Diplexers vs. Duplexers

Key Takeaways

• A three-port RF device that uses two signal paths in a transmission line or antenna is called a diplexer. 

• A three-port device that separates transmit and receive signals from an antenna into different signal paths of channels is called a duplexer. 

• The functions of diplexers and duplexers are not interchangeable. Diplexers separate signals based on frequency, whereas duplexers separate the transmit and receive path of signals based on their direction. 

Among the various RF components, diplexers and duplexers are widely used in transmitters, receivers, transceivers, radars, sensing applications, etc.

Among the various RF components, diplexers and duplexers are widely used in transmitters, receivers, transceivers, radars, sensing applications, etc. Comparing diplexers vs. duplexers is a common topic of discussion, as the two RF components are different. The diplexer and duplexer perform different functions, even though they are used together in RF circuits. A diplexer separates signals based on frequency, whereas a duplexer separates the transmit and receive path of signals based on direction. The duplexer is employed to separate signals of the same frequency. 

Diplexers vs. Duplexers: What’s the Difference?

Diplexers 

Function

A three-port RF device that allows using two signal paths in a transmission line or antenna is called a diplexer. In diplexers, the signal paths are sometimes called channels. The diplexer enables the transmission or reception of two different signals from the same antenna. Diplexers employ frequency division by filters to separate the different paths. The filters can be high-pass filters, low-pass filters, or bandpass filters. For the best diplexer results, the attenuation and quality of the filters must be based on the closeness of the signals, the signal power levels, and non-linearities.

As illustrated in the circuit above, the diplexer allows different circuits or devices to share a common communication channel. There are two filters in diplexers to filter different frequencies handled by a single antenna. The frequency A signal passes through filter A, whereas the frequency B signal takes the path consisting of filter B to the same antenna. There should be a significant difference between the frequencies, which helps the filter sort them easily.

For the diplexer to work satisfactorily, the frequency bands need to be wide apart. The performance of the diplexer is enhanced when working on such signals rather than two frequency band signals, which are closer to each other. 

Applications

Diplexers find applications in telecommunication systems where the same antenna is employed for carrying signals of different frequencies. Diplexers are also used in cellular base stations where the same antenna is utilized for transmitting CDMA, GSM, and LTE signals.

Diplexers are rarely used in radars. One such example application is in wideband multifunction radar, where the diplexer is used to separate the received signals to multiple receive channels based on frequency. 

Duplexers

Function

A three-port device that separates transmit and receive signals from an antenna into different signal paths of channels is called a duplexer. The duplexer separates the signal paths based on the signal direction. The duplexer is an RF device that allows the signal antenna to be a part of two-way communication. The duplexer helps the two-way communication antenna to transmit and receive signals at the same frequency.

The figure above illustrates a duplexer that separates the signal received from the antenna into two different paths. In duplexer-based circuits, magnetic circulators or switched systems are employed for establishing isolation between the transmitting and receiving signals.

The two parameters influencing the operation of a duplexer are:

1. Isolation between the receive channel from the transmit channel
2. Operating bandwidth 

Applications

In radar systems, there is a need to isolate high-power transmitter signals from the receiver circuit. However, both signals need to be operated from a single antenna. In such radar systems, duplexers are installed to reasonably isolate the transmit and receive signals. Duplexers are widely used in telecommunication applications. In 5G systems, duplexers are used for transmitting and receiving signals at the same frequency, which enhances spectrum utilization. 

Diplexers vs. Duplexers: A Summary

The functions of diplexers and duplexers are not interchangeable. Understanding the difference between diplexers vs. duplexers will help you when working on RF circuits.

Cadence OrCAD supports RF circuit development projects consisting of diplexers, duplexers, and circulators. Leading electronics providers rely on Cadence products to optimize power, space, and energy needs for a wide variety of market applications. If you’re looking to learn more about our innovative solutions, talk to our team of experts or subscribe to our YouTube channel.