. In that sense it's a reduction of gain, however it increases Amperes level proportionally.

After that your task is to find values for an LC network, so that when your initial signal (at original V & A) goes through your network, it's converted to the more efficient V & A for your load.

Perhaps you're on the right track with your series CL, load across L.
Also see what happens when you put the load across C. Measure volts & amps.

Test your network for resonant frequency, with load and without load. Is it 60 GHz?

 

[Sam315]

The goal of impedance matching is to maximize power going to the load. For your given Watts and frequency, there is a combination of volts and Amperes which achieves this. Ohm's law lets you calculate these particular values.

It's possible in some situations that you want lesser voltage instead of greater voltage. In that sense it's a reduction of gain, however it increases Amperes level proportionally.

After that your task is to find values for an LC network, so that when your initial signal (at original V & A) goes through your network, it's converted to the more efficient V & A for your load.

Perhaps you're on the right track with your series CL, load across L.
Also see what happens when you put the load across C. Measure volts & amps.

Test your network for resonant frequency, with load and without load. Is it 60 GHz?

Hello BradtheRad, Thank you for the reply. It was helpful.

I selected the biasing voltage Vgs by simulationg Id Vs Vd plot when I was doing for the single transistor design.

The technology I am using has limited Vdd which is 800mV and my Vgs accordingly is also cannot exceed 600mV. Similarly when I cascode the transistor I chose the Vgs accordingly.

My main concern is that I have to design the matching network with transmission line and since transistor lines are a bit difficult (for me as a beginner) to design I started with the basic LC circuit simulation to obtain the desired values.

For input matching network, I was successful to do that and I matched my S11 parameter to the desired frequency(60GHz) and I got the S21 almost close to 12dB without output matching network.

I got the loadpull simulation. I was struggling with how to perform output matching simulation so that I can get maximum efficiency and a output power of 10dBm.

I have calculated by LC circuit and managed to get that but now how can I replace the L and C with the transmission line?
Thank you again

 

[BradtheRad]

If you take a look at Falstad's animated simulator (free to use online and free to download at falstad.com/circuit)...
It contains a menu of circuits with a submenu Transmission Lines. They might be helpful to your research.

Below is a screenshot of one named "Impedance matching (L section)".

(Falstad's is the one I gravitate toward, although I know little about transmission line theory.)

 

[BigBoss]

You have done a "Complex Load Pull Simulation" and you don't know what to do for "Simple Matching Circuit" ...??