# FNBW vs HPBW-Difference between FNBW and HPBW

This page compares antenna FNBW vs HPBW and mentions difference between FNBW and HPBW. FNBW stands for First Null Beamwidth and HPBW stands for Half Power Beamwidth. The other comparison and difference between terms are also mentioned.

Introduction:
Figure below depicts antenna radiation pattern with major lobe and back lobe and side lobes. It also shows FNBW and HPBW.

Following are the useful parameters with respect to antenna radiation pattern.
• Main Lobe: It is the radiation lobe which is in the direction of maximum radiation.
• Minor Lobe: Any radiation lobe which is other than the main lobe.
• Side Lobe: Any radiation lobe which is in any direction other than the directions of intended radiation.
• Back Lobe: The radiation lobe which is opposite to the main lobe.
• Beamwidth:Antenna beamwidth is the measure of directivity of antenna. The antenna beamwidth is angular width. It is expressed degrees or radians. It is measured on major lobe of the radiation pattern of the antenna including FNBW and HPBW.

## Antenna FNBW-First Null Beamwidth

• The term FNBW stands for First Null Beamwidth.
• It is angular width which is measured between first nulls or first side lobes on antenna radiation pattern.
• Beamwidth defines the resolution capability of the antenna. This means it defines ability of the system to separate two adjacent targets. The factors which affects the beamwidth are as follows.
-Antenna dimensions
-Wavelength

## Antenna HPBW-Half Power Beamwidth

• The term HPBW stands for Half Power Beamwidth.
• It is angular width measured on the main beam of the antenna radiation pattern.
• The angular width on major lobe between two points where power is half of the maximum radiated power is known as HPBW (i.e. -3-dB beamwidth).
• At this point on the pattern, power decreases to half of its maximum value.
• HPBW defines resolution capability of the antenna to distinguish between two sources which is equal to about half of the first null beamwidth (i.e. (FNBW/2) = HPBW). Usually (FNBW/2) is slightly greater than the HPBW.
• This implies, when two sources separated by angular distances equal or greater than HPBW of an antenna with uniform distribution can be resolved.