I’m trying to design a circuit using a Freescale 802.15.4 radio (2.4GHz) and a chip antenna and I’m not sure where to begin. I know I need to match inductance and capacitance, but I cannot seem to find a resource to help and point me in the right direction.
Does anybody out there know of a good source of information on 2.4GHz chip antenna feed path designs (or even printed antenna designs)? Any help would be appreciated. Thanks!
I whizzed past something on Nordic’s site.
Look through the data sheets and such on the right hand side.
I didn’t view them, but there were a couple sheets on antenna design there.
good luck!
Ross
Thanks. I don’t have a lot of time now, but I will check that out. I appreciate the reply. Thanks!
Out of curiosity, has anyone tried just making a 1/4-wave whip for these 2.4GHz modules? It seems like if I have the space, it would have better performance than a chip antenna and it’d be cheap and simple. Just solder a length of wire to the PCB and make sure it has a ground plane under it.
I notice that the RF-MiRF just uses a trace as an antenna, and it gets decent range. OTOH, the Laipac modules use an etched loop antenna and get even better range. But a piece of wire would be super simple.
The major concerns are impedance matching. I’m no expert, but most designs that use anything but a custom 50ohm antenna need to be measured and a matching network designed. I don’t think many of us have the hardware to determine if our antennas are improperly matched 
Yeah, I thought of that too after I posted. A 1/4 wave should have a low impedance at the feed point. Detuning it a little could get you 50 ohms, but it’d be reactive, not resistive. A simple matching network should fix that but if I’m going to design and implement a matching network I might as well just use a “real” antenna or a chip antenna. I’ve never done much RF stuff and I think that starting with 2.4GHz stuff might be kind of jumping in at the deep end.
OTOH, depending on the module, driving a non-50-ohm impedance might not be a problem. The mismatch’d probably reduce the power output, but if the whip antenna is enough better than the chip antenna, maybe you’d still come out ahead.
I guess it’s probably not worth the trouble unless I’m building a bazillion of the things.
wiml:
Out of curiosity, has anyone tried just making a 1/4-wave whip for these 2.4GHz modules? It seems like if I have the space, it would have better performance than a chip antenna and it’d be cheap and simple. Just solder a length of wire to the PCB and make sure it has a ground plane under it.I notice that the RF-MiRF just uses a trace as an antenna, and it gets decent range. OTOH, the Laipac modules use an etched loop antenna and get even better range. But a piece of wire would be super simple.
I used a 1/2-wavelength wire with no ground plane and I get good range with a 2.4 GHz module. It turned out to be about 2.5 inches long or so…