Wave transmission lines and networks – Coupling networks – Balanced to unbalanced circuits
Reexamination Certificate
2001-01-12
2003-05-13
Lee, Benny T. (Department: 2817)
Wave transmission lines and networks
Coupling networks
Balanced to unbalanced circuits
Reexamination Certificate
active
06563395
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high power amplifier mainly used at a cellular phone base station, and a balun circuit for the high power amplifier.
2. Related Art of the Invention
A high power amplifier capable of propagating several tens to several hundreds of watts has recently been used at a digital mobile communication base station. This kind of high power amplifier comprises a plurality of push-pull amplifiers combined in parallel to obtain high power, wherein each push-pull amplifier comprises two identical transistors connected in parallel and supplied with signals 180 degrees out of phase with each other. The explanation of the push-pull amplifier has been given on pages 113 to 116 of “Radio Frequency Transistors” written by Norm Dye and Helge Granberg, published by Butterworth/Heinemann. Therefore, no detailed explanation is given here. This power amplifier circuit requires a power splitter/combiner circuit and baluns at both the input and output of the circuit.
A conventional high power amplifier will be described below referring to FIG.
11
. In
FIG. 11
, the numeral
501
designates a n-way power splitter, the numeral
502
designates a n-way power combiner, the numerals
503
,
504
designate n baluns, and the numeral
505
designates n pairs of push-pull amplifiers. A power splitter/combiner circuit used in this configuration will be described below while referring to
FIGS. 12 and 13
.
FIGS. 12 and 13
illustrate the configurations of Wilkinson power splitter circuits.
FIG. 12A
illustrates a general Wilkinson power splitter circuit. The numeral
601
designates an input terminal, the numeral
602
designates n quarter-wavelength lines, the numeral
603
designates n isolation resistors, and the numeral
604
designates n output terminals.
FIG. 12B
illustrates a tree configuration of 2-splitters capable of being configured as a plane circuit. The numeral
605
designates an input terminal, the numeral
606
designates two quarter-wavelength lines, the numeral
607
designates an isolation resistor, the numeral
608
designates four quarter-wavelength lines, the numeral
609
designates two isolation resistors, and the numeral
610
designates four output terminals. In addition,
FIG. 13
illustrates an asymmetric power splitter type. The numeral
611
designates an input terminal, the numerals
612
,
613
,
616
and
617
designate quarter-wavelength lines having characteristic impedances different from one another, the numerals
614
and
618
designate isolation resistors, and the numerals
615
,
619
and
620
designate impedance transformer circuits. The explanation of the Wilkinson power combiner circuit has been given on pages 205 to 210 of “Foundations of Microwave Circuits and Applications thereof” written by Yoshihiro Konishi, published by Sogo Denshi. Therefore, no detailed explanation is given here.
FIG. 14
illustrates the configuration of a conventional balun. The numeral
701
designates an unbalanced terminal, the numeral
702
designates a quarter-wavelength coaxial line having a characteristic impedance of 50&OHgr;, the numeral
703
designates an in-phase output terminal, and the numeral
704
designates an opposite-phase output terminal. The explanation of the balun has been given on pages 179 to 181 of “Radio Frequency Transistors” written by Norm Dye and Helge Granberg, published by Butterworth/Heinemann. Therefore, no detailed explanation is given here.
On the basis of the above-mentioned configurations, the conventional high power amplifier has obtained high power for transmission at a base station by combining a plurality of output powers of push-pull amplifiers.
Although the Wilkinson power splitter circuit shown in
FIG. 12A
can evenly split power into n-way ports at one time, the circuit cannot be attained as a plane circuit. For this reason, the configurations shown in
FIGS. 12B and 13
are used generally. The configuration shown in
FIG. 12B
, however, lends to a large loss in splitter/combiner configuration due to a long transmission path. In addition, the configuration also has a problem of low versatility, because power can be split and propagated only to 2
n
paths. Furthermore, the configuration shown in
FIG. 13
has a problem of unbalanced power splitting, because transmission paths are different lengths from one output to another. Moreover, the balun shown in
FIG. 14
is large in circuit size because of the use of the coaxial line, thereby having a problem of difficulty in miniaturization.
SUMMARY OF THE INVENTION
In order to solve these problems encountered in the conventional high power amplifier circuit, an object of the present invention is to provide a balun with an incorporated high power amplifier circuit having a drastically reduced circuit size due to use of decreased number of components.
The balun in accordance with the present invention, having been configured by using a coaxial line, is configured by using a multilayer board and by providing coupling lines on the layers above and below a strip line, thereby to obtain two opposite-phase outputs. With this configuration, baluns with power splitter/combiner circuits can be formed on a single multilayer board, whereby the high power amplifier circuit can be miniaturized. In addition, since the balun can propagate two opposite-phase outputs, the number of splits can be reduced, whereby the circuit size of the splitter can be made smaller. In addition, since n-splitting
-combining can be carried out at one time, loss can be reduced, whereby the efficiency of the power amplifier can be improved.
In order to attain the objects, one embodiment of the present invention offers a balun having:
a multilayer comprised of dielectric layers and conductor pattern layers stacked alternately;
a main line disposed on one of said conductor pattern layers;
a plurality of coupling lines each facing a part of said main line, disposed on one or more of said conductor pattern layers different from said conductor pattern layer on which said main line is disposed, so as to be electromagnetically coupled with said facing part of said main line, and grounded electrically respectively;
an input line disposed on one of said conductor pattern layers; and
output line pairs with respective pairs being connected across corresponding coupling line ends,
wherein one end of said main line is connected to said input line, the other end thereof is electrically grounded, the power of a signal input to said input line is split and propagated to each of said output terminal pairs via each of said coupling lines, and a signal propagated from one output line of each said output line pair is 180 degrees out of phase with the other signal propagated from the other output line.
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Dye, et al., “Radio Frequency Transistors,” Butterworth/Heinemann, 1993, pp 113-116 and pp 179-181.
Bassett,Microwaves, 19:7, 47-52, Jul. 1980.
Takao Hasegawa, et al., “Multi-Branch Power Dividers Using Multilayer MMIC Technology,” IEICE Transactions on Electronics, vol. E75-C, No. 6, Jun. (1992), pp. 707-712.
Kenjiro Nishikawa, et al., “Miniaturized Wilkinson Power Divider Using Three-Dimensional MMIC Technology,” IEEE Microwave and Guided Wave Letters, vol. 6, No. 10, Oct., 1996, pp. 372-374.
T. Gokdemir, et al, “Design and Performance of GaAs MMIC CPW Baluns Using Overlaid and Spiral Couplers,” 1997 IEEE MTT-S International Microwave Symposium Digest, published Jun. 8, 1997, pp. 401-404.
Copy of European Communication for counterpart application No. EP 99 11 7393, dated Apr. 19, 2001.
Ishida Kaoru
Kosugi Hiroaki
Kugou Shin'ichi
Miyaji Masayuki
Lee Benny T.
Smith , Gambrell & Russell, LLP
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