PCB 4:1 balun perfomance evaluation - Canadian TV, Computing and Home Theatre Forums

Reply
 
LinkBack Thread Tools Search this Thread Display Modes

post #1 of 16 (permalink) Old 2018-04-18, 06:33 AM Thread Starter
 
Join Date: May 2017
Posts: 195
PCB 4:1 balun perfomance evaluation




https://ypylypenko.livejournal.com/26123.html


Yurii Pylypenko is online now  
Sponsored Links
Advertisement
 
post #2 of 16 (permalink) Old 2018-04-18, 03:17 PM
Veteran
 
Join Date: Nov 2008
Location: San Diego, CA
Posts: 3,191
Do you have a photo of the other side of the PCB Balun???

I wonder if HFSS can calculate the Insertion Loss, assuming (guessing???) "typical" PCB Ohmic and Dielectric Losses....incl. perhaps a min/max guess, since mfr may have gone out of their way to select better than "typical" materials???

Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands
holl_ands is offline  
post #3 of 16 (permalink) Old 2018-04-18, 03:19 PM Thread Starter
 
Join Date: May 2017
Posts: 195
0.15 dB IL (with FR4, tan=0.02, e=4.4), -20...-25 dB radiation to free space

most loss come from mismatch-loss

more photo & data via URL
Yurii Pylypenko is online now  
 
post #4 of 16 (permalink) Old 2018-04-18, 04:10 PM Thread Starter
 
Join Date: May 2017
Posts: 195
For top perfomance (squize every possible bit) it's quite easy to DIY practically lossless (air gap) microstrip balun, optimized for specific band (e.g. minimize SWR in 470-690, or get SWR=1 for specific channel). Insulators can be used only as supports (most feedline air only), metal box can be used (with 150 Ohm strip or round wire pairs, soldered to the ends of this box, acting as a ground/coax shield wire itself).

So far, I learn exact dimensions for more generalized geometry: https://ypylypenko.livejournal.com/26409.html to get SWR=1.0 @ 600 MHz.
Found L for X=0, working on R=75

Also it's possible to develop antenna/balun as a whole. Antenna is not Z=300 +j0, it has arbitrary R+jX in wide band.
With out-of-the-box baluns (PCB or ferrite) output SWR is unknown, since transformation ratio is not 4:1 as claimed for simplification.

With custom microstrip balun one can predict and optimize SWR @ 75 Ohm coax load.
Yurii Pylypenko is online now  
post #5 of 16 (permalink) Old 2018-04-19, 11:35 AM
Veteran
 
Join Date: Nov 2008
Location: San Diego, CA
Posts: 3,191
Probably doesn't make much of a difference, but I looks like HFSS model geometry is slightly offset from actual photo (see overlay in your link above).....

What is Insertion Loss vs Frequency???? For completeness, can you measure (or find a measurement and/or spec) for the actual Balun???

Although different design and somewhat different Freq Range, here is what ADTech measured for two of A-D's Back-to-Back PCB Baluns....about 0.6 to 0.9 dB each:
Baluns (Brands, Designs, Losses, DIY Loops, etc.)

FYI: 4:1 Balun measurements summarized for Ferrite and other PCB Baluns:
Baluns (Brands, Designs, Losses, DIY Loops, etc.)
I can't see "3rd Party Hosted" charts.....also found towards bottom of my fol. webpage:
https://imageevent.com/holl_ands/files/ota

Updated link to Johnrmckee's measurements for low-loss Philips Outdoor Ferrite Balun: [Unfortunately no p/n or photo]
http://www.avsforum.com/attachments/15540
UHF: 0.5 to 0.9 dB (470-698 MHz)
Hi-VHF: Under 0.6 dB
Lo-VHF: Under 0.7 dB

Note that Philips Outdoor Ferrite Balun and A-D's PCB Balun had about the SAME LOSS across the entire [N.A.] UHF Band....and that MOST Ferrite Baluns are significantly worse, esp on higher Freqs....

Last edited by holl_ands; 2018-04-19 at 01:18 PM.
holl_ands is offline  
post #6 of 16 (permalink) Old 2018-04-19, 03:11 PM Thread Starter
 
Join Date: May 2017
Posts: 195
Quote:
Probably doesn't make much of a difference, but I looks like HFSS model geometry is slightly offset from actual photo (see overlay in your link above).....
I'm not interested in the very exact graphs for this very exact sample. There are dozens of similar (but not identical) PCB-baluns around.
I bought this one for test, as little as $0.6
Whether this particular piece has resonance @770 or @670 MHz is not important to me.
It has quite poor tolerances (build quality), PCB traces width/gaps are very coarse/inconsistent (not 150 Ohm, not homogeneous).

