What is Antenna Beamwidth?

Antenna beamwidth is the angular span of the main lobe of the antenna radiation pattern, which is the region of the pattern where most of the power is radiated.  The beamwidth is commonly measured at the angle between two points on either side of the main lobe (also known as the half-power points or -3dB point), where the power radiated drops to half of its maximum value. The beamwidth is measured in degrees, and it may be measured in the horizontal or vertical planes.

Radiation pattern of a unidirectional antenna

The beamwidth of an antenna is an important parameter because it determines the directionality and coverage area of the antenna. A narrow beamwidth indicates a highly directional antenna that is well-suited for long-range communication, while a wider beamwidth is better suited for short-range communication and for covering a broader area. The beamwidth will vary due to a number of different factors, such as the antenna type, antenna design, orientation, and radio frequency. 

Antenna beamwidth is a helpful analytical parameter for a number of practical applications,  including:

• To plan antenna coverage in a given area.      
• To determine whether neighboring antennas will interfere with each other.
• To assist in improving the performance of communication links.
• Network mobility development.

Understanding Half Power Beam Width (HPBW) and First null Beam Width (FNBW) in the radiation pattern of an antenna: 

Half Power Beam Width (HPBW): It is the angle between the two points (called half power points or -3 dB point) on the radiation pattern where the power is half of the maximum value. A narrower HPBW indicates a more directional antenna with a higher gain, while a wider HPBW indicates a less directional antenna with a lower gain. Click here to learn more about HPBW.

Understanding HPBW and FNBW in radiation pattern of an antenna

First null beamwidth (FNBW): It is the angle between the first nulls adjacent to the main lobe where the power is zero. The FNBW is an important parameter for antenna designers because it determines the antenna's ability to reject signals/interference from unwanted directions. A narrower FNBW indicates a better ability to reject signals from unwanted directions, while a wider FNBW indicates a lower ability to reject signals/interference from unwanted directions.

Relationship between beamwidth and gain

Antenna beamwidth and gain have an inverse relationship. Decreasing the beamwidth i.e., a narrow beamwidth will result in a higher gain. This is because, with a narrow beamwidth, power transfer will be increased in a particular direction.

Relationship between the signal-to-noise ratio (SNR) and Beamwidth

As Beamwidth relates closely to directivity and gain, changes in beamwidth provide proportional changes in both these parameters. For a narrow beamwidth antenna, gain and directivity are higher; this will increase the signal-to-noise ratio (SNR) favorably. The SNR is the ratio of signal strength to unwanted interference (noise), higher SNR is always desirable/good.