Wave transmission lines and networks – Coupling networks – Wave filters including long line elements
Reexamination Certificate
2000-11-21
2003-09-16
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Coupling networks
Wave filters including long line elements
C333S206000
Reexamination Certificate
active
06621381
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a low-profile TEM mode (dominant mode) quarter wavelength (&lgr;/4) dielectric resonator having a high unloaded quality factor compared to a conventional dielectric resonator, and to a two-pole bandpass filter using this low-profile TEM mode dielectric resonator.
In the two-pole bandpass filter according to the present invention, the coupling between two adjacent resonators is provided by evanescent mode waveguide.
A resonator according to the present invention is expected to be used in a filter, a voltage controlled oscillator (VCO) and an antenna for mobile communication. A filter of the present invention can be used in a cellular phone system such as wide band CDMA (Code Division Multiple Access), and another communication system where filtering is required.
DESCRIPTION OF THE RELATED ART
The followings are known literatures:
[1] Arun Chandra Kundu and Ikuo Awai, “Low-Profile Dual Mode BPF Using Square Dielectric Disk Resonator,” Proceedings of the 1997 Chugoku-region Autumn Joint Conference of Electric/Information Associated Congress, Hiroshima, Japan, pp. 272 (October, 1997).
[2] Arun Chandra Kundu and Ikuo Awai, “Distributed Coupling in a Circular Dielectric Disk Resonator and its Application to a Square Dielectric Disk Resonator to Fabricate a Low-Profile Dual Mode BPF”. 1998 IEEE MTT-S Digest, pp. 837-840, June 1998, Maryland, USA
[3] Yoshihiro Konishi, “Novel Dielectric Waveguide Components—Microwave Application of New Ceramic Materials,” IEEE Proc., Vol. 79, No. 6, pp. 726-740, June, 1991.
In the literatures [1] and [2], Arun Chandra Kundu who is one of inventors of the present application has proposed a new type TEM dual-mode dielectric disk resonator having the following configuration, and a bandpass filter (BPF) using the resonator.
This dielectric resonator is a dual mode resonator having a square planer shape in 5 mm×5 mm, and its top and bottom surfaces are covered with silver. The top silver layer is floating, and the bottom silver layer is grounded. The interior of the two silver layers are filled with dielectric material of a relative permittivity or relative dielectric constant of 93. All of the side walls of the disk resonator are open surfaces exposed to the air. Accordingly, radiation easily occurs with leakage of electromagnetic field through these open surfaces. An electric field becomes at the maximum on each open surface, and becomes at the minimum along each symmetry plane of the resonator. Therefore this kind of resonator is called a half wavelength (&lgr;/2) dielectric disk resonator.
FIG. 1
illustrates the result of a theoretically and experimentally verifying relationship between the thickness and the unloaded quality factor Q
0
regarding this disk resonator, and a similar graph is described in the literature [1]. As apparent from the figure, the unloaded quality factor Q
0
becomes at the maximum (≈250 (experimental value)) when the thickness is 1 mm and the length and the width of the resonator is 5 mm×5 mm using dielectric material with a relative dielectric constant of 93.
Recent mobile terminals demand super compact bandpass filter, and hence it is required to promote further low profiling and compacting of dielectric resonators used inside the portable terminals. However, it is very difficult except that material having a higher dielectric constant is used in order to further miniaturize the dielectric resonator with keeping high performance.
In addition, if a 2 GHz bandpass filter is formed with using the conventional resonator described in the literature [2], the size of the filter become 8.5 mm×8.5 mm×1.0 mm, and its unloaded quality factor becomes 260. The recent mobile terminals, however, demand more compact and higher-performance filters.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a TEM mode dielectric resonator having a minimized size without changing a resonant frequency and an unloaded quality factor.
Another object of the present invention is to provide a bandpass filter using a TEM mode dielectric resonator, whereby the size can be minimized with keeping the performance of the filter.
According to the present invention, a TEM mode &lgr;/4 dielectric resonator includes a rectangular dielectric block having a top planar surface, a bottom planar surface and four side surfaces, a first metal layer coated on the top planar surface, a second metal layer coated on the bottom planar surface, and a third metal layer coated on one of the four side surfaces.
FIG. 2
illustrates the configuration of a conventional &lgr;/2 dielectric resonator, and
FIG. 3
illustrates the fundamental configuration of a &lgr;/4 dielectric resonator according to the present invention.
In
FIG. 2
, reference numeral
20
denotes a dielectric block with a rectangular planar shape,
21
a silver layer coated on a top surface of the dielectric block
20
, and
22
a silver layer coated on a bottom surface of the dielectric block
20
. The top silver layer
21
is floating, and the bottom silver layer
22
is grounded. All of the four sidewalls of the dielectric block
20
are open to the air. In
FIG. 2
, the length and width of the &lgr;/2 dielectric resonator is denoted by “a” and its thickness is denoted by “t”.
Supposing that the TEM mode propagating along z-axis direction in this &lgr;/2 dielectric resonator, the negative maximum electrical field exists on a plane at Z=0 and the positive maximum electrical field on a plane at z=a, as shown by arrows
23
in FIG.
2
. The minimum (zero) electrical field obviously exists on a plane
24
at z=a/2 that is the symmetry plane of the &lgr;/2 resonator.
It is possible to obtain two &lgr;/4 dielectric resonators by dividing such &lgr;/2 dielectric resonator. along this symmetry plane
24
and providing conductors on the divided surfaces.
FIG. 3
illustrates a &lgr;/4 dielectric resonator formed in this manner. In the figure, reference numeral
30
denotes a dielectric block with a rectangular parallelepiped shape,
31
a silver layer coated on a top surface of the dielectric block
30
, and
32
a silver layer coated on a bottom surface of the dielectric block
30
. The top silver layer
31
is floating, and the bottom silver layer
32
is grounded. One of side walls of the dielectric block
30
is a shorted end surface of a silver-coated layer
34
for shorting the top and bottom silver layers
31
and
32
, and other three side walls are open to the air. In
FIG. 3
, also, arrows
33
denote a direction of an electrical field, and arrows
35
a direction of current.
The &lgr;/4 dielectric resonator shown in FIG.
3
and the &lgr;/2 dielectric resonator shown in
FIG. 2
have the same resonant frequency in principle. Due to a high relative dielectric constant of 93, electromagnetic field confinement property is strong enough. Thus, the electromagnetic field distribution of the &lgr;/4 resonator and &lgr;/2 resonator is almost the same. As shown in
FIGS. 2 and 3
, the volume of the &lgr;/4 resonator is half as that of the &lgr;/2 resonator. In consequence, a total energy of the &lgr;/4 resonator is half as that of the &lgr;/2 resonator. Nevertheless, an unloaded quality factor of the &lgr;/4 resonator remains almost the same as that of the &lgr;/2 resonator since the energy loss decreases to 50% as that of the &lgr;/2 resonator. Accordingly, it is possible to drastically miniaturize the &lgr;/4 dielectric resonator without changing the resonant frequency and also the unloaded quality factor.
It is preferred that the rectangular dielectric block of the above-mentioned dielectric resonator is made of a ceramic dielectric material.
It is preferred that the resonator further includes a metal pattern partially formed on the one side surface that is different from the side surface on which the third metal layer is coated. The metal pattern may be formed on the side surface opposite to the side surface on
Endou Kenji
Kundu Arun Chandra
Chang Joseph
Pascal Robert
TDK Corporation
LandOfFree
TEM-mode dielectric resonator and bandpass filter using the... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with TEM-mode dielectric resonator and bandpass filter using the..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and TEM-mode dielectric resonator and bandpass filter using the... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3018455