Filter device and dual-band radio system in which the filter device is used

• US 6,115,592 A
• Filed: 08/20/1996
• Issued: 09/05/2000
• Est. Priority Date: 08/24/1995
• Status: Expired due to Fees

• Current Assignee: Taiyo Yuden Company Limited (Taiyo Yuden Co)
• Original Assignee: Fujitsu Limited
• Inventors: Ohmori, Hideki, Hashimoto, Kazushi, Ueda, Masanori, Ikata, Osamu, Fujiwara, Yoshiro
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): BANKS HAROLD, MARSHA DENISE
• Application Number:
  US08/700,099
• Time in Patent Office: 1,477 Days
• Field of Search: 333/126, 333/129, 333/132, 333/133, 333/134, 333/167, 333/175, 333/185, 333/193, 333/195, 333/246, 333/247, 361/782, 361/811, 361/820, 361/821, 257/728, 257/687, 257/678, 174/524, 174/505, 174/50.51, 174/50.52, 310/313 R, 455/84, 455/296, 455/302, 455/303, 455/307, 455/137, 455/289, 455/73
• US Class Current: 455/307
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H03H 2240/00 Indexing scheme relating to filter banks
• CPC Class Codes: H03H 2250/00 Indexing scheme relating to dual- or multi-band filters
• CPC Class Codes: H03H 9/0576 including surface acoustic wave [SAW] devices
• CPC Class Codes: H03H 9/6476 the tracks being electrically parallel
• CPC Class Codes: H03H 9/6483 Ladder SAW filters
• CPC Class Codes: H03H 9/72 Networks using surface acoustic waves
• CPC Class Codes: H03H 9/725 Duplexers
• CPC Class Codes: H04B 1/52 Hybrid arrangements, i.e. arrangements for transition from single-path two-direction transmission to single-direction transmission on each of two paths or vice versa
• CPC Class Codes: H04B 5/00 Near-field transmission systems, e.g. inductive or capacitive transmission systems
• CPC Class Codes: H04B 5/22 Capacitive coupling
• CPC Class Codes: H04B 5/266 One coil at each side, e.g. with primary and secondary coils

Abstract

A filter device includes at least two filter elements provided in a package, each of the filter elements passing only signals within a predetermined frequency band, the predetermined frequency bands of the filter elements having center frequencies which are distinct from each other. An input terminal is connected to and shared by respective inputs of the filter elements. An output terminal is connected to and shared by respective outputs of the filter elements.

Claims

1. A filter device comprising:

a package;

at least two filter elements, provided in said package, each of said at least two filter elements passing only signals within a predetermined radio frequency band used by a radio signal portion of a dual-band radio system, said predetermined radio frequency bands of said at least two filter elements having center frequencies which are distinct from each other;

an input terminal connected to and shared by respective inputs of said at least two filter elements;

an output terminal connected to and shared by respective outputs of said at least two filter elements;

a first phase matching unit provided between the input terminal and the inputs of said at least two filter elements, wherein said first phase matching unit comprises a first transmission line connected to the input terminal and connected to one of said at least two filter elements, a first inductor, and a first capacitor, said first inductor and said first capacitor being connected to the input terminal and connected to another one of said at least two filter elements; and

a second phase matching unit provided between the output terminal and the outputs of said at least two filter elements, wherein said second phase matching unit comprises a second transmission line connected to the output terminal and connected to said one of said at least two filter elements, a second inductor, and a second capacitor, said second inductor and said second capacitor being connected to the output terminal and connected to said another one of said at least two filter elements,

wherein said at least two filter elements include surface acoustic wave filter elements each of which passes only the signals within the predetermined radio frequency band;

wherein said first and second phase matching units rotate a phase of the frequency passband for impedance matching with respect to said at least two filter elements;

wherein said at least two filter elements, said first phase matching unit, and said second phase matching unit are packaged on a surface of said package;

wherein said package comprises a cap which hermetically seals said at least two filter elements in said package;

wherein said package has a leadless-chip-carrier structure, said at least two filter elements being packaged on a first surface of said package, and at least one of the first phase matching unit and the second phase matching unit being packaged on a second, opposite surface of said package;

wherein said first phase matching unit comprises a first transmission line connected to the input terminal and connected to one of said at least two filter elements, and said second phase matching unit comprises a second transmission line connected to the output terminal and connected to said one of said at least two filter elements; and

wherein said at least two filter elements and said at least one of the first phase matching unit and the second phase matching unit are eclectically connected to each other via said first and said second transmission lines.

2. The filter device according to claim 1, wherein said at least two filter elements comprise surface acoustic wave filter elements, each surface acoustic wave filter element including a number of surface acoustic wave resonators arrayed in a ladder formation, said surface acoustic wave filter elements including:

a first surface acoustic wave filter element, which constitutes one of said at least two filter elements, having parallel resonators disposed at inputs of said first surface acoustic wave filter element and at outputs of said first surface acoustic wave filter element; and

a second surface acoustic wave filter element, which constitutes another one of said at least two filter elements, having series resonators disposed at an input of said second surface acoustic wave filter element and at an output of said second surface acoustic wave filter element.