12 years ago I did similar baluns for CDMA-850 Yagi's, this is from "Sprint Layout" PCB tool (now I understand that this drawing has a lot of minor faults):


Now, with HFSS I'm able to simulate and understand what perfomance consists of.

Quote:
What is Insertion Loss vs Frequency???? For completeness, can you measure (or find a measurement and/or spec) for the actual Balun???
Loss in this balun is of 3 kinds:
1) PCB-heat loss (depend highly on material tangent loss, for e=4.4, h=1.5mm, tan=0.02 - heat loss is ~0.15 dB)
2) radiation loss, radiation is about -22...-25 dB, which corresponds to -0.015...0.025 dB loss
3) mismatch loss. for SWR=1.5 it's -0.177, for SWR=2 it's -0.511)

If good matched, I expect @ SWR=1.5 loss -0.3 dB, half of which comes from epoxy quality, half from mismatch.

With special HF PCB materials (Rogers, Neltec, Izola) or other insulators (air, teflon) heat loss can drop from 3.4% to 1-1.5% (-0.04...-0.07 dB)

-0.075 dB mismatch-loss corresponds to SWR=1.3

I expect that top perfomance -0.15 dB (0.06 + 0.07 + 0.02) is achievable, but not measurable, since tolerances for measuring equipment cables are worse.

In real world applications, combined mismatch loss (antenna + balun) has most influence on total insertion loss. Since antenna is not R=300 +j0, actual SWR after PCB balun can be both better or worse than on R=300 ohm ideal load. Specially designed balun can compensate antenna own reactances (mostly by traces Length, choosing appropriate Freq for L/4 length) and R<>300 (choosing trace width/gap other than 150 to compensate input R<>300)
Yurii Pylypenko is online now  
post #7 of 16 (permalink) Old 2018-04-25, 10:29 AM Thread Starter
 
Join Date: May 2017
Posts: 195
2 more variations by polish manufacturer:


neither support f<270 MHz, but lower one labeling claim 47-860 (upper claim 470-860 which is true)
Yurii Pylypenko is online now  
post #8 of 16 (permalink) Old 2018-04-26, 03:41 AM Thread Starter
 
Join Date: May 2017
Posts: 195
Continue improving: https://ypylypenko.livejournal.com/26409.html





Line #1 (0.75 mm strip, 8 mm gap) narrowed to Zo=300 Ω, so it become matched and can go further.

Due to narrowing, jumper #2 shortened to 4.77 mm (ideally it's length should be zero)





Animation @ f=1000 MHz


Further optimization needed at low-impedance side:
- narrow gap to Zo=150 Ω
- rounded turns
- verify 75Ω pin location exactly at half/way (including Ω-jumper)
- draw 75Ω line, so 75Ω feed is outside balun and doesn't interfere with balun

Last edited by Yurii Pylypenko; 2018-04-26 at 04:19 AM.
Yurii Pylypenko is online now  
post #9 of 16 (permalink) Old 2018-04-27, 02:40 AM Thread Starter
 
Join Date: May 2017
Posts: 195
Yurii Pylypenko is online now  
post #10 of 16 (permalink) Old 2018-04-28, 06:51 AM Thread Starter
 
Join Date: May 2017
Posts: 195
Yurii Pylypenko is online now  
post #11 of 16 (permalink) Old 2018-05-15, 10:46 AM Thread Starter
 
Join Date: May 2017
Posts: 195
In 2014, Moscow company "Locus" claimed controversial 300 Ohm LNA (patented)






They claim 2 dB Nf improvement (1.5 vs 3.5 dB) over traditional LNA with ferrite coil balun.

v1 current consumption was 70 mA, so it was early withdrawn.
v2 consumes I=35 mA
Yurii Pylypenko is online now  
post #12 of 16 (permalink) Old 2018-05-17, 09:35 PM
Veteran
 
Join Date: Jan 2009
Posts: 4,359
Where is the evaluation?
Any bottom line / at the end of the day, real world measurements/comparison of one vs another in actual operation?
SNR / margin achieved one vs another? At the end of the day is all that matters.
How did we get from PC Board baluns to an LNA produced in Moscow?

Confused as to what the point of all this is?
Am I supposed to design artwork and etch this PC board balun in my basement and try it myself?
Guessing that would be a train wreck.

