FAQs Archive

Q: What is the difference between a hybrid combiner and a filter combiner?

Both combine signals to a common path, but do so in different ways. Filter combiners are band specific devices used to combine signals from different frequency bands. In a 2:1 combining situation, there is no 3dB combining loss, but there may be a higher insertion loss than that found in a hybrid device. Microlab has a range of standard diplexers corresponding to the common wireless bands with typical >50dB isolation between input ports. The BK-26N is such a filter combiner. The basic 2 input, 2 output hybrid combiner can be used to combine any two signals in the band without interaction of the signals. The two signals, A and B, can be far apart or close together, and each of the outputs will have an output of (A+B)/2. In a 2-to-1 combine, only one output is used, so one of the outputs must be terminated in 50W. These devices typically offer 20 dB minimum of isolation between input ports. Microlab/FXR hybrids, such as the CA-84N, offer 25 – 35 dB isolation across the band of 700-2700 MHz for superior performance in broad-band wireless applications. Microlab also offers broadband 3 x 3 and 4 x 4 hybrids for multi-input combining applications as may be required in neutral host in-building systems. These can be found as CM-81 and CM-84 series.

Q: Is it necessary to equalize the Rx signals as well?

Rx signals, delivered from the fiber system to the RF network, may be too high for the network receivers. This scenario would distort the signal and reduce overall receiver sensitivity. It is not necessary to equalize Rx signals, but signal levels need to be set to a range that meets the actual network receiver requirements