Broadside vs. End-Fire Array Antennas: Differences Explained

This article compares broadside array antennas and end-fire array antennas, highlighting the key differences between them. It also briefly covers collinear antennas as a related type of driven array antenna.

There are three main types of driven array antennas:

• Collinear
• Broadside
• End-Fire

Collinear antennas consist of two or more half-wave dipoles mounted end-to-end, commonly used in UHF and VHF bands. Let’s delve into the broadside and end-fire antenna types.

Broadside Array Antenna

Figure 1 shows a broadside array antenna. This type of antenna, which can be considered a stacked collinear antenna, is made up of half-wave dipoles spaced apart by one half-wavelength.

Typically, two or more elements are combined in this design. Each element is connected to the others and to the transmission line. The crossover transmission line ensures correct signal phasing.

Broadside arrays produce highly directional radiation patterns, with the main lobe radiating broadside, or perpendicular, to the plane of the array. Similar to collinear antennas, broadside antennas exhibit a bi-directional radiation pattern.

The radiation pattern is characterized by a narrow beamwidth and high gain.

End-Fire Array Antenna

Figure 2 (a) depicts one configuration of an end-fire array antenna. It employs two half-wave dipoles spaced at a distance of one half-wavelength.

Both elements are driven by a transmission line. This antenna has a bi-directional radiation pattern but offers a narrower beamwidth and higher gain compared to a single dipole.

Another method of constructing an end-fire array is shown in Figure 2 (b). This configuration utilizes multiple (in this case, five) driven elements spaced at a fraction of a wavelength (D).

By adjusting the number of elements and their spacing, a highly directional antenna can be created. This antenna is uni-directional, unlike the bi-directional design in Figure 2 (a).

The specific element spacing causes the lobe in one direction to be canceled while reinforcing the lobe in the opposite direction. This enhances both gain and directivity.