RF Antenna FAQs

June 22, 2017 at 8:00 AM

 

 

Antennas are critical components to any wireless network, so having a good grasp of antenna technology can be very important for anyone engineering, designing or managing a wireless network. With so many antenna options and so much information to digest, it’s no wonder people have a lot of questions when it comes to antennas. Here, we’ll highlight some of the questions we’re asked most frequently.

 

How do I choose the correct Wi-Fi antenna? 

There are two main types of antennas - Directional and Omni-directional:

          

-   Directional antennas emit an RF signal in a focused beam, like how a car headlight focuses light in one direction. They are great if your application is a  point-to-point Wi-Fi link. For example, if you’re transmitting a signal from one building to another, you would use a directional antenna.

 

-   Omni-directional antennas radiate an RF signal in a 360-degree pattern. These antennas are ideal if you need the Wi-Fi signal to cover a 360-degree radius.

       

-   If you have a point-to-multipoint application, such as a campus environment, using a combination of directional and Omni-directional antennas would be your best bet.

 

What is antenna polarity?

Antenna polarity is the orientation of the radio wave’s electric field with respect to the Earth's surface. Antennas can be vertically polarized, horizontally polarized or a combination of the two. For more information, check out our antenna polarization blog post.

 

What is antenna gain? 

Antenna gain is a relative measure of an antenna’s ability to direct or concentrate radio frequency energy in a particular direction or pattern. Antenna gain is typically measured in dBi or dBd. Click here for more info.

 

What is 802.11? 

802.11 is an IEEE standard for implementing wireless local area network (WLAN) communications in the 2.4, 3.6 and 5 GHz frequency bands. There are numerous 802.11 standards and new versions continue to be developed. Existing standards include 802.11a, 802.11b, 802.11g, and 802.11n, 802.11ac, 802.11ac Wave 2, 802.11ah, 802.11ax, 802.11ay and 802.11af.

 

What is a decibel (dB)? 

A decibel (dB) is a unit of measurement for the intensity of a sound or the power level of an electrical signal by comparing it with a given level on a logarithmic scale. Decibels are commonly used in radio and sound measurement. One decibel is 1/10 of a Bel.

 

What is dBi ? 

Decibels-isotropic (dBi) are decibels relative to an isotrope. This unit of measure defines the gain of an antenna system relative to an isotropic radiator at radio frequencies. 

 

What is an isotrope? 

A theoretical isotrope is a single point in free space that radiates energy equally in every direction, similarly to the Sun.

 

What is frequency? 

Frequency is the number of cycles of alternating current in one second. It is measured in hertz (Hz).

 

What is a microwave? 

A microwave refers to all radio frequencies above the 1 GHz range. They are shorter than normal radio waves but longer than infrared radiation. Microwaves are used in radar, communications, for heating in microwave ovens and in various industrial processes.

 

What is multipath interference? 

Multipath interference is when signal reflections and delayed signal images interfere with the desired, un-delayed, larger signal. It causes picture ghosting in over-the-air analog TV and errors in digital transmission systems.

 

What is path budget?

Path budget is a mathematical model of a wireless communications link. It takes into account a wide variety of factors that can affect operating range and performance. Path budget is sometimes referred to as "link" budget.

 

What is path loss? 

Path loss is the weakening of a signal over its path of travel. This can be caused by factors such as terrain, obstructions and environmental conditions. It is measured in decibels.

 

What is fade margin? 

Fade margin is the loss of signal along a signal path caused by environmental factors such as terrain, atmospheric conditions, etc. It is measured in decibels.

 

What is a point-to-point network? 

A point-to-point network is a communications channel architecture that runs from one point to another. Directional antennas would be used in a point-to-point wireless link.

 

What is a point-to-multipoint network? 

A point-to-multipoint network architecture runs from one point to several other points. For this type of network, you would use both Omni-directional and directional antennas.

 

What is radio frequency? 

Radio frequency (RF) is typically a frequency from 20 kHz to 100 GHZ. RF is usually referred to whenever a signal is radiated through an enclosed medium, like a transmission cable or air.

 

What is a radio wave? 

A radio wave is an electromagnetic wave of a frequency used for long-distance communication. It is a combination of electric and magnetic fields varying at a radio frequency and traveling through space at the speed of light.

 

What is very-high frequency? 

Very high frequency (VHF) is the designation for radio waves in the range of 30 to 300 MHz.

 

What is ultra-high frequency? 

Ultra-high frequency (UHF) designates radio waves that are in the 300 to 3,000 MHz range.

