Impedance matching vs. one-element reactance canceller - Page 1
Forum section: electronics / rf-microwave

author: kellogs
author_rank: Regular Contributor
timestamp: January 26, 2025, 03:51:32 pm
content: As far as I can see around the internet, an impedance matching network, usually Pi, is present in radio designs. Mostly for unbalanced source and load (?).But what about the case where there is a balanced source and unbalanced load ? To my nooby mind there ought to be one L or C series element at the source for cancelling its reactance followed by a lattice network balun for resistance transformation and nothing else. One can use a VNA to calculate both stages. Why am I not finding any such designs ?Thank you

author: A.Z.
author_rank: Super Contributor
timestamp: January 26, 2025, 04:56:37 pm
content: Quote from: kellogs on January 26, 2025, 03:51:32 pmhttps://www.reddit.com/r/amateurradio/comments/wdkpcf/how_does_a_balun_work/?rdt=48862BALUN DOES NOT IMPLY IMPEDANCE TRANSFORMATIONIT IMPLIES CURRENT OR VOLTAGE BALANCING (usually currents)

author: radiolistener
author_rank: Super Contributor
timestamp: January 26, 2025, 06:19:03 pm
content: Quote from: A.Z. on January 26, 2025, 04:56:37 pmyou can combine balun with impedance matching. For example 1:1 impedance ratio transformer works as balun. But if you use 1:4 impedance ratio transformer it will works as balun and impedance matching circuit simultaneously

author: kellogs
author_rank: Regular Contributor
timestamp: January 26, 2025, 10:19:37 pm
content: Quote from: A.Z. on January 26, 2025, 04:56:37 pm"A lattice network balun for resistance transformation" - I think you have missed this part.P.S. no shouting please, I can hear well.

author: szoftveres
author_rank: Regular Contributor
timestamp: January 27, 2025, 04:00:36 am
content: See:https://siliconlabs.my.site.com/community/s/article/discrete-matching-solutions-for-efr32-series-1-sub-ghz-designs?language=en_USAlso page 27, 33, 34:https://www.silabs.com/documents/public/application-notes/an923-2-series-2-subghz-matching-guide.pdf

author: A.Z.
author_rank: Super Contributor
timestamp: January 27, 2025, 05:52:01 am
content: https://www.allaboutcircuits.com/technical-articles/understanding-the-guanella-transmission-line-transformer/

author: A.Z.
author_rank: Super Contributor
timestamp: January 27, 2025, 06:19:34 am
content: Quote from: A.Z. on January 27, 2025, 05:52:01 amalsohttps://www.highfrequencyelectronics.com/index.php?option=com_content&view=article&id=699:balun-basics-primer-a-tutorial-on-baluns-balun-transformers-magic-ts-and-180-hybrids&catid=100&Itemid=189#:~:text=A%20balun%20is%20a%20three,of%20the%20other%20balanced%20output.

author: kellogs
author_rank: Regular Contributor
timestamp: January 27, 2025, 10:08:01 am
content: Quote from: szoftveres on January 27, 2025, 04:00:36 amFrom page 30: "C4 is only required at 169 MHz to limit the Q of the RX matching network"Maybe this has to do with why use a matching network rather + balun rather than one single matching element + balun ?

author: kellogs
author_rank: Regular Contributor
timestamp: January 28, 2025, 04:34:23 pm
content: Part II of this paper describes the single element matching:https://eecs.ku.edu/sites/eecs/files/documents/1351695673_IEEE(Final)-5.pdfSo I still do not know why this is not widely used, but Q-wise I have found wide(r) band options:- matching only - cascaded L networks:https://www.highfrequencyelectronics.com/Mar08/HFE0308_Tutorial.pdf- matching & balun - contracted network:https://www.cambridge.org/core/journals/international-journal-of-microwave-and-wireless-technologies/article/fourelement-lcbaluns-for-power-matching-arbitrary-impedances/9D74E6355EB664ABF0834AD86F2EB739

author: rfdave#gmail.com
author_rank: Contributor
timestamp: January 31, 2025, 01:37:43 am
content: It's my understanding that Baluns can be used for impedance matching, but are limited by the turns ratio in the balun, so it works for 50 Ohm to 2 kOhm, types of impedances, but it's not really suitable for moderate impedance differences. For narrowish bands, L and T networks work well, and are relatively low loss with suitable selection of inductors. There are analytic expressions to do L and T impedance matching if you go looking. RF Design Magazine has a bunch of articles that cover that.If you're interested in wideband matching, look for material on the Real Frequency matching. This book is, I believe, the starting point "Wideband circuit design". H.J. Carlin. 1998. CRC Press but it get math heavy pretty fast.

author: Geoff-AU
author_rank: Frequent Contributor
timestamp: January 31, 2025, 03:30:33 am
content: Quote from: rfdave#gmail.com on January 31, 2025, 01:37:43 amI have a balun for 50:200 ohm matching, it works nicely. You can get them for 50:75 ohm transformation as well.A "balun" is traditionally a device for BALanced to UNbalanced transitions. But these days it's a word like "stick" that is rather generic and useless on its own without further clarification. The usual jobs for baluns are balanced to unbalanced transitions, choking off common mode currents, and impedance transformations. A balun can do some of those things, or all of those things, or none of those things (if you really screw things up).Quote from: kellogs on January 26, 2025, 03:51:32 pmBecause a single L or C element will only provide the required conjugate match at ONE frequency. Kinda useless for most things that have frequency agility.

author: kellogs
author_rank: Regular Contributor
timestamp: February 01, 2025, 09:18:25 am
content: Quote from: Geoff-AU on January 31, 2025, 03:30:33 amAny method will only provide the required conjugate match at ONE frequency. Perhaps you were thinking about the resulting Q-factor ?

author: kellogs
author_rank: Regular Contributor
timestamp: February 15, 2025, 01:17:51 pm
content: Inthis paperan 150 ohm differential dipole is being baluned & matched to a 50 ohm unbalanced line via a pair of 2 cascaded LPF and 2 cascaded HPF L-networks for a 100% bandwidth.Intuitively, matching the same 50 ohm unbal line to a narrow band 0.4 ohm dipole will change the number of cascaded stages and bandwidth that I can realistically achieve - which I do not know how to come about...I guess start by measuring the antenna impedance over the BW of interest - expecting high variability, then limit the BW to lower the variability ? Lower it to what ?QuoteQuoteAnd maintain 2 sections for the cascade ?