Power divider/combiner

Details Power divider/combiner Power divider/combiner

2000-02-11

2002-12-03

Nguyen, Patricia (Department: 2817)

Wave transmission lines and networks

Plural channel systems

Having branched circuits

C333S120000, C333S125000, C333S128000, C333S136000

Reexamination Certificate

active

06489859

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power diver/combiner for dividing or combining mainly high-frequency signals in a microwave band and a millimeter-wave band.
2. Description of the Related Art
A conventional power divider/combiner will be described with reference to the drawings.
FIG. 11
is a diagram showing a circuit configuration of the conventional power divider/combiner reported in, e.g., “Foundations for Microwave Engineering Second Edition,” written by R. E. Collin, McGraw-Hill International Editions Electrical Engineering Series, p445, McGraw-Hill Inc., 1992.
Referring to
FIG. 11
, there are shown an input line
10
, output terminals
2
, a branch line
3
with an electrical length being a ¼ wavelength, of which one end is connected at a diverging point
31
to the input line
10
and the other ends are connected to the output terminals
2
, an isolation resistor
5
connected to between the output terminals
2
, and load impedances
21
connected to the output terminals
2
.
Next, an operation of the conventional power divider/combiner explained above will be described with reference to the drawings.
FIG. 12
is a diagram showing how the prior art power divider/combiner operates.
The high-frequency signal inputted to the input line
10
is divided at the diverging point
31
to the branch lines
3
. The signals assuming the same phase and having an equal amplitude flow to the output terminals
2
which are therefore take an equal electric potential, while no current flows to the isolation resistor
5
.
At that time, the branch lines
3
function as a ¼ wavelength impedance transformer, whereby an impedance as viewed from the input line
10
toward the output terminals
2
side is equal to a characteristic impedance of the input line
10
, and the high-frequency signal is divided without causing any reflection.
On the other hand, the high-frequency signals, when inputted to the output terminals
2
, are combined at the diverging point
31
and thus outputted to the input line
10
.
Further, even when there is a difference in potential between the output terminals
2
, as shown in
FIG. 12
, a high-frequency signal A (¼+¼=½ wavelength delay) flowing through one of the branch lines
3
from one of output terminals
2
and a high-frequency signal B (with no delay) flowing to the isolation resistor
5
, become opposite in phase and equal in amplitude at the other output terminal
2
, and are therefore offset each other. As a result, the current flows to the isolation resistor
5
and is absorbed, and the isolation between the output terminals
2
is ensured.
In the conventional Wilkinson type power divider/combiner described above, a passing phase of the isolation resistor
5
is required to be zero in order to ensure the isolation between the output terminals
2
. If a thin film resistor is used as the isolation resistor
5
, however, a length of the resistor can not be ignored as compared with the wavelength of the high-frequency signal, and the high-frequency signals A, B shown in
FIG. 12
do not assume the opposite phases. Therefore, the signal inputted to one of output terminals
2
is not offset at the other output terminal
2
, and there arises a problem in that the isolation between the output terminals
2
declines.
Further, when viewed from the input terminal
10
, the isolation resistor
5
having the electrical length appears as a open stub, and hence there also exists such a problem that an I/O reflection characteristic declines.
SUMMARY OF THE INVENTION
It is a primary object of the present invention, which was devised to obviate the problem described above, to provide a power divider/combiner capable of ensuring an isolation between output terminals even with using of an isolation resistor having a length that can not be ignored as compared with a wavelength of a high-frequency signal in use, and exhibiting an excellent I/O reflection characteristics.
To accomplish the above object, according to a first aspect of the present invention, there is provided a power divider/combiner comprising an input terminal; two output terminals, two branch lines each connecting the input terminal and the output terminal and having a line length that is ¼ of a set wavelength or a multiple of integer of half a wavelength and ¼ of the set wavelength, an isolation resistor connected to between the output terminals, and a transmission line interposed between each of the output terminals and the branch lines.
The power divider/combiner according to a second aspect of the present invention may further comprise a capacitance element having one end connected to the input terminal and the other end grounded.
The power divider/combiner according to a third aspect of the present invention may further comprise a open stub connected to the input terminal.
The power divider/combiner according to a fourth aspect of the present invention may further comprise a low impedance line interposed between the input terminal and a connecting point between the two branch lines.
In the power divider/combiner according to a fifth aspect of the present invention, the isolation resistor may be connected between the output terminals through a connection line.
According to a sixth aspect of the present invention, there is provided a 2-way power divider/combiner constructed by connecting at multi-stages the 2-way power dividers/combiners according to the second through fifth aspects of the invention, wherein the 2-way power dividers/combiners disposed at the second stage onward are provided with neither the capacitance element, nor the open stub, nor the low impedance line.


REFERENCES:
patent: 4310814 (1982-01-01), Bowman
patent: 4401955 (1983-08-01), Yorinks et al.
patent: 5634208 (1997-05-01), Nishikawa et al.
patent: 57181204 (1982-11-01), None
patent: 738309 (1995-02-01), None
patent: 07038309 (1995-02-01), None
patent: 09321509 (1997-12-01), None
R. E. Collin, Foundations for Microwave Engineering, 2nd Edition, pp. 442-450, 1992.
Japanese Abstract 56058310 published May 21, 1981.
Sean R. Mercer, Ph.D., “Linear Simulators Offer Successful Microstrip Modeling For Wilkinson Power-Splitters”, RF Design, Cardiff Publishing Co., Englewood, Co. US, vol. 19, No. 9, Sep. 1, 1996 pp. 38, 42, 45-46 and 48.
Maurin, et al., “Microstrip Three-Way Power Combiners Using A Standard MIC Technology”, Proceedings of the 26th, Prague, Sep. 9-13, 1996, Proceedings of the European Microwave Conference, Swanley, Nexus-Media, GB, vol. 2, Conf. 26, Sep. 9, 1996, p. 839-843.

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