What is the purpose of a parasitic antenna coupler?
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What is the purpose of a parasitic antenna coupler?

Posted Date: 2024-01-24

A parasitic antenna coupler (Parasitic Element Coupling Device) is a coupler that contributes to broadband and miniaturization of antenna characteristics. For antennas that require wider frequency bandwidths such as Wi-Fi 6E, Wi-Fi 7, and cellular networks, the antenna part can be miniaturized by broadening the bandwidth and improving antenna efficiency.

Product principle and structure

A parasitic antenna coupler is a coupler that strongly couples a feed antenna and a parasitic element (parasitic antenna) to further widen the bandwidth and improve antenna efficiency. Therefore, even for small antennas where parasitic elements are difficult to apply, good antenna characteristics can be obtained by mounting this coupler.


Schematic diagram and effect of parasitic antenna coupler (broadband and improved antenna efficiency)

Murata uses its proprietary multi-layer technology to place the transformer coils in close proximity, achieving strong electromagnetic coupling without the use of magnetic materials. This resulted in the development of this coupler, which improves antenna characteristics and contributes to miniaturization.

Advantages of Parasitic Antenna Couplers

Advantage 1: Broadband antenna and improved antenna efficiency

Broadbanding can be achieved by using a parasitic antenna coupler for the antenna section. The graph below compares antenna characteristics (return loss) and antenna efficiency through simulations with and without a parasitic antenna coupler. It can be seen from the figure that by strongly electromagnetic coupling the parasitic element and the feed antenna and increasing the antenna resonance of the parasitic element, broadband can be achieved and antenna efficiency can be improved.

Advantage 2: Miniaturization of antenna

The effect of improving antenna efficiency through parasitic antenna couplers enables miniaturization of the antenna part.

Generally speaking, if the feed antenna and the parasitic element are juxtaposed to achieve weak electromagnetic coupling and the antenna is miniaturized, the coupling between the parasitic element and GND becomes stronger and the coupling with the feed antenna becomes further weakened. Therefore, the function of the antenna as a parasitic element is reduced, and the antenna efficiency becomes worse.

Because the parasitic antenna coupler strongly electromagnetically couples the parasitic element to the feed antenna, good antenna efficiency can be expected even for small antennas.

Advantage 3: Reduce the impact of cable losses

Matching is improved by strongly electromagnetically coupling parasitic elements to the antenna with a parasitic antenna coupler.

This prevents multiple reflections between the antenna and the module. Can reduce the impact of insertion loss when using long cables.

Evaluation conditions

evaluation result

Product overview

We have a product lineup for each frequency band.

Usage examples

It can be used in a variety of products equipped with antennas, such as laptop computers and smartphones.

· laptop
・Smartphone/Mobile phone
· tablet
・  xR(AR、VR、etc.)
・DSC (Digital Camera)
・Game (portable game console)
· television
· Wireless Router

Adoption examples

There is smartphone and laptop adoption performance.

Smartphone adoption examples

This is an example of adoption of a smartphone using a frame antenna.

Parasitic elements are placed on the substrate and coupled with a parasitic coupler to achieve wide bandwidth.


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