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Posts: 2
Registered: ‎04-04-2014
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Si4012 with chip antenna

Hi,

I want to make a very small transmitter with Si4012, and the problem is the PCB antennas are too big for my project. Is it possible to use a 433MHz ceramic chip antenna? I suppose yes, because such atennas have 50 ohm impedance, but I'm not an RF expert and had bad experiences using chip antennas with a GSM/GPRS modem. Do somebody has any experience?

Thanks

Gyula

Posts: 254
Registered: ‎09-10-2013

Re: Si4012 with chip antenna

Note that the RF amplifier is two sided, so the 4012 may not be your best choice.  Can you pick a single-ended transmitter?

 

Also, I would think that your range will be greatly reduced with a chip antenna, but I'm not sure about that.  Is that OK for your application?

Posts: 93
Registered: ‎02-19-2014

Re: Si4012 with chip antenna

Jeff:

 

As Dan has mentioned, the Si4010 / Si4012 chips are designed to drive a differential antenna structure (i.e., loop antenna) and works best with a differential load impedance of approximately 500 ohms.

 

It is possible (although somewhat component intensive) to construct a balun circuit out of discrete L-C components that matches the differential Si4012 output to a single-ended 50 ohm load.  If you constructed such a balun match, then you could bolt on any 50 ohm antenna of your choice.

 

See our app note AN369 for a discussion of the balun match concept.

 

Eric

 

Posts: 2
Registered: ‎04-04-2014

Re: Si4012 with chip antenna

Thank you, I'll try the matching circuit described in the appnote.

Posts: 2
Registered: ‎04-18-2014

Re: Si4012 with chip antenna

With all the extra discrete components, how much power is typically lost in using a dipole chip antenna with the Si4010?

Posts: 93
Registered: ‎02-19-2014

Re: Si4012 with chip antenna

In our experience, we typically lose about 0.5 to 1.0 dB in the discrete matched solution, due to finite Q-factor of the inductors.

 

However, please note that the antenna efficiency / gain of a typical printed differential loop antenna is often no better than about -5 to -10 dBi.  Printed antennas are cheap, but they are not awesome performance.  So you *might* actually come out ahead by implementing the discrete L-C balun match to a single-ended chip antenna and suffering the loss of the discrete components, depending upon how efficient your chip antenna is.

 

Eric

 

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Posts: 2
Registered: ‎04-17-2017

Re: Si4012 with chip antenna

Will this chip work at all without any antenna ?

 

I've programmed it via a MCU, no errors read back; however nothing gets registered by the SDR sniffer (less than half a meter away from the transmitter Si4012 chip; the SDR has an antenna and it works fine for other transmitters). I have used the excel spreadsheet to get all my values, power has been set to the maximum for PA. The only thing I can think of is the missing differential antenna.

 

Thank you