Products > Test Equipment
Picotest Injector Teardowns
Sighound36:
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?
Jay_Diddy_B:
--- Quote from: Sighound36 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 fot he design?
--- End quote ---
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
Jay_Diddy_B:
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
Sighound36:
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)
2N3055:
Nice demonstration of usefulness of TDR..
Great work (as always!!) Jay..
Regards,
Sinisa
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