Monopole vs. Dipole Antennas: Key Differences Explained

This article explores the differences between monopole and dipole antennas, two popular choices for cellular phones, broadcasting, and wireless communications, largely due to their omnidirectional characteristics.

Monopole Antenna

Figure 1: Monopole antenna with its radiation pattern. The figure also shows a folded monopole antenna.

The monopole antenna essentially leverages an “image” created through a metal or ground plane. You’ll find variations of the monopole antenna like the inverted-L and inverted-F types. These are particularly common in handheld portable telephones.

Dipole Antenna

Figure 2: Dipole antenna with its radiation pattern. The figure also shows a folded dipole antenna.

The most common type is the half-wave dipole, which consists of a wire or rod that’s half a wavelength long. The antenna is divided into two quarter-wavelength sections, and the transmission line connects at the center point.

A dipole antenna usually has an impedance of around 73 Ohms. Typically, these half-wave dipole antennas are mounted horizontally, resulting in horizontal polarization. The radiation pattern resembles a doughnut shape. As the wavelength multiples change (lambda), so does the radiation pattern, as illustrated in Figure 2.

Key Differences Summarized

To put it simply, the monopole antenna uses a ground plane to create a virtual “half” of an antenna, whereas the dipole antenna is a complete antenna consisting of two radiating elements.