Typical Insertion Loss of Broadband Matching Network in real applications...

[RFegg]

for those who have practical experience or designed broadband matching networks, say a 4-section LC network, what's your typical measured insertion loss at VHF and UHF regions?

 

[E Kafeman]

It depends on a lot of factors. Needed impedance ratio adjustment, stray capacitance, losses in components and PCB traces. In general are losses higher for upper part of the matching frequency range.
I do a lot of broadband antenna and RF filter matching, low power, compact, using 0402 components or smaller. Typical frequency range 300 MHz- 3 GHz.
As a rule of thumbs, assume each component to add losses corresponding to 0.1-0.2 dB including costs for PCB traces. If a component don't adds benefits higher than that, find a better solution.
A less stable RF ground for the impedance network can cost extra loss. High frequency in combination with high inductive values are often problematic but can also be turned to an advantage.

If you not done so already, check AnTune, an impedance matching software that can take these factors in account and automatically find an optimized solution.
It is the only software of this kind that can read directly from your network analyzer and present an optimized matching network in real time. It is also possible to feed it with a regular S-parameter file.
The software finds dynamically both optimized topology and component values, taking account what components that you prefer (brand/size/type).
Especially when designing antennas, for me is it an important function to have live information. If resulting bandwidth not is good enough, bend the antenna a bit and directly get results if resulting antenna impedance in combination with a recalculated network results in a wider bandwidth at less cost.

Many that designs antennas makes the mistake to add a matching network, afterwards that the antenna is reasonable optimized at center frequency and assumed final in design. The chance to find a simple impedance network that then improves what is missing at band-edges without affecting center frequency is none.
If some losses are accepted (increased VSWR) at center frequency can improvements be reached at band-edges, but it is a poor solution as it results in an increased average over bandwidth loss.
For total best optimized result must matching network be included as a part of antenna design from a very early stage. That makes it possible to get widest bandwidth with minimum loss for the network in combination with the antenna, not just the losses for a matching network part.

 

[RFegg]

It depends on a lot of factors. Needed impedance ratio adjustment, stray capacitance, losses in components and PCB traces. In general are losses higher for upper part of the matching frequency range.
I do a lot of broadband antenna and RF filter matching, low power, compact, using 0402 components or smaller. Typical frequency range 300 MHz- 3 GHz.
As a rule of thumbs, assume each component to add losses corresponding to 0.1-0.2 dB including costs for PCB traces. If a component don't adds benefits higher than that, find a better solution.
A less stable RF ground for the impedance network can cost extra loss. High frequency in combination with high inductive values are often problematic but can also be turned to an advantage.

If you not done so already, check AnTune, an impedance matching software that can take these factors in account and automatically find an optimized solution.
It is the only software of this kind that can read directly from your network analyzer and present an optimized matching network in real time. It is also possible to feed it with a regular S-parameter file.
The software finds dynamically both optimized topology and component values, taking account what components that you prefer (brand/size/type).
Especially when designing antennas, for me is it an important function to have live information. If resulting bandwidth not is good enough, bend the antenna a bit and directly get results if resulting antenna impedance in combination with a recalculated network results in a wider bandwidth at less cost.

Many that designs antennas makes the mistake to add a matching network, afterwards that the antenna is reasonable optimized at center frequency and assumed final in design. The chance to find a simple impedance network that then improves what is missing at band-edges without affecting center frequency is none.
If some losses are accepted (increased VSWR) at center frequency can improvements be reached at band-edges, but it is a poor solution as it results in an increased average over bandwidth loss.
For total best optimized result must matching network be included as a part of antenna design from a very early stage. That makes it possible to get widest bandwidth with minimum loss for the network in combination with the antenna, not just the losses for a matching network part.

thanks for the informative response...

but my application is on Power amplifier where typically the optimum loads are very small and for my case around 1 to 4 ohms and small capacitive reactance to be matched to a 50-ohm load...my concern is that the efficiency will be greatly affected if my insertion loss it significant....but due to the broad BW requirement where i use 4 section LC network will really induce significant insertion loss when using real components...

so i like to have some practical actual values that is quite expected from this say in a vhf or uhf bands....

 

[E Kafeman]

A big number in impedance ratio was one of the things I did mention in the first row. 1:50 is rather big in my RF-world as any losses in first part of matching network, will be multiplied with same ratio as remaining network impedance ratio.
Typical insertion loss at these frequencies is handheld low power things. They are numerical the most common types.
It is a very vital factor to know if your PA is something magnitudes bigger then a Bluetooth PA.
With that low PA impedance I guess its output power level require something better then 0402 to handle power losses and you is maybe not that limited in available space? Is it a handheld PA or stationary?
If you have space enough, why not start with a current transformer? What losses that are acceptable, gives a clue about how thick wires to select both for transformers and coils.