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I've written a Windows utility that checks Touchstone files for |S11| > 1. It handles version 1.1 files, the kind NanoVNAs generate, as well as version 2.0. It lists maximum |S11| and the number of frequencies where |S11| > 1. This utility may come in handy if you experience odd problems processing NanoVNA data as I did.

Just download the ZIP, extract the files, ignore the ground probe stuff, put S11.EXE in a directory containing Touchstone files, and double-click on it.



Brian

Try to connect through any free VPN, pointing to Netherlands... They can!

On Fri, Jul 22, 2022 at 08:59 AM, Neil Preston W0NRP wrote:

I am trying to figure out if the Nano can display the lumped impedance and
phase angle numerically without having to calculate from r + jX. I expected
to read that from the POLAR menu, but some searching reveals that is just a
coefficient from -1 to +1.

???

I assume when you say "lumped impedance and phase angle" you mean display |Z| (sqrt of [r^2+X^2]) and impedance phase angle. The NanoVNA and the two popular PC programs (NanoVNA Saver and NanoVNA app) can calculate and display |Z| but do not have an impedance phase angle display capability. The "phase" option in the trace menu is the reflection coefficient phase angle which is not the same thing as impedance phase angle.

The polar display is for the reflection coefficient not impedance.

The easiest way to calculate the impedance phase angle is to import the Touchstone S11 file into a spreadsheet and do the calculation and plotting there.

Roger

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

I am trying to figure out if the Nano can display the lumped impedance and phase angle numerically without having to calculate from r + jX. I expected to read that from the POLAR menu, but some searching reveals that is just a coefficient from -1 to +1.

???

On 7/22/22 8:36 AM, Zack Widup wrote:

You should measure the impedance at the frequency you plan on using. I have
found fairly large variations over a few MHz in this range before.
Zack W9SZ

Most simple antennas, near their design frequency, have an impedance curve that looks a lot like a RLC resonance. The real part changes fairly slowly, but the imaginary part changes quickly.


On the attached graph (impedance of a dipole), you can see that X changes from about -40 to +40 going from 90 to 100% of a half wavelength (resonance is at about 95% half wavelength), while R goes from 53 to 75 ohms over the same frequency range.

A 5% variation in frequency isn't huge (at 2.45 GHz, 5% is 120 MHz) - If you think of the antenna as a filter, it's not even down 3dB at 5%.

Zmag is the absolute value of the Z.

So if you put a L or C in to "cancel" the reactive part,

On Fri, Jul 22, 2022 at 06:14 AM, Miro, N9LR wrote:

I just ordered COILCRAFT TTWB-1-ALD on ebay (US seller), 20pcs for $25
including S&H (seller accepts "best offers"!)



0.3 - 190MHz @1dB, 0.08-450 @3dB, 6.5mmx6.5mm, SMD

Good, let us know how you get on with them, I'm sure there are others interested in using baluns with the nanoVNA.

Kind regards

Ed

You should measure the impedance at the frequency you plan on using. I have
found fairly large variations over a few MHz in this range before.

Zack W9SZ

On Fri, Jul 22, 2022 at 6:34 AM Diane BONKOUNGOU <dianebonk2@...>
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.

<>
Virus-free.
www.avg.com
<>
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

Hello Douglas,
Thanks for your response.
Best regards

Le ven. 22 juil. 2022 à 12:55, Douglas Butler <sherpadoug@...> a
écrit :

I just ordered COILCRAFT TTWB-1-ALD on ebay (US seller), 20pcs for $25 including S&H (seller accepts "best offers"!)



0.3 - 190MHz @1dB, 0.08-450 @3dB, 6.5mmx6.5mm, SMD

On 7/22/22 2:00 AM, Diane BONKOUNGOU wrote:

Hi all, I am a beginner in RF system design and have some questions.
I have a PCB trace antenna, I need to tune it to 2.45GHz, this is for Bluetooth low-energy communication.
I want to use a pi-network for the tuning process. I chose pi-network because it is selective and allows to set the quality factor Q of the circuit and the bandwidth (BW) of the antenna as Q=F/BW.
-Can someone tell me when to choose the pi-network high pass or low pass for antenna matching?
I have seen in the document "AN1275: Impedance Matching Network Architectures" by Silabs that the high-pass network allows high frequencies to pass through the antenna and the low-pass pi-network blocks the passage of high frequencies through the antenna, which also means that the matching network must allow DC current to pass through the antenna.
What does it mean to allow DC current to pass through the antenna?
In general, I know that the signal transmitted by the antenna is an AC signal. Could I feed (transmit) a DC signal to an antenna?

