Wave transmission lines and networks – Coupling networks – Balanced to unbalanced circuits
Reexamination Certificate
2002-07-26
2004-11-16
Tokar, Michael (Department: 2819)
Wave transmission lines and networks
Coupling networks
Balanced to unbalanced circuits
C333S025000, C333S032000, C333S033000
Reexamination Certificate
active
06819200
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to balun and impedance transformers and more specifically to broadband balun and impedance transformers for push-pull amplifiers.
BACKGROUND OF THE INVENTION
Broadband push-pull power amplifiers have the advantage of higher output power (twice that of a single-ended amplifier) with even harmonic cancellation and high efficiency. For push-pull power amplifiers to work properly, a broadband balun with excellent amplitude and phase balance is needed. Additionally, for practical amplifier designs, an impedance transformer that can transform low impedances (e.g. 3 to 4 ohm) to an external load impedance (e.g. 50 ohm) over, for example, a 700 MHz to 2.4 GHz frequency range is required. The balun/transformer also needs to provide DC biasing to the push-pull amplifier.
Many prior art power amplifier applications address the need for a transformer but not the need for a balun, while many mixer applications address the design of baluns that cannot be used in conjunction with an impedance transformer. A balun is used mainly to connect a balanced source to an unbalanced load, or vice versa, and a balun typically provides no impedance transforming function.
Accordingly, it would be desirable to have a combination of impedance transformer and balun to create a broadband impedance transformation while at the same time being able to provide balanced differential ports for push-pull amplifier applications.
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Chen, T., Chang, K. W., Bui, Stacey B., Wang, H., Dow, G. S., Liu, L. C. T., Lin, T. S. and Titus, W. S., “Broadband Monolithic Passive Baluns and Monolithic Double-Balanced Mixer” IEEE vol. 39, No. 12, Dec. 1991.
Pavio Anthony M.
Zhao Lei
Freescale Semiconductor Inc.
Nguyen Khai
Tokar Michael
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