Amplifiers – With control of power supply or bias voltage – With control of input electrode or gain control electrode bias
Reexamination Certificate
2003-01-29
2004-09-07
Nguyen, Patricia (Department: 2817)
Amplifiers
With control of power supply or bias voltage
With control of input electrode or gain control electrode bias
C330S134000, C330S279000, C455S126000
Reexamination Certificate
active
06788138
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a transmission power control circuit, and more particularly, to a transmission power control circuit controlling a transmission power of a transmitting wave using a detector.
BACKGROUND ART
Generally, in a prior art wireless terminal apparatus such as a portable telephone, a feedback control using a detector was performed to control a transmission power of a transmitting wave output.
Referring to
FIG. 24
, a transmission power control circuit
10
according to a prior art technique included: a variable gain amplifier
1
; a distributor
2
; a detecting circuit
3
; a reference voltage generating circuit
4
; and a power control section
5
.
Variable gain amplifier
1
amplifies a transmission signal with a gain according to a given control voltage V
C
to generate a transmitting wave output. Distributor
2
takes out part of a transmission power P
OUT
of a transmitting wave output. Detecting circuit
3
detects part of the transmission power obtained by distributor
2
and generates a detection voltage V
DET
according to transmission power P
OUT
. That is, detection voltage V
DET
changes according to transmission power P
OUT
.
Reference voltage generating circuit
4
generates a reference voltage V
REF
corresponding to a designated level of transmission power P
OUT
. Power control section
5
generates control voltage V
C
according to a negative-fed back voltage K
0
·V
DET
obtained by multiplying detection voltage V
DEF
from detecting circuit
3
by a detection voltage feed-back ratio K
0
, and to V
REF
from reference voltage generating circuit
4
, based on the following equation (1).
V
C
=V
REF
−K
0
·V
DET
(1)
By detecting part of transmission power P
OUT
of a transmitting wave output using distributor
2
and detecting circuit
3
in such a way to further apply negative-feedback, there can be performed close loop control to cause transmission power P
OUT
and a designated value P
CMD
of transmission power to coincide with each other.
To be concrete, in a case where transmission power P
OUT
is higher than a designated level, detection voltage V
DET
becomes higher to, in response to this, lower control voltage V
C
outputted from power control section
5
. As a result, a gain of variable gain amplifier
1
is set small, which works so as to reduce transmission power P
OUT
. To the contrary, in a case where transmission power P
OUT
is set to a value lower than a designated value, in response control voltage V
C
is set high, which works so as to raise transmission power P
OUT
to be large. By performing such a close loop control, control can be executed so that an error between transmission power P
OUT
of a transmitting wave output and a designated level is reduced to the least possible value.
Referring to
FIG. 25
, reference voltage generating circuit
4
includes a transmission power designating section
7
; a control section
8
; and D/A converter
9
. Transmission power designated value P
CMD
indicating a designated level of a transmission power is converted to reference voltage V
REF
by control section
8
and D/A converter
9
. That is, reference voltage V
REF
is set in correspondence to transmission power designated value P
CMD
.
Power control section
5
includes: an operational amplifier
10
; and resistance elements
11
and
12
. Detection voltage V
DET
from detecting circuit
3
is transmitted to a node N
0
corresponding to the inverted input terminal (−terminal) of operational amplifier
10
through resistance element
12
. Reference voltage V
REF
from D/A converter
9
is inputted to the non-inverting input terminal (+terminal) of operational amplifier
10
. Resistance element
11
is coupled between the inverted input terminal and the output terminal of operational amplifier
10
. Therefore, detection voltage feed-back ratio K
0
shown in
FIG. 28
is determined according to a ratio between resistance elements
11
and
12
.
In such a way, in an architecture of transmission power control circuit
10
according to a prior art technique, it was a precondition that detecting circuit
3
can output a detection voltage corresponding to a transmission power all over a dynamic range of transmission power P
OUT
. However, in a case where a dynamic range of transmission power is set wide, generally, it is rather difficult to broaden a measurable range of detecting circuit
3
than to broaden a dynamic range of a gain of variable gain amplifier
1
. With a wider measurable range of detecting circuit
3
, a detecting circuit tends to become complex and up-scaled, resulting in a high cost.
DISCLOSURE OF THE INVENTION
It is an object of the present invention is to provide a transmission power control circuit capable of ensuring a wide dynamic range of transmission power using a general inexpensive detecting circuit having a simple architecture.
According to the present invention, a transmission power control circuit includes: a variable gain amplifier for amplifying a transmission signal with a gain according to a control voltage to output a transmitting wave; a distributing section for taking out part of the transmitting wave; a detecting section for detecting an output of said distributing section to generate a detection voltage corresponding to a transmission power of the transmitting wave; and a control section receiving an electrical signal indicating a designated level of the transmission power and the detection voltage to set the control voltage. The control section performs a changeover between a first control state setting the control voltage by close loop control according to the detection voltage negative-fed back, multiplied by a feedback ratio and a reference voltage corresponding to the designated level, and a second control state setting the control voltage by open loop control according to the designated level, according to a relationship between a measurable power range of the detecting section and the transmission power.
The control section preferably performs the changeover between the first and second control states according to the detection voltage.
Furthermore, the control section preferably performs the changeover between the first and second control states according to a designated level of the transmission power.
Moreover, the control section preferably includes: a first signal converting section converting a detection voltage to a first digital signal; a control computing section receiving a second digital signal indicating a designated level of a transmission power and the first signal to perform a digital computing for setting a control voltage based on one of the first and second control state, which is selected according to comparison between the first and second digital signals; and a second signal converting section converting an output of the control computing section to an analog signal to generate the control voltage.
In such a transmission power control circuit, relationships between a designated level of a transmission power and a reference voltage are not set separately inside and outside a measurable range of the detecting circuit but a dynamic range of a transmission power can be widely ensured using a detecting section with a general architecture.
Furthermore, the control section preferably includes: a feedback ratio adjusting section for gradually reducing a feedback ratio from a prescribed level as a transmission power comes closer to a non-measurable power range in a prescribed boundary range between a measurable power range and non-measurable power range of a detection section in the first control state.
As a result, a sudden change can be prevented in a transmission power in a prescribed boundary range corresponding to a changeover region between the first control state and second control state.
The feedback ratio adjusting section more preferably changes a feedback ratio according to a detection voltage.
The feedback ratio adjusting section more preferably changes a feedback ratio according to a designated level of a tran
Mitsubishi Denki & Kabushiki Kaisha
Nguyen Patricia
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
LandOfFree
Transmission power control circuit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Transmission power control circuit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Transmission power control circuit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3255933