In general belief, smaller capacitors have better charactristic(more capacitive behaviour) in high frequency than bulky capacitors.
On contrary in one of my RF project (8.5GHz - 9.5GHz) when checking for different package size as bypass capacitor between each of my microwave block (Mixer, Switches and etc) I suspect above rule of thumb
After some inspection on S-Param of Kemet RF capacitors, I noticed that for the same value of capacitor, SRF(Self Resonant Frequency) become higher as package size increases. So a 805 package have higher SRF than 603 and the same rule for 603 and 402 (SRF_603 > SRF_402).
I see the same result in KSIM simulator from Kemet. Here is the summarized result
10pF C0603 C0G 10VDC-8 C0603C100K8GAC : SRF = 2.089GHz
10pF C0805 C0G 10VDC-8 C0805C100K8GAC : SRF = 2.399GHz
As can be seen in simulator (and verified by VNA in lab) the SRF not decrease with size instead SRF increases with even more than 300MHz. Why is that the case?
- note: I will add the sparam plot soon.
- note2: I see same result in reply #11 and other replies on this page.