DIVIDERS AND COMBINERS
Block Diagram
Figure 4-11. Block diagram of a two-way power divider.
The Divider's and Combiner's Function
Dividers divide. Visually, a signal goes cruising down path N (see Figure 4-11) and half the signal's power goes down path A, while the other half goes down path B. The signal gets divided in half. Its shape stays the same, but the power is reduced. Dividers are also referred to as power dividers.
Dividers can divide by numbers other than two. A four-way power divider has paths C and D and one quarter of the original signal's power goes down each path. Dividers always divide the input signal equally among all of the outputs.
If it were flipped over and two different signals were sent down paths A and B, then the signal on path N would become a combination of the two signals. What do you suppose RF engineers call this flipped-over divider? A combiner. A two-way power divider (or combiner) is shown in Figure 4-12. All power dividers and combiners are passive devices.
Figure 4-12. A two way power divider. Courtesy of TRM, Inc.
System Use
Why are dividers needed? Perhaps there is a wireless system which requires the use of two identical transmitters in the same place (don't ask why). Two transmitters require two of everything, including two power amplifiers, two mixers, two sources, etc. Or do they? What if a single oscillator is used and its output is divided in half (by the divider). Then one of the signals is sent to one mixer and the other signal is sent to the other mixer. Assuming dividers are cheaper than oscillators (which they are), this reduces the cost of the hardware. Dividers are used when RF engineers want to send the same signal to more than one place in an RF system.
The key performance parameter for combiners and dividers, as well as most other passive devices, is insertion loss. The lower the insertion loss, the more of the signal which makes it through the device, which is a good thing.