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Types and Functions of RF Multiplexer

RF multiplexers play a crucial role in several applications. The main function of this device is to combine RF signals in a port. There are different types of multiplexers. We have the quadplexer, duplexer, and triplexer. This classification is mostly based on the number of their input and output.

What is a RF Multiplexer?

RF multiplexer is a device that combines many RF signals in a port or divides a signal from a port into multiple signals on different paths. The reason it is commonly referred to as a multiplexer is that this device puts many signals together as a single output. However, a device which divides a signal input into various signal outputs is a demultiplexer.

Multiplexers are available in different types. We have CDM, FDM, and TDM. One of the major functions of a multiplexer is that it enhances a channel’s ability to transmit data. RF multiplexers work in a similar way with the RF switch as regards routing RF signals. However, multiplexers make use of more ports. They enable the routing of several RF signals into a single port.

The main purpose of an RF multiplexer is that it distributes and multiplexes high-frequency signals. The operating frequency of this device is between hundreds of MHZ to ten GHz. An RF mux differs based on the number of output and input ports. A 1 input 16 output is a 1X16 multiplexer while a 1 input and 4 output is referred to as 1 x4 multiplexer.

For faster signal processing, RF multiplexer transforms from analog signals to digital signals. Due to this the high-speed digital multiplexer also known as digital multiplexer was invented. High speed multiplexers are ideal for distributing high-speed digital signals. Also, they are well suited for use in multi-band operation.

Through the digital communication system, it is easy to reduce signal error and physical energy loss.

Working Principle of RF Multiplexers

RF Multiplexer Board
RF Multiplexer Board

The filtering technology and switching technology determine the working principle of an RF multiplexer. In an RF signal input port, electronic switch control devices realize the switching between various ports. Filters suppress stray signals and interference signals. There is a need for a matching network between the signal output port and input port. This helps in ensuring transmission efficiency and proper signal matching.

In most cases, the appearance is in styles of 1 input with 3 outputs (1×3),  1 input with 8 outputs (1 X8), and 1 input with 2 outputs (1X2).  For instance, there is a need to connect multiple antennas to an RF module in wireless communication systems. In such a scenario, the RF multiplexer has the capability to multiplex the signals antennas’ signals to an input port.

RF multiplexers distribute these signals to various outputs via the port to determine the signal transmission and interconnection between various antennas. These devices are applicable in common fields like satellite communication, radar, wireless communication, and more. Also, you can make use of RF multiplexers in different applications like in the construction of test instruments and communication systems.

In these applications, the multiplexer can enhance system performance, and the efficiency of signal transmission.

There are RF multiplexers that have multiple frequency bands. These multiplexers are primarily designed for use in radio frequency applications. They have the capability to combine several RF signals in one output signal.

Types of RF Multiplexers

RF multiplexers are classified as analog and digital multiplexers. The analog RF multiplexer is further categorized as wavelength division multiplexing (WDM) and frequency division multiplexing (FDM). Furthermore, the digital RF mux features a time division multiplexing (TDM).

There are different types of RF mux for analog signal sources. However, the most common types are triplexer multiplexer and quadplexer multiplexer. A Triplexer has 1 input and 3 output while a quadplexer has 1 input and 4 output. These multiplexers are categorized based on the number of RF inputs and outputs.

A Triplexer Multiplexer

RF triplexer is a device that puts together signals of three frequency bands and then separates them. This type of multiplexer features a single input port and three different output ports. Every output port can transfer signals within a particular range of frequency. A RF triplexer is applicable in wireless communications systems. This is because this device can make use of three various frequency bands to carry out data, voice, and video transmission. RF triplexer is also referred to as 1 input 3 output (1×3) multiplexer.

A quadplexer multiplexer

RF quadplexer combines signals of four various frequencies and then separates them. This device is similar to how RF triplexer work. Both devices are designed for signal transmission and processing of various frequency bands simultaneously. The only difference between a quadplexer and triplexer is that a quad can process four different signal sources at the same time.

Asides from quadplexers and triplexers, there are other RF multiplexer types. These are RF pentaplexer and RF hexaplexer.

Parameters to Consider in RF Multiplexer Design

There are some design parameters to consider during RF multiplexer design.

Insertion loss

Impedance mismatch and the loss of the device are factors that cause insertion loss. It is therefore crucial to minimize the insertion loss in order to enhance the signal’s transmission efficiency. Doing this determines a lot of things in the RF multiplexer design.

Phase balance

An RF multiplexer has different output ports and each of these ports has a different signal phase. Therefore phase balance describes the difference of the signal phase between these ports. Phase balance affects the transmission efficiency of distributed and multiplexed signals.

Working frequency range

In RF multiplexer design, the working frequency range is an important parameter to consider. This is because this range has to match with the application’s signal frequency range. Also, there is a need to consider the center frequency and Bandwidth value.  

Number of channels

This refers to the number of output ports and input ports an RF multiplexer comprises. The capabilities of signals to distribute and multiplex will depend on the number of channels. In the long run, this will have an impact on the complexity of the RF multiplexer design.


This is the impact of signal isolation between various output ports or input ports. In reality, the mutual interference between signals becomes smaller when the isolation is higher.

Regardless of the type of multiplexer, it is crucial to note the value of parameters in a range of frequency.

What is the Difference between an RF Switch and RF Multiplexer?


An RF multiplexer differs from an RF switch based on some parameters. The RF switch is capable of switching between various RF paths. This switch is commonly used for automatic routing of signals, turning On and OFF of RF signals, Tx/Rx switching, and wireless test.

RF switches have some specifications which include return loss, rise time, frequency range, isolation, insertion loss, and power handling capacity. There are two main type of RF switches based on mechanical layout. These are drop-in and connectorized.

On the other hand, RF multiplexers combine many RF signals in a port or divide signal from a port into several signals. When routing RF signals, both RF switch and RF multiplexer work in the same way.  RF switches that are in higher output modes like 8X1 are known as RF multiplexers. On the other hand, RF switches that are lower output are known as relays.

The summary of this is that an RF switch switches RF signals while RF multiplexers mix RF signals and put them in one output.

What is RF Channel Multiplexing?

This process involves dividing a radio transmission path into many parts in which multiple communication channels can be transferred. Multiplexing can be in the form of code division, frequency division, and time division. Time division refers to dividing into time slots while frequency division divides radio transmission path into frequency bands. Code division involves dividing the radio transmission path into coded data that overlaps.

Furthermore, code division multiplexing (CDM) enables multiple users to transmit radio channels by including codes to every data signal sent to and received from the radio transceivers. The codes transmit the data signal to a much wider bandwidth. This bandwidth is more than what is needed to transfer data signals without the code.

You can make use of several coded channels on a similar RF channel without disrupting each other. It achieves this by combining channelization codes that can detect every physical channel. RF channel transmission involves developing a radio communication channel that takes up a radio channel bandwidth. This bandwidth is greater than the frequency bandwidth needed to transmit the signal.

It is possible to develop bigger RF channels. You will need to multiply the information by channel codes. When the proportion of chips to information bits changes in a spectrum communication system, this is referred to as variable spreading rate.


During RF multiplexer design it is important to take note of some parameters. Parameters such as isolation, number of balance, and phase balance determine a lot. RF multiplexers are often used in wideband systems. In this application, there is a need to increase the bandwidth in order to enhance a down-conversion scheme.

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