Wave transmission lines and networks – Plural channel systems – Having branched circuits
Reexamination Certificate
1998-11-12
2001-06-19
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Having branched circuits
C333S175000, C333S185000, C333S193000
Reexamination Certificate
active
06249194
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a composite filter and a radio communication apparatus. In particular, the present invention relates to a composite filter comprising a surface acoustic wave filter and an LC filter, and a radio communication apparatus using the composite filter.
2. Description of Related Art
In
FIG. 8
, a RF block diagram of a portable telephone terminal which is an example of a general radio communication apparatus is shown. The portable telephone terminal operating in a single frequency band such as 800 MHz, 1.5 GHz, etc. includes an antenna ANT, a duplexer for antenna DPX, a transmitting RF portion Tx, a receiving RF portion Rx, and a synthesizer portion SYN. The input portion of the transmitting RF portion Tx is connected to a modulator portion MOD, and the output portion of the receiving RF portion Rx is connected to a demodulator portion DE respectively. The transmitting RF portion Tx is composed of a high output amplifier PA, a buffer amplifier BA, band-pass filters F
1
, F
2
, a low-pass filter F
3
, and a mixer MIX
1
, and performs a function to output a transmitting signal in receipt from the modulator MOD to the antenna ANT through the duplexer for antenna DPX. On the other hand, the receiving RF portion Rx is composed of a low-noise amplifier LNA, band-pass filters F
4
, F
5
, and a mixer MIX
2
, and caries out a function to output a receiving signal received from the antenna ANT through the duplexer for antenna DPX to the demodulator DE.
And, a conventional portable telephone terminal has been built up in such a way that, although not illustrated, a circuit board made of glass-epoxy resin, ceramics etc., has the various amplifiers PA, BA, LNA formed as chip-parts, a duplexer for antenna DPX made up of dielectric filters, and each of filters F
1
through F
5
mounted thereon.
However, in the above-mentioned portable telephone terminal making each of the conventional components as a chip-component has led to greater integration and this integration has increased the number of parts and has complicated the assembly process.
SUMMARY OF THE INVENTION
The present invention is provided to overcome the above described problems and provides a composite filter in which the number of components can be reduced and the assembly process of which is made easier. The invention also provides a radio communication apparatus using the composite filter.
A preferred embodiment of the present invention provides a composite filter, comprising: a laminated body formed by laminating a dielectric layer and an electric conductor layer; a concave portion provided on at least one major surface of said laminated body; external terminals provided on at least a side surface of said laminated body; an LC filter made of an inductance element and a capacitance element respectively formed by said electric conductor layer of said laminated body; a surface acoustic wave filter arranged in said concave portion of said laminated body; a cover for sealing said concave portion; two of said external terminals constituting the input terminals of said surface acoustic wave filter and of said LC filter respectively and two of said external terminals constituting the output terminals of said surface acoustic wave filter and of said LC filter respectively; and said surface acoustic wave filter and said LC filter are independent without being connected to each other in said laminated body.
According to the above described composite filter, because a surface acoustic wave filter and an LC filter are integrated through one laminated body, the number of parts can be reduced and the assembly process can be made easy. At the same time, nearly the same function as that of the discrete chip parts is made available.
Further, in nearly the same size as a surface acoustic wave filter made as a conventional discrete chip part, a composite filter having the two functions of a surface acoustic wave filter and an LC filter is made available.
Furthermore, because both a surface acoustic wave filter and an LC filter have their own independent input and output terminals, insertion of other electronic parts is made possible between the surface acoustic wave filter and LC filter. Therefore, the radio communication apparatus to be equipped with a composite filter is able to have the freedom of design widened.
In the above described composite filter, the surface acoustic wave filter and the LC filter may be band-pass filters respectively. If one filter is arranged at a later stage after the other filter, the attenuation value can be made larger at frequencies outside the pass band. Accordingly, the attenuation value can be made large over a relatively wide band.
In the above described composite filter, the pass band of the LC filter may include the pass band of the surface acoustic wave filter. If the LC filter having the pass band wider than that of the surface acoustic wave filter is arranged at a stage after of the surface acoustic wave filter having a narrow pass band, a high-frequency signal passes the LC filter after the high-frequency signal has passed the surface acoustic wave filter and at frequencies outside the pass band of the surface acoustic wave filter the attenuation value can be made even larger. Therefore, the attenuation value can be large over a relatively wide band.
In the above described composite filter, the pass band of the surface acoustic wave filter may not overlap with the pass band of said LC filter. This composite filter can be used when different frequencies are made to pass through. Therefore, the freedom of usage can be widened.
A preferred embodiment of the present invention also provides a radio communication apparatus, comprising: the above described composite filter; and the surface acoustic wave filter and the LC filter constituting the composite filter serving as a filter constituting part of a transmitting RF portion or a filter constituting part of a receiving RF portion.
According to the above described composite filter, because a surface acoustic wave filter and an LC filter constituting a composite filter are used as a filter in a transmitting RF portion or a receiving RF portion, the number of parts constituting a radio communication apparatus can be reduced. Consequently, the radio communication apparatus can be made small-sized.
Other features and advantages of the present invention will become apparent from the following description of an embodiment of the invention which refers to the accompanying drawings.
REFERENCES:
patent: 5410742 (1995-04-01), Yajima
patent: 5525942 (1996-06-01), Horii et al.
patent: 5815052 (1998-09-01), Nakajima et al.
patent: 6025761 (2000-02-01), Watanabe et al.
patent: 19633954 (1997-02-01), None
patent: 0638953 (1995-02-01), None
patent: 0 747 988 A1 (1996-12-01), None
patent: 3-220911 (1991-09-01), None
patent: 9-098056 (1997-04-01), None
patent: 10-032521 (1998-02-01), None
patent: 10-145270 (1998-05-01), None
patent: 10224174A (1998-08-01), None
Patent Abstracts of Japan, vol. 1998, No. 13, Nov. 30, 1998.
Nakajima Norio
Ochii Akihiro
Watanabe Takahiro
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
Pascal Robert
Summons Barbara
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