Antenna 3 dB Beamwidth Calculator

Calculate the half-power (3 dB) beamwidth in degrees for a circular aperture antenna.

Step 1: Enter Antenna Parameters

Wavelength, $\lambda$ (m)

e.g., 0.03 m (corresponds to 10 GHz)

Aperture Diameter, $D$ (m)

e.g., 0.5 m

Calculate Beamwidth

Calculated 3 dB Beamwidth

Beamwidth, ${\theta }_{3dB}$ (degrees):

Recalculate

Antenna 3 dB Beamwidth Calculator (In-Depth Explanation)

The 3 dB beamwidth (or half-power beamwidth) of an antenna is a critical parameter that indicates the angular width of the main lobe where the radiated power is at least half of its maximum value. For a circular aperture antenna, this beamwidth is primarily determined by the antenna's physical size (aperture diameter) and the operating wavelength. This guide explains how to estimate the beamwidth in degrees using a straightforward formula.

Table of Contents

1. Overview of Antenna Beamwidth
2. Key Concepts and Parameters
3. Beamwidth Formula for Circular Aperture Antennas
4. Step-by-Step Calculation Process
5. Practical Examples
6. Common Applications
7. Conclusion

---

1. Overview of Antenna Beamwidth

The beamwidth of an antenna describes the angular spread of its radiated energy, typically measured at the half-power (3 dB) points. For circular aperture antennas, which are common in high-frequency applications, the half-power beamwidth is a function of both the wavelength of operation and the aperture diameter. A narrower beamwidth indicates a more focused and directive antenna.

---

2. Key Concepts and Parameters

To calculate the 3 dB beamwidth for a circular aperture antenna, you need to consider:

• Wavelength ($\lambda$): The operating wavelength of the antenna (in meters).
• Aperture Diameter ($D$): The effective diameter of the circular aperture (in meters).
• Half-Power Beamwidth (${\theta }_{3dB}$): The angular width (in degrees) of the main lobe where the radiated power drops to half (3 dB below) its peak.

---

3. Beamwidth Formula for Circular Aperture Antennas

A widely used approximation for the half-power beamwidth of a circular aperture antenna is:

Where:

• $\lambda$ is the wavelength (in meters).
• $D$ is the diameter of the circular aperture (in meters).
• The constant 58.4 arises from converting the approximate beamwidth from radians to degrees ($1.02\text{radians}\approx {58.4}^{\circ }$).

---

4. Step-by-Step Calculation Process

1. Input the Wavelength ($\lambda$): Enter the operating wavelength in meters.
2. Input the Aperture Diameter ($D$): Enter the effective diameter of the antenna in meters.
3. Apply the Formula: Compute the 3 dB beamwidth using:
   ${\theta }_{3dB}\approx \frac{58.4\lambda }{D}$
4. Interpret the Result: The result is the half-power beamwidth in degrees, indicating the angular span where the antenna radiates most of its power.

---

5. Practical Examples

---

6. Common Applications

• Microwave Communication: Designing directional antennas for satellite and terrestrial links.
• Radar Systems: Shaping antenna beams to optimize target detection and resolution.
• Remote Sensing: Employing antennas in weather radars and imaging systems.
• Broadcasting: Engineering antennas for focused transmission in various frequency bands.

---

7. Conclusion

The Antenna 3 dB Beamwidth Calculator for a circular aperture resonator in the TE₁₀₁ mode (or similar modes) provides an essential estimate of the antenna's directivity. By applying the formula:

where $\lambda$ is the wavelength and $D$ is the aperture diameter, you can quickly determine the half-power beamwidth in degrees. This information is critical for antenna design and helps ensure that the antenna meets the directional and performance specifications required for various high-frequency applications.