Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
2000-12-21
2004-03-02
Maung, Nay (Department: 2684)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S114200, C455S063100, C370S206000, C375S146000
Reexamination Certificate
active
06701163
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a base station apparatus and a method for suppressing a peak power for a cellular system of an automobile telephone, a portable telephone and the like.
BACKGROUND ART
A cellular system for an automobile telephone, a portable telephone and the like, the demand of which is rapidly increasing in recent years, is a system where a base station is located at the center of each cell and the base station and one or more communication terminals in the cell simultaneously perform radio communication in multiple access.
A code division multiple access (CDMA) system, one of the multiple access systems, is a system where a signal spread in a wide band that is obtained by multiplying modulated information data by a spreading code is transmitted from the transmission side and the information data is demodulated on the reception side by performing the despreading of a received signal by multiplying it by the same spreading code as that on the transmission side at the same timing as that on the transmission side. Because each user can utilize the same frequency band in the CDMA system, the increase of channel capacity can be schemed. Consequently, the CDMA system is widely noticed for a cellular system.
However, each user utilizes the same frequency band at the same time in the CDMA system, a base station should transmit a plurality of signals by multiplexing them. Consequently, the CDMA system has a problem that a transmission amplitude at a peak time becomes very high in comparison with an average amplitude. For preventing the distortion of a transmission signal even at the time of a peak, an amplifier having a large linear operating range should be used. Then, a high voltage power source is needed, which makes the apparatus larger.
Accordingly, for overcoming the problem, methods for suppressing the transmission amplitude at a peak time have conventionally been examined. There is a conventional base station disclosed in Japanese laid-open patent publication Hei 10-126309 as a base station that can suppress the transmission amplitude at a peak time.
FIG. 1
is a block diagram showing the structure of a conventional base station. Incidentally, in the following description, a case where QPSK modulation is used in primary modulation will be described as an example. Furthermore, it is supposed that a base station is performing radio communication with three users A-C.
In
FIG. 1
, a modulation section
1
performs the QPSK modulation of a transmission signal A to be transmitted to a user A, and outputs an in-phase component and an orthogonal component of the signal after the modulation to a spreading section
4
. Similarly, a modulation section
2
performs the QPSK modulation of a transmission signal B to be transmitted to a user B, and outputs an in-phase component and an orthogonal component of the signal after the modulation to a spreading section
5
. A modulation section
3
performs the QPSK modulation of a transmission signal C to be transmitted to a user C, and outputs an in-phase component and an orthogonal component of the signal after the modulation to a spreading section
6
.
The spreading section
4
performs spread processing in which a peculiar spreading code is multiplied to the transmission signal A modulated in the QPSK modulation, and outputs the spread signal to a multiplexing section
7
. Similarly, the spreading section
5
performs spread processing in which a peculiar spreading code is multiplied to the transmission signal B modulated in the QPSK modulation, and outputs the spread signal to the multiplexing section
7
. The spreading section
6
performs spread processing in which a peculiar spreading code is multiplied to the transmission signal C modulated in the QPSK modulation, and outputs the spread signal which has been performed by the filter
10
, and when the measured value is larger than a previously set permissible amplitude value, the amplitude controlling section
13
controls the attenuation amount of the in-phase component of a transmission signal at an attenuation section
17
. Similarly, the amplitude controlling section
14
measures the amplitude value of a signal, the band restriction of which has been performed by the filter
11
, and when the measured value is larger than a previously set permissible amplitude value, the amplitude controlling section
14
controls the attenuation amount of the orthogonal component of a transmission signal at an attenuation section
18
.
A delay section
15
delays a signal of an in-phase component outputted from the multiplexing section
7
for a time equal to a necessary time for a series of attenuation amount operating processing performed in the interpolation section
8
, the filter
10
and the amplitude controlling section
13
, and the delay section
15
outputs the delayed signal to the attenuation section
17
. Similarly, a delay section
16
delays a signal of an orthogonal component outputted from the multiplexing section
7
for a time equal to a necessary time for a series of attenuation amount operating processing performed in the interpolation section
9
, the filter
11
and the amplitude controlling section
14
, and the delay section
16
outputs the delayed signal to the attenuation section to the multiplexing section
7
.
The multiplexing section
7
divides spread signals outputted from the spreading sections
4
-
6
into in-phase components and orthogonal components to add them respectively. The multiplexing section
7
then outputs an in-phase component signal to an interpolation section
8
and a delay section
15
, and outputs an orthogonal component signal to an interpolation section
9
and a delay section
14
.
The interpolation sections
8
and
9
increase their sampling rates by M (M is a natural number) times, and perform zero-insertion interpolation where zero is inserted at a sampling point where no signal exists, respectively.
A filter
10
performs the band restriction of an interpolated signal outputted from the interpolation section
8
by means of a filter coefficient set in a filter coefficient memory
12
previously, and outputs the signal after the band restriction to an amplitude controlling section
13
. Similarly, a filter
11
performs the band restriction of an interpolated signal outputted from the interpolation section
9
by means of a filter coefficient set in the filter coefficient memory
12
previously, and outputs the signal after the band restriction to an amplitude controlling section
14
.
The amplitude controlling section
13
measures the amplitude value of a signal, the band restriction of
18
.
The attenuation section
17
attenuates the amplitude of the in-phase component of a transmission signal under the control of the amplitude controlling section
13
. Similarly, the attenuation section
18
attenuates the amplitude of the orthogonal component of a transmission signal under the control of the amplitude controlling section
14
.
Interpolation sections
19
and
20
increase their sampling rates by M (M is a natural number) times, and perform zero-insertion interpolation where zero is inserted at a sampling point where no signal exists, respectively.
A filter
21
performs the band restriction of an interpolated signal outputted from the interpolation section
19
by means of a filter coefficient set in the filter coefficient memory
12
previously, and outputs the signal after the band restriction to a D/A conversion section
23
. Similarly, a filter
22
performs the band restriction of an interpolated signal outputted from the interpolation section
20
by means of a filter coefficient set in the filter coefficient memory
12
previously, and outputs the signal after the band restriction to a D/A conversion section
24
.
The D/A conversion section
23
converts a transmission signal of a digital in-phase component outputted from the filter
21
to an analog signal. Similarly, the D/A conversion section
24
converts a transmission signal of a digital orthogonal component outputted from the filter
22
Gantt Alan T.
Matsushita Electric - Industrial Co., Ltd.
Maung Nay
Stevens Davis Miller & Mosher LLP
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