In the design of a video recorder’s RF power amplifier, the power supply line serves not only as an energy transmission channel but also as a critical pathway for the ingress and egress of various high-frequency electromagnetic interferences. These interferences may originate from external sources such as grid switching noise and clock harmonics from digital circuits, or they may arise from the amplifier’s own reverse-conducted noise generated during operation in the VHF frequency band. Without effective suppression, high-frequency noise on the power line can directly couple into the RF amplification chain, leading to carrier phase jitter, modulation distortion, and spectral broadening. This ultimately manifests as degraded video signal quality, with visible artifacts such as streaks or noise in the image. Within this precise and sensitive RF environment, feedthrough capacitors have become indispensable core components for power line interference suppression, thanks to their unique structural design and excellent high-frequency response characteristics.
The value of feedthrough capacitors lies first in the electrical advantages brought by their “through-type” physical structure. Unlike ordinary capacitors, they employ a three-terminal design: the inner electrode is connected in series with the power line, creating a direct blocking path for interference signals; the outer electrode is tightly connected to the amplifier’s metal housing via a large-area contact surface, establishing a low-impedance, short-path grounding channel. This structure achieves an optimal “power-capacitor-ground” layout from a physical perspective, enabling high-frequency interference currents to be diverted to the ground with minimal loop inductance rather than entering subsequent circuits. Particularly when addressing the critical interference frequency range of 10MHz to 1GHz, their extremely low parasitic inductance (typically below 1nH) ensures excellent insertion loss even within the VHF RF range, effectively avoiding the performance degradation or outright failure of traditional capacitors at high frequencies due to lead inductance.
In practical installation, the placement and grounding quality of the feedthrough capacitor directly determine its effectiveness. It is typically installed between the power input port and the first-stage voltage regulation or filtering circuit, acting as a “gatekeeper.” During installation, it is essential to ensure that its metal housing makes full-circumference, low-impedance contact with the amplifier chassis. If necessary, silver-plated grounding straps or conductive gaskets are used to enhance high-frequency grounding. This installation method not only blocks external interference from entering but also effectively suppresses the reverse radiation of high-frequency switching noise generated internally by the amplifier through the power line. Thus, it fulfills the dual requirements of electromagnetic compatibility—protecting the device from external interference while preventing the device from becoming an interference source. As RF technology continues to advance toward higher frequencies and greater integration, this power filtering solution based on feedthrough capacitors remains a cornerstone for ensuring the reliability of high-quality wireless video transmission.
