Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
2002-03-22
2004-12-14
Urban, Edward F. (Department: 2685)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S069000, C455S101000, C455S114200, C455S127200, C375S299000, C375S315000
Reexamination Certificate
active
06832097
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is base upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-086230, filed Mar. 23, 2001, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radio communication apparatus for controlling a transmission power in a variable way in accordance with a reception power and a transmission power controlling apparatus used in the radio communication apparatus.
2. Description of the Related Art
FIG. 1
is a block diagram showing a radio communication apparatus provided on an existing mobile telephone terminal.
In the radio communication apparatus, a transmit signal applied from a modulator, not shown, is processed by a variable amplifier
1
, up-converter
2
and bandpass filter
3
and a power amplifier
4
to provide a transmit signal of a state capable of radio transmission. The transmit signal is passed through a duplexer
5
and antenna switching unit
6
normally to a standard antenna
7
where it is radiated as a radio wave.
An external antenna
17
can be connected to the antenna switching unit
6
. Whether or not the external antenna
17
is connected is monitored by an antenna detection circuit
8
. If the external antenna
17
is connected, the external antenna
17
is selected by the antenna switching unit
6
under control of the antenna detection circuit
8
. With the external antenna
17
thus connected, the transmit signal outputted from the power amplifier
4
is supplied through the duplexer
5
and antenna switching unit
6
to the external antenna
17
where it is radiated as a radio wave.
A radio wave is received by the standard antenna
7
or external antenna
17
as a received signal. The received signal is sent through the antenna switching unit
6
and duplexer
5
to a receiver
9
. The received signal is converted to a digital-like baseband signal by the receiver
9
and an A/D converter
10
and then supplied to a baseband processing section not shown.
The transmission power can be controlled by a gain of the variable amplifier
1
and it is basically determined by a reception power. That is, it is considered that a greater reception power ensures a better state of a radio channel. Therefore, even if the transmission power is made lower, an adequate communication quality can be maintained and the transmission power can be lowered. If, on the other hand, a reception power is smaller, then the transmission power is increased so as to secure an adequate communication quality.
Therefore, a designation value generation section
11
monitors an output of the A/D converter
10
and determines a gain capable of achieving a transmission power corresponding to the reception power. A gain control section
12
basically outputs a gain controlled value for allowing an amplification to be done, by the variable amplifier, with the gain determined by the designation value generation section
11
. Then, the gain controlled value is converted by the D/A converter
13
from a digital form to an analog version to obtain a gain control signal. The gain control signal is applied to a variable amplifier
1
.
By a first loop thus constituting an open loop, a basic transmission power control is carried out.
If, however, the transmission power is so controlled by the first loop only, when a reception power involves a largely lowered state, control acts toward largely increasing a transmission power. And there is a risk that the transmission power will exceed a maximum transmission power determined legally or from a standpoint of a system involved.
In order to stabilize the transmission power to a maximal transmission power, therefore, a second loop is provided which comprises a detection circuit
14
, reference circuit
15
and comparator
16
. If a gain determined by the designation value generation section
11
exceeds a given threshold value, the transmission power control by the first loop is stopped and the transmission power control by the second loop is carried out.
As a result, the reception power/transmission power relation is as shown in FIG.
2
and the transmission power is restricted by the maximum transmission power.
FIG. 2
shows an example in which the maximal transmission power is 21 dBm.
The gain determinations by the first and second loops are done under a condition based on the use of the standard antenna
7
in either case. However, there are often the cases where a loss differ between the standard antenna
7
and the external antenna
17
. Stated in more detail, the external antenna
17
is often greater in a loss than the standard antenna
7
from the standpoint of its longer cable length, etc. Under the situation above, even if the gain of the variable amplifier
1
is the same, there occurs the difference in transmission power between using the standard antenna and using the external antenna
17
.
In the case of performing the transmission power control by the first loop, the difference in the loss appears also in the reception power due to the difference between the antennas used. In order to compensate the difference in the loss, the setting of the gain is carried out. Stated in more detail, as shown in
FIG. 2
, suppose that the reception power at the time of using the standard antenna
7
is P
RX
and hence the operation point is located at a point A and control is made such that the transmission power becomes 16 dBm. In this case, suppose that the external antenna
17
is connected and the loss are increased to 2 dBm. Then the reception power detected by the designation value generation section
11
is lowered to P
RX
−2 as indicated by an arrow B. And the designation value generation section
11
increases a gain so as to increase the transmission power to 18 dBm as indicated by an arrow C. And the operation point is varied to a point D. As a result, an output level from the variable amplifier
1
is increased up to a level corresponding to the transmission power of 18 dBm. Since a loss by the external antenna
17
is involved as indicated by an arrow E, the actual transmission power becomes 16 dm, so that the operation is performed at the same point A as at the time of using the standard antenna
7
.
As shown in
FIG. 3
, suppose that the operation point at the time of using the standard antenna
7
is located at a point F near a threshold value “21”. In this state, suppose that the external antenna
17
is connected and the loss is 2 dBm increased. Then the reception power detected by the designation value generation section
11
is lowered to P
RX
−2 as indicated by an arrow G. In this case, the designation value generation section
11
tries to increase a gain so as to increase the transmission power to 22 dBm, but it exceeds the threshold value. And the second loop operates. That is, the transmission power at the time of using the standard antenna
7
is suppressed under the action of the second loop to a gain of 21 dBm and the operation point becomes a point I. Then, as indicated by an arrow J, a loss by the external antenna
17
is involved and the actual transmission power becomes 19 dBm. And the operation is done at an operation point K different from that at the time of using the standard antenna
7
. For this reason, the transmission power is lowered.
As set out above, the conventional apparatus was not able to properly control the transmission power at all times.
BRIEF SUMMARY OF THE INVENTION
The present invention is achieved with the above-mentioned situations in view and, accordingly, the object of the present invention is to provide an apparatus which can properly control a transmission power even if either of a standard first antenna and external second antenna is used.
In one aspect of the present invention, there is provided a radio communication apparatus for varying a transmission power in accordance with a reception power in a range not exceeding a predetermined maximum transmission power, comprising: a variable amplifier
Aisaka Hideki
Niwa Masanori
Phan Huy
Urban Edward F.
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