Dave,

If I were you, I would trim the antenna for resonance and then use a
microstrip transmission line transformer to convert between the rx/tx
impedance and the antenna's impedance.

Alternatively, there are definitely 50 ohm PCB 2.4GHz antennas. I do not
have any designs off-hand but I'm sure Google does!

Sean



On Fri, May 30, 2014 at 6:36 PM, David VanHorn <microbrix@gmail.com> wrote:

> Doing a little work with PCB antennas for 2.4GHz, I have a question.
>
> I have the option to tune the element lengths for resonance or best
> impedance match.  With a simple dipole, resonance would be around 72 ohms=
..
> If I tune for best impedance match, then I will be off resonance.
>
> Intuitively it has always seemed best to me to tune for resonance and the=
n
> match the impedance.  If I do this, then I end up right on the non-reacti=
ve
> line, and I need both an L and C to transform the impedance down to 50
> ohms. Both are lossy.
>
> At 2.4 GHz, in very space constrained antennas, everything has costs but
> they are way less trivial than in less space constrained systems or at
> lower frequencies.
>
> So the question is, from those who have experience here, which is likely =
to
> result in overall lower loss in a real implementation, trimming for
> resonance and matching, or tuning for match and letting it be non-resonan=
t.
>
> Alternatively, resonant structures that can be near 50 ohms on a real PCB=
?
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