DIY: Building a High-Performance Wi-Fi Patch Antenna to Boost Your Connection

Introduction: Why Build a Wi-Fi Patch Antenna? #

Have you ever repurposed a Wi-Fi card without an antenna and noticed unstable or slow connections? That’s exactly what motivated me to start this project.

To resolve this issue, I decided to design a DIY patch antenna specifically tuned to the 2.4 GHz band. A patch antenna is compact, easy to fabricate, and provides good directivity—perfect for improving the network performance of a desktop PC.

In this project, I will cover:

1. Designing the antenna using classical calculations and CST Studio simulations.
2. Fabricating the antenna with a CNC LPKF machine and designing a protective box using SolidWorks.
3. Testing network performance to measure improvements with and without the antenna.

The goal is to create an affordable and efficient solution while exploring possibilities for future enhancements, such as dual-band coverage.

Step 1: Design and Dimension Calculations #

Why a Patch Antenna? #

A patch antenna consists of three main components:

1. A metallic patch that radiates the signal.
2. A dielectric substrate (FR4 in this case) that separates the patch from the ground plane.
3. A ground plane that directs the radiation.

This design is ideal for Wi-Fi because it provides:

• Good adaptation to a specific frequency (here 2.4 GHz).
• Moderate directivity for targeting the area around your router.
• A compact structure, suitable for limited spaces.

Dimension Calculations #

The patch and feed line dimensions are calculated based on the target frequency ((f_r = 2.4 GHz)) and the substrate properties ((\epsilon_r = 4.4)). Key steps include:

1. Patch width ((W)): [ W = \frac{c}{2f_r\sqrt{\epsilon_r}} ] where (c) is the speed of light.
2. Effective length ((L_{eff})): Adjusted to account for fringing effects.
3. Microstrip line: Tuned for a 50-ohm impedance to minimize energy losses.

Using an online calculator (Everything RF), the optimized dimensions are:

• Patch width: 38 mm.
• Patch length: 30.8 mm.
• Microstrip line width: 3.1 mm.
• Feed point: 7.7 mm.

Step 2: Simulation with CST Studio #

Why Use CST Studio? #

I used CST Studio Suite, a powerful electromagnetic simulation tool, to validate the antenna’s performance before fabrication. This software enables:

• Virtual testing of the design to avoid costly errors.
• Analysis of key parameters like S11 and VSWR.
• Visualization of radiation patterns and efficiency in the target frequency range.

Key Parameters #

• S11 (Reflection Coefficient): Measures the power reflected by the antenna. A value below -10 dB ensures over 90% of the power is transmitted, critical for good adaptation.
• VSWR (Standing Wave Ratio): Indicates how efficiently power is transmitted. A VSWR close to 1 is ideal; a value below 2 is acceptable for Wi-Fi applications.

Simulation Results #

• S11: Minima at -12 dB at 2.4 GHz, confirming proper adaptation.
• VSWR: Stable at 1.9, sufficient for effective transmission.
• Radiation patterns: Moderate directivity with a 45° coverage angle, ideal for domestic use.

Step 3: Antenna Fabrication #

Etching the Patch #

With validated dimensions, I etched the antenna on an FR4 substrate using a CNC LPKF machine. The DXF file generated in CST Studio was imported directly into the CNC software, ensuring precise fabrication.

Designing the Protective Box #

To protect the antenna and facilitate installation, I designed a box in SolidWorks and printed it in PETG using a Bambu Lab 3D printer. PETG is durable and resistant to temperature variations, making it ideal for this application.

Step 4: Real-World Testing #

Testing with a VNA #

A vector network analyzer (VNA) was used to evaluate the antenna’s performance:

• S11: Measured at -12 dB at 2.4 GHz, indicating proper adaptation.
• VSWR: Measured at 1.9, confirming efficient power transmission.

Network Testing with Acrylic Suite #

To assess the antenna’s impact on network performance, I tested the connection before and after installing the antenna:

• Without antenna: RSSI of -74 dBm, unstable signal, limited to 144 Mbps.
• With antenna: RSSI improved to -49 dBm, stable connection, increased speed to 542 Mbps.

These results demonstrate that the antenna significantly improves both stability and speed.

Step 5: Limitations and Future Improvements #

The current monopolar design is limited to the 2.4 GHz band, which is sufficient for basic Wi-Fi but does not cover the advantages of the 5 GHz band. A future version could integrate dual-band coverage and utilize the two ports on the Wi-Fi card for MIMO, enhancing both stability and speed.

Conclusion #

This project demonstrates that building a high-performance Wi-Fi antenna at a low cost is entirely feasible.

Using modern tools like CST Studio, a CNC, and a 3D printer, this patch antenna has significantly improved network quality. With future adjustments, it could be adapted for dual-band or IoT applications, making it even more versatile.

If you have questions or suggestions, feel free to send a mail ! 😊

Tools and References #

Tools Used #

• Software: CST Studio, SolidWorks, Acrylic Suite.
• Equipment: CNC LPKF, Bambu Lab 3D printer (PETG), Vector Network Analyzer (VNA).

References #

• Patch Antenna Calculator: Everything RF.
• CST Studio Guides: Official documentation.
• Theoretical Resources: Articles from ResearchGate and IEEE Xplore.