31-01-2013, 11:33 AM
CONSTRUCTION AND USE OF BROADBAND TRANSFORMERS
[attachment=49035]
INTRODUCTION
Wound magnetic devices that are designed to transfer energy over a wide frequency range
Most broadband transformers are wound on ferrite toroids or rods
Used in telecomm equipment
Balun or binocular cores are used for broadband transformers that must accommodate RF power
TRANSFORMERS ON BALUN CORES
Balun cores are made from ferrite.
The permeability of the material core is s 850 to 900 for applications from 1.8 to 30 MHz.
Are created by using two rows of ferrite toroids, side by side
Cores are glued together by means of quick setting epoxy cement to form two separate tubes of toroids
FREQUENCY BASED BROADBAND TRANSFORMERS
Low and Medium Frequency
Manganese zinc ferrites, such as Fair-Rite 77 or 78 materials, are very suitable
Core geometry should be such as to minimize the Rdc/L ratio
Parameter that is most critical is the shunt reactance (ωL)
High Frequency
Uses nickel zinc ferrites as the preferred core material
Band pass lies wholly above 500 kHz
USES OF BROADBAND-TRANSFORMER
Used at the output of an active mixer
For matching a 50-ohm antenna to a grounded gate RF amplifier in a receiver or converter
Applied in push-pull RF power amplifier that uses two broadband transformers
CONCLUSION
Can be designed to provide dc isolation, impedance matching and specific current or voltage ratios
Balun transformers are used in test equipment, mixers, receivers, transmitters and antenna circuits
Coverage from 1.8 to 30 MHz.
Efficiencies in the high 90% range.
[attachment=49035]
INTRODUCTION
Wound magnetic devices that are designed to transfer energy over a wide frequency range
Most broadband transformers are wound on ferrite toroids or rods
Used in telecomm equipment
Balun or binocular cores are used for broadband transformers that must accommodate RF power
TRANSFORMERS ON BALUN CORES
Balun cores are made from ferrite.
The permeability of the material core is s 850 to 900 for applications from 1.8 to 30 MHz.
Are created by using two rows of ferrite toroids, side by side
Cores are glued together by means of quick setting epoxy cement to form two separate tubes of toroids
FREQUENCY BASED BROADBAND TRANSFORMERS
Low and Medium Frequency
Manganese zinc ferrites, such as Fair-Rite 77 or 78 materials, are very suitable
Core geometry should be such as to minimize the Rdc/L ratio
Parameter that is most critical is the shunt reactance (ωL)
High Frequency
Uses nickel zinc ferrites as the preferred core material
Band pass lies wholly above 500 kHz
USES OF BROADBAND-TRANSFORMER
Used at the output of an active mixer
For matching a 50-ohm antenna to a grounded gate RF amplifier in a receiver or converter
Applied in push-pull RF power amplifier that uses two broadband transformers
CONCLUSION
Can be designed to provide dc isolation, impedance matching and specific current or voltage ratios
Balun transformers are used in test equipment, mixers, receivers, transmitters and antenna circuits
Coverage from 1.8 to 30 MHz.
Efficiencies in the high 90% range.