Why are power dividers used?
When should power dividers or power splitters be used?
ANSWER: Reactive coaxial power dividers are employed when coupling multiple antennas into a single common feed, or splitting from a single common feed so that the use of multiple antennas and their additive effect from either gain or pattern or both can be incorporated into a single coaxial feed line.
Why are power dividers used?
ANSWER: The simple answer is to maintain system impedance. Power dividers (sometimes called power splitters) are RF tuned devices that maintain a specified input and output impedance over a specified frequency, given a specified continuous average power (CW) rating and specified number of splits. As an example, if four (4) antennas are needed at a particular location due to their additive gain effect and it is desirable to feed all 4 with a single coaxial cable, coupling the 4 antennas together so that they operate as a single array for connection into a single feed line can only be done with the use of a power divider that will maintain the input impedance of the antennas and the output impedance of the feed line. Most transmission lines are 50 ohms, as are most broadcast and base station antennas. Omitting the use of a power divider and simply hard-wiring 4 antennas together of 50 ohms each will divide the impedance at the input of the combined array resulting in 12.5 ohms input impedance (=50/4), which is now mismatched with the 50 ohm coaxial feed line. Installing a power divider, which is tuned to maintain a 50 ohm input and 50 ohm output impedance for the number of specified divisions, will overcome the impedance mismatch problems associated with interconnecting multiple antennas.
Some advantages of reactive coaxial power dividers over other types include: i) readily available raw materials enabling the manufacturing of different designs to varying specifications, ii) they can be designed and tuned to exhibit very low return loss and, iii) they can handle higher input power than other stripline types due to the use of larger conductors. A distinct disadvantage of reactive coaxial power dividers is that the divisional ports inherently have low isolation.
Reactive Power Dividers | Series vs Parallel Design
There are two main coaxial power divider design variations to consider; a Parallel design or a Series design. Parallel coaxial power dividers are dividers that have a single common connector on one end of the divider with the divisional connectors situated on the opposite end. A Series coaxial power divider design has the divisional connectors on each end of the divider, with the common connector being situated at the midway (center) point of its length.
The required VSWR band width spec, along with number of output ports needed and CW rating, are the determining factors in power divider size, shape, and cost.