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Why the embedded chip or patch antennas are resonant on the wrong – to high – frequency? EA#

Your enclosure will interfere with your embedded antenna

Just have a closer look on some 2400 MHz chip antennas or GPS patch antennas. Some manufacturers offers the embedded antennas with different resonant frequencies. The resonant frequencies are a little bit higher than the frequency you plan to receive.

Why the antennas are resonant on the wrong – to high – frequency?

Embedded antenna and jump of resonance frequency

Embedded antenna and jump of resonant frequency

The answer: As soon you slide your final PCB in your plastic enclosure in the resonant frequency of your antenna will be lower. That means you need embedded antennas that offers in the air (without enclosure) a higher frequency. The jump of the resonant frequency will be interfered by the Epsilon R of the plastic, the thickness of the plastic, and the distance of the plastic to the antenna. Plastic is already the wrong word. Any dielectric material like ABS, glass or acrylic glass will interfere as well. You can´t calculate the jump without a simulation, but you can estimate it if you have experience from former wireless projects. Anyhow, the resonant frequency will jump for sure.
Without experience in RF technology it is highly recommended to hire a third party for consulting. A RF skilled consulter will be able to select the right embedded antenna for your wireless application. Such RF engineers often have access to a huge amount of different antennas. They will be able to optimise the matching circuit between the embedded antenna and the RF generator (e.g. ANT, WIFI, Bluetooth or GSM module) as well.
If you have a need for antenna consulting , then just drop an email to harald.naumann (at) gsm-modem.de

Updated: 2013-07-19 — 9:59 PM

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