Balanced input/output filter circuit and device

Details Balanced input/output filter circuit and device Balanced input/output filter circuit and device

2001-11-15

2003-07-15

Pascal, Robert (Department: 2817)

Oscillators

Automatic frequency stabilization using a phase or frequency...

Plural oscillators controlled

C331S1070DP, C333S167000, C333S175000

Reexamination Certificate

active

06593816

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a balanced input/output filter device. In particular, the present invention relates to a ceramic-laminated planar filter comprising balanced input/output terminals.
2. Description of the Related Art
Generally speaking, surface acoustic wave filters are important band-pass filter devices in communications. Although the surface acoustic wave filters have good frequency responses in rejection band, they have disadvantages of cost and size. Therefore, laminated planar filters are employed to decrease the size of products and the cost of production.
A balanced-input-output configuration of laminated planar filters suitable for next-generation super-compact portable telephones is disclosed in 1999 IEEE MTT-S Digest from pages 1143 to 1146.
FIG. 1
depicts an equivalent circuit diagram of a conventional two-order balanced input/output band-pass filter. A conventional two-order balanced input/output band-pass filter comprises a positive input terminal
111
and a negative input terminal
112
, a positive output terminal
121
and a negative output terminal
122
, and ceramic resonators
13
and
14
. The ceramic resonators
13
and
14
are coupled between the positive input terminal
111
and a negative input terminal
112
and between the positive output terminal
121
and a negative output terminal
122
, respectively. In addition, a conventional two-order balanced input/output band-pass filter further comprises six coupling capacitors
15
,
16
,
17
,
18
,
19
, and
20
. Capacitors
15
,
19
,
17
are coupled between the positive input terminal
111
and the positive output terminal
121
, and capacitors
16
,
20
,
18
are coupled between the negative input terminal
112
and the negative output terminal
122
.
FIG. 2
depicts the ceramic-laminated planar structure of the circuit in FIG.
1
. As shown in
FIG. 2
, parallel metal layers (
15
~
20
) constitute capacitor structures, and resonators are composed by transmission lines
13
and
14
. The transmission lines
13
and
14
are series-connected to the parallel metal layers and are shorter than a quarter wavelength.
FIG. 3
depicts a frequency response plot of the ceramic laminated planar structure in FIG.
2
. As shown in
FIG. 3
, the frequency response of the rejection band of conventional two-order balanced input/output band-pass filter is poor. Therefore, the conventional balanced input/output band-pass filter cannot eliminate signals with undesired frequency.
To overcome this disadvantage, the conventional method is to add the orders of the conventional balanced input/output band-pass filter. Therefore, the conventional two-order balanced input/output band-pass filter circuit must add more ceramic resonators and coupling capacitors to improve the effect of filtering noise.
However, the approach mentioned above uses more elements. Therefore, the cost of fabricating and the size of filter will both increase, which will limit the design of communication apparatus. Moreover, the increase in quantity of elements used increases the insertion loss, so the intensity of the signal to be transmitted will be decreased, worsening the efficacy of the communication apparatus.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a balanced input/output filter circuit, under the configuration of a two-order balanced input/output bandpass filter circuit. In the present invention, both sides of the ceramic resonators are serially connected to a pair of inductors and capacitors, respectively. Therefore, the intensity of the signal in rejection band will attenuate effectively without increasing elements of the circuit; moreover, the purpose of decreasing insertion loss and the size of the units will be achieved.
To achieve the above-mentioned object, the present invention provides a balanced input/output filter device. The balanced input/output filter device according to the present invention comprises two resonators, a pair of coupling capacitors, a positive input terminal and a negative input terminal, and a positive output terminal and a negative output terminal.
Both sides of one resonator are serial connected to spiral-type inductors on the other metal layers, and both sides of the other resonator are serial connected to parallel-type capacitors on the other metal layers. The coupling capacitors couple between the spiral-type inductors and the parallel-type capacitors respectively, and the output and input terminals are coupled to the spiral-type inductors and parallel-type capacitors respectively, which are coupled to the resonators.


REFERENCES:
patent: 6133809 (2000-10-01), Tomohiro et al.
patent: 08250905 (1996-09-01), None

Affiliated with

Also associated with

Rating

Balanced input/output filter circuit and device does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Balanced input/output filter circuit and device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Balanced input/output filter circuit and device will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3000897