JPH1198031A - Transmitter and its automatic power control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide automatic power control which maintains transmitter output power at a constant level against the change of a transmission frequency and an ambient temperature with a simple circuit. SOLUTION: Output value in each frequency and temperature of a directional coupler 3 and a detector 4 is stored as target output value in memory 13 when an output of a power amplifier 2 is prescribed value. The gain of a variable gain amplifier is subjected to feedback control by using target output value that corresponds to a temperature sensor 15 and a transmission frequency. Control quantity to the variable gain amplifier 1 when an output becomes the prescribed value and an output of the detector 4 coincides with target value is stored in memory 14 in accordance with the frequency and temperature at that time, and control quantity is read from the memory 14 to perform gain control of the amplifier 1 at the time of a frequency and a temperature to which the storage value is given.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmitter and an automatic power control method for controlling its transmission power.

[0002]

2. Description of the Related Art In a radio transmitter, an automatic power control circuit (APC circuit) is used to keep its transmission power at a predetermined value. FIG. 3 is a block diagram showing a configuration of a transmitter using a conventional automatic power control method. An input transmission signal is amplified by a variable gain amplifier 1 and a power amplifier 2 and then passed through a directional coupler 3. Is output. Part of the output power of the power amplifier 2 is divided by the directional coupler 3 and detected by the detector 4. The DC amplifier 5 amplifies the output of the detector 4 and controls the gain of the variable gain amplifier 1 based on the output, thereby performing feedback control so that the output power of the power amplifier 2 becomes a specified value. However, in order to keep the output power constant over the entire range of the input signal level, the variable gain amplifier 1
When the level of the input signal is lower than a certain threshold value, the DC amplifier 5 has a constant output and stops its amplifying operation. Like that.

[0003]

In the conventional circuit described above, the output voltage of the detector is fed back as a measured value of the transmission power at that time, but the detector 4 and the directional coupler 3 are not fed back.
Changes its characteristics depending on the frequency and the ambient temperature. However, transmitters and the like of portable wireless systems are often used by switching the transmission frequency over a wide range.
In particular, in the case of a portable device or the like, the temperature change in the use environment is large. For this reason, the output of the detector fluctuates, and it becomes difficult to accurately control the transmission power to a predetermined value. Therefore, if changes in frequency and temperature are compensated for by devising the circuit configuration, there is a problem that the circuit configuration and adjustment are inevitably complicated.

[0004] It is an object of the present invention to provide a transmitter and a method for automatically controlling power of a transmitter, which use a microcomputer to compensate for the frequency and temperature characteristics of a feedback circuit with a simple configuration.

[0005]

According to the present invention, there is provided a variable gain amplifier, a power amplifier for amplifying and transmitting the output of the variable gain amplifier, and an output power of the power amplifier. A power sensor to be measured and a target output value obtained by measuring the output of the power sensor when the output of the power amplifier is a predetermined value given in advance for each output frequency and ambient temperature of the power amplifier are stored. A second memory for storing a controlled variable having a value for each of the output frequency and ambient temperature, the values of which are initially all "undefined values"; The control amount of the sensor and the second memory corresponding to the output frequency and the ambient temperature of the power amplifier at the control time point is an “undefined value”, and the control amount of the second memory corresponding to the output frequency and the ambient temperature is When the difference between the target output value of the memory and the power sensor output at that time is equal to or greater than a predetermined error, the control amount at that time is changed so that the difference becomes smaller, and the control amount is changed to the variable gain amplifier. When the difference between the target output value and the power sensor output becomes equal to or smaller than the error by the feedback control, the control amount at that time is set as a corresponding value in the second memory as “ When the control amount of the second memory corresponding to the output frequency and the ambient temperature of the power amplifier at the time of control is not an “undefined value”, the control amount is stored in place of the “undefined value”. And a control means for controlling the gain of the variable gain amplifier.

Further, in the present invention, the output of the power sensor when the output power of the power amplifier reaches a predetermined value given in advance is measured in advance for each output frequency of the power amplifier and the ambient temperature, and is set as a target output value. 1 in the memory, and furthermore, the output frequency and the control amount for each ambient temperature for variably controlling the output power of the power amplifier,
A second memory for storing a control amount whose initial values are all "undefined values", the second memory corresponding to the output frequency and the ambient temperature of the power amplifier at the time of control; Control amount is an “undefined value”, and the difference between the target output value of the first memory corresponding to the output frequency and the ambient temperature and the power sensor output at that time is equal to or greater than a predetermined error. At the time, feedback control is performed such that the control amount at that time is changed so that the difference is reduced and the gain of the power amplifier is controlled by the control amount, and the target output value and the power sensor output are controlled by the feedback control. When the difference is equal to or less than the error, the control amount at that time is stored as a corresponding value in the second memory instead of the “undefined value”, and the power amplifier at the control time is further stored. When the control amount of the second memory corresponding to the output frequency and the ambient temperature is not an “undefined value”, the gain of the power amplifier is controlled by the control amount. I do.

[0007]

Embodiments of the present invention will be described below in detail. FIG. 1 is a block diagram showing a configuration example of a transmitter according to the present invention. In place of a DC amplifier 5 which is a conventional feedback element, A / D converters 10, 16 and a CPU are provided.
11, a D / A converter 12, memories 13 and 14 (both are nonvolatile memories), and a temperature sensor 15 are provided.
Here, the frequencies used in the transmitter are F1, F2,.
Fn, and the ambient temperature range under the operating environment is divided into small ranges, and the representative temperatures in each range are represented by T1, T2,.
m. At this time, the memory 13 stores the ambient temperature in a small range represented by the representative temperature Tj when the operating frequency Fi and the ambient temperature Tj are used. The output Pij of the detector 4 when the transmission power is at a predetermined value.
(1 ≦ i ≦ n, 1 ≦ j ≦ m) are measured and stored in advance. This is used as a target output value of the detector 4.

On the other hand, when a target output value Pij at the operating frequency Fi ambient temperature Tj is given to the memory 14,
The magnitude Dij of the control signal for controlling the gain of the variable gain amplifier 1 so that the transmitter output becomes a predetermined value is stored during the actual operation as described later, but the initial values are all "undefined values". ".

The operation of the automatic power control method in the transmitter having the above configuration will be described with reference to the flowchart shown in FIG. The processing shown in this flowchart is executed by the CPU 11, and when the control time comes, the detector 4
The measurement signal P obtained by digitizing the output of the A / D converter 10 is taken in (steps 201 and 202). Then, this measurement signal P is compared with a predetermined threshold value P0,
If P0 or less, no control processing is performed (step 2).
03). This is because, as described in the related art, the control for keeping the output constant is not performed in the range where the input signal is small.

If P> P0 in step 203, the current operating frequency Fi is fetched from a control unit (not shown) of the transmitter, and the output of the temperature sensor 15 is A / D
The ambient temperature T digitally obtained by the converter 16 is taken in (step 204). Next, this ambient temperature T is converted from the value into the representative temperature Tj, and the control signal D corresponding to the operating frequency Fi and the ambient temperature Tj is referred to the memory 14.
Check whether ij is “undefined value” (steps 204 and 20)
5). Since Dij of the memory 14 is initially all "undefined values", at this time, the above-mentioned Fi, Tj
Is read out (step 20).
6) It is checked whether the difference between this and the actual measurement signal P captured in step 202 is smaller than a predetermined error δ (step 207). If the difference is not smaller than the error δ, the control signal up to that time is set to a value Dij modified so that the gain of the variable gain amplifier 1 increases or decreases according to whether P> Pij or P <Pij (step 208), and outputs it to the variable gain amplifier 1 (step 211).

If the feedback control is repeated in this manner, the difference | P-Pij |
Gradually decreases, and eventually becomes equal to or smaller than the error δ. This state means that the output of the transmitter is almost at a predetermined value, as can be seen from the way of giving the target output value Pij of the memory 13. Therefore, when the condition of step 207 is satisfied, the value of the control signal Dij at that time is stored in the memory 14
Is stored as a value corresponding to the operating frequency Fi and the ambient temperature Tj (step 209), and the stored value is output as it is (step 211).

