teardrop type power divider question

[yefj]

Hello,I have built a microstrip line structure as shown below In photo and article 1.
my lines are er=9.4 h=0.433 line width W=0.015mm spacing between lines 0.065mm and 2 micron thickness.
The line impedance properties is 140 Ohm.
However I need also to build a feeding network for these lines.
I was suggested to use this nature article with the intrested shape.
Howeven i dont see the impedance power dividing logic in this tear drop shape.
I know its supposed to be a transformer of some sort,but there is a huge discontinuety in the width between W1(tear drop shape) and Wt(line width).
What is the impedance logic in this huge transition?
Thanks.

Inverse design of compact power divider with arbitrary outputs for 5G applications - Scientific Reports

Since the recent on-demand applications need more sophisticated circuits and subsystems, components with configurable capabilities attract attention more than before in commercial systems, specifically the fifth generation (5G). Power dividers play a crucial role in 5G phased array systems, and...

www.nature.com

https://www.nature.com/articles/s41598-022-17212-0/figures/2

 

[volker@muehlhaus]

I guess the teardrop is just a wideband taper from Zline to Zline/4, to match the 4 parallel lines connected there.

 

[yefj]

Hello Volker,Why did they use Lt?
Its a transformer , but we have already a transformer ( the big taper)

 

[volker@muehlhaus]

Why did they use Lt?

I just read the full article and it's more complicated than your screenshot shows ... the section with Wt, Lt is actually the quarter wave transformer.

 

[yefj]

Yes I know its a quarter wave transformer.
Why did they use it ,if we already have the taper as transformer.