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Here is an image of an LNB circuit:

image

Probably you heard something about length-tunned traces that they use in high-frequencies PCBs. There is something similar to the length-tunned traces in the PCB(blue circle) but it's not length-tunned trace because they are cutted-out. What could be they?

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It is a special transmission line filter topology, called "hairpin filter" because the line sections look like hair pins.

It is most likely used as a band-pass filter of some sort in this circuit.

More on these filters can be found on the wikipedia page for distributed element filters: https://en.wikipedia.org/wiki/Distributed_element_filter

The following document shows a few examples for hairpin band-pass filters:

http://www.w1ghz.org/filter/Recipes_for_Printed_Hairpin_Filters.pdf

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  • \$\begingroup\$ +1 very useful. DO you know any good recipes for differential elements? \$\endgroup\$ – Ale..chenski Nov 28 '18 at 3:11

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