Low Loss Coaxial Cable for Wireless Applications

June 26, 2013 at 10:00 AM

 

Closeup of Low Loss Coaxial Cable Stripped to Show Components

Even in a wireless network, cables and wires are still used to connect components together (access points to amplifiers, amplifiers to antennas, etc). Each component needs cabling to interact.

 

If you are a wireless engineer and need to interconnect components, chances are you are using low loss coaxial cabling. While 50 Ohm RG-style coax is sometimes used, the attenuation is usually too much for any length over just a few feet. This is where low loss coaxial cable comes in.

 

 

Coaxial Cable and RG-Style Coax

 

All coaxial cable works the same way: the signal is run over two "axes" (thus the name). Coaxial technology is one of the oldest signal cabling types, and is still used today for a specific reason: it is robust and can carry a signal very well over a long distance. In general, the thicker the cable, the less "loss" or attenuation of signal there is over the length of the cable.

 

The original standards for coaxial cable were set forth by the US military. These cables used the term "RG" (for "Radio Guide" or "Radio Government") followed by a number to designate the standard. This worked well at the time, but as technology became more and more utilized in commercial and non-military applications, the restrictions of the standard became less rigid (to the point where RG316, for instance, may have very different properties today depending on who manufactures it).

 

 

Times Microwave LMR® Cables

 

No matter who makes the RG-style cables, they have one fundamental problem: the signal degrades over the length of the cable until it is no longer useable. For shorter use in labs or machine-to-machine applications, this is not a problem. But in wireless applications, the signal integrity up until it is broadcast through the antenna is critical.

 

For that reason, Times Microwave Systems developed a low loss version of coax that it branded as its LMR® series coax. The newly-engineered solution offered far lower loss and better RF shielding, making them a much better choice for wireless systems than the RG styles.

 

Outside of Times Microwave Systems' product (the term LMR® refers specifically to Times Microwave Systems product and is trademarked for their use), several other companies now offer low-loss coaxial cables. These generally follow a similar naming convention as what Times Microwave Systems uses: a three-digit "series" number that refers to both the thickness of the cable and the low loss properties.

 

For instance, 100-series low loss coax is thinner and has greater loss than 200-series, which is thinner and has greater loss than 400-series, etc.

Diagram of most common low-loss coaxial cables

Note that with thicker cable factors such as cable weight and flexibility must be considered. However, there are now ultra-flex versions of thicker series like the 400-series that offer similar loss characteristics but are far more flexible.

 

Quick note: L-com has been manufacturing high-quality coaxial cables and components for over thirty years.
 
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