Note that when the load looks resistive the VSWR versus frequency is at a minimum.
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On August 2, 2022 4:38:51 PM MDT, W0LEV <davearea51a@...> wrote:
And please remember resonance is not necessarily at 1:1 SWR. It may or may
not be. Resonance is *defined* by (consult the complex portion of the
measured impedance): +jX = -jX. The resistance term is purely resistive
(consisting "mostly" of the radiation resistance) while the reactive
component is strictly reactive: capacitive or inductive.
Dave - W?LEV
On Mon, Aug 1, 2022 at 10:01 AM Diane BONKOUNGOU <dianebonk2@...>
wrote:
Hello Roger,
Thanks for reminding me, I will post on the other topic how I went about
correcting the electronic delay introduced by the SMA cable. My cable was
too long to correct the electronic delay at its end after doing the
calibration at the NanoVNA end that's why I had a lot of circles in the
Smith chart. I cut the cable further and have a quarter circle in the Smith
chart and then use the Edealy parameter in the NanoVNA to correct.
Best regards
Le ven. 22 juil. 2022 ¨¤ 17:03, Roger Need via groups.io <sailtamarack=
[email protected]> a ¨¦crit :
On Fri, Jul 22, 2022 at 04:34 AM, Diane BONKOUNGOU wrote:
Hello,
Hi, I am a beginner in antenna design and tuning.
I want my antenna to have a resonant frequency of 2.45GHz for
low-energy
Bluetooth communication.
And I want to know what to consider for the matching process.
I have made some measurements with Nanovna of my antenna. I have a
resonance
frequency of 2.28GHz and at this frequency, I have an impedance of
47.8-7.06j.
Can I take the value of this impedance at this frequency for the
matching
process or do I have to take the value of impedance at 2.45GHz?
Where to take the value of impedance for tuning?
Thanks.
You never posted in the other topic what you finally did to correctly
measure the antenna with the NanoVNA. If you don't establish the
"reference plane" rightat the antenna your impedance measurements will be
way off and you won't be able to design a matching network. Even if you
get a decent "reference plane" the antenna must be measured in circuit so
that you have a the same ground plane as when the antenna will be used.
Also the outer shield of your test cable may form part of the antenna
and
this will affect the measurements.
At these GHz frequencies you will have better results if you tune the
antenna for resonance at the desired frequency instead of building a
matching network. The reason I say this is that VSWR and Return Loss
will
only change slightly if your reference plane is not right on but the
impedance will be off a fair amount. The reason is that the magnitude of
the reflection coefficient stays the same and only the phase angle
changes
if the cable is slightly long or short. However the phase angle rotation
results in a different impedance calculation. Even if you get a
reasonable estimate of impedance you then have the issue of designing
with
components and PCB design at Bluetooth frequencies.
Roger
--
*Dave - W?LEV*
*Just Let Darwin Work*
--
Dave - W?LEV
