EEVblog Electronics Community Forum
Electronics => RF, Microwave, Ham Radio => Topic started by: Karamel on August 30, 2017, 08:09:52 pm
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Hi,
I am new at radio frequency job and I need to design bluetooth beacon circuit. I, therefore, need to discuss something about RF here. I want two request from you. First, please, let's start basic conception and tell me like this. Second, please, support me with documents, books, pages etc.
I have already researched something from internet and I saw some ways to gives solution about antennas. However, I need to learn from you.
- I have seen PCB antenna and ceramic(chip) antenna. What is/are the difference(s)?
- PCB antenna looks cheap but there are too many shapes which I can not understand why they are like this. For example, There are two example.
(https://i.hizliresim.com/1g8ygG.png) (https://hizliresim.com/1g8ygG)
This had been connected to ground one side. Why?
(https://i.hizliresim.com/LnBanb.jpg) (https://hizliresim.com/LnBanb)
And this looks only wire. It just has a shape.
Where should I begin? What should I understand their shapes?
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There is http://www.cypress.com/file/136236/download (http://www.cypress.com/file/136236/download) a documentation about this issue and there are also some reference designs.
I can quickly copy them and solve this design problem but still I wanna learn. It looks like very deep circumstance.
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- PCB antenna looks cheap but there are too many shapes which I can not understand why they are like this. For example, There are two example.
(https://i.hizliresim.com/1g8ygG.png) (https://hizliresim.com/1g8ygG)
This had been connected to ground one side. Why?
It looks like that application note answers your questions, at least to start.
That antenna is an Inverted-F:
https://en.wikipedia.org/wiki/Inverted-F_antenna (https://en.wikipedia.org/wiki/Inverted-F_antenna)
The design has two advantages over a simple monopole: the antenna is shorter and more compact, and the impedance matching can be controlled by the designer without the need for extraneous matching components.
It's shown in paragraph 7.1 of your app note.
Like you say, it is a big subject, involving electromagnetic fields and waves as well as impedance matching.
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I have taken Electromagnetic Field and Waves lecture but it was fundamental of EMFW. There was no topic for antennas. Only, until Maxwell's equations.
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Those are the similar questions that on my mind when i was fresh engineer. What is this complex shape... How does it resonate... What will happens if i shorten that trace... etc. I have to say that don't let them confuse you. Just stick to example design and app notes. There are not many PCB antenna out there. Manufacturers already provided some design guides. Here are the good documents that TI and NXP published
http://cloud.tapatalk.com/s/59ad67edc15f1/swra161b.pdf (http://cloud.tapatalk.com/s/59ad67edc15f1/swra161b.pdf)
http://cloud.tapatalk.com/s/59ad67c0638f6/AN11564.pdf (http://cloud.tapatalk.com/s/59ad67c0638f6/AN11564.pdf)
Nexus 5 cihaz?mdan Tapatalk kullan?larak gönderildi
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Theory will only get you so far. I suggest you start with an example design, cut a prototype board then tune it manually. If you have a network analyzer shoot the antenna from its input port and observe its resonant frequency with all your plastics and surrounding parts and batteries and whatnot in place. Get some copper tape and a dremmel and do some trial and error. For minor tweaks: resonance too low - shorten antenna, resonance too high - lengthen antenna. It's not the most scientific method probably the fastest path to results.
If you don't have access to a network analyzer you'll have to get creative and it'll be a it more tedious, put your radio in TX mode and measure signal strength at a fixed distance and position, maybe outdoors if possible. You could sweep frequencies and peak hold a spectrum analyzer or sweep channels and measure RSSI with another radio. Look for the trend pointing to its resonant point and tweak accordingly.