Microwave PCB design

Simon G8DMN

Looking at various microwave PCB layouts, I see small quadrant shapes half-way along thin tracks feeding DC to amplifier stages. I presume they are capacitors forming a low-pass filter with the inductance of the thin tracks. However, despite searching online, I can find nothing about these gadgets, e.g. why quadrant shaped, how big etc. Can anyone point me at some information? Thanks for any help.
Simon G8DMN

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