The signal synthesizer in satellite communications serves as the core hub of the satellite communication payload and ground station systems. Its task is to accurately combine and route multiple upconverted signals, local oscillator signals, and modulated data streams to generate a final transmission signal with high spectral purity. This process imposes nearly stringent requirements on phase noise, harmonic suppression, and spurious levels—any minor electromagnetic interference can lead to spectral degradation of the combined signal or elevated out-of-band spurious emissions, ultimately affecting the signal-to-noise ratio and bit error rate performance of the communication link. Against the backdrop of extreme temperature cycling, vacuum conditions, and continuous cosmic radiation in space, the power amplifier circuits, phase-locked loops, and high-speed digital control modules within the combiner generate abundant high-frequency noise, with spectra extending up to tens of GHz. If such interference couples into sensitive signal paths via the power layer, reference clock lines, or RF traces, it can directly compromise the spectral purity and phase coherence of the combined signal. In this precise and demanding application scenario, feedthrough capacitors have become key components for ensuring the noise suppression performance and long-term reliable operation of signal synthesizer, thanks to their extremely low parasitic inductance and excellent high-frequency response characteristics.
The core advantage of feedthrough capacitors lies in their innovative “through-type” coaxial structural design. Unlike traditional multilayer ceramic capacitors or planar capacitors, their signal path vertically penetrates the capacitor dielectric, completely eliminating parasitic inductance introduced by bond wires, pads, or vias, while the metal housing forms a complete Faraday shield. This structure allows them to maintain near-ideal capacitive impedance characteristics even in the Ka-band and higher frequency ranges, with self-resonant frequencies (SRF) reaching tens of GHz. This provides an almost zero-impedance grounding path for ultra-high-frequency noise above GHz levels. When noise from the phase-locked loop charge pump, power supply ripple harmonics, or digital switching noise in the signal combiner attempts to contaminate RF signals through common ground paths or radiative coupling, feedthrough capacitors can efficiently channel it into the system’s ground plane, akin to “electromagnetic absorbers,” thereby suppressing noise propagation and coupling at the source.
As satellite communications advance toward the Q/V frequency bands and terahertz communications, the bandwidth and complexity of signal combiners continue to increase, imposing even more stringent requirements on the cleanliness of the internal electromagnetic environment. Feedthrough capacitor technology is evolving in parallel toward higher self-resonant frequencies, lower equivalent series resistance (ESR), and three-dimensional heterogeneous integration. In the silent battlefield of vast space, this tiny component consistently guards the purity and stability of every combined signal with its precise electromagnetic filtering capability, ensuring that humanity’s communication across the stars remains uninterrupted.
