Wineglass Array UWB antenna

 Jan 2025 - July 2025

Role: Main Engineer / Designer

Overview:

Conventional direction-finding antenna hardware uses three radiators with three beams to determine direction. However, the coverage is limited to three areas, leaving blind spots that are not detected. The proposed method multiplies the number of beams to six, increasing coverage while maintaining the same number of radiators.

Design goal

- A three-element antenna with six beams to enhance coverage

- Wide-band performance matching with a wineglass shape through a Bezier curve

- Direction finding application operating in high-band of UWB (6 - 9 GHz)

Birfurcated Beams antenna:

A long dipole antenna (greater than 0.5 wavelength) will have a directive radiation pattern. However, the input impedance of the antenna will be very high. To demonstrate this effect, we build a dipole antenna with length 0.8 of wavelength at 6 GHz. We noted that the normalized radiation pattern on the longer dipole is more directive toward the radiator, with two beams. 

Circular array antenna:

Step 1. Using the long dipole antenna in a circular array will provide the necessary pattern for a bifurcated beam pattern per element. However, the impedance matching (S11) at the operating frequency of 6 - 9 GHz is highlighted in yellow.

 

Step 2. We redesigned the element with the wineglass element from previous work (wineglass antenna). The wideband performance is inherited from 4 to 7 GHz. However, the mutual coupling (S21) is very high.

 

Step 3. To reduce mutual coupling, we removed the sharp edges to lower reflections in the ground plane.

 

The radiation pattern still has two beams for each element. 

Further detail optimization of the Bezier curve is performed with the HFSS Adaptive Multiobjective Optimization algorithm. The goal is to improve performance in mutual coupling and bandwidth. 

The final deign is fabricated and the measurement and simulation result is shown below with the radiation performance:

Achievement:

- Circular array antenna with 6 beams expanding its coverage

- Windband antenna covering from (6 - 9 GHz)

- Satisfying mutual coupling between ports below -12.7 dB in the operating frequency

Master's Final Thesis :

"Design of wineglass shape UWB antenna on flexible substrate using Bezier curve optimization" - Seoul National University of Science and Technology, 2025

Wineglass-Shaped UWB Antenna

Feb 2024- Dec 2024

Role: Main Engineer / Designer

Overview:

This project aims to 

- Create a compact and flexible ultra-wideband (UWB) antenna optimized for wearable and space-constrained applications. 

- Design targets a wide impedance bandwidth (3.2–8.7 GHz), high radiation efficiency, and mechanical flexibility, making it suitable for next-generation localization and communication systems.

📐 Design Method:

1. Conventional Bell-shape challenges

• Started with a traditional bell-shaped monopole prototype (problem with mid-band frequency highlighted in yellow)
•  Reducing the width of the antenn (18 mm to 12 mm) mismatch in the mid-band frequency
• Cannot miniturize furtur in with just elliptical or circular geometry 

2. Impelmentation Wineglass shape with Bezier Curve

• Beizer curve for more adaptive and smooth strucutre as shown below.
• Pushing the ground plane closer to the radaitor moved the second resonent closer to the lower frequency.
• In creasing the surface coupling between the radiator and ground, improve the matching in mid-band frequency.
• How about the high-band frequency ? 

3. Trident feed 

• Added trident feed to improve high-frequency performance
• Moving the parameter t shifts the second resonance to a higher frequency while maintaining the midband below -10 dB.

4. Final design 

• Final parameters and dimensions are shown in the figure below.

• Fabricated on polyimide thin-film (total thickness: 125 μm) for flexibility:

🏁 Result & Achievement:

• Operating bandwidth: 3.2 GHz to 8.7 GHz (2.7:1 ratio)

• Consistent >70% radiation efficiency with omnidirectional pattern

• Ultra-compact size: 35 × 12.4 × 0.125 mm³ (~0.37λ₀ × 0.13λ₀ × 0.0013λ₀)

• Measurement confirmed simulation accuracy

Conference:

Ly, C.; Chung, J.-Y. A compact UWB Thin-film antenna design on a spline curve and Trident Feed. KIEES Summer Conference 2024

Journal:

Ly, C.; Chung, J.-Y. A Trident-Fed Wine Glass UWB Antenna Based on Bézier Curve Optimization. Electronics 2025, 14, 2560. https://doi.org/10.3390/electronics14132560

Bell-Shape UWB antenna

Sep 2023 - Feb 2024

Role: Test Engineer (Simluation, Fabrication, and Measurement)

Overview:

The main objective of this project is to design a compact UWB antenna on FCCL substrate (thickness = 150 um).

- Use polyimide substrate with adhesive that has a high dielectric constant (Dk = 8) and low loss tangent (Df = 0.008).

- Antenna design using a conventional bell shape for the lower band of UWB (3 - 5 GHz).

- Improve the gain from the previous design

Why FCCL Substrate? 

In a compact mobile phone like the Apple iPhone, space is very valuable, and usually, antennas are the most space-constraining hardware after the battery. To make a smaller and more compact antenna, engineers start to use flexible and thin substrates because of their conformal capability. Compared with an FR4 substrate, which is usually 1.6 mm thick, the polyimide-based substrate used in this work is ten times thinner at only 0.15 mm. 

Antenna Design:

The design of the antenna was performed by another team member. The bell-shaped design is chosen because it is a conventional method to generate the UWB pulse. The antenna's bell-shaped geometry is a combination of elliptical (ground) and semi-arc (radiator) used to control the curvature. The final design of the antenna is fabricated with several samples to test for different gain performances. 

To improve the gain, the aperture of the antenna needed to be increased, so several designs were made with different sizes. To maintain matching of the antenna over the operating frequency, the elliptical and arc parameters are tuned for each design.

The fabrication sample for each design is tested with the VNA for the reflection coefficient (S11) and in the anechoic chamber for radiation performance as shown below.

Achieved:

The results of this project are as follows:

- Compact UWB antenna design on thin-film substrate

- Wideband performance with a bell-shaped pattern

- Gain improved from 3dBi to 5dBi by simply increasing the aperture.

Publication: 

- Dao, D.N.; Chung, J.-Y. A Miniaturized Thin-Film UWB Monopole Antenna Implemented with High-Dk Adhesive. Electronics 2023, 12, 3445. https://doi.org/10.3390/electronics12163445