RF Interview Essentials 6.0: Mastering Capacitors: Bypass, Decoupling & LC Resonance for RF Applications

Your guide to capacitors and their applications in RF design.

Dear Subscriber,

Thanks for sticking around! In this article, we’ll talk about capacitors and their applications in RF hardware design. We all know an RF interview isn’t complete unless the interviewer asks about the bypass capacitor and its placement — so I decided to write about this essential topic.

When it comes to RF design, capacitors might seem like simple two-terminal components — but they play a pivotal role in filtering, stability, and impedance control across circuits operating at MHz and GHz frequencies.

Every RF engineer learns early on that capacitors “block DC and pass AC.” Yet in the high-frequency world, that’s just the beginning of the story. Capacitors shape signal integrity, prevent oscillations, and fine-tune the delicate balance of impedance across RF paths. What looks like a humble 100 nF chip can determine whether your power amplifier delivers clean output or your LNA drowns in noise.

Below are some of the most frequently asked interview questions about capacitors and their role in RF hardware design — explained with practical clarity and design insight.