Wave transmission lines and networks – Plural channel systems – Nonreciprocal gyromagnetic type
Reexamination Certificate
1999-08-10
2002-03-19
Bettendorf, Justin P. (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Nonreciprocal gyromagnetic type
C333S024200
Reexamination Certificate
active
06359526
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a nonreciprocal circuit device including a dielectric wave guide, and a radio device including the nonreciprocal circuit device.
2. Description of the Related Art
A conventional circulator including a nonradiative dielectric wave guide (hereinafter, referred to as an NRD guide) is described in Electronic Data Communications Academy Bulletin EMCJ92-54, MW92-94 (1992-10), “60 GHz Band NRD Guide Gunn Oscillator,” and Electronic Data Communications Academy Research Papers C-I, Vol. J77-C-I, No. 11, pp. 592-598, November 1994, “60 GHz Band FM Gunn Oscillator using an NRD Guide”.
FIG. 13
shows the structure of the conventional circulator containing the above NRD guide. In
FIG. 13
, three dielectric strips
3
,
4
, and
5
are disposed between conductor plates
1
and
2
to form the NRD guide. Ferrite sheets
6
and
7
are arranged at the portion where the three dielectric strips are butted together. Magnets
8
and
9
are placed on the outer sides of the conductor plates
1
and
2
in such a manner as to sandwich the ferrite sheets
6
and
7
.
A ferrite resonator comprising the ferrite sheets
6
and
7
is excited by an electromagnetic wave which is transmitted through the dielectric strips. A DC magnetic field is applied vertically to the surfaces of the ferrite sheets
6
and
7
. In this case, due to the ferromagnetic characteristics of the ferrite sheets, the permeability of the ferrite sheets differs depending on the rotation direction of the high frequency magnetic field. As a result the polarized wave faces rotate, functioning as a circulator.
In a nonreciprocal circuit device including a dielectric wave guide such as the above-described circulator, the dielectric strips are arranged to extend radially from the center of the circulator. Therefore, dielectric strips of another circuit unit can seldom be linearly connected to the dielectric strips. To form a circuit with the dielectric wave guides, bending of the dielectric strips at some points is indispensable. However, in a bent portion of the dielectric strip, an LSM01 mode, which is the main transmission mode, becomes asymmetric with respect to the lateral direction. Thus, the conversion of the LSM01 mode to an LSE01 mode occurs. Accordingly, although it has been considered to design the bent portion so that all the electric power is completely converted to the LSM01 mode at the terminal of the bent portion, there is the problem that the bent portion cannot be formed to have a desired bending angle and radius of curvature.
Accordingly, the applicant of the present invention filed Japanese Patent Application No. 7-257803 in which an NRD guide (hereinafter, referred to as a hyper NRD guide) is described in which a groove into which a dielectric strip is to be fitted is formed on a conductor plate so that the cut-off frequency of the LSM01 mode is lower than that of the LSE01 mode in the propagation range of the dielectric wave guide; and in the non-propagation range, the space between the conductor planes of the conductor plates is made narrow so that the propagation can be carried out exclusively in the LSM01 mode.
The structure of the hyper NRD guide applied to the circulator is shown in
FIG. 11
, for example. The conductor plates
1
and
2
have grooves
21
and
22
respectively formed on the opposing surfaces thereof. The conductor plates
1
and
2
are so assembled that the dielectric strips
3
,
4
, and
5
and the ferrite sheets
6
and
7
fit into the grooves. The ferrite sheets
6
and
7
function as a ferrite resonator, couple a signal propagated in the LSM01 mode along one of the dielectric strips, and simultaneously rotate the polarized wave faces to propagate the signal in the LSM01 mode to another dielectric strip. With the above-described structure of the circulator including the hyper NRD guide, no mode-conversion to the LSE01 mode occurs, and thereby, the loss caused by the mode conversion can be reduced.
FIG. 12
is an upper plan view of the ferrite sheets
6
and
7
and the dielectric strips
3
,
4
, and
5
which are fitted into the groove
22
of the conductor plate
2
shown in FIG.
11
. In the above-described structure in which the grooves
21
and
22
are respectively formed on the conductor plates
1
and
2
and the dielectric strips
3
,
4
and
5
and the ferrite sheets
6
and
7
are fitted into the grooves
21
and
22
, an electromagnetic field is disturbed on the periphery of the ferrite sheets
6
and
7
if the side walls of the grooves
21
and
22
of the respective conductor plates
1
and
2
are disposed very close to the side faces of the ferrite sheets
6
and
7
. As a result, in the ferrite resonator, the ferrite sheets
6
and
7
and the dielectric wave guides
3
,
4
and
5
are not matched. For this reason, the thicknesses (shown by the arrows in
FIG. 12
) of the dielectric portions parallel to the tangential directions of the ferrite sheets
6
and
7
are increased, and thereby, the distances between the side faces of the ferrite sheets
6
and
7
and the side walls of the grooves on the respective conductor plates
1
and
2
are undesirably widened.
However, with the above-described structure, an electromagnetic wave is propagated through the dielectric portions on the periphery of the ferrite sheets
6
and
7
, so that the magnetic field coupling of the ferrite sheets
6
and
7
is weakened. As a result, in the case of the circulator having three ports, as shown in
FIG. 12
, for example, not only is an electromagnetic wave propagated from one of the ports to one of the other two ports, but also the electromagnetic wave is leaked to the remaining port. That is, the characteristics of the circulator as a nonreciprocal circuit device deteriorate.
The foregoing problem is caused not only in the case of the hyper NDR guide but also in a device in which grooves are formed in conductor plates and dielectric strips are arranged in the grooves.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a nonreciprocal circuit device including a dielectric wave guide device which has a structure in which a dielectric strip is fitted into grooves formed on conductor plates, and in which the nonreciprocal characteristics of the devices are prevented from deteriorating. The invention further provides a radio device including the nonreciprocal circuit device.
According to the present invention, there is provided a nonreciprocal circuit device which comprises a dielectric strip extending radially from the center in at least two directions, arranged between two conductor plates constituting parallel conductor planes, and a ferrite sheet arranged in the center of the dielectric strip. A substance having a lower dielectric constant than the dielectric strip is arranged between at least a side face of the ferrite sheet and the conductor plates adjacent to the side face of the ferrite sheet. Accordingly, matching of the resonance mode of the ferrite sheet and the mode of the dielectric wave guide can be easily achieved, and also, since the dielectric constant on the periphery of the ferrite sheet is reduced, the magnetic field coupling to the ferrite is not reduced, giving excellent nonreciprocal characteristics.
In order to provide the substance having a low dielectric constant, concave portions are formed in the centers of the conductor plates, and the substance having a lower dielectric constant than the dielectric strip (for example, an air space) is arranged at the periphery of the ferrite sheet. Further, on the conductor plates, are formed the grooves into which the dielectric strip is inserted to a predetermined depth, the width of the dielectric strip is increased in the centers of the conductor plates and in the direction along the parallel conductor planes of the conductor plates, and the substance having a low dielectric constant (for example, an air space) is arranged at the widened location and between the side walls of the grooves and the side face of the
Ishiura Yutaka
Ohira Katsuyuki
Tokudera Hiromu
Bettendorf Justin P.
Murata Manufacturing Co. Ltd.
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