RF Hardware · Simulation · Measurement

Interdigital Ultra-Compact SSPP Low-Pass Filter

A primarily self-directed undergraduate research line connecting electromagnetic design, CST simulation, PCB fabrication, VNA measurement, a first-author paper, a granted invention patent, and the undergraduate thesis.

SSPP filter design, PCB prototype, and response evidence — Filter design and prototype evidence from the published work. Simulation and measurement results are distinguished below.

Invention patent certificate for the interdigital ultra-small low-pass SSPP filter — Invention patent certificate · Grant publication date: 8 September 2026.
View original certificate (PDF) ↗

What I did

Designed and optimized the interdigital SSPP unit, matching regions, and central waveguide structure.
Used CST Microwave Studio for dispersion, dimensions, unit count, S-parameters, electric-field and surface-current studies.
Built the FR-4 PCB prototype, attached SMA connectors, and measured it with a Keysight N5234B vector network analyzer.
Led the data processing and first-author paper work.

Simulation and measurement

Evidence type	Documented result
Simulation	0–5.66 GHz passband; 5.95–12 GHz stopband with more than 24 dB suppression; reported 105 dB/GHz roll-off factor near 5.74 GHz
Measurement	5.53 GHz cutoff; measured passband return loss above 20 dB and out-of-band suppression above 35 dB in the paper comparison table
Size	0.5 × 0.16 λ₀²

The paper, granted patent, and undergraduate thesis are continuations of the same technical work. They are presented as one research line rather than three independent achievements.

Read the paper