VET Antenna

What is is VET?
Variable Electrical Tilt.
There are two types of antennas as regarding to electrical tilt. one is fixed electrical tilt and the other one is variable electrical tilt.
If an antenna is having a facility of varying  its electrical tilt,  such type of antenna is called as VET Antenna.


What is the difference between electrical tilt and mechanical tilt?
With electrical tilting, front and back lobes tilt in same direction : for example, an electrical downtilt will make both front lobe and back lobe tilt down. This is the property used in the above example where the signal is pointed down in all directions. On the contrary, mechanical downtilting will make the front lobe tilt down and the back lobe tilt up.

mechanical tilt is almost always fixed whereas electrical tilt can be controlled using remote actuators and position sensors, thus reducing operating expenses




This adjustment can be done from remotely, by certain solutions. One such solution is called RET solution of COMBA TELECOM.
Here i have explained how this system works.

This image explains how to remotely control the electrical tilt of an antenna
More details at http://www.comba-telecom.com/productandservice.aspx?ID=127

The RET solution can be used for  setting of electrical down-tilt angle of Variable Electrical Tilt (VET) antennas. A typical RET solution setup is shown in the diagram  above. The components used in this system is explained here:

Central Control Unit (CCU)

The CCU is the major component for controlling and monitoring the RCU, TMA and antenna line devices that are AISG compliant. It can be programmed to work with various manufacturers’ VET antennas by simply uploading the appropriate antenna definition/configuration files into it.

 Remote Control Unit(RCU)

RCU-003(II-2) is a compact and light weight actuator that mechanically connects to the electrical phase shifter of Comba VET antenna for remote adjustment of electrical down-tilt angle. It is designed to comply with AISG 2.0 standards and works with AISG compliant Node B and antenna line devices.

Smart Bias Tee

The Smart Bias Tee is used to inject DC voltage and to modulate and demodulate remote control signals, via the RF coaxial cable, to antenna line devices such as TMA and RCU. It is designed to comply with AISG 2.0 standard and can be used as a lightning protection device for the BTS/Node B.

Variable Electrical Tilt (VET) Antenna

The VET antenna has an in-built electrical phase shifter module that allows remote electrical tilting of its vertical radiating beam. Comba has a comprehensive range of VET antennas for different frequency bands, different horizontal half power beam width and gain to suit different cellular coverage needs.

AISG Tower Mounted Amplifier (ATMA)

The ATMA is installed near the antenna at the tower top to improve receiver sensitivity of the base station, and call quality. Comba’s ATMA is designed to work with RCU in accordance to AISG standards.



AISG Control Cable

The AISG control cable is a five core cable that is fitted with a circular 8-pin Male connector on one end and a Female connector on the other. This cable is used to connect and transmit signals between AISG antenna line devices.



COMETS

COMETS is a RET system manager software that is programmed to perform remote setting of electrical down tilting angle of VET antennas and monitoring of AISG antenna line devices alarms. It consists of a server and client architecture running on an IP backbone, as show below.

More details at http://www.comba-telecom.com/productandservice.aspx?ID=127