Radio circuit apparatus and radio communication equipment

Details Radio circuit apparatus and radio communication equipment Radio circuit apparatus and radio communication equipment

1999-07-26

2001-05-01

Nguyen, Lee (Department: 2746)

Telecommunications

Transmitter and receiver at same station

With transmitter-receiver switching or interaction prevention

C455S073000, C455S076000, C455S078000, C455S086000

Reexamination Certificate

active

06226499

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to miniaturizing the entirety of a radio circuit apparatus such as a cellular phone utilized in a high frequency radio communication system which employs the time division multiplex system.
2. Related Art of the Invention
In recent years, along with the development of mobile communication related markets such as that of cellular phones, a variety of application products utilizing a radio circuit apparatus appear in the market, and the miniaturization of radio circuit apparatus is becoming more and more important.
FIG. 5
shows an example of the structure of a conventional radio circuit apparatus. In this figure,
401
is a reference oscillator,
402
is a first local oscillator,
403
is a second local oscillator,
404
is a transmitting circuit,
405
is a receiving circuit,
406
is a shared device and
407
is an antenna. The output signal of the reference oscillator
401
is inputted to the first local oscillator
402
and the second local oscillator
403
. And the output frequency of the second local oscillator
403
is fixed when the radio circuit apparatus is transmitting and when it is receiving, respectively.
In the transmitting circuit
404
,
411
is a modulator,
412
is a filter,
413
is a transmitted frequency converter,
414
is a filter and
415
is a power amplifier. When the radio circuit apparatus is transmitting, the modulator
411
modulates the output signal of the second local oscillator
403
with a base band signal (a modulated signal).
The output signal of the modulator
411
is inputted into the transmitted frequency converter
413
after being reduced in the unnecessary frequency components by the filter
412
, and converted into a frequency of a transmitted signal by the output signal of the first local oscillator
402
. The output signal of the transmitted frequency converter
413
is amplified at the power amplifier
415
after being reduced in the unnecessary components by the filter
414
, and transmitted from the antenna
407
through the shared device
406
.
In the receiving circuit
405
,
421
is a low noise amplifier,
422
is a first received frequency converter,
423
is a filter and
424
is a second received frequency converter. A signal received on the antenna
407
is inputted into the low noise amplifier
421
through the shared device
406
. The output signal of the low noise amplifier
421
is inputted into the first frequency converter
422
, and converted to the first intermediate frequency by the output signal of the first local oscillator
402
. The output signal of the first frequency converter
422
is reduced in the unnecessary frequency components by the filter
423
. The output signal of the filter
423
is inputted into the second frequency converter circuit
424
to be converted to the second intermediate frequency by the output signal of the second local oscillator
403
.
In the above mentioned structure, however, when the radio circuit apparatus is transmitting, a harmonic component of the output signal from the second local oscillator
403
is generated in the transmitted frequency band, and the harmonic component tend to become an unnecessary frequency component for cellular phones close by. To prevent this problem, a large number of filters need to be provided, and as a result, the radio circuit apparatus as a whole would be bulky.
SUMMARY OF THE INVENTION
The present invention has a purpose, in light of the above problems, to provide a radio circuit apparatus and radio communication equipment to be able to be miniaturized without generating an unnecessary frequency component within the transmitted frequency band.
The first invention of the present invention (corresponding to claim
1
) is a radio circuit apparatus utilized in a time division multiple access system characterized by comprising:
a local oscillator,
a frequency divider,
a modulator,
a transmitted frequency converter,
a first received frequency converter, and
a second received frequency converter,
wherein, when the radio circuit apparatus is transmitting, an output signal of the local oscillator is inputted to the transmitted frequency converter and is inputted into the frequency divider and then divided into a predetermined dividing number to be a signal of a transmitted intermediate frequency; the modulator modulates the signal of the transmitted intermediate frequency with a modulating signal to be outputted to the transmitted frequency converter; and the transmitted frequency converter converts an output signal of the modulator to a transmitted signal by the output signal of the local oscillator,
when the radio circuit apparatus is receiving, an output signal of the local oscillator is inputted into the first received frequency converter; the first received frequency modulator outputs an received signal to the second received frequency converter after converting the received signal into a signal of a first received intermediate frequency by the output signal of the local oscillator; the second received frequency converter converts the signal of the first received intermediate frequency into a signal of the second received intermediate frequency by a signal of a fixed frequency,
output frequencies of the local oscillator are switched between when the radio circuit apparatus is transmitting and when the radio circuit apparatus is receiving.
The second invention of the present invention (corresponding to claim
8
) is a radio communication equipment characterized by comprising;
a radio circuit apparatus according to the present invention, a power amplifier, a shared device and an antenna, wherein the output signal of the transmitted frequency converter is inputted to the power amplifier to be amplified,
when the radio circuit apparatus is transmitting, an output signal of the power amplifier is selected by the shared device to be outputted from the antenna,
when the radio circuit apparatus is receiving, a received signal inputted from the antenna is selected by the shared device to be inputted into the first received frequency converter.


REFERENCES:
patent: 4812783 (1989-03-01), Honjo et al.
patent: 5428824 (1995-06-01), Kasai
patent: 5483679 (1996-01-01), Sasaki
patent: 5689819 (1997-11-01), Nishimura et al.
patent: 5793819 (1998-08-01), Kawabata
patent: 5825813 (1995-03-01), Na
patent: 5831483 (1997-01-01), Fukuda
patent: 5892405 (1997-04-01), Kamikubo et al.
patent: 5929677 (1997-11-01), Murata

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