DB4E/VHF Yagi rotor FM Bandstop ap-8700 preamp 4way split LG lcd.
majortom is online now  
post #13 of 16 (permalink) Old 2018-05-18, 02:55 AM Thread Starter
 
Join Date: May 2017
Posts: 195
Quote:
How did we get from PC Board baluns to an LNA produced in Moscow?
Produce your own. This is novel technique I've never heard before, it seems interesting to me, so I posted it in this balun topic.
It's controversial but sounds promising. You amplify differential signal, so any balun loss after pre-Amp doesn't influence SNR. I didn't find any real world measurements for that, only allegations at some russian DX forums.

Quote:
Where is the evaluation?
in 1st post. I need to know wideband properties of PCB baluns (several similar types are sold here for $0.6-$1). I've heard controversial claims from local TV/SAT enthusiasts that these PCB baluns work better than ferrite @ 700..860 MHz, but worse at 470-650 MHz. I've also seen many type of DIY baluns at different forums (both PCB and bifilar-wire air type) with claims that they are better than those selling for $0.6.
There are also claims that @ 50 Ohm cable/load they work better than @ 75 etc

Also I wanted to add balun into my HFSS antenna models. Antenna is not Z=300 +j0, it has R different from 300 and X different from 0. I wanna see combined output Zo and optimize antenna/balun as a system, not to assume they are 300 +j0.
If antenna has SWR=2 and balun has SWR=1.5 at given frequency (@ ideal 300 Ohm load), combined SWR can be both >2 and <2 depending how balun R/X combines with antenna R/X

So I simulated one of most popular PCB (made in poland) in HFSS, to see:
1) where are frequency cut-offs, VHF-Hi DVB-T2 might be introduced in my area soon, so people are curios whether these existing baluns will work or not)
2) Wideband impedance curve
3) what is heat insertion loss for FR4. when people DIY PCB balun from better materials (Rogers, Izola, Neltec, foamed PVC) - is it worth or not?
4) is trace/topology from industrial design adequate, or poor designed

Most IL comes from ML (SWR), due to reactances and poor topology (trade-off for miniaturization)

I'm looking for balun+LNA for my 2-bay UHF bowtie project
CM4251 & H2 Hybrid

Existing (at my local market) options are:
1) LNA with ferrite 4:1 balun
2) PCB or ferrite baluns
3) 75 ohm coax-through LNA

Polish PCB balun suits well Uda-Yagi folded dipole, but doesn't suite well bowties.

Polish company Anprel/Dipol modify their bowties line shape to suite their PCB:


it works extremely poor (SWR>5, work poor with LNA, doesn't work with passive balun), you can not acomodate coax cable - you must align it along between TR line

I hope to accomodate my bottle-shaped PCB design with 2bay CM4251-like bowtie
Also want to DIY 1R5D Uda-Yagi from holl_ands album, but since it is extremely high-Q type Yagi, want to verify model with balun.

Last edited by Yurii Pylypenko; 2018-05-18 at 03:11 AM.
Yurii Pylypenko is online now  
post #14 of 16 (permalink) Old 2018-05-18, 07:20 AM
Veteran
 
Join Date: Jan 2009
Posts: 4,359
roger that, I am with you now...
I agree, it looks like something that COULD work well but like you would be skeptical until trying it myself.

DB4E/VHF Yagi rotor FM Bandstop ap-8700 preamp 4way split LG lcd.
majortom is online now  
post #15 of 16 (permalink) Old 2018-05-19, 01:14 AM
 
Join Date: Jan 2009
Posts: 452
Yurii just a question , can the HFSS sim, do a coil wrapped balun, made out of 75 ohm copper coax cable.
If so.
I be interested to know my 4:1 home made coil balun how it stands up.
I start off with a 24 inch piece of coax
I take a 3/4 inch piece of electrical conduit, drill a hole big enough and 1/2 inch down from the end
so the coax will insert from the outside then pull it out 4 inches
Then I rap it 4 3/4 turns around the conduit
Drill another hole and push the coax in then out to the lenght , to match the starting 4 inch cut to match .
then I take a 50 foot piece of coax and run it up the middle of the coil to match the two 4 inch pieces.
Then wire it up as a 4:1 balun.
Tested and works from 170 MHz to 700 MHz
And out performs any store bought balun. That I have used.
I know it's not a pcb balun , I'm just wondering if you get bored. Or have time
Thank you
wildwillie is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Canadian TV, Computing and Home Theatre Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome