What Are Diplexers and How Do They Work?
When certain devices conduct signal transmission for their standard operations, they may take advantage of frequency-domain multiplexing, that of which is a technique that serves to divide the total bandwidth into non-overlapping frequency bands for carrying separate signals. This is highly beneficial when one needs to send multiple independent signals over a single cable or optical fiber, and such multiplexing is made possible through passive RF filters known as diplexers. As a filter component featuring three ports, two frequency bands may share an antenna so that separate signals can be transmitted and received simultaneously. In this blog, we will discuss diplexers in more detail, allowing you to have a better understanding of how they are used.
With their three ports, diplexer components are commonly found within multiband systems where there is an antenna capable of handling two frequency bands. While the antenna will handle sending and receiving signals for both frequency bands, it is the duty of the diplexer to sort all signals in accordance with their frequency. With the three ports, one serves for receiving signals, one serves for sending them, and the third attaches to the antenna. The receiving and sending ports both have filters, ensuring that undesirable frequencies are barred from passing through. For those that pass through the filter component, the diplexer will then isolate the frequency before transmitting the signal to the correct port for standard functions to be carried out.
Depending on the particular system one is operating and its purpose, there are a number of RF diplexers that one may take advantage of. Additionally, various technologies are also implemented within a typical RF diplexer to establish and enhance its capabilities for frequency handling, and these parts include wavelength diplexer topologies, planar diplexer topologies, lumped elements, and ceramic chips.
The waveguide diplexer is a technology featuring two bandpass filters and a circulator, and they are known for their low insertion losses and high quality. Due to their high power handling capabilities, increased selectivity, and a lack of need for tuning, waveguide diplexers are quite beneficial. Nevertheless, it is important to consider that they are often heavier and are hard to reproduce, thus affecting certain types of applications. They are also more expensive than some options, limiting their benefits in other applications.
Planar diplexers are fairly similar to waveguide diplexers, albeit smaller for more compact placement. With their small size, a planar diplexer offers ample integrability, allowing them to benefit lightweight systems and applications as they are placed alongside other system components. Unlike waveguide diplexers, planar diplexers are also cheaper, and they can be duplicated fairly easily. Despite this, their power handling capabilities fall short of other various options, and they have a lower quality factor as well. Despite that, their cost and size still makes them very useful for certain needs.
When shopping for various diplexers, it is important to not mix them up with duplexers, those of which are other three port RF devices that utilize an antenna for sending and receiving signals. Despite this, they do not separate signals with filters based on frequency, thus the two parts are not interchangeable for the same applications. While a duplexer may benefit a radar system for high power transmitter signal isolation, a diplexer may benefit a similar system through the transmission of receipt of multiple signals on the same antenna.
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