Hi, this video shows how to perform active matching with BetaMatch.
Active Matching means matching towards a source with impedances that may be complex,-
- and where the values will vary across the frequency bands of interest.
It is quite common that Active Matching helps when designing antennas for mobile phones
This is because power amplifiers often have optimum load impedances that are not close to 50 Ohm.
Receivers, on the other hand, are often close to 50 Ohm.
Matching the antenna to only 50 Ohm across all bands will then give poor performance at the TX part of the band.
This can many times be improved significantly by matching towards the actual impedances -
- that the source has at the varous frequencies. This is what is called Active Matching.
In this example we will use the default antenna called "Dual Band".
If it is not already loaded it can be loaded from 'Help Menu -> Load Demo Data' select 'DualBand' and click OK.
We will change the electrical delay to 50 pS ...
and the components we will use are the Murata inductors and capacitors size 0402.
We will set the frequency bands to TriBand EU, which is the 900-, 1800- and 1900MHz bands.
We will optimize this antenna with a normal source impedance of 50 Ohm. We will start a 4 components optimization -
The optimization is now finished as you can see the best 4 component network is a T-network with only 3 components.
We store these results into 'Memory 1'.
The results look good and from the accepted power data we can see that we have 78% or more at the low band -
- and 70% or more at the upper bands.
but, assume that we use this matching network and that we do active measurements on our phone -
- and then we find that TRP at the 900MHz band was at least 2dB lower than we expected.
We then did a push-pull measurement of the power amplifier and the found that the optimum load impedance -
- at the TX part of the 900MHz band is not 50 Ohm but rather 20 - j20 Ohm.
Let us enter this new load impedance and see what accepted power we can expect.
870MHz ... 20 Ohm ... -j20 Ohm. Then at 925MHz we have 50 Ohm again.
We can compare these results with the previous results with 50 Ohm.
We can see that we have dropped from 78% to 42% at 880MHz, which is a drop of more than 2.5dB.
It is clear that our design, that worked well with 50 Ohm load, is not going to work well at all with a -
- power amplifier that has an impedance that is that far from 50 Ohm.
So, what we will do now is to run another optimization where the impedance of the PA is also entered.
So we start another 4 component optimization now ...
This new matching network has similar performance as the previous matching network at the band edges.
But this new matching is now matched towards the actual impedances of the working phone.
This means that we should have increased our TRP at the 900-band by more than 2dB with this new matching network.
We can also se in the Smith Chart that the low band -
- that used to be here with the 50 Ohm match now has been shifted and is located -
- here between 20 - j20 Ohm and 50 Ohm in order to obtain a good match at the low band for both these impedances.
That concludes this demonstration of Active Matching with BetaMatch.
My name is Max Landaeus and my contact details are on the screen right now.
Feel free to contact me if you have any questions or other feedback. Thanks for your time and attention.