Antennas · RF & microwave

Antenna design & full-wave electromagnetic simulation

My antenna work spans horn and ultra-wideband (UWB) antennas, millimeter-wave radiators and waveguide mode converters. I design antennas and verify them with full-wave modeling in COMSOL, CST Microwave Studio and Ansys HFSS, with selected designs then validated against measurement.

3D-printed horn with a PTFE focusing lens (10 GHz)

A conical horn spreads its beam once the wave leaves the aperture. A biconvex PTFE lens placed in the aperture turns the diverging wavefront into a converging one, so the power gathers in a spot about 100 mm in front of the horn. The horn was 3D-printed and metallized, and the lens was machined from PTFE (relative permittivity 2.2).

COMSOL, 10 GHz: the field Ex over one phase cycle, horn alone (top) and horn with lens (bottom). The triangles mark the focus.
The 3D-printed, metallized conical horn (yellow) with the white PTFE lens fixed to its aperture, on a lab bench.
The printed horn with the PTFE lens. From: A. Michael, N. Balal, Electronics 14, 3191 (2025), CC BY 4.0.
COMSOL 3D view of the horn and lens in front of a field plane: the beam narrows beyond the lens.
COMSOL 3D view: horn and lens in front of the Ex field plane.

In the model the on-axis power peaks 101.5 mm in front of the aperture. The focal spot is about 27 mm wide at half power (0.9 λ at 10 GHz), against 138 mm for the horn alone at the same distance. The measured axial power also peaks about 100 mm from the aperture. The model is 2D axisymmetric, with perfectly conducting walls and a lossless lens.

Normalized radiation pattern of the printed horn without the lens at 10 GHz, from -20 to 20 degrees: simulation (line) and measurement with error bars (points).
Radiation pattern of the printed horn without the lens at 10 GHz: simulation and measurement. From: A. Michael, N. Balal, Electronics 14, 3191 (2025), CC BY 4.0.
Far-field pattern of the horn without the lens at 10 GHz computed in COMSOL Multiphysics (blue points) and CST Studio Suite (red line); the two curves overlap on the main lobe.
The same horn without the lens, modelled in COMSOL (points) and in CST Studio Suite (line), 10 GHz. Horizontal axis: angle in radians, boresight at π/2; vertical axis: normalized pattern. The two solvers agree on the main lobe and on the side-lobe positions. From: A. Michael, N. Balal, Electronics 14, 3191 (2025), CC BY 4.0.

Wideband antipodal Vivaldi antenna

A Vivaldi antenna is a slot that widens exponentially toward its open end. Each frequency radiates from the part of the flare where the slot is about half a wavelength wide, so one antenna covers a wide band. In the antipodal version the two flares are printed on opposite sides of the board and fed from a microstrip line through a tapered ground. This design uses a 60 × 70 mm Rogers RO4003C board with a 50 mm aperture, half a wavelength at 3 GHz.

COMSOL 3D view of the antipodal Vivaldi board: top copper flare and microstrip in orange, bottom copper flare and ground in blue, lumped port in red.
COMSOL geometry: top copper (orange), bottom copper (blue), 50 Ω port (red).
Realized-gain pattern from 3 to 11 GHz, one frame per GHz.
Simulated |S11| of the Vivaldi antenna from 2 to 12 GHz: below -10 dB from 3.61 GHz to 12 GHz except between 4.96 and 5.64 GHz, with check points from a second mesh.
|S11| at the 50 Ω port, sampled every 0.5 GHz with 0.1 GHz steps near the band edges. Squares: a coarser mesh. The lower band edge moves by 1% between the two meshes.

In the simulation |S11| stays at or below −10 dB from about 3.6 GHz to the end of the sweep at 12 GHz, with a narrow region near 5 GHz where it rises to about −9 dB. The band starts 20% above the 3 GHz set by the aperture width. Boresight realized gain is about 8.3 to 9.1 dBi between 6 and 11 GHz. The copper is modelled as a zero-thickness perfect conductor and the feed as a lumped port without a connector, and the antenna has not been built or measured.

Normalized electric-field magnitude in the board plane of the Vivaldi antenna at 3, 6 and 10 GHz, with the copper outlines of the two flares.
|E| in the board plane at 3, 6 and 10 GHz (dB, normalized), with the copper outlines of the top (solid) and bottom (dashed) layers.

3D-printed rectangular-to-circular waveguide mode converter (X band)

A rectangular waveguide carries the TE10 mode, while a circular horn is fed with TE11. The converter changes the cross-section over 150 mm, from a standard X-band rectangular guide (22.86 × 10.16 mm) to a circular guide of 11.9 mm radius. Two prototypes, one printed in plastic and one in metal, were measured on a vector network analyzer from 8 to 12 GHz and compared with CST Microwave Studio.

CST Microwave Studio electric-field arrows at 10 GHz in the mode converter: a vertical field, strongest at the centre, across the rectangular input (left) and the TE11 pattern across the circular output (right).
CST Microwave Studio, 10 GHz: electric field at the rectangular input (left, z = 0) and at the circular output (right, z = 150 mm). © 2025 IEEE. Reprinted from N. Balal, A. Michael, PIERS-Fall 2025, doi:10.23919/PIERS-Fall62445.2025.11394043.

Antenna measurements

The lab has an anechoic chamber, a vector network analyzer and an XYZ scanning system. I measure S-parameters and radiation patterns and compare them with the simulation of the same structure. The XYZ system also maps the field near an antenna, for example the power along the axis of the lens horn above.

The lab's XYZ scanning system: a motorized three-axis gantry on a table, facing the yellow 3D-printed horn on a tripod.
The XYZ scanning system, set up for the axial power measurement of the lens horn. From: A. Michael, N. Balal, Electronics 14, 3191 (2025), CC BY 4.0.

What the antenna models calculate

The full-wave model yields the reflection coefficient (return loss, S-parameters), near- and far-field radiation patterns, gain, aperture efficiency and bandwidth. This supports horn and UWB antennas, waveguide-to-radiator transitions and rectangular-to-circular mode converters, including 3-D-printed millimeter-wave hardware: I have designed and experimentally validated Ka-band horn antennas and X-band mode converters.

Horn antennasUWB mmWaveWaveguide mode converter Radiation patternCOMSOL · CST · HFSS 3D-printed & validated

Selected antenna publications

Antenna design and validation

Technical questions and research collaboration: nezahb@ariel.ac.il

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