Telecommunications – Transmitter – Power control – power supply – or bias voltage supply
Reexamination Certificate
1999-03-16
2001-05-29
Maung, Nay (Department: 2744)
Telecommunications
Transmitter
Power control, power supply, or bias voltage supply
C455S091000, C455S115200
Reexamination Certificate
active
06240279
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a transmission power control apparatus used for a transmission power control in a CDMA (code division multiple access) radio communication apparatus, for example, and a transmission power control unit used in such a transmission power control apparatus.
2. Description of the Related Art
For example, in a CDMA radio communication apparatus, the transmission power is controlled in accordance with the reception power.
FIG. 6
shows the configuration of a conventional radio transmitter having a function of performing such a transmission power control.
The radio transmitter is composed of an AGC amplifier
1
, a power amplifier
2
, and an antenna
3
.
In a data transmitting operation, the AGC amplifier
1
and the power amplifier
2
are activated in response to a burst-on signal as a transmission request. A transmission signal is amplified by the AGC amplifier
1
and the power amplifier
2
and then supplied to the antenna
3
. The transmission signal is transmitted from the antenna
3
.
In the above radio transmitter, the transmission power control is performed in such a manner that the gain of the AGC amplifier
1
is varied in accordance with a power control signal that is generated through a calculation that is performed by a receiving section (not shown) based on the reception power. The gain of the power amplifier
2
is fixed. However, since the AGC amplifier
1
can provide a negative gain, a total gain that is lower than the gain of the power amplifier
2
can be obtained.
For example, if the gain of the power amplifier
2
is 30 dB and the dynamic range Of the gain of the AGC amplifier
1
is −20 to 50 dB, the dynamic range of the total gain of the radio transmitter is 10-80 dB.
FIG. 7
shows graphs showing relationships between the reception power and the gain of an AGC amplifier
1
, the gain of a power amplifier
2
, and the total gain in the radio transmitter of FIG.
6
. As shown in
FIG. 7
, when the necessary total gain is relative low (i.e. the reception power is low level), the gain of the AGC amplifier
1
is negative because the gain of a power amplifier
2
is fixed.
FIG. 8
shows a relationship between the transmission power and the reception power in the above radio transmitter. In a range where the transmission power is relatively high, the power consumption decreases as the transmission power decreases. However, in a range where the transmission power is lower than a certain value, almost no decrease occurs in the power consumption even if the transmission power decreases.
The above fact means that unduly high power is consumed in the range where the transmission power is low. This is not preferable particularly in mobile communication apparatus (e.g. cellular telephone) or the like that use a battery whose capacity is limited. It causes the reduction of available speech time. Particularly, if the mobile communication apparatus is used as the CDMA radio communication apparatus (e.g. CDMA cellular telephone), this is very serious problem because the CDMA system requires wider dynamic range than other digital system like PDC (Japanese Personal Digital Cellular). So, if the consumed power in the range where the transmission is low becomes reduced, the available speech time is expected to be much longer.
As described above, conventionally, the transmission power is controlled by adjusting the gain of a variable gain amplifier while a certain gain is secured by a fixed gain amplifier. This causes a problem that a decrease in transmission power causes almost no decrease in power consumption in a range where the transmission power is lower than a certain value. It means that the power utilization efficiency is low.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above circumstances in the art, and an object of the invention is therefore to provide a transmission power control apparatus which can decrease the power consumption as the transmission power decreases and can increase the power utilization efficiency, as well as a transmission power control unit used in such a transmission power control apparatus.
To attain the above object, according to a first aspect of the invention, there is provided a transmission power control apparatus comprising variable gain amplifying means such as an AGC amplifier for amplifying an input signal at a specified gain: fixed gain amplifying means such as a power amplifier connected in series to the variable gain amplifying means, for amplifying, at a fixed gain, the input signal amplified by the variable gain amplifying means, the variable gain amplifying means and the fixed gain amplifying means being for adjusting a level of a transmission signal to control transmission power; bypassing means constituted of two switches and a bypass line, for example, for forming a bypass route for transmitting the transmission signal so as to bypass the fixed gain amplifying means; and gain control means constituted of a processing device and an AND gate, for example, for specifying the gain of the variable gain amplifying means so that the transmission power has a necessary value, for causing the bypassing means to form the bypassing route if the necessary value of the transmission power is smaller than a predetermined threshold value, and for, if necessary, specifying the gain of the variable gain amplifier at a value that includes a gain part that the fixed gain amplifying means should bear if it were not bypassed, in a state that the bypass route is formed by the gain control means.
With the above configuration, when the necessary transmission power is greater than the predetermined threshold value, the variable gain amplifying means and the fixed gain amplifying means provides a sufficiently large gain. When the necessary transmission power is smaller than the predetermined threshold value, the bypassing means formed the bypass route and separates the fixed gain amplifying means. A necessary gain is obtained by the variable gain amplifying means alone, whereby the power consumption of the fixed gain amplifying means is reduced.
According to a second aspect of the invention, in the transmission power control apparatus according to the first aspect, a predetermined, first threshold value and a predetermined, second threshold value that is greater than the first predetermined value are set as the predetermined threshold value: and the gain control means causes the bypassing means to form the bypass route in response to an event that the necessary value of the transmission power becomes smaller than the first threshold value in a state that the bypass route is not formed, and causes the bypassing means to finish formation of the bypass route in response to an event that the necessary value of the transmission power becomes greater than the second threshold value in a state that the bypass route is formed.
According to a third aspect of the invention, in the transmission power control apparatus according to the first aspect, a predetermined, first threshold value and a predetermined, second threshold value that is greater than the first value are set as the predetermined threshold value; and the gain control means specifies the gain of the variable gain amplifying means in accordance with reception power in a receiving device, causes the bypassing means to form the bypass route in response to an event that the reception power becomes greater than a value corresponding to the first threshold value in a state that the bypass route is not formed, and causes the bypassing means to finish formation of the bypass route in response to an event that the reception power becomes smaller than a value corresponding to the second threshold value in a state that the bypass route is formed.
According to the second and third aspects of the invention, the fixed gain amplifying means is connected and disconnected with hysteresis, which prevents the fixed gain amplifying means from being connected and disconnected repeatedly at a high freq
Hirai Katsumi
Nitta Tatsuo
Banner & Witcoff , Ltd.
Kabushiki Kaisha Toshiba
Maung Nay
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