Antennas

The antenna is the first element of the input system to any wireless signal receiving system (for broadcast systems, it's the final element); the rest of the system works with the signal provided by the antenna. For optimal system performance, choose the correct antenna.

Before you select an individual antenna, determine what the general type of application is and what type of signal is involved. Will your system be, for example:

• Receiving or broadcast?
• Short range? Long range?
• Used for Broadcast, Earth Station Applications, VHF Communications, UHF Communications, Cellular Base Station, Microwave Links
• Fixed? Portable? Mobile?
• Emergency? Standby? Continuous service?

Once you know these things, you can also determine which part of the RF spectrum you're working with.

Obviously, you need to select the antenna that meets your frequency requirements (or wavelength, depending on how that's specified). But many other factors also apply. For example:

• Indoor or outdoor?
• Tower, rooftop, or desktop?
• Is the connection coaxial or some other system?
• Steel or fiberglass?
• Directional? Omnidirectional?

In many cases, antenna installation is straightforward. In others, the situation can be complicated enough to require engineering. Factors to consider:

• Mechanical mounting. Is the mounting surface suitable to the anticipated mechanical stress?
• Structural considerations. For example, wind shear (of particular importance to outdoor antenna installations).
• Location. You need to site the antenna in a structurally sound spot that also allows for properly aiming the antenna. Some other considerations also apply to location. As with real estate, location is pretty critical.
• Access. You need to mount your antenna in a location where it's not prone to damage and where it's reasonably secure, but you also need to be able to get at it and safely perform maintenance and/or repair.
• Interference. Don't locate an antenna close to utility lines or other sources of signal noise problems.
• Aiming. In many applications, the antenna isn't considered directional. But in other systems, poor aiming can degrade system performance below acceptable limits. Follow standard industry practices for the system you're installing.
• Obstructions. You're limited to how much power you can pump out, if broadcasting. If you're receiving, there's a limit to how strong that signal will be. In either case, you must consider instructions such as structural steel members of buildings. In many cases, such as when building out a wireless Internet system inside a commercial building, obstructions create gaps in coverage. Additional hardware (e.g., repeaters) is required to fill the gaps.

You can find the antenna or waveguide standard you need by going to the IEEE Website's Standards libarary and selecting "Antennas and Propagation." There are over two dozen of these standards.

But that's not all:

• The particulars for design, installation, and maintenance of antennas in specific system are often covered in the IEEE standards that pertain to the systems or applications.
• You can find books on antenna design in general terms, for specific types of antennas, and for specific types of systems and applications.
• You can locate IEEE Transactions and Symposia on antenna types and applications.

If you're doing much work with antennas, consider attending IEEE conferences related to your particular area of interest. You may also find an IEEE Society holds meetings in or near your city.

Of course, if you just need to buy an antenna you have come to the right place. If you don't see what you need here, contact us and we can probably get it for you.