How "Wide Band" of a 1:1 Balun are you looking for????
I haven't seen anything, but I DID find fol. via Google Search for "wideband lpda balun":
Research Gate Articles only require FREE Website Registration, so start there.
IEEE Article Download MAY require fairly expensive IEEE Membership and Current Subscriptions to each Journal you want to see OLD Articles in [If I remember that correctly....]. [Reminds me....I need to renew my "Senior Discount" Membership....and somehow make room for storing more Hardcopy Journals.]
OR w/o IEEE membership, you can simply spend $$$'s to download MOST individual articles....or make a copy at a well equipped (i.e. University) Library. But I nearly always have problems locating Articles in "Conference Proceedings".
BTW: Sometimes, you can find a FREE Download by searching by Author & Title....esp. if you find their HOME Website [frequently a University]....
I looked at the extended summary for Mirzapour's IEEE Article....the "Balun" is described as a "mode converter balun" [Google it], which is more commonly implemented as the well known [and easy to implement in Substrate for SHF] "TAPERED TRANSMISSION LINE" that transistions from one impedance to another (so, what about Balanced to Unbalanced?):
Radio Antenna Engineering - Tapered Transmission-line
BTW: I used a LINEAR
TAPERED TRANSMISSION LINE [aka "Triangular", rather than the more "accurate" (i.e. Idealized) Exponential Taper] in the fol. Hi-VHF Zig-Zag LPDA (with Center Booms)....note the unusually LONG pair of wires at the FRONT that were tweaked until SWR was acceptable [this was before nikiml's Optimizer]:
PS: I ACTUALLY implemented and unsuccessfully tried to squeeze the WAY TOO BIG Hi-VHF Zig-Zag LPDA (NO BOOM, both Stacked and Wedge versions) into my son's Attic, trying to NULL OUT nearby Ch12. NO Boom version did NOT require the Tapered Transmission Line: