RF Electronics Chapter 3: Transformers and Hybrids Page 63
2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0.
In some instances, many signals need to be combined or a signal needs to be split many
ways. The hybrids described above can be cascaded to provide a many way
splitter/combiner. However, each of those hybrids will include a 25 Ω to 50 Ω impedance
transformation transformer. Some savings can be made by using a 4 way hybrid as shown
in figure 3.20, where three of two way hybrids are used together to combine 4 input
signals and then have a 12.5 Ω output, which can be transformed to 50 Ω by using a 2:1
transformer, as shown in figure 3.20. This saves two transformers, each of which will
have some losses associated with it. In addition, the 4:1 impedance transformation is
exact, while the 2:1 impedance transformation is actually a 2.25:1 impedance
transformation with the 3:2 turns ratio of the transformer. Two of the hybrids below
operate at a 50 Ω impedance and one operates at a 25 Ω impedance. The number of turns
on the transformer coils needs to be adjusted to allow for this.
References
1. H. Granberg, "Broadband transformers and power combining techniques for RF",
Mototola Application Note AN749. https://community.nxp.com/t5/Other-NXP-
Products /Helge-Granberg-AN749-EB104-and-the-legacy-of-Freescale/m-p/
261491
2. Minicircuits.Application note AN20-001 "How RF Transformers work"
http://www.minicircuits.com/app/AN20-001.pdf
3. Minicircuits.Application note AN20-002 "Application Note on Transformers"
http://www.minicircuits.com/app/AN20-002.pdf
RF Electronics: Design and Simulation
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