Dielectric filter, dielectric duplexer, and transceiver...

Details Dielectric filter, dielectric duplexer, and transceiver... Dielectric filter, dielectric duplexer, and transceiver...

1999-09-07

2001-06-19

Lee, Benny (Department: 2817)

Wave transmission lines and networks

Plural channel systems

Having branched circuits

C333S219100, C333S202000

Reexamination Certificate

active

06249195

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to dielectric filters, dielectric duplexers, and transceivers for use in micro-wave or millimeter-wave communications.
2. Description of the Related Art
With the shift toward using frequencies in the micro-wave band and the millimeter-wave band, a plane-circuit type dielectric filter including dielectric resonators has been proposed, in which installation of the dielectric resonators and formation of configurations thereof can be easily and elaborately conducted by patterning of an electrode.
FIG. 8
illustrates a first embodiment of a conventional dielectric filter. The figure shows an exploded perspective view of the conventional dielectric filter.
As shown in
FIG. 8
, a conventional dielectric filter
110
a
includes a dielectric substrate
120
a
having an electrode formed on mutually opposing surfaces thereof, a lower case
112
, and an upper case
111
. In the electrode formed on the front surface of the dielectric substrate
120
a,
electrodeless portions or openings
121
a
through
121
e
are formed, whereas at opposing positions in the electrode formed on the back surface of the substrate, other electrodeless portions (not shown) having the same configuration as those on the front side are formed. Dielectric resonators
122
a
through
122
e
are composed of the parts defined by the openings
121
a
through
121
e
and the upper and lower cases
111
and
112
. The resonance frequency is determined by the configuration of the openings
121
a
through
121
e
and the thickness of the dielectric substrate
120
a,
and other well-known factors.
The lower case
112
is composed of a substrate
113
and a metal frame
114
mounted thereon, and the dielectric substrate
120
a
is mounted on the metal frame
114
, inside of which a step
115
is formed. An electrode
116
is formed on a surface of the substrate
113
. Furthermore, input-output micro-strip lines
130
and
131
are formed on the surface of the substrate
113
as input-output couplers, and an electrode (not shown) is formed on substantially the entire back surface of the substrate
113
.
The dielectric substrate
120
a
is mounted on the step
115
inside the lower case
112
, in which the substrate
120
a
is fixed by a conductive adhesive material or the like. The upper case
111
is fixed on the metal frame
114
of the lower case
112
. When input signals are input to the micro-strip line
130
, the micro-strip line
130
and the dielectric resonator
122
a
are electromagnetically coupled and the dielectric resonator
122
a
resonates in the TE010 mode. Since the adjacent dielectric resonators
122
a
through
122
e
are electromagnetically coupled as well, signals are output from the micro-strip line
131
on the output side. In this case, the dielectric filter
110
a
serves as a five-stage band pass filter.
The unloaded Q (hereinafter referred to as Q0) of the TE010-mode dielectric resonator is higher than the Q0 of a rectangular-slot mode dielectric resonator, which will be described below. For example, in the 26 GHz band, Q0 of a TE010-mode dielectric resonator is approximately 1900, whereas Q0 of a rectangular-slot mode dielectric resonator is approximately 700. As shown here, since Q0 of the dielectric resonator is higher when the TE010 mode is used, a dielectric filter with small insertion losses can be obtained.
A second conventional dielectric filter will be illustrated by referring to FIG.
9
.
FIG. 9
shows an exploded perspective view of a conventional dielectric filter, in which the same parts as those in the first conventional dielectric filter shown in
FIG. 8
are given the same reference numerals and thus detailed explanations thereof are omitted.
In the conventional dielectric filter
110
b
shown in
FIG. 9
, the configurations of openings
123
a
through
123
e
of an electrode formed on a dielectric substrate
120
b
are rectangular, which are different from those in the first conventional example. These openings form dielectric resonators
124
a
through
124
e.
Making the configurations of the openings
123
a
through
123
e
rectangular permits the resonance mode to be the rectangular-slot mode. Since the rectangular-slot mode weakens the degree of confinement of the electromagnetic field, the coupling (hereinafter referred to as Qe) between the dielectric resonators and the input-output couplers, and the coupling between the dielectric resonators
124
a
through
124
e
can be facilitated.
Regarding the above description of
FIGS. 8 and 9
, an illustration will be given by referring to graphs shown in
FIGS. 10 and 11
.
FIG. 10
is a graph showing the relationship between Qe and the distances between the input-output couplers and the dielectric substrate, in which the solid line indicates the TE010-mode dielectric resonator and the broken line indicates the rectangular-slot mode dielectric resonator. In
FIG. 10
, as well as in
FIG. 9
, it can be seen that the rectangular-slot mode permits coupling between the input-output couplers and the dielectric resonators to be facilitated.
FIG. 11
shows a graph indicating the relationship between the coupling coefficients and the distances between the openings of the electrode forming the dielectric resonators, in which the solid line indicates the TE010-mode resonator and the broken line indicates the rectangular-slot mode dielectric resonator. In
FIG. 11
, as well as in
FIGS. 10 and 9
, it is shown that the rectangular-slot mode permits coupling between the dielectric resonators to be facilitated.
Meanwhile, in the field of high-frequency technology, the demand for improved characteristics has recently increased, such that dielectric filters having insertion losses of approximately 2 dB or lower are now being required.
The invention provides an improvement in the insertion loss characteristic of a dielectric filter with respect to its specific band. “Specific band” is defined by the following formula:
Specific band=(design band width/design central frequency)×100%
The response characteristics of a filter (insertion loss, and out-of-band attenuation) depend on design band width, the order of the filter, and the unloaded Q of a resonator forming the filter, etc. Relationships between the values of these parameters and the insertion loss and attenuation of the filter are as follows:
TABLE 1
Insertion Loss
Design band width
wide
narrow
Order of the filter
small
large
Unloaded Q
large
small
Insertion loss
small
large
TABLE 2
Attenuation Outside Passband
Order of the Filter
small
large
Attenuation outside
small
large
the pass band
In designing response characteristics of a filter, the above relationships are considered and each parameter is adjusted.
As shown in the above Table 1, the wider the design band width, the smaller the insertion loss of the filter. That is, the insertion loss of a filter which exhibits a large specific band is small. Also, the smaller the order of the filter, the smaller the insertion loss; and the larger the unloaded Q, the smaller the insertion loss.
As shown in Table 2, the order of the filter affects the amount of attenuation outside the passband.
When using a TE010 mode resonator (circular shape) for forming a filter, a relatively small design band width can be realized. The unloaded Q of the resonator (1/the loss of the resonator) is large.
On the other hand, a rectangular slot resonator realizes a wide design band width. But, its unloaded Q is small.
An ideal resonator to minimize the insertion loss of a filter should be able to realize a wide design band width and a large unloaded Q as shown in Table 1. But, in practice, a TE010 mode resonator is not able to realize as wide a design band width as a rectangular resonator. This results in the filter having excessive insertion loss. Further, since the rectangular resonator has a wide band width, its unloaded Q is small, which also increases the insertion loss.
FIG. 12
is a graph showing the relationship between the specific band and the insertion loss in a

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