Fw: [vna] measurement of quartz crystal

Mon Dec 26 16:04:11 UTC 2005

Hi Tom,

Have you acknowledged the bug that I reported on my former e-mail below?
I wonder when new version of the software comes up?

Best 73,

  Koji

----- Original Message ----- 
From: "Koji Terai" <kj_terai at ybb.ne.jp>
To: "TAPR/Ten-Tec VNA Users List" <vna at lists.tapr.org>
Sent: Tuesday, December 06, 2005 5:04 PM
Subject: Re: [vna] measurement of quartz crystal

> Hi, Tom!
>
> Thank you for your agile res.
>
> Yes, I knew the phase detector is not capable to determine measuring
> parameters at a lot of attenuation as the manual already addresses, and I 
> just tried
> it with a crystal with little hope. I think that to measure a crystal is 
> one of most difficult
> trials and I might be too demanding.
>
> I understand that frequency sweep will take a longer time when measuring a 
> network
> which has long-delay such as very narrow width B.P.F.s.
>
> While measuring crystals, I found a strange thing that I tried to place a 
> marker on a curve displayed
> but the marker did not appear on the right place where I clicked on, and I 
> am
> wondering if this strange thing relate to the software bugs you found.
>
> The VNA has just been released, and I hope that the VNA will be brushed up 
> by you developer
> and other users in terms of software and hardware from now on.
>
> I will be happy if I have a notification when a new version of the 
> software is released.
>
>
> 73 w/ best regards,
>
>  Koji/ JA3XNO
>
> ----- Original Message ----- 
> From: "Tom McDermott" <tom.mcdermott4 at verizon.net>
> To: "'TAPR/Ten-Tec VNA Users List'" <vna at lists.tapr.org>
> Sent: Tuesday, December 06, 2005 11:36 AM
> Subject: RE: [vna] measurement of quartz crystal
>
>
> Hi Koji:
>
> The phase detector of the VNA is not capable of measuring correctly when 
> the
> input signal is attenuated a large amount (both S21 and S11 measurements).
>
> I have also found some bugs in the software that affect crystal filters:
>
> * Severe S21 measurement error when the time delay of the network is high
> (the VNA sweeps too fast for long-delay networks).
>
> * Error in the frequency generation routine that causes the VNA software 
> to
> have a stop_frequency error for very narrow sweeps (few kilohertz),
> grid=1020, and it also forgets to set the frequency error from the 
> detector
> calibration.
>
> I have fixed these errors, they will be incorporated in the next software
> release on the TAPR website.
>
>
> -- Tom, N5EG
>
>
>
>
>
>> -----Original Message-----
>> From: vna-bounces at lists.tapr.org
>> [mailto:vna-bounces at lists.tapr.org] On Behalf Of Koji Terai
>> Sent: Monday, December 05, 2005 2:07 AM
>> To: TAPR/Ten-Tec VNA Users List
>> Subject: Re: [vna] measurement of quartz crystal
>>
>>
>> Hi Tom,
>>
>> Thank you for your res and suggestions.
>>
>> So far, I had no chance to use VNAs, but I read some books
>> before that
>> described importance
>> of defining measurement planes and consistency of a
>> testfixture to be used. Any way I have just started to use
>> the VNA and I have to learn more about
>> measurement
>> by the VNA.
>>
>> The way I tried was that I measured crystals in S12 mode and
>> tried to read
>> out f(o) and f(a)
>> from curves of magnitude and phase, but as for f(o), I had to expand
>> frequency pitch
>> to read the frequency very precisely then the peak was
>> displayed very flat,
>> almost it turned a line
>> and I could not find where the peak was. So I gave up reading
>> our f(o) from
>> a magnitude and I
>> read f(o) from a curve of phase instead, but as for f(a), a
>> curve of phase
>> changed in every sweep
>> so that I could not determine f(a). I think that a crystal
>> exhibits great
>> attenuation at f(a) and the VNA
>> is not able to determine phase change at around f(a) due to
>> the limitation
>> of the phase detector of
>> the VNA. I am not sure the way I tried was correct or not, or
>> there are some
>> better way to measure
>> a crystal at this moment.
>>
>> Koji/ JA3XNO
>>
>>
>> ----- Original Message ----- 
>> From: "Tom McDermott" <tom.mcdermott4 at verizon.net>
>> To: "'TAPR/Ten-Tec VNA Users List'" <vna at lists.tapr.org>
>> Sent: Sunday, December 04, 2005 8:08 AM
>> Subject: RE: [vna] measurement of quartz crystal
>>
>>
>> Hi Koji:
>>
>> The TAPR VNA can be calibrated against an external reference
>> oscillator for good frequency accuracy. However in order to
>> determine accurately the 4 motional parameters (Ls, Rs, Cs,
>> Cp) of the crystal requires extreme precision of the fixture
>> stray reactances. I am not an expert in crystal filters, but
>> I think the 4-parameter model is used pretty extensively in
>> filter modeling. 100 Hz frequency accuracy is not a problem,
>> but stray reactances are a problem.
>>
>> I think Agilent has a software package to extract the
>> motional parameters from swept S parameters. The TAPR unit
>> does not have this software, but it perhaps could be an
>> interesting exercise; certainly for those who enjoy working
>> on software.
>>
>> Key to measurement is that the fixture parallel measurement
>> will be contaminated by fixture parallel capacitance. This
>> will rotate the series resonance frequency away from R + j
>> Zero X and must be compensated. The parallel anti-resonance
>> will have the same issue. S-parameters will show the crystal
>> resistance as compared to 50 ohms but the fixture will rotate
>> the phase angle. The fixture perhaps can be calibrated out of
>> the measurement if the crystal is replaced with a 50 ohm
>> resistor, but I have never tried it.
>>
>> -- Tom, N5EG
>>
>>
>>
>>
>>
>>
>> > -----Original Message-----
>> > From: vna-bounces at lists.tapr.org
>> [mailto:vna-bounces at lists.tapr.org]
>> > On Behalf Of Koji Terai
>> > Sent: Saturday, December 03, 2005 9:14 AM
>> > To: vna at lists.tapr.org
>> > Subject: [vna] measurement of quartz crystal
>> >
>> >
>> > Hi, everyone! I would like to know if the VNA is able to determine
>> > resonant frq. and antiresonant frq. of a quartz crystal in
>> accuracy of
>> > 100 Hz. I plan to construct Cohn type crystal filters, and
>> I tried to
>> > measure crystals but I was not able to measure these two
>> frequencies
>> > definitely, especially ant frequency measurement was very
>> critical. I
>> > am looking forward to a good solution for this.
>> >
>> >  Koji
>> >
>> >
>> >
>> > _______________________________________________
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>> > vna at lists.tapr.org
>> https://lists.tapr.org/cgi-bin/mailman/listinfo/vna
>> >
>>
>>
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