Wave transmission lines and networks – Plural channel systems – Having branched circuits
Reexamination Certificate
1998-12-04
2002-02-12
Lee, Benny (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Having branched circuits
C333S117000
Reexamination Certificate
active
06346863
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to directional couplers, and more particularly, to a directional coupler for use in a mobile communication apparatus.
2. Description of the Related Art
FIG. 4
shows a conventional directional coupler. In
FIG. 4
, a directional coupler
20
is formed of a first microstripline
21
serving as a first distributed-constant line and a second microstripline
22
serving as a second distributed-constant line disposed substantially in parallel to each other, coupled with each other, and formed spirally in a substantially quadrangular shape with the first microstripline
21
being disposed inside of the second microstripline
22
. The first microstripline
21
is connected to an input electrode
23
at one end thereof and to an output electrode
25
at the other end thereof. The second microstripline
22
is connected to an output electrode
24
at one end thereof and to an isolation electrode
26
at the other end thereof. The space g
4
between the first and second microstriplines
21
and
22
disposed adjacently with the same number of turns is set narrower than the space d
4
between the adjacent turns of the pair of first and second microstriplines
21
and
22
. The lengths of the first and second microstriplines
21
and
22
are set substantially equal to one fourth the wavelength at the target frequency.
When a signal is input to the input electrode
23
with a terminating resistor (not shown) being connected to the isolation electrode
26
in the directional coupler
20
configured as described above, two signals with a phase difference of approximately 90 degrees are obtained from the output electrodes
24
and
25
at substantially the same amplitude level.
In the conventional case, however, the second microstripline
22
is longer than the first microstripline
21
by the lengths of several corners. Therefore, the phase difference between the two outputs of the directional coupler
20
shifts from the ideal state, namely, 90 degrees.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a directional coupler in which a shift of the phase difference between two outputs from 90 degrees can be reduced.
The foregoing object is achieved according to the present invention through the provision of a directional coupler in which first and second distributed-constant lines disposed substantially in parallel to each other and coupled with each other are formed spirally with the first distributed-constant line being disposed inside of the second distributed-constant line, wherein the space between the first and second distributed-constant lines disposed adjacently with the same number of turns is set wider than the space between the adjacent turns of the pair of first and second distributed-constant lines.
The directional coupler according to the present invention may also be provided with only a portion where the space between the first and second distributed-constant lines disposed adjacently with the same number of turns is set wider than the space between the adjacent turns of the pair of first and second distributed-constant lines.
With such a configuration, a deviation from 90 degrees of the phase difference between two outputs can be reduced in a directional coupler according to the present invention.
According to a directional coupler of the present invention, since the first and second distributed-constant lines disposed substantially in parallel to each other and coupled with each other are formed with the first distributed-constant line being disposed inside of the second distributed-constant line; and the space between the first and second microstriplines disposed adjacently with the same number of turns is made at least partially wider than the space between the adjacent turns of the pair of first and second microstriplines; a shift of the phase difference between the two outputs of the directional coupler from 90 degrees is made small, and the frequency band width of the directional coupler is made wide. In addition, with this structure, the space between the first and second microstriplines disposed adjacently with the same number of turns can be changed in a wide range, and the coupling degree of the directional coupler becomes easier to adjust.
REFERENCES:
patent: 3999150 (1976-12-01), Caragliano et al.
patent: 4777458 (1988-10-01), Pardini
patent: 5818308 (1998-10-01), Tanaka et al.
patent: 2839874 (1979-04-01), None
W. P. O'Reilly, “Transmitter Power Amplifier Design-4”, Wireless World, vol. 82, No. 1481, Jan. 1976, pp. 61-65, Fig. 5A.
European Search Report dated Mar. 10, 1999.
Sasaki Yutaka
Tanaka Hiroaki
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