As described above, when the operation is repeated, the control signal Dij of the memory 14 gradually decreases from the "undefined value" to the required control signal corresponding to the operating frequency and the ambient temperature. To go. This is a learning operation for storing a control signal necessary for the usage environment. If Dij has already been given to the working frequency Fi and the ambient temperature Tj fetched in a certain control cycle and they are no longer "undefined values", then steps 205 to 21 are executed.
0, and the given control signal Dij is stored in the memory 1
4 and output (steps 210 and 21).
1). That is, at this time, steps 207, 208, 21
No novel control by a feedback loop via 1 becomes necessary, and a control signal Dij necessary to keep the output at a predetermined value is immediately obtained, and the response speed of the control is increased.

[0013]

According to the present invention, an inexpensive digital circuit centered on a microprocessor can be used without using a complicated, difficult to adjust and expensive directional coupler or detector.
There is an effect that a transmitter having a stable output, which is not affected by the operating frequency and the ambient temperature, can be realized, and further, there is an effect that transmission power control with a quick response can be performed by the learning effect.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a transmitter according to the present invention.

FIG. 2 is a flowchart showing an operation of automatic transmission power control in the transmitter of FIG.

FIG. 3 is a block diagram illustrating a configuration example of a conventional transmitter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Variable gain amplifier 2 Power amplifier 3 Directional coupler 4 Detector 11 CPU 13 Memory 14 Memory 15 Temperature sensor

Claims (2)

[Claims] 1. A variable gain amplifier, a power amplifier for amplifying and transmitting an output of the variable gain amplifier, a power sensor for measuring an output power of the power amplifier, and a predetermined value given by the output of the power amplifier in advance A first memory for storing a target output value obtained by measuring the output of the power sensor at each output frequency and ambient temperature of the power amplifier in advance at the time of: A second memory for storing a controlled variable whose values are initially all "undefined values"; an ambient temperature sensor; and an output frequency and an ambient temperature of the power amplifier at the time of control. The difference between the target output value of the first memory corresponding to the output frequency and the ambient temperature and the power sensor output at that time when the corresponding control amount of the second memory is an “undefined value” Is greater than or equal to a predetermined error, feedback control is performed such that the control amount at that time is changed so as to reduce the difference and the control amount is output to the variable gain amplifier, and the target output value is obtained by the feedback control. And when the difference between the power sensor output and the power sensor output is equal to or less than the error, the control amount at that time is stored as a corresponding value in the second memory instead of the “undefined value”, and further at the control time, Control means for controlling the gain of the variable gain amplifier with the control amount when the control amount of the second memory corresponding to the output frequency and the ambient temperature of the power amplifier is not an “undefined value”. A transmitter, comprising: 2. The power sensor output when the output power of the power amplifier reaches a predetermined value given in advance is measured in advance for each output frequency and ambient temperature of the power amplifier, and is stored in the first memory as a target output value. In order to store the control amount for each of the output frequency and the ambient temperature for variably controlling the output power of the power amplifier, all of the initial values of which are "undefined values". A control amount of the second memory corresponding to the output frequency and the ambient temperature of the power amplifier at the time of control is an “undefined value”, and the output frequency and the ambient temperature are controlled. When the difference between the target output value of the first memory corresponding to the above and the power sensor output at that time is equal to or greater than a predetermined error, the control amount at that time is changed so that the difference becomes smaller, and Performs feedback control to control the gain of the power amplifier, and when the difference between the target output value and the power sensor output becomes equal to or smaller than the error by the feedback control, the control amount at that time is stored in the second memory. Is stored in place of the “undefined value”, and the control amount of the second memory corresponding to the output frequency and the ambient temperature of the power amplifier at the time of control is not the “undefined value”. And controlling the gain of the power amplifier using the control amount when the power amplifier is controlled.