Author Topic: Picotest Injector Teardowns  (Read 2412 times)

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Online Sighound36

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Re: Picotest Injector Teardowns
« Reply #50 on: May 27, 2020, 03:47:17 pm »
Pretty respectable trace there for a 3Ghz bandwidth  :)

Ok not being an RF guy, so shoot me  :-DD, would it not be better to have less capacitors with a larger value? Or is this a fundamental issue with this portion of the design?
« Last Edit: May 27, 2020, 06:17:13 pm by Sighound36 »
Seeking quality measurement equipment at realistic cost with proper service backup. If you pay peanuts you employ monkeys.
 

Offline Jay_Diddy_B

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Re: Picotest Injector Teardowns
« Reply #51 on: May 27, 2020, 06:11:30 pm »
Pretty respectable trace there for a 3Ghz bandwidth  :)

Ok not being an RF guy, so shoot me  :-DD, would it not be better to have less capacitors with a larger value? Or is this a fundamental issue with this portion fot he design?

The capacitors I used are each 10uF 50V X5R 1210. The idea of such a high value is to get a low frequency -3dB point.

12 x 10uF / 2 = 60uF

R= 25 \$\Omega\$

F = 1/(2  x Pi x R x C) = 26.5 Hz

Regards,
Jay_Diddy_B
 
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Offline Jay_Diddy_B

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Re: Picotest Injector Teardowns
« Reply #52 on: May 27, 2020, 06:17:21 pm »
Hi,
Here are some TDR measurements  made with a Tektronix 11801 and SD24 sampling head.
The Bias injector was place between two lengths of semi-rigid 50 \$\Omega\$ cables:





From left to right

The 50 Ohm cable
the first 'wiggle' is the transition from the cable to the board, the SMA edge launch.
Then a short piece of 50 Ohm track.
two sections of 45 Ohms, about 25mm long, where the capacitors are
50 Ohm track
SMA connector
50 Ohm cable


I have marked the measured impedances on this drawing of the board assembly:



to raise the impedance where the capacitor are, I need to widen the gap between the traces and the ground plane.

Regards,
Jay_Diddy_B
« Last Edit: May 27, 2020, 06:24:30 pm by Jay_Diddy_B »
 

Online Sighound36

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Re: Picotest Injector Teardowns
« Reply #53 on: May 27, 2020, 06:44:15 pm »
In a very crude way that is the situation I was attempting to elude to  :-[

Great stuff Jay, really do not know where you find the time but top man  8)
Seeking quality measurement equipment at realistic cost with proper service backup. If you pay peanuts you employ monkeys.
 
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Online 2N3055

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Re: Picotest Injector Teardowns
« Reply #54 on: May 27, 2020, 10:06:06 pm »
Nice demonstration of usefulness of TDR..

Great work (as always!!) Jay..

Regards,

Sinisa
 

Online tv84

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Re: Picotest Injector Teardowns
« Reply #55 on: May 27, 2020, 10:14:41 pm »
I have marked the measured impedances on this drawing of the board assembly:

(Attachment Link)

to raise the impedance where the capacitor are, I need to widen the gap between the traces and the ground plane.

Damn! This is an optimization of my suggested change!!!   :clap:  :clap:   Respect!

(I had removed it because, afterwards, I thought it was something irrelevant... )

« Last Edit: May 27, 2020, 10:17:27 pm by tv84 »
 

Offline sixtimesseven

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Re: Picotest Injector Teardowns
« Reply #56 on: June 02, 2020, 04:08:22 pm »
Hello All,

I am not sure if this is the best place to start a discussion about PicoTest Line Injectors. They are useful tools, but tend to be on the expensive side. I wanted to upload what I have to be archived, and for those who wish to design their own or at least are interested in such topics. I hope this helps someone, somewhere.

Picotest J2120A Line Injector
Price: $525
BOM:

(4) Capacitors
  • C1||C2 = 35.7uF
  • C3||C4 = 1.98uF
(1) Resistor
  • 10k
(1) nMOS
J2120A front and rear pics attached.

Picotest J2130A DC Bias Injector
Price: $525
BOM:

(24) Capacitors
  • Parallel, Series network = 27uF
(1) Resistor
  • 10k
I do believe the equivalent network of the 24 caps is 27uF, I may wish to double check when I get a chance.

J2130A front and rear pics attached.

Ridley Injector Isolator Transformer
No specifications really. The manufacturer looks to be Avel Lingberg.
Model CA8518.

I hope this comes out clean, first time poster. Hell of a time with the pics.

*EDIT*
Added front picture of the J2120A.

Another nice one would be the "2180A" preamplifier to up the sensitivity of 8bit scopes. I wonder how they have done it in such a small package.
 


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