Receiver

Details Receiver Receiver

1999-03-26

2002-04-02

Bost, Dwayne (Department: 2681)

Telecommunications

Receiver or analog modulated signal frequency converter

Signal selection based on frequency

C455S164100, C455S165100, C455S168100, C455S232100, C455S242200, C455S307000

Reexamination Certificate

active

06366765

ABSTRACT:

BACKGROUND OF THE INVENTION
(i) Field of the Invention
The present invention relates to a receiver which is applicable to a plurality of mobile radio communication systems by one unit and which receives a signal while switching the communication system and, more particularly, to a receiver in which a circuit scale is reduced to intend the miniaturization of a device.
(ii) Description of the Related Art
As communication systems used for a mobile radio cellular system, for example, there are a time division multiple access (TDMA) system, a frequency division multiple access (FDMA) system, and code division multiple access (CDMA) system.
A receiver for such a plurality of communication systems (hereinbelow, simply referred to as a receiver) which has a function for receiving signals of the plurality of communication systems and can receive a signal by switching to one communication system arbitrarily selected will now be described.
A conventional receiver will now be explained with reference to FIG.
13
.
FIG. 13
shows a constructional block diagram of the conventional receiver.
As shown in
FIG. 13
, the conventional receiver comprises an antenna
1
, a gain variable LNA (low noise amplifier)
2
, an AGC (automatic gain control) control unit
6
, a mixer
8
, an LPF (low pass filter) bank
9
′, a switching circuit
10
, an A/D converter
11
, a demodulating unit
12
′, a control unit
13
′, and a variable oscillator
21
.
The component elements of the conventional receiver will now be explained hereinbelow.
The antenna
1
is a receiving antenna.
The gain variable LNA
2
is an LNA (Low Noise Amplifier) which can control a gain.
The AGC control unit
6
controls the gain of the gain variable LNA
2
so that a received signal level in an output of the switching circuit
10
, which will be described herein later, is set constant.
The variable oscillator
21
is a variable oscillator for outputting a signal having the same local frequency as a carrier frequency used in the communication system in accordance with a frequency control signal from the control unit
13
′ which will be described herein later.
The mixer
8
frequency converts an input signal to a base band signal by a local oscillation frequency supplied from the variable oscillator
21
.
The low pass filter (LPF) bank
9
′ is a bank having LPFs
9
-
1
to
9
-n through which signals of bands used in the communication systems can pass in accordance with the plurality of applicable communication systems.
The switching circuit
10
receives all of outputs from the LPFs
9
-
1
to
9
-n and outputs only the output from the LPF
9
designated in accordance with a switching control signal to designate the LPF
9
to be used on the basis of the communication system selected by the control unit
13
′, which will be described herein later, to the post stage.
The A/D converter
11
converts the output from the selected LPF
9
to a digital signal.
The demodulating unit
12
′ has demodulating functions in the plurality of applicable communication systems and performs demodulation by selecting the demodulating function of the designated communication system in accordance with a demodulating unit control signal to designate the communication system outputted from the control unit
13
′ which will be explained hereinbelow.
The control unit
13
′ outputs the frequency control signal to designate the same local frequency as a carrier frequency used in the communication system to the variable oscillator
21
in accordance with the one communication system arbitrarily selected from the outside, outputs a switching control signal to switch the LPF
9
which is applicable to the communication system to the switching circuit
10
, and further, generates the demodulating unit control signal to designate the communication system to the demodulating unit
12
′.
The operation of the conventional receiver will now be described with reference to FIG.
13
.
In the conventional receiver, the frequency control signal to designate the same local frequency as the carrier frequency used in the communication system is outputted to the variable oscillator
21
by the control unit
13
′ in accordance with the arbitrary communication system selectively inputted from among a plurality of applicable communication systems from the outside. A signal having the designated frequency is oscillated to the mixer
8
by the variable oscillator
21
.
The switching control signal of the LPF
9
suitable to the selected communication system is outputted from the control unit
13
′ to the switching circuit
10
. Further, the demodulating unit control signal to designate the demodulation system based on the selected communication system is outputted from the control unit
13
′ to the demodulating unit
12
′.
A received signal received by the antenna
1
is amplified by the gain variable LNA
2
and the resultant signal is frequency converted to a base band signal by the mixer
8
by using a signal which is outputted from the variable oscillator
21
and which has the same local frequency as the carrier frequency used in the designated communication system. The resultant signal is fetched to all of the LPFs
9
in the LPF bank
9
′. Only bands used in the communication systems are outputted from the LPFs
9
.
In accordance with the communication system selected by the switching circuit
10
, only the output from the LPF
9
designated by the control unit
13
′ is outputted to the A/D converter
11
.
At that time, the signal passed through the switching circuit
10
is fetched to the AGC control unit
6
and the gain of the gain variable LNA
2
is controlled by the AGC control unit
6
so that the level of the signal is held constant.
The signal is converted to a digital signal by the A/D converter
11
and the resultant signal is demodulated by the demodulating unit
12
′ by the communication system selected in accordance with the demodulating unit control signal from the control unit
13
′.
As a conventional technique in which a plurality of communication systems are properly used by using a plurality of band pass filters having different characteristics, for example, there are a “Frequency Band Switching Common Device” proposed in Japanese Patent Application Laid-Open No. 10-247861(1998) disclosed on Sep. 14, 1998 (Applicant: Kokusai Electric Co., Ltd., Inventor: Katsumi Tanaka et al.) and an “Antenna Common Device” proposed in Japanese Patent Application Laid-Open No. 10-41704(1998) disclosed on Feb. 13, 1998 (Applicant: Goyo Electronics Co., Ltd., Inventor: Masahiro Shindo et al.).
Each of those conventional techniques relates to a cellular phone of such a dual mode that an analog system and a digital system share the same frequency band, in which a plurality of filters are used in a reception side.
In the above conventional receiver, however, it is necessary to individually prepare the LPF
9
every corresponding communication system, so that there is a problem that a circuit scale remarkably increases.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a receiver for switching a plurality of communication systems to receive a signal, in which a circuit scale is reduced to intend the miniaturization of a device.
According to the present invention, there is provided a receiver which can be applicable to a plurality of communication systems and which receives a signal by the communication system arbitrarily selected from among the plurality of communication systems, comprising converting means for converting a received signal to a base band signal by a local oscillation frequency based on the selected communication system, setting means for setting a peculiar tap coefficients based on the selected communication system, and synthesizing means for weighting the base band signal with the set tap coefficients to synthesize them, and demodulating means for the signal synthesized by weighting by a demodulation system based on the selected c

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