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