Wave transmission lines and networks – Coupling networks – Wave filters including long line elements
Reexamination Certificate
1999-05-27
2001-07-17
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Coupling networks
Wave filters including long line elements
C333S206000, C333S219100, C333S222000
Reexamination Certificate
active
06262639
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a bandpass filter using dielectric resonator which is used to a mobile radio communication base station such as a cellular mobile telephone, a personal communications service (PCS) and a wireless local loop (WLL), more particularly to a bandpass filter which is transmitting to a few loss signals which lie in a desired frequency band while intercepting all the frequencies outside the desired frequency band by forming the stepped dielectric resonators, and a bandpass filter having a variable notch cable outside the filter to show a desirable attenuation characteristic.
2. Description of the Related Art
Generally, a bandpass filter is the parts used at the mobile radio communication base station such as a cellular mobile telephone, a personal communications service (PCS) and a wireless local loop (WLL), and a radio frequency (RF) band. The role which a bandpass filter is to fulfill is transmitting to a few loss signals which lie in a desired frequency band while intercepting all the frequencies outside the desired band.
A conventional bandpass filter described above has been used to radio-based communications systems operating in the microwave range.
FIG. 1B
is a perspective view showing a conventional bandpass filter,
FIG. 1C
is a top view of FIG.
1
B.
As shown in FIG.
1
B and
FIG. 1D
, a bandpass filter comprises a metallic housing
12
formed by a plurality of cavities, a dielectric resonator
11
installed in the cavities each of the housing
12
, an input/output connector
13
installed on the both side end of the housing
12
, a coupling loop
15
combined with the input/output connector
13
, a partition
14
, which has windows
14
a
for combining resonance mode forms a boundary among cavities, frequency control plate
16
, and tuning bar
17
.
FIG. 1A
is a perspective view showing a dielectric resonator using a bandpass filter.
As shown in
FIG. 1A
, a uniform dielectric resonator
11
is formed to a cylinder shape. The filter using uniform dielectric resonators involves the needless signals by resonating not only the fundamental mode (TE
01&dgr;
) but also the higher-order mode. Accordingly, the filter having uniform dielectric resonators has a bad effect on a communications system by needless signals, which is resulted from the higher-order mode, in the neighborhood of the fundamental mode by the higher-order mode.
Also, it is extremely necessary to have a bandpass filter showing high quality coefficient (Q) in the low band region and low insertion loss in the pass band region. In most of the cases, the attenuation characteristic of the specified region to decrease interference between the neighboring channels and the transmitter/receiver bands and must be excellent.
In this case, a conventional method is to use the dielectric resonator having the high quality coefficient. However, this method is not only difficult to accomplish, but also involves a high manufacturing cost. To improve the attenuation characteristic, a conventional bandpass filter has been proposed to install a notch cable in the housing.
FIG. 2A
is a perspective view showing a bandpass filter using conventional dielectric resonators.
FIG. 2B
is a top view of FIG.
2
A.
As shown in
FIGS. 2A and 2B
, when RF signal is applied, the propagation is induced by the first dielectric resonator
21
′ through a coupling loop
25
. The signal power through the window
24
a
of a partition which is controlling a coupling capacity of the signal power and a band width is transmitted to the second dielectric resonator
21
″. By the same method, Signals of the desired frequency band are transmitted to the output connector
23
′. At this time, the higher attenuation is generated in the specified band region by a notch cable
26
inserted into the housing
22
. Symbol
27
is a housing cover.
However, above described method decreases a quality coefficient (Q) and increases a loss, because the notch cable changes the inside structure of the filter. Also, transformation and reestablishment after manufacturing of the filter is impossible. The needless wave may arise at certain frequency because of generating another resonance mode by the inserted notch cable
26
, also the wave may be distorted by changing the electromagnetic shape in course of resonance.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved bandpass filter using dielectric resonators, which suppress a needless wave generation of near the fundamental mode by forming the stepped dielectric resonators.
It is another object of the present invention to provide a dielectric resonator bandpass filter, which improves the attenuation characteristic with changing inside structure by installing a variable notch cable.
In accordance with an aspect of the present invention, there is provided a bandpass filter using dielectric resonator comprising: a housing having a plurality of cavities, wherein said plurality of cavities are isolated from each other by partitions and wherein each said partition have a coupling window; input/output connectors formed at both ends of said housing so as to pass output signals from a transmitter; coupling loops connected to said input/output connectors so as to excite an applied signal power and to combine resonance modes; dielectric resonators installed in said cavities of said housing so as to resonate a signal power transmitted from said coupling loop to the desired frequency band, said dielectric resonators including: a) a first resonator group formed in both said cavities which are adjacent to said coupling loops; and b) a second resonator group formed in said cavities which are positioned between both said cavities which are adjacent to said coupling loops, wherein said resonators of said second resonator group are stepped resonators; a plurality of frequency control means corresponding to said dielectric resonators, being disposed on a top of said dielectric resonators and being apart from said dielectric resonators by a predetermined distance, whereby the second resonator group removes a needless wave characteristic generated by resonance of the higher-order mode, by moving a higher-order mode characteristic from the first resonator group to a higher frequency band than a fundamental mode frequency.
REFERENCES:
patent: 5608363 (1997-03-01), Cameron et al.
patent: 5739733 (1998-04-01), Cameron
patent: 5949309 (1999-09-01), Correa
patent: 5969584 (1999-10-01), Huang et al.
patent: 6002311 (1999-12-01), Wey et al.
Jang Chang Su
Ryu Han Jong
Seo Su Dug
Shu Tae Won
Yoo Young Cheol
Ace Technology
Lowe Hauptman & Gilman & Berner LLP
Nguyen Patricia T.
Pascal Robert
LandOfFree
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