US 2003/0197578 A1 · Bandpass filter unit and communication apparatus

Abstract

A bandpass filter unit includes first and second bandpass filters having substantially the same pass-band characteristics. The first and second bandpass filters are connected in parallel with each other. At least one phase shifter for shifting the phase is connected to at least one of the first and second filters. Accordingly, reflected waves occurring in the first and second bandpass filters cancel out each other at an input terminal pair and an output terminal pair.

Drawings

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Drawings

Claims21

Dependent claims

A bandpass filter unit comprising:

a first filter;
a second filter having a characteristic with respect to a frequency at least in a frequency band for use that is substantially identical to a characteristic of said first filter, said second filter being connected in parallel with said first filter;
a first phase shift unit for shifting the phase by x degrees being cascade-connected to an input terminal of said first filter at a stage after parallel connecting points of the input terminal of said first filter and an input terminal of said second filter;
a second phase shift unit for shifting the phase by y degrees being cascade-connected to an output terminal of said first filter at a stage before parallel connecting points of the output terminal of said first filter and an output terminal of said second filter;
a third phase shift unit for shifting the phase by z degrees being cascade-connected to the input terminal of said second filter at a stage after the parallel connecting points of the input terminals of said first filter and said second filter;
and
a fourth phase shift unit for shifting the phase by w degrees being cascade-connected to the output terminal of said second filter at a stage before the parallel connecting points of the output terminals of said first filter and said second filter;
wherein x, y, z, and w substantially satisfy conditions expressed by equations (1) through (3):
2x−2z=180+n×360 (n is a certain integer);
(1) 2y−2w=180+m×360 (m is a certain integer);
(2) and x+y=z+w+l×360 (l is a certain integer) (3).

8 more elements

Dependencies are inferred from the claim text.

Description8,459 words

Summary2,294 words

#1. Field of the Invention

#The present invention relates to bandpass filter units and communication apparatuses, and more particularly, to a bandpass filter unit that is configured to suppress reflected waves at input and output terminals.

#2. Description of the Related Art

Brief description of the drawings16 figures

#FIG. 1 illustrates the circuit configuration of a bandpass filter unit according to a first preferred embodiment of the present invention;

#FIG. 2 is a circuit diagram illustrating a modified example of the bandpass filter unit shown in FIG. 1;

#FIG. 3 is a circuit diagram illustrating another modified example of the bandpass filter unit shown in FIG. 1;

Detailed description5,820 words

#The present invention is described in detail below with reference to the accompanying drawings through illustration of preferred embodiments thereof.

#FIG. 1 is a circuit diagram illustrating the schematic configuration of a bandpass filter unit 100 according to a first preferred embodiment of the present invention.

#In the bandpass filter unit 100, a first bandpass filter 1 and a second bandpass filter 2 having substantially the same characteristics in the pass band are used. That is, the first and second bandpass filters 1 and 2 having substantially the same input/output impedance characteristics and transmission characteristics with respect to the frequency are connected in parallel with each other between an input terminal pair 9 and an output terminal pair 10.

Facts

Application

10/408,281Filed 7 Apr 2003

Priority

JP 2002-11493517 Apr 2002

Published

23 Oct 2003

Term ends

Not estimatedThe source records don’t support an estimate.

Classification3 codes

H03H 7/01
Multiple-port networks comprising only passive electrical elements as network components: frequency selective two-port networks
H03H 9/64
Filters: using surface acoustic waves
H03H
Impedance networks

Bandpass filter unit and communication apparatus

Life of this patent

Bandpass filter unit and communication apparatus

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims21

Description8,459 words

Drawings

Classification3 codes

Life of this patent

Description8,459 words