Explanation of LoadPull in RF power amplifier

It seems that Load Pull is one of the most useful conception in the RF Power Amplifier.I am confused with Load Pull for a long time.What's it?Anybody who can give me some explanation?Thanks!

Re: LoadPull

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Re: LoadPull

dicket said:

It seems that Load Pull is one of the most useful conception in the RF Power Amplifier.I am confused with Load Pull for a long time.What's it?Anybody who can give me some explanation?Thanks!

Click to expand...

If you have Ansoft Designer software it has a good example of load pull measurements. You can go in the help section and search for load pull. That information might be useful.

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dicket said:

It seems that Load Pull is one of the most useful conception in the RF Power Amplifier.I am confused with Load Pull for a long time.What's it?Anybody who can give me some explanation?Thanks!

Click to expand...

If you have Ansoft Designer software it has a good example of load pull measurements. You can go in the help section and search for load pull. That information might be useful.

LoadPull

Using simulator to understand the load pull is a good idea. In ADS there is an design template to do that. you can take a look and try to understand what they try to do. The PA text book from Cripp is also useful.

Re: LoadPull

Hi dicket,
The idea behind the load pull is shortly;
If you use small signal conjugate matching, you assume gain vs. power characteristic is linear. However, since the amplifier is dealing with higher input power levels linearity of the amplifier beraks down in the limits. So, you can not get the desired ouput power as Pout=Pin*G, you get lesser.
To avoid this situation load pull simulation with a variable impedance, measures the output power level for each of the impedance value and then decides at which load value for a given input power level, the device gets the maximum value.

I hope the explanation is clear,
good luck,

Re: LoadPull

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To avoid this situation load pull simulation with a variable impedance, measures the output power level for each of the impedance value and then decides at which load value for a given input power level, the device gets the maximum value.

How to determinate the field within which we can change the impedance,for example,how to choose the value of s11_rho and s11_center in the following image?

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How to determinate the field within which we can change the impedance,for example,how to choose the value of s11_rho and s11_center in the following image?


Added after 3 minutes:

The mentioned image above is shown as:

Re: LoadPull

hi again,

How to determinate the field within which we can change the impedance,for example,how to choose the value of s11_rho and s11_center in the following image?

Click to expand...

In the schematic, there is a load tuner placed at output. During the simulation its impedance will be automatically changed. There is no need for you to thing of it. Results of the simulation will give you load pull contours, on which the output power level is same. You can decide the center of contours ,s11_rho, the number of simulation data points, pts, and the radius of the load pull contours,s11_center, in the right up side box. If you are not so sure of what to do, you can leave them as they are at the beginning.

The important thins are:
determine the input frequency and write it in the VAR box
input power level
and the load and source impedances in the harmonics. if you don't want them to change in the harmonics leave this box as its too.

Hope it helps,

Re: LoadPull

Hi,tsubasa
To NE651R479A,what are the appropriate values for s11_rho and s11_center?The datasheet is in the attachment.

LoadPull

I will use FLC167WF. Can't we use the s-parameters given in the datasheet for matching. If we can't what is the purpose of publishing these parameters?
If I can't use these parameters how can I use the loadpull technique for output matching?

Re: LoadPull

huvarda said:

I will use FLC167WF. Can't we use the s-parameters given in the datasheet for matching. If we can't what is the purpose of publishing these parameters?
If I can't use these parameters how can I use the loadpull technique for output matching?

Click to expand...

If you use it for PA, the S-paraneters will not work. You need the load-pull either in software and hardware. The software load pull, for example in ADS, you need a good device model. The best way id to use the load pull system (the tuner) to find out the optimal load impedance for maximum power.