Calculate matching result is possible but it is harder to design wide band optimized topologies and values in ADS for lossy components.
Real resistance ratio is about 150 times from 0.3 to 50 Ohm. It is a bit too much to match in a single step. It can easily cost a lot of losses.
Real resistance measurements below 1 Ohm and even minor calibration error can cause big final mismatch.
Doubt that 0.3+j1.8 Ohm is a constant impedance for whole 900-1300 MHz range? Even minor variations by frequency will affect wide band matching result.
If there is space enough can a PCB transformer or stub matching be to prefer, at least as a part of matching network as it can be designed with low resistive losses and less demand for an ideal ground plane.
With a such low impedance must probably matching network components be designed to handle possible losses as heat and max inductor current must be considered..
Assuming 0.3+j1.8 Ohm is actual impedance over whole freq.range and assuming ideal lossless matching components, then is tuning not that complicated to achieve for a VSWR less then 1:2.
Lossless example using standard values for reactive components.
View attachment 166693
Schema antenna symbol is here your transistor.
C1 value is 82pF. It is a very low impedance at 1300MHz.
C1 is an ideal component. A very ideal ground is then needed to be able to handle this capacitor properly or else will not expected matching result be achieved. This network have no DC decoupling which also can be a factor to take in account.
Ideal components is what often is used for these kinds of matching calculations but that will not result in optimal real world matching and ideal component calculations is often not what works best in real world, neither values or topology.
Implementing S-parameters for matching components gives somewhat more realistic result.
Optimal matching VSWR is in this case a bit less good when using real world components and it result in a different topology for optimal matching result:
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It is still a big capacitor to ground, which will demand very ideal circumstances to work as expected.
As a comparison showing how critical component properties are in this case, assume exact above matching component values but inductor L3 is replaced by a Murata LQW18AN with same inductance value:
View attachment 166699
Impedance match is quite different at 1300 MHz as result of changing type of inductor.
It is partly possible to compensate for this by using a higher inductance value if using this type of inductor but point is that value is not an absolute factor when calculate an impedance matching network..
Adding smaller variations in pads locations, ground plane current path, and minor variations in capacitor losses and resulting total matching can vary quite a lot.
All above matching typologies are hard to implement due big impedance ratio and due to this a need for more or less lossless components and ideal ground.
By reducing impedance match goal to something less demanding and by adding a matching component is it somewhat easier to actually achieve theoretical calculated result also as a measured result.
A such proposal:
View attachment 166703
It is still not an easy task to implement this 4-pole matching network with its serial and parallel resonances, which can make component values more critical but we have got rid of the extrem component value for a first big capacitor to ground as in previous network.
Careful measurement is recommended to verify, and if needed, adjust each pole step by step to be able to take in account for non ideal losses and delays and practical problems related to very low impedance measurements. Doing so is it possible to get a decent match very similar to above calculated Smith chart curve.
One reason that this network is easier to implement is that we are using L1 reactive unlinearity to our tuning advantage as its SRF is around 2-3 GHz.
Do the exercise in ADS and replace this inductor with something else of same value to see difference.
Network real world transmission loss is about 1.5 dB if a stable ground plane.