UniFi - Introduction to Antenna Radiation Patterns

 Overview


This article will explain how to understand antenna radiation plots and how this should impact your wireless deployments.

Table of Contents


  1. What is a Radiation Pattern?
  2. What is Antenna Gain?
  3. Plane Patterns: Understanding Azimuth and Elevation
  4. Visualizing Plane Patterns
  5. 3D Radiation Patterns
  6. How to Use Radiation Patterns for Deployments
  7. Related Articles

What is a Radiation Pattern?


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In every wireless device, antennas perform the essential function of converting electric power into radio waves so that data can be sent and received over the wireless spectrum. All antennas, whether it be a simple dipole antenna or an array of multiple antennas, will take power and transmit it in a distinct three-dimensional shape radiating out from the antenna. These patterns can be conceptualized with the use of graphed patterns called antenna radiation patterns.

Typically, these graphs show the shape of a radiation pattern by measuring gain at one or multiple frequencies, by either taking cross-sections from various angles (known as plane patterns) or by using plots/graphs that convey the three-dimensional shape of an object (3-D patterns).

Ubiquiti has provided both types of graphs for each current UniFi Access Point model to help UniFi administrators better understand and plan on how to deploy UniFi access points in their environments. This article will not share each AP model’s distinct radiation pattern (the radiation patterns for each UniFi AP model can be found in our UniFi - UAP Antenna Radiation Patterns) but rather will explain how to read and understand the provided antenna radiation patterns.


What is Antenna Gain?


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Essential to understanding antenna radiation patterns is knowing what they measure. Antenna gain measures how efficiently an antenna sends and receives signal in a particular direction. This is quantified using decibels-isotropic, which is typically abbreviated to dBi. An isotropic antenna is an antenna that theoretically broadcasts in all directions equally. Or in other words, an isotropic radiator is like an inflated balloon that is a perfect sphere.

Therefore dBi measures the directivity/efficiency of antenna gain relative to this theoretical antenna. If you look at the ring in the example below, the red ring at 0 dBi represents the antenna pattern of an isotropic radiator at the same power strength (in this case 5.2 GHz).

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In this example the antenna has 10dB greater efficiency in the direction of 0 degrees than the isotropic radiator. This example has greater efficiency in all directions other than 270 degrees, which means you wouldn’t want to deploy an access point with this antenna with all your clients positioned around the 270 degree point.


Plane Patterns: Understanding Azimuth and Elevation


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There are two main types of plane patterns: azimuth and elevation. Azimuth represents the bird’s eye view of the antenna pattern, which shows gain reaching out on the horizons.

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With Ubiquiti’s provided azimuth plots, envision the pattern as if you were standing directly under a ceiling-mounted access point and looking up with the plot going out in all directions horizontally from the access point.

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The different colored rings represent how the azimuth view changes when you stand slightly askew from directly below the AP in 10 degree increments (Theta: 70, 80 and 90 degrees).

How far from the AP these lines are drawn indicate how much gain the AP transmits in that direction. The scale is provided by increments of dBi starting at outside perimeter with 10, 5, 0, -5, -10, etc.

The second type of plane patterns is the elevation plane diagrams. The elevation plane diagram represents a cross section of the antenna radiation pattern if you were to look at it from eye level with the access point from a particular angle on the horizon.

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Since most UniFi access points are designed to be mounted on the ceiling or wall, signal has been optimized for the direction opposite of the mounting side or in the direction facing the U symbol. For that reason, Ubiquiti has opted to exclude the elevation from 90 - 270.


Visualizing Plane Patterns


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Once you understand how to read antenna radiation patterns, it is very helpful to visualize the plot in a three-dimensional manner.

Let’s take a look at a 3D rendering of a generic example of a combined azimuth, and perpendicular elevation plots to help us better visualize what the plots previously discussed show us:

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In this example,we are looking up at a ceiling mounted AP. Based on the orientation of the U we can use sample antenna radiation data to visualize each plane in relation to each other. The red plane is the azimuth, the blue is the elevation from 0/180, and the green is the elevation from 90/270. Note that the pattern/gain is not to scale and in a real-life deployment would broadcast much farther than the shapes show. What this does do is give you an indication of the shape of the antenna radiation pattern and tell you for the most part, that this should pretty much provide adequate signal in all directions.

Understanding the positioning of these plane patterns relative to the AP can help you get a rough idea of what the three-dimensional shape of an antenna pattern would look like.


3D Radiation Patterns


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As an alternative to plane patterns- 3D radiation patterns can make it much easier to visualize the real world shape of radiation patterns. Sometimes these 3D patterns can be provided as a rendered 3D shape, but also can be provided for in a multi-colored pattern like the one below:

image1.png

 

This pattern incorporates both azimuth plane and elevation plane diagrams in all directions. The varying color throughout the graph can be identified using the color scale on the right.

The angles from 0 - 360 along the perimeter/circumference represents the azimuth in all directions from the center of the AP. To help visualize we provided an image with each of the 5 colored dots to indicate the orientation of the graph.

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As you can see, the 3D plot is a visual representation of directional gain if you were to stand facing the AP.

The animated image below shows what each increasing ring within the graph represents, with an incremental scale of 15, 30, 45, 60, 75 and 90 degrees.

image2.gif

Most of the 3D radiation plots we provide in the UniFi - UAP Antenna Radiation Patterns article like the one above only cover the space radiating out from the AP in the plane going out from the face of the AP. However, for a few of our APs that are not intended to be mounted to a wall or a ceiling, like the UniFi Mesh Access Points, rather than the elevation going to 90 degrees, the graph scale is expanded to 180 degrees.

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Example: UAP-AC-M Radiation Plot                     

 


 

How to Use Radiation Patterns for Deployments


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When preparing for a wireless deployment, antenna radiation patterns can come in handy. Let’s look at an example:

 

radiation_pattern_office.png

In this example image, we could use radiation patterns to help us see where we should place a UniFi AP to have optimal gain as to have the best connection with a wireless device like a TV or a smart thermostat. Keep in mind however, that when considering smaller spaces like a living room this antenna gain will make much less of a difference than might appear in this example.

When using these plots consider the general shape of signal and use it to inform how you deploy your UniFi access points i.e. placing a UAP-AC-PRO on the ceiling over a particular area rather than at the clients’ horizon.

Do not be overly concerned about the small variations in signal as these will not likely contribute to any meaningful difference in performance, i.e. moving a desk three feet to the right to capitalize on what looks to be roughly a 1 dB improvement of signal in a given direction. While it may look to be different per the graph, the general shape should be the guiding aspect of your wireless deployment.

Antenna radiation patterns are a valuable tool when planning a network with optimal performance in mind. See our Related Article below to study the UniFi AP's radiation patterns.


Related Articles


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UniFi - UAP Antenna Radiation Patterns