High-Frequency (RF) Simulation

Analysis of TE10 mode propagation in air-filled and alumina-loaded WR-90 waveguides

A compact HFSS study comparing cutoff frequency, guided wavelength, field confinement, and insertion loss for a standard air-filled guide versus a 96% alumina-filled configuration.

Air cutoff

6.56 GHz

Baseline WR-90 propagation threshold.

Alumina cutoff

2.19 GHz

Dielectric loading lowers the operating threshold.

Measured loss

0.26-0.72 dB

Insertion loss range from alumina loss tangent.

Project completion date: November 9, 2025

Download full report (PDF)

Waveguide theory

The project focuses on the dominant $TE_{10}$ mode in a WR-90 rectangular waveguide. The comparison isolates one design variable: replacing the air volume with 96% alumina to study how relative permittivity reshapes propagation behavior.

Engineering domain

High-frequency RF engineering, microwave theory, waveguide propagation, and electromagnetic field interpretation.

Core analysis

Cutoff frequency, guided wavelength, S-parameter response, field concentration, and dielectric attenuation.

Software used

ANSYS Electronics Desktop with HFSS for 3D electromagnetic modeling and post-processing.

HFSS simulation setup

Objective

The goal was to conduct a quantitative comparison of $TE_{10}$ propagation in a standard WR-90 waveguide and in the same geometry fully loaded with alumina. The HFSS setup evaluates how dielectric loading changes cutoff frequency, guided wavelength, field concentration, and insertion loss.

Project milestones

Modeled both air-filled and alumina-filled WR-90 configurations against theoretical formulas.
Compared $TE_{10}$ cutoff frequency using analytical relations and HFSS validation.
Visualized E-field and H-field concentration for both material cases.
Compared guided wavelength at 10 GHz to show dielectric loading impact.
Quantified insertion loss through S-parameter post-processing in HFSS.

Field & S-parameter results

Cutoff shift

Alumina loading reduces cutoff from 6.56 GHz to 2.19 GHz, making the same physical guide behave like a lower-frequency structure.

Field confinement

The high-permittivity region concentrates electric and magnetic fields, changing the spatial energy distribution inside the guide.

Loss trade-off

The alumina case introduces measurable insertion loss, quantified between approximately 0.26 dB and 0.72 dB.

Simulation gallery

Air-filled waveguide

S-parameter plot for air-filled WR-90 waveguide — ANSYS HFSS simulation — Baseline result set used to validate the WR-90 air-filled model before comparing the dielectric-loaded guide.

Electric field magnitude animation from HFSS waveguide simulation — Baseline result set used to validate the WR-90 air-filled model before comparing the dielectric-loaded guide.

Alumina-filled waveguide

S-parameter plot for alumina-loaded WR-90 waveguide — ANSYS HFSS simulation — Dielectric-loaded result set showing the lower cutoff frequency, stronger field concentration, and measurable insertion loss.

Conclusion

The simulation confirms the expected electromagnetic trade-off: alumina loading enables a much lower cutoff frequency in the same WR-90 envelope, but it also increases field concentration and introduces dielectric loss.

Cutoff frequency: Alumina lowered the cutoff frequency from 6.56 GHz to 2.19 GHz.
Field concentration: Fields became more concentrated inside the high-permittivity material.
Insertion loss: Dielectric attenuation was quantified at approximately 0.26 dB to 0.72 dB.

Future work

A logical next step would be to investigate a partially filled waveguide. Simulating a dielectric slab with variable thickness would help identify a practical compromise between miniaturization, field confinement, and insertion loss.