Things You Need to Know About Combiner and Duplexer
Time : 2022-05-18


In the wireless mobile phone communication system, the main function of the combiner is to combine the input multi-band signals and output them to the same indoor distribution system.

The combiner is generally used at the transmitting end. Its function is to combine two or more radio frequency signals from different transmitters into one and send it to the radio frequency device transmitted by the antenna, while avoiding the mutual influence between the signals of each port.

Pic. 1 UIY Hybrid combiner Series

A combiner generally has two or more input ports and only one output port.

Port isolation is a relatively important indicator, which is used to describe the ability of two signals to not affect each other, and generally requires more than 20dB.

Pic.2 Hybrid combiner UIY 2In2Out 350-520MHz Hybrid Coupler

The 2In2out combiner has two input ports and two output ports, and is often used to synthesize two wireless carrier frequencies and feed them into an antenna or distribution system. If only one output port is used, the other output port needs to be connected to the load.


Combine the signal receiving and sending of the signal mobile phone into one antenna.

In the GSM system, since the sending and receiving are not in the same time slot, the mobile phone can save the duplexer for isolating the sending and receiving, and just use a simple sending and receiving combiner to combine the sending and receiving signals into one antenna without interfering with each other.


In engineering applications, it is necessary to combine the two frequencies of the 800MHz

C network and the 900MHz G network to output. By adopting the combiner, a set of indoor distribution system can work in the CDMA frequency band and the GSM frequency band at the same time.

Pic. 3 UIY 2In2Out 698-2700MHz Hybrid Combiner

Another example is in the radio antenna system, after the input and output signals of several different frequency bands (such as 145MHZ and 435MHZ) are combined through the combiner, a feeder is used to connect to the radio, which not only saves a feeder, but also avoids the hassle of switching between different antennas.

2. Duplexer:

The duplexer is the Inter-frequency duplex radio, which is the main accessory of repeater.

The function is to isolate the transmitting and receiving signals to ensure that the receiving and transmitting can work normally at the same time. It is composed of two sets of band-pass filters with different frequencies to avoid the transmission of the local transmission signal to the receiver.

Pic. 4: UIY Duplexer Series

Usually the differences of V-band, U-band duplexer transmit and receive frequency is 5MHz, and same as the working bandwidth 5MHz to ensure the duplexer isolation of more than 80dB.

It has proved that using a duplexer is better than using two antennas to transmit and receive.

400~470MHz TX->RX 5MHz

140~170MHz TX->RX 5MHz

3. Difference Between Combiner and Duplexer

3.1 Different uses

  • Duplexers are generally used at the output and input of the device to isolate signals in different frequency bands.

For example: the uplink and downlink signals of mobile communication.

  • Combiners are generally used in power synthesis in hardware circuits. For example: to get a 40dbm signal, two power amplifiers with an output power of 20dbm can be used to combine.

3.2 Different structures:

  • the inside of the duplexer are filter cavities;the inside of the combiner is a coupling circuit.

3.3 Different signal processing methods:

  • the duplexer only handles different frequency signals,while the combiner can handle both the same frequency and different frequencies.