[SI-LIST] Re: Balun measurement

Ron this particular balun is the only one that has tight enough gain and 
phase for me to consider.  It's not your typical $20.00 balun, more like 
about $1000.00.  You can download the data sheet from PSPL's web site.  
The phase match varies by a small fraction of a dB over a wide range and 
the amplitude match is similarly good to about 0.1dB.   The big 
limitation is that the matching starts to come apart at low 
frequencies.  It is good enough for pure 8b10b at 3-5Gbps.  It will not 
handle OOB.  Our Portland lab has a fast 4 port VNA, and a nice 
TDR/TDT.  Not everyone has access to that kind of equipment.  For a shop 
that doesn't have access to a 4 port VNA, or a good TDT it is an 
affordable option to evaluate the interconnect where the interconnect is 
most likely to give them trouble.  It is not going to do compliance testing.

Best Regards,


Steve.


ronald miller wrote:
> Content-Type: text/plain; charset=us-ascii; format=flowed
> Content-Transfer-Encoding: 7bit
> Hi Steve
>
> Very tight doesn't ring true to me for SI applications, especially with 
> baluns which I have designed and used
> for years.   For Radio, and microwave they are acceptable.
>
> Also, 100Mhz to 4 Ghz will not wok for models in data.  The 4-Port 
> network analyzer will work or you can
> use a TDR/TDT to model differential lines.
>
> If you have a balun with 2 to 3 degree phase and less than .1 db gain 
> across the whole band you may have
> something useful.
>
> Incidentally, 20 years ago we used a model for SAW device which 
> according to the gain and phase across
> a limited bandwidth should have worked fine for an IF filter, but it did 
> not.  Had to go back to an LC filter.
>
> Why?  The reflections on which SAW devices depend for operation 
> introduced delays that were outside
> the normal measurements.  The steady state measurement of the devices 
> frequency response across the band
> looked good and for a steady signal it was fine.  However, as soon as 
> modulation was added widening the band
> of the signal spectrum, the SAW screwed up the data.  Cause??  Excessive 
> group delay, but only visible with
> modulated signal.  This is a time domain device being used in the 
> frequency domain.  Similar problems occur
> when using frequency domain devices in the time domain.... especially 
> measurements for models.
>
> The point?  SI is concerned with time domain data modulated across an 
> extremely wide bandwidth and with
> harmonics as much as 3 to 5 times the fundamental.  Baluns cannot be 
> designed forthe accuracy needed for
> models in digital data transmission systems.  Each adjustment they make 
> to broaden the bandwidth of the
> balun will cause unintended distortions in delay even if  magnitude and 
> phase.seem to be OK across the band
> you haveselected.
>
> Ron
>
>
> steve weir wrote:
>
>   
>> Ron generally that is true.  However, PSPL has an interesting Tx line 
>> balun: 5310-104 that has very tight gain matching and phase linearity 
>> over the 100MHz to 4GHz range.
>>
>> Best Regards,
>>
>>
>> Steve.
>> ronald miller wrote:
>>  
>>
>>     
>>> dont use baluns for measurements.... using network analyzers.
>>> They are only useful for narrowband applications...
>>>
>>> ron
>>>
>>> john wrote:
>>>
>>>  
>>>    
>>>
>>>       
>>>> All,
>>>>
>>>>
>>>> I measured a 1:1 balun as a three port network, port 1 is the unbalanced 
>>>> input, port 2 is the 'through' connection and port 3 is the indirect
>>>> connection. I only have a two port VNA so the unused ports were 
>>>> terminated with 50 Ohms during the measurements
>>>>
>>>>
>>>> Port 1 -----OOOOOOOOO--------o Port 2
>>>>           o-OOOOOOOOO--o
>>>>           |            |
>>>>           |            |
>>>>          ---           |
>>>>          GND           |
>>>>                        |
>>>>                        ----o Port 3
>>>>
>>>>
>>>>
>>>> With this 1:1 Balun the Balanced port has differential impedance of 50 
>>>> Ohms so terminating with the VNA/terminator into 50 Ohms on say ports 2 
>>>> and 3 gives a large impedance mismatch. The the application circuits for 
>>>> the chip to which the balanced input connects shows a 100 Ohm resistance 
>>>> directly across the pins of the balance port (2-3) which is then tracked 
>>>> at 100 Ohms differential to the device where it is internally terminated 
>>>> with 100 Ohms. Now using the same test board, I solder a resistor 
>>>> (infarct three 300 Ohms in parallel) across ports 2 and 3 and re-measure 
>>>> I have should have the correctly terminated case.
>>>>
>>>> I took the balun off the test board and measured the terminator across 
>>>> ports 2 and 3.
>>>>
>>>> I then simulated the terminated case using the s-parameters from the 
>>>> first measurement and those from the resistor only measurement and 
>>>> compare them to the terminated case measurement.
>>>>
>>>> In general there is reasonable correlation in shape between S11, S22 and 
>>>> S33. However the simulated S11 has less loss than the measurement of the 
>>>> terminated case. the simulated S22 and S23 again have the same overall 
>>>> shape as the measured results although the anti-resonances are not as 
>>>> great.
>>>>
>>>> The through S21/S12 S13/31 however show little correlation between the 
>>>> simulated and measured results having large anti resonances where the 
>>>> measured results do not.
>>>>
>>>> As this is part of an overall simulation I would like to get the Balun 
>>>> measured and simulating correctly before addressing the rest of the 
>>>> simulation.
>>>>
>>>>
>>>> Can anyone suggest a better way of measuring the balun ?
>>>>
>>>>
>>>> Regards
>>>>
>>>>
>>>> John
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> ------------------------------------------------------------------
>>>> To unsubscribe from si-list:
>>>> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>>>>
>>>> or to administer your membership from a web page, go to:
>>>> http://www.freelists.org/webpage/si-list
>>>>
>>>> For help:
>>>> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>>>>
>>>>
>>>> List technical documents are available at:
>>>>               http://www.si-list.net
>>>>
>>>> List archives are viewable at:     
>>>>            http://www.freelists.org/archives/si-list
>>>> or at our remote archives:
>>>>            http://groups.yahoo.com/group/si-list/messages
>>>> Old (prior to June 6, 2001) list archives are viewable at:
>>>>            http://www.qsl.net/wb6tpu
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>    
>>>>      
>>>>
>>>>         
>>>  
>>>    
>>>
>>>       
>>  
>>
>>     
>
>   


-- 
Steve Weir
Teraspeed Consulting Group LLC 
121 North River Drive 
Narragansett, RI 02882 

California office
(408) 884-3985 Business
(707) 780-1951 Fax

Main office
(401) 284-1827 Business 
(401) 284-1840 Fax 

Oregon office
(503) 430-1065 Business
(503) 430-1285 Fax

http://www.teraspeed.com
This e-mail contains proprietary and confidential intellectual property of 
Teraspeed Consulting Group LLC
------------------------------------------------------------------------------------------------------
Teraspeed(R) is the registered service mark of Teraspeed Consulting Group LLC

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field


List technical documents are available at:
                http://www.si-list.net

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
  

Other related posts: