Chapter 1: Introduction to Antenna Patterns

July 28, 2023

ABSTRACT
In any wireless system, antennas play a key role. It is helpful to understand a little bit about how they function and some of the performance parameters that are important to the antenna. An antenna radiates energy in all directions and that radiation is quantified in terms of the antenna’s radiation pattern. This post is an introduction to antenna patterns and describes a little bit about how you might encounter these patterns in your system.

Stephen V. Saliga, Ph.D.
Vice-President, Engineering

Antennas are a critical component in any wireless communication system. The design, construction and installation of antennas can have a significant impact on the performance and reliability of a radio network. To explore these issues in more detail I developed a series of short articles on definitions related to antennas and antenna theory with a focus on the practical application of antennas in real life. Let’s start with some fundamental definitions related to antenna radiation patterns. It’s often helpful to think of antennas in the transmitting sense but be aware that everything holds true in the receive direction too!

An antenna’s radiation pattern is a graphical representation (plot) of the radiation properties of the antenna as a function of spatial coordinates. Again, assuming the antenna is transmitting, we can think of the radiation pattern (in 3D) as a description of how power is radiated from the antenna. It would show where the radiation intensity is high, low, where the peak radiation is, where there is no radiation, etc. All in 3D. Generally, these patterns are plotted in standard polar coordinates. An example radiation pattern is shown below in 3-dimensions.

Often it’s helpful to make a few cuts through the 3D pattern for further analysis. These cuts are often done in the “azimuth plane” and one or two “elevation plane” cuts. The azimuth plane is probably the plane parallel to the floor or the ground. Elevation plane cuts are made in planes perpendicular to the azimuth plane. These plane cuts are shown above alongside the 3D pattern. Lots of antenna performance parameters are derived from these 2D plots and we will start to consider performance in subsequent posts. All these 2D radiation patterns (plane cuts) are typically shown in either polar coordinates or standard cartesian coordinates, whichever is easiest.

You can see how these cuts are made through the 3D pattern. The elevation plane pattern is more complicated having been derived by cutting through the yz plane. The azimuth plane pattern is a circle having been derived by a cut through the xy plane.

PCTEL makes many different types of purpose-built antennas for critical applications including public safety communications, precision agriculture, and smart metering. You can explore all these on our website (www.pctel.com) where you’ll encounter many antenna parameters and concepts that I’ll be exploring in future posts.