 

All about Antenna Polarity

March 16, 2017 at 8:00 AM

 

Whether you’re installing one antenna or an entire tower-full of them, antenna polarization is one of the most important pieces of the puzzle to consider, yet it is also one of the least understood properties of wireless communication.

 

Most antennas are typically mounted horizontally or vertically and the way they are mounted determines their polarization. For the best network performance, antennas used in point-to-point wireless applications should have the same polarization as each other. A wireless links can be established with antennas of different polarity, but usually it compromises the network performance and connectivity.

 

Though there are some cases where using antennas with different polarization is beneficial in reducing interference. For example, if you’re mounting several antennas on a tower, your best plan is to stagger vertically and horizontally polarized antennas to decrease interference.

 

Some wireless applications won’t work with horizontal or vertical polarization. In these cases, there are other polarization schemes to explore including: dual-polarized, cross-polarized and circular-polarized antennas.

 

The diagram below outlines the different antenna polarity types.

Read All About It: Wi-Fi Antenna White Paper

June 30, 2016 at 8:00 AM

 

Omni, Yagi, Rubber Duck, Patch....with all of these antennas it’s no wonder that our customers frequently ask which antenna is right for their wireless application. Fortunately, we have a white paper to help answer that question.

 

When planning a wireless network, deciding which antenna is best for your application can be confusing. Different wireless networks require different antenna configurations.

 

Our white paper takes a deeper look at the types of antennas available for various WLAN applications and includes examples for typical point-to-point and multi-point wireless network architectures.

 

Topics Include:

·       Omni-directional antennas

·       Directional antennas

·       Common Wi-Fi network applications

             - Office buildings

             - Homes

             - Outdoor cafés

             - College campuses

 

Click here to read our Wi-Fi antenna white paper.

 

All of our free white papers are available from our website by clicking here.

 

The Low-Down on Log Periodic Antennas

June 23, 2016 at 8:00 AM

 

Deciding which frequency to use for your wireless application can be a downright tedious. But what if you didn’t have to choose?  What if there was an antenna that combined several frequencies into one? Log periodic antennas have that capability. Here, we’ll give you the low-down on them.

 

In the world of Wi-Fi antennas, log periodic antennas stand-out as superior multi-taskers. They are directional, wide-band, narrow-beam antennas that utilize multiple elements. They can be used for a variety of wireless applications where a wide range of frequency coverage is desired.

 

Performance-wise, the broadband characteristics of log periodic antennas allow for very good gain and directivity while operating on multiple frequencies. And because they combine several frequencies into one antenna, they eliminate the need for purchasing different antennas for each frequency, which also simplifies installation.  

 

Log periodic antennas are ideal for Distributed Antenna Systems (DAS) networks, where support for cellular, PCS and Wi-Fi communication frequencies is required. These antennas can also be used in any application that uses broadband frequencies in a wireless network.

 

Some applications include:

•  802.11a/b/g/n and 802.11ac Wi-Fi Networks

•  Distributed Antenna Systems (DAS)

•  Ultra Wide Band, UWB applications

•  Homeland Security and Public Safety Services: Fire, Police, Security

 

If you need a versatile antenna that combines multiple frequencies, a log periodic antenna may be your best bet. L-com offers several log periodic antennas and can even manufacture custom antennas to your specifications.

 

Antenna Arrays 101

April 7, 2016 at 8:00 AM

 

Not sure what an antenna array is? Want to brush-up on the subject? We’ve got everything you need to know right here with this week’s post… Antenna Arrays 101.

 

What it is:

An antenna array is a set of two or more antennas working together to form a single Omni-directional signal.

 

How it works:

When two or more directional Wi-Fi antennas are grouped together, the signals combine and are able to work as a single antenna with improved directional characteristics.  This is usually done with panel-style antennas connected by an RF splitter to a single access point or Wi-Fi amplifier. The number of antennas in an array can be as few as two or as many as four.

 

Why it‘s used:

An antenna array provides better performance and coverage than a single Omni-directional antenna

Additional benefits include:
    • o   Increased overall gain
    • o   Diversity reception
    • o   Cancellation of interference from specific directions
    • o   Sensitivity toward certain directions
    • o   Ability to determine the arrival direction of incoming signals
    • o   Maximizes the Signal to Interference Plus Noise Ratio (SINR)

 

Applications:

Antenna arrays are used in outdoor point-to-multipoint applications.
   
L-com offers three configurations: 4 - 90° panels, 3 - 120° panels and 2 - 180° panels. To ensure maximum wireless signal coverage, these antenna arrays feature 0°-20° down-tilt capability to compensate for the installation location geography.
 

There you have it, the basics of an antenna array - antennas working together to achieve better coverage than a single Omni-directional antenna.

 

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