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I'm designing a hardware for a hobby purpose involving SIM900. I'm a newbie when it comes to antenna design. I was wondering what would be the best antenna choice to start with. Even though chip antennas do have some design complexities involves, I'm bend on using them since they're kind of compact. My question is whether chip antennas will be able to radiate enough power to transmit to cellular base stations. I haven't seen any SIM900 modules with chip antennas.

http://simcom.ee/modules/gsm-gprs/sim900/

Thanks.

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  • \$\begingroup\$ What does the plethora of pdf data sheets to be found in your linked site tell you about antennas you can use? \$\endgroup\$ – Andy aka Jul 24 '16 at 15:36
  • \$\begingroup\$ I checked the documents, but none says about the antenna type to be used. There is a mention of 'co-axial cable pad' in this document under antenna design. simcom.ee/documents/SIM900/… \$\endgroup\$ – sdk Jul 24 '16 at 16:14
  • \$\begingroup\$ @sdk did you manage to solve this problem? \$\endgroup\$ – ShP Oct 10 '17 at 22:33
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I would take a look at the Taoglas PA.22a chip antenna or the Pulse W3073.

They tend to be a little pricey on low quantities, but they are purpose built quad-band (850/900/1800/1900 MHz) antennas that should work with the SIM900 if appropriately designed.

A well matched and well designed chip antenna will certainly radiate enough power based on the max-power output of the SIM900 (1W-2W).

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As far as I've been able to determine, SIM900 presents a 50 ohm RF output impedance to a load so, if that's right, it behooves you to design an antenna which will present a 50 ohm load to that output, at the frequency of interest. The simplest solution is a vertical whip of some kind, and if you don't know how to determine its length and how to get a conjugate match if you can't get the whip resistive, then you'd probably be better off just buying a Commercial Off The Shelf 50 ohm whip cut for the frequency you're interested in. If you're interested in the nitty-gritty of antenna design, Google "antenna design."

Be aware that if you want your widget to be street legal, even for hobby purposes, you'll have to get it certified as complying with current standards since 2 watts is actually a lot of power, lately.

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  • \$\begingroup\$ Thanks for the answer. So you're suggesting something like a wire antenna, right? I read a document from Cypress saying that I need to have the length of the wire to be half or quarter of the wavelength. So now, should now in light of what you have said, does that mean I need a dipole or quarter pole wire antenna with 50 ohm impedance? Can you shed some light on making my own 50 ohm antenna. I'll google anyways. What about the inductance of the antenna conductor? Shouldn't that too be taken into account when calculating the antenna impedance. \$\endgroup\$ – sdk Jul 25 '16 at 6:44
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    \$\begingroup\$ Pointing out that a whip is the simplest solution shouldn't be construed as a suggestion, it's merely an observation. Comments isn't designed for technical discussion, and at your current level of development I suggest that Google may be the way to get the most bang for your buck. Also, try this \$\endgroup\$ – EM Fields Jul 25 '16 at 7:39

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