Amplifiers – With semiconductor amplifying device – Including plural amplifier channels
Reexamination Certificate
1999-03-02
2001-03-13
Pascal, Robert (Department: 2817)
Amplifiers
With semiconductor amplifying device
Including plural amplifier channels
C330S286000
Reexamination Certificate
active
06201445
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power amplifier, specifically to a push-pull high output, high frequency power amplifier operating at a high efficiency in a microwave band.
2. Description of the Related Art
A conventional high frequency power amplifier will be described.
Conventionally, a push-pull power amplifier circuit for operating two power amplifying elements (for example, FETs) in reverse phases from each other and synthesizing output signals from the power amplifying elements to provide an output signal is known.
FIG. 4
is a block diagram of a conventional high frequency power amplifier
400
disclosed in Japanese Laid-Open Publication No. 5-29851.
In
FIG. 4
, a signal input from an input terminal
401
is divided into two signals by a power divider
402
. The two signals have reverse phases from each other and have the same amplitude as each other. The two signals are input to a pair of FETs
405
through input-side matching circuits
403
, respectively. The pair of FETs
405
are connected in parallel. A gate of each FET
405
is biased through a resistor
404
, and a drain of each FET
405
is biased through a coil
409
. A distributed constant line
406
, provided in connection with an output of each FET
405
, is connected to a power synthesizer
411
through a capacitor
410
. The distributed constant lines
406
are connected to each other, through a capacitor
407
for controlling third-order harmonic components, at a point of each distributed constant line
406
which is a distance away from the output of the corresponding FET
405
, the distance being {fraction (1/12)} of the fundamental wavelength to be amplified. The distributed constant lines
406
are also connected to each other, through a capacitor
408
for controlling fundamental wave components, between the connection points of the distributed constant lines
406
and the capacitor
407
, and the power synthesizer
411
.
The two signals having the reverse phases and the same amplitude and amplified by the pair of FETs
405
are input to the power synthesizer
411
through an output-side matching circuit
420
. The matching circuit
420
includes the distributed constant lines
406
, the capacitor
407
, the capacitor
408
, and capacitors
410
. Then, the signals are synthesized and output to an output terminal
412
.
In such a conventional high frequency power amplifier
400
, a load impedance with respect to the third-order harmonic components at the output of the FET
405
becomes as high as open, e.g., nearly 100 &OHgr;, due to the distributed constant lines
406
and the capacitor
407
. Thus, the pair of FETs
405
operate at a high efficiency.
In this specification, the expression “as high as open” refers to “as high as, for example, nearly 100 &OHgr;”.
A high frequency power amplifier for transmitting signals used in wireless communication devices such as, for example, cellular phones is generally demanded to have a high output and a high efficiency in operation. In order to make maximum use of the inherent characteristics of the power amplifying elements used in a high frequency power amplifier, the load impedance needs to have a value in a limited range at an input and an output of the power amplifying element. Accordingly, very fine adjustments are required to configure a matching circuit.
In the conventional high frequency power amplifier
400
, the capacitor
408
for controlling the fundamental wave components and the capacitor
407
for controlling the third-order harmonic components are connected to the same distributed constant lines
406
. In such a structure, control of the load impedance at the outputs of the power amplifying elements is complicated, thereby making it difficult to optimize the load impedances with respect to both the fundamental wave components and the third-order harmonic components.
SUMMARY OF THE INVENTION
A high frequency power amplifier according to the present invention includes: a pair of power amplifying elements; a power divider, provided in the vicinity of an input terminal of the high frequency power amplifier, for supplying the pair of power amplifying elements with signals, respectively, the signals having an identical amplitude with each other and having reverse phases from each other; and a power synthesizer, provided in the vicinity of an output terminal of the high frequency power amplifier, for synthesizing signals output from the pair of power amplifying elements, the signals having an identical amplitude with each other and having reverse phases from each other. Output terminals of the power amplifying elements are connected to each other through a third-order harmonic component controlling circuit, and the third-order harmonic component controlling circuit includes a series connection of a transmission line having a length of {fraction (1/12)} of a fundamental wavelength, a capacitor, and another transmission line having a length of {fraction (1/12)} of the fundamental wavelength.
In one embodiment of the invention, input terminals of the power amplifying elements are connected to each other through the third-order harmonic component controlling circuit.
In one embodiment of the invention, the third-order harmonic component controlling circuit is provided on a high dielectric constant substrate.
According to the present invention, optimum matching with respect to the fundamental wave components is easily realized while maintaining the load impedance with respect to the third-order harmonic components at the inputs and outputs of the power amplifying elements as high as open.
When the impedances at the inputs and outputs of the power amplifying elements are excessively low, an internal matching system can be adopted in order to facilitate impedance matching in such a manner that compact high dielectric constant substrates are provided in the vicinity of the inputs and outputs of the power amplifying elements and connected therewith by bonding wires, thereby raising the impedances at the inputs and outputs. In such a system, the third-order harmonic component controlling circuit is provided on the dielectric constant substrate for internal matching.
Thus, the invention described herein makes possible the advantages of providing a highly efficient and compact high frequency power amplifier for easily optimizing load impedances with respect to both the fundamental wave components and the third-order harmonic components.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.
REFERENCES:
patent: 5111157 (1992-05-01), Komiak
patent: 5274341 (1993-12-01), Sekine et al.
patent: 5999058 (1999-12-01), Saitou et al.
Ono F et al: “A 50W Low Distortion Gaas Mesfet For Digital Cellular Base Stations” Gaas Ic Symposium: IEEE Gallium Arsenide Integrated Circuit Symposium Technical Digest 1996, Orlando, FL, Nov. 3-6, 1996, No. Symp. 18,Nov. 3, 1996, pp. 103-106, XP000659840.
Institute of Electrical And Electronics Engineers.
Maeda Masahiro
Morimoto Shigeru
Matsushita Electric - Industrial Co., Ltd.
Nguyen Khanh Van
Pascal Robert
Renner , Otto, Boisselle & Sklar, LLP
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