In handover testing, there are two types of ports: input and output. Input ports represent antennas: base stations, access points, cell towers, or some other type of connection to the communications network. Output ports represent handsets or mobile devices. The terms “input” and “output” in this case are naming conventions, as all paths for a handover test system operate bi-directionally. There are three types of handover configurations:
- Full fan-out;
- Limited fan-out;
- Manual handover.
As with a transceiver test system, a full fan-out handover system means all inputs can talk to all outputs. Each input port is connected to an RF divider/combiner to split the signal into multiple paths corresponding to the number of output ports. Each path has an attenuator. Then each path enters a divider/combiner for the associated output port. To find the number of paths in a full fan-out handover system, multiply the number of input ports by the number of output ports. An 8x4 system would have a 1x4 divider/combiner and 4 attenuators for each input port and a 1x8 divider/combiner for each output. That makes 32 attenuators and 12 total divider/combiners.
In a limited fan-out, each input has an attenuator, so the same signal strength reaches all the antennas. All the inputs lead into a single divider/combiner, which in turn leads to another divider/combiner connected to the outputs. For the 8x4 configuration, there are only 8 attenuators and 2 divider/combiners. The number of components is far smaller, but you can’t independently adjust attenuation for each path from a handset to an antenna.
Manual handover systems also use a limited fan-out configuration. The difference between manual and programmable limited fan-out is that, in a manual system, manual rotary attenuators replace programmable ones. Manual handover systems are the simplest and least expensive type and are usually employed in early R&D.
Find the right size
Options are great to have. They also complicate the process of making decisions. No one can tell you what is best for your specific needs because no one else has to balance your schedule, complexity, and budget. However, chances are you can find the right type of testing equipment to meet your specific needs.