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Internal Smart Bias Tee Capability of Base Station Antennas

May 02, 2016

Internal Smart Bias Tee Capability of Base Station Antennas

Remote electrical tilt (RET) is a base station antenna capability that enables RET operators to alter the direction of their antenna beams remotely. This allows them to adjust their networks without having to move the antennas physically or climb up a cell tower. It is done using electrical equipment, and standards have been established by the Antenna Interface Standard Group (AISG).

An AISG controller is connected to antenna line devices (ALDs) with a smart bias tee and the signal is transmitted up the tower using the feeder line. Normally, the AISG controller is located near or at the base station.  It can be integrated into the base station, rack mounted or even hand-held. The ALDs are typically located near or at the antennas. Antenna RET motors, tower-mounted amplifiers, or other RF path equipment can be used for this.

The controller can be connected to the ALDs by using a separate data cable from the ALDs to the controller. This could however add additional fees to tower leases, and many sites therefore use other approaches. As base station radios nowadays have integrated AISG controllers, AISG signal can be injected directly onto the main feeder line. Smart bias tees can therefore be used at the top of the tower to establish a link between ALDs and the feeder line.

The smart bias tee can also be built directly into the antenna. This approach has a number of advantages:

  • Antenna can also have AISG connectors for inputs and outputs, allowing flexibility and daisy chaining. Antenna can be installed in different configurations, including connecting a controller that controls several ALDs on a single feeder run.
  • As installers don't have to install another directional device, installation errors are reduced and it can never be left out by mistake.
  • Tower leasing fees can be reduced as the number of components are reduced.

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  • This is off-topic but I love’s pictures. They truly capture the subject. Here, you have information on base station antennas and a picture that captures the essence of the article. I also like how your “case study” stories have plenty of pictures of the technology and how it looks when installed.

    Luca Kuhns on
  • A low frequency bias tee is an important component and the smart bias tee function can save expenses and headaches. Who wants to have to send a technician out when you can have someone make the adjustments remotely? Sure, if necessary you can send the technician out, but why pay for a service call unless it’s absolutely needed. Thanks for the bias tee tutorial. Technology is changing day by day (or it least it seems) so it’s important to keep up to date.

    Gavin Miller on
  • Sounds like a helpful innovation, especially if you’re the person who has to climb up to adjust the antenna. Are there any issues with inclement weather affecting the ability to transmit these instructions to antenna or is it a situation similar to a cell phone booster, where the signal is enhanced to overcome interference?

    Garrett Yates on
  • 20 years ago, the only smart device I’d heard of was a smart bomb. Now, there are smart cars, smart phones, and smart antennas. I’ve read elsewhere that cell phone boosters and DAS installations use antennas so can you use a smart antenna with them? It sure would make life easier for a business that uses them and needs something adjusted, but no one is at the business, or no one knows how to adjust them.

    Robin Henderson on

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