Folks will chose high or low pass to meet spurious emission requirements. For instance, if your transmitter has 3rd harmonic, using a low pass matching network can help knock that down to below the (typical) -40 dBc or -60 dBcrequirement.

As to why you might want to pass DC - AC coupled ungrounded antennas can build up static charge. If you don't have some way to discharge that static, then if the voltage gets high enough, you might have a spark (which generates broadband RF power) or a component failure (e.g. a capacitor exceeds its voltage rating). Some antennas though, are inherently grounded, so in that case, you don't care.

You would want to pass DC through to your antenna if the antenna might have a pre-amp that needs the DC for power. Also in some cases, DC grounding the antenna is good practice for safety, like when dealing with radio detonators for fireworks, explosives, or just in the presence of fuel fumes. DC grounding means no static buildup.

SherpaDoug

What matters is the impedance of the antenna at the frequency where you will use it. Impedances at other frequencies, resonant or not, don't really matter.

SherpaDoug

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.

Maybe it easier to build the antenna that it has 50 ohms input then tune a mismatch with a network
Dg9bfc sigi

Am 22.07.2022 12:08 schrieb F1AMM <18471@...>:

If it is above all an impedance adaptation that you are looking for, it is easier to use an 'L' adapter. It will be low pass or high pass. You will choose it as impedance step-up or step-down.

You can consider that a pi-adapter consists of 2 L-adapters one behind the other. For example on a classic pi: capacitor in parallel, inductor in series, capacitor in parallel, you cut (in your mind) the inductor in two. The one on the right is step-down and the one on the left is step-up. They are both low pass.

A pi is especially of interest when the adapter must be fairly universal. This is not your case since you are going to measure your antenna with your nanaoVNA. The adaptation will be fixed (raise or lower).
--
Fran?ois F1AMM

Hi all, I am a beginner in RF system design and have some questions.

I have a PCB trace antenna, I need to tune it to 2.45GHz, this is for Bluetooth low-energy communication.
I want to use a pi-network for the tuning process. I chose pi-network because it is selective and allows to set the quality factor Q of the circuit and the bandwidth (BW) of the antenna as Q=F/BW.

-Can someone tell me when to choose the pi-network high pass or low pass for antenna matching?
I have seen in the document "AN1275: Impedance Matching Network Architectures" by Silabs that the high-pass network allows high frequencies to pass through the antenna and the low-pass pi-network blocks the passage of high frequencies through the antenna, which also means that the matching network must allow DC current to pass through the antenna.

What does it mean to allow DC current to pass through the antenna?
In general, I know that the signal transmitted by the antenna is an AC signal. Could I feed (transmit) a DC signal to an antenna?

Thanks,

On 7/21/22 10:37 AM, W0LEV wrote:

Jim, not just the UK. It's not the net Nazis. I could not access it
either. Something to do with no 'academic access" and, of course, not an
IEEE member. I'm not sure even an IEEE member would allow access.

It's available in IEEE Xplore.

Thanks for forwarding the paper, but I hope I can read it as its not the
sharpest "copy".
Dave - W?LEV

The scan on the IEEE pdf isn't bad. Moire on the halftone figures. Drawings and text is sharp.

On Thu, Jul 21, 2022 at 10:12 AM, Dragan Milivojevic wrote:

Had no idea that the UK censors the internet. Good reason to get a VPN.
Anyway: !AvpPJnaZGO4PiHD2Qt_oLBZfweoD?e=dxDhWi

Thanks,

Blocked last year due to court order/injunction

Kind regards

Ed

Charlie, that's true although this isn't in a car , it's in a bespoke design I am doing and I am in control of the termination at both ends.