RF Power Splitter Concept to Completion (035)
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- čas přidán 7. 08. 2024
- In this video I walk through the process of developing an R.F. Power Splitter.
I start with the basic concept and an ugly bench experiment and work through to a totally awesome implementation showing the process along the way.
I provide the complete design of the final project in a ZIP file (see below) so you can simply download it and do it yourself.
While my example is that of a 3 port, 50 Ohm device, what you learn here will equip you to build a splitter with as many ports and with whatever characteristic impedance you need.
Promised Links:
Formulas
drive.google.com/file/d/1AmBC...
PCB ZIP File
drive.google.com/file/d/11eQ3...
Time Markers for Your Convenience
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00:05 Initial Comments and Introductions
01:36 The Basic Design
02:52 The Equations
03:06 Rs - The Series Resistor
03:29 Av(dB)-Power Loss Input to Output
03:45 Vout for a given Vin
03:55 Pin(max) Maximum Input Power
04:19 My Experiment
04:21 Goals
04:34 Calculate Rs
05:05 Calculate Av(dB)
05:34 VERSION 1: Proof of Concept
05:40 The Build
06:18 The Performance
06:19 SWR
06:52 THRU
07:27 VERSION 2: The Better Build
07:33 The Build
07:52 The Performance
07:52 SWR
08:37 THRU
09:29 What's the Problem?
09:46 Version 3: A More Compact Build
09:50 The Build
10:15 The Performance
10:15 SWR
10:46 THRU
11:05 What's wrong?
11:10 VERSION 4: Eliminate the Leads altogether!
11:51 The Build
11:54 A Tour
12:20 PCB Design
13:09 Component Selection
15:05 What will be my Pin(max)?
16:13 Performance
16:16 SWR
16:47 THRU
17:32 Final Evaluation to 500 MHz
18:10 Final Comments and Toodle-Oots
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Thanks for this, I was amazed at the difference short leads make. I can now see where surface mount components come into their own.
Yeah, isn't it amazing! I was also surprised by it. The higher the frequency, the more "magic" invades working with RF. 🙂
Awesome video!!! Enjoyed it,|God bless you
Thanks! And may He bless you, too!
very good video
Thanks for letting me know. :-)
I very much enjoyed watching this. Thank you for putting it on CZcams.
And yes, as you kept saying, I could accomplish it.
Or rather, I could have accomplished it when I was younger (I am retired now).
However, it would have represented a significant investment of time from my point of view.
Why would you not go from theory and calculation straight to final implementation?
At one point I looked into specifying an RF project to be done by an RF designer/fabricator.
This guy was a one-person shop, but he always went straight to surface-mount custom PCB for every prototype, using a board manufacturer from the very beginning.
If necessary he would tweak the values and the design until he got the results he wanted.
(Of course his cost per project was high.)
Since your design for this splitter never had to deviate from your calculations, it seems to me you could have done it that way too, and in less time.
Well, I *thought* I could accomplish this using leaded resistors using the really nice, blue enclosure. So, try #2 was *supposed* to be my end product ... until I saw its performance. Try#3 was an experiment to see if I could do it with leaded resistors at all; if this worked I would have bent up a MUCH prettier enclosure for it. When its performance turned out less than desired, I had to go back to the drawing board and figure what would work.
Having never done impedance controlled traces on a PCB before, this launched a whole investigation and experimentation into how to do that (See my previous 2 videos on this). Then, try#4 was my first attempt at the final PCB-based solution. If it didn't work as well as I wanted, try#5 would have been born, but it didn't have to be.
The advantage of going through all of this was that I (and my viewers) got to see what wouldn't work so well and what does, indeed, work.
I do that with 3 * 50 ohm resistors right from the drawer connected in triangle mode.
Would have enjoyed though to see your measurement setup and procedure.
Hmmmm... that's an interesting configuration. I didn't see that one in my research on the subject. An, lo and behold, it works, too! Way cool!
@@eie_for_you I'd be curious to see your results with your measurement setup. Be aware that BNC connectors are beoming "unclean" above 500 MHz as well. So a comparison with a port to port direct feedthrough might be informative.
You can use your PCB right away with 3 x 50 ohm SMD resistors - 49 ohms are fine too.. By mounting them in various orientations like flat on the board or tilted 90 degrees you can influence the reactance from capacitive to inductive and smooth out the wiggles - perhaps. Have fun.
Well, it depends on the BNC connector as to how it behaves above 500 MHz. Amphenol RF PN 031-70578-12G is good to 12 GHz. One has to pick their connectors carefully and buy only good quality connectors from a known manufacturer like Amphenol.
@@eie_for_you I know what you mean, but the part number you selected is a 75 ohm type costing 15 € at Farnell's. The 50 ohm type is the 031-70535-12G for the same.
Nonetheless, the 12 GHz limit is just the geometrical limit due to the wavelength being below higher transmission modes . It does not say anything about the RF properties in terms of impedance fidelity.
I never knew that about BNCs. Certainly WAY better than PL-259/SO-239 (UHF) connectors. I still prefer N over all of them for a lot of the same reasons.
How topical!! I'm looking at designing something along the likes of the MFJ-1708B, but their design is using a wideband RF toroid to keep losses at around -3dB instead of -6dB - though a mix 61 toroid solution is only good up to around 300MHz. any thoughts?
One of my concerns with inductor-based solutions is frequency response and impedance. This resistive solution works from D.C. to 1 GHz. I wish I could be more help, but I have not dived into the wild world of toroids too deeply ... yet. It's on my list of things to do.
Ferrites fail to work at frequencies beyond 300 MHz. Try with a coax balun ciruit.