How To Measure Antenna Gain Using A Network Analyzer?

To measure antenna gain using a network analyzer, first calibrate the analyzer, then connect the antenna and measure the return loss (S11) to ensure proper impedance matching. Perform far-field measurements to compare the test antenna's received power to that of a reference antenna with known gain.

Blog Post: How to Measure Antenna Gain Using a Network Analyzer

Antennas are key components in wireless communication systems, and accurately measuring their gain is crucial for performance evaluation. Using a network analyzer simplifies this task with precise impedance and power measurements. Here’s a step-by-step guide:

1. Calibrate the Network Analyzer

Before starting, calibrate the analyzer to eliminate errors. Use the Short-Open-Load-Thru (SOLT) method or similar calibration techniques suitable for your setup. This ensures accurate reflection coefficient (S11) and transmission measurements.

2. Measure Impedance Matching (Return Loss)

• Connect the antenna to the analyzer using a coaxial cable.
• Measure the return loss (S11 parameter) to confirm the antenna’s impedance matches the system (typically 50Ω). Poor matching reduces efficiency and may give inaccurate gain values.

3. Set Up the Test Environment

For accurate results:

• Perform measurements in an anechoic chamber to avoid interference.
• Position the antenna in its far-field region, determined by the formula: $$R_f = \frac{2D^2}{\lambda}$$ where $D$ is the antenna's largest dimension, and $\lambda$ is the wavelength.

4. Use a Reference Antenna

• Place a reference antenna with a known gain in the setup.
• Record its received power (P_ref) at specific frequencies.

5. Replace with the Test Antenna

• Swap in the test antenna, keeping the position and orientation consistent.
• Record its received power (P_test) under identical conditions.

6. Calculate Antenna Gain

The gain (G) of the test antenna can be derived as:

Here, $G_{\text{ref}}$ is the known gain of the reference antenna.

7. Validate Results

Verify the results across different frequencies to confirm consistent antenna behavior.

Conclusion

Measuring antenna gain using a network analyzer combines precision with simplicity, ensuring that the antenna operates effectively within its intended system. With proper calibration and setup, this method provides reliable results that engineers can use for system optimization.