ANT-2.4-LCW-ccc Data Sheet

Matching Network

Linx tests all our antennas in ideal scenarios where effects from conductive surfaces, non-conductive

surfaces or human proximity issues are eliminated. As a designer, you do not have much control over the

environment your product will be used in.

Linx has always worked closely with our customers, and we know what the primary concerns and pitfalls

are for designers and how to prepare for them. Whether you are designing for a monopole or a dipole

antenna, or an external or even an embedded surface mount antenna, the most common question is, “Why

isn’t my design working?”, and frequently it turns out the design needed a matching network.

As your product design progresses, the chances for proximity effect increases as other components are

added. Some components can act like ground planes, if they have large conductive surface areas, and

can cause interference. This interference is called proximity effect, which can cause a downward shift in

the center frequency of the circuit, depending on how strong the effects are. Proximity effect is commonly

caused by components like pc boards, batteries, motors, sensors, actuators and even non-conductive

enclosures like radomes. Interference can also occur from human proximity, like when using a hand-held

mobile device.

Although our dipole antennas have been designed to minimize these effects, we strongly recommend the

use of a matching network, so you can ensure that you retain optimum signal levels. A matching network is

a circuit that balances the impedance and ensures there is minimum reflected energy coming back from the

antenna. This enables the integrator to optimize the performance in a specific band or to level performance

across all bands. The most common matching network design is called a Pi circuit, placed between the

antenna and the radio; it is a simple circuit of two capacitors to ground on either side of a series inductor.

The values can be selected to electrically tune the antenna. It does take test equipment, such as a network

analyzer, to get this right though. Often a design ends up having little or no proximity effect, eliminating the

need to retune the matching section. In these cases, the matching section can have a zero ohm resistor in

place of the Inductor, leaving the other two shunt components un-populated.

The values of the matching components are determined experimentally on the product’s board. Since there

are many variables that play into the antenna’s final performance, it is very difficult to predict what it will

do on any specific design. It is best to design in the matching network, see what the antenna does on the

prototype and then dial the performance in with the network components. Not all of the components may

be needed on a particular design, so they do not need to be populated in production; but it is a good idea

to have the component pads on the board in case they are needed. The components should be placed

close to the antenna connection. The component pads should be placed on the 50-ohm line between the

radio and the antenna.

Linx Technologies offers a service to help customers tune our antennas to their circuit boards. Please contact Linx for more details.

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