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07-14-2014 02:12 PM
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?
Solved! Go to Solution.
07-14-2014 04:05 PM
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?
07-14-2014 05:02 PM
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.
01-07-2015 12:31 PM
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.
04-17-2017 06:29 PM
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.