3. The filter device according to claim 2, wherein said first surface acoustic wave filter element has a center frequency lower than a center frequency of said second surface acoustic wave filter element.

4. The filter device according to claim 1, wherein said package comprises:

a laminated member having conductive layers and insulating layers alternately laminated, said laminated member including recessed portions; and

a cap which seals said at least two filter elements in the recessed portions of said laminated member.

5. The filter device according to claim 1, wherein said package comprises a laminated member, said laminated member having conductive layers and insulating layers alternately laminated, and said first and said second transmission lines being constituted by one of the conductive layers of said laminated member.

6. The filter device according to claim 1, wherein said first and said second transmission lines are positioned on an external surface of said package.

7. The filter device according to claim 1, wherein said first and said second transmission lines are positioned on an external surface of said package, and said at least two filter elements are positioned on said external surface of said package.

8. The filter device according to claim 1, further comprising:

a connection terminal connected to said at least one of the first phase matching unit and the second phase matching unit,

at least one of the first phase matching unit and the second phase matching unit comprising an inductor and a capacitor.

9. The filter device according to claim 8, wherein said connection terminal externally connects said at least one of the first phase matching unit and the second phase matching unit to said filter device.

10. The filter device according to claim 1, wherein

said at least two filter elements, said first phase matching unit, and said second phase matching unit are packaged on a surface of said package.

11. A radio system comprising:

a radio signal transmitter unit processing modulated signals at an input of the radio signal transmitter unit to generate a transmitting radio signal at an output, said transmitting radio signal being transmitted to an external station;

a radio signal receiver unit processing a signal at an input of the radio signal receiver unit to generate a receiving radio signal at an output;

a modulator unit generating the modulated signals at outputs of the modulator unit from processed signals at inputs of the modulator unit through a modulation;

a demodulator unit generating demodulated signals at outputs of the demodulator unit from the receiving radio signal from the radio signal receiver unit at an input of the demodulator unit through a demodulation;

a base-band signal processor unit generating the processed signals at outputs of the base-band signal processor unit from an audio signal at an input of the base-band signal processor unit through a base-band signal processing, said outputs of said base-band signal processor unit being connected to the inputs of the modulator unit, said signal processor unit having another output at which an audio signal is generated from the demodulated signals at other inputs of the base-band signal processor unit through a base-band signal processing, said other inputs of said base-band signal processor unit being connected to the outputs of the demodulator unit,

each of said transmitter unit and said receiver unit comprising at least one filter device, said at least one filter device comprising;

a package;

at least two filter elements, provided in said package, each of said at least two filter elements passing only signals within a predetermined radio frequency band used by a radio signal portion of a dual-band radio system, said predetermined radio frequency bands of said at least two filter elements having center frequencies which are distinct from each other;

an input terminal connected to and shared by respective inputs of said at last two filter elements; and

an output terminal connected to and shared by respective outputs of said at least two filter elements;

a first phase matching unit provided between the input terminal and the inputs of said at least two filter elements, wherein said first phase matching unit comprises a first transmission line connected to the input terminal and connected to one of said at least two filter elements, a first inductor, and a first capacitor, said first inductor and said first capacitor being connected to the input terminal and connected to another one of said at least two filter elements; and

a second phase matching unit provided between the output terminal and the outputs of said at least two filter elements, wherein said second phase matching unit comprises a second transmission line connected to the output terminal and connected to said one of said at least two filter elements, a second inductor, and a second capacitor, said second inductor and said second capacitor being connected to the output terminal and connected to said another one of said at least two filter elements,

wherein said at least two filter elements include surface acoustic wave filter elements each of which passes only the signals within the predetermined radio frequency band;

wherein said first and second phase matching units rotate a phase of the frequency passband for impedance matching with respect to said at least two filter elements;

wherein said at least two filter elements, said first phase matching unit, and said second phase matching unit are packaged on a surface of said package;

wherein said package comprises a cap which hermetically seals said at least two filter elements in said package;

wherein said package has a leadless-chip-carrier structure, said at least two filter elements being packaged on a first surface of said package, and at least one of the first phase matching unit and the second phase matching unit being packaged on a second, opposite surface of said package;

wherein said first phase matching unit comprises a first transmission line connected to the input terminal and connected to one of said at least two filter elements, and said second phase matching unit comprises a second transmission line connected to the output terminal and connected to said one of said at least two filter elements; and

wherein said at least two filter elements and said at least one of the first phase matching unit and the second phase matching unit are eclectically connected to each other via said first and said second transmission lines.