JP2000278063A - Power amplifier circuit and method for controlling its transmission output - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a power amplifier circuit used for frequency hopping system or the like that controls a high frequency signal whose frequency changes over a broad frequency band and having notches and peaks so as to make its output level constant and amplifies the resulting high frequency signal. SOLUTION: In this transmission output control method, an output level characteristic of the power amplifier circuit with respect to frequency and temperature is measured in advance and data to correct the fluctuation are stored in a table 11 for each set of frequencies and temperatures in pairs. A CPU 10 retrieves the table 11 by using a frequency signal and a detected temperature as a key and gives a power control signal CP to a variable attenuator 2 to allow the attenuator 2 to control a transmission output level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power amplifier circuit and a transmission output control method thereof, and more particularly to a power amplifier circuit which is turned on / off by a time slot and which is suitable for a system which is switched between a plurality of frequency channels and its transmission. It relates to an output control method.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a configuration example of a transmission power amplifier circuit used in a frequency hopping system (FH system), a TDMA system, or the like. An input high-frequency signal RF is determined by the system. Each time slot generally has a signal of a different frequency channel. Therefore, a circuit from the preamplifier 1 to the directional coupler 4 has a characteristic of operating in a wide band. Also, high-frequency signals do not always exist in all time slots. The transmission request signal T is a signal that turns off the operations of the preamplifier and the power amplifiers 1 and 3 when only the reception operation is performed.

The high-frequency signal amplified by the preamplifier 1 and the power amplifier 3 is transmitted from an antenna 5, but a part of the power Pf is branched by a directional coupler 4 and its level is detected by a detector 6. Then, the difference from the reference voltage V0 is obtained by the comparator 7 as the power control signal CP. This control signal CP
Is used as a control voltage of the variable attenuator 2, and is controlled by the above feedback loop so that the transmission power is constant. The high-frequency signal Pr reflected by the antenna 5 is branched by the directional coupler 4, its level is detected by the detector 6, and compared with the reference voltage V 1 by the comparator 8. As a result, if the reflected wave level is higher,
The monitor signal M is output to the system assuming that the antenna and the feeder system may be abnormal.

[0004]

In the prior art described above, the detector 6 is in a feedback loop.
When a signal comes after a time slot having no high-frequency signal in the FH system or the TDMA system, output level control cannot be accurately performed during a response delay of the detector.
This has the problem that the effect increases as the time slot interval becomes shorter. Further, although the directional coupler is also included in the feedback loop, there is a problem that a change in the feedback amount due to this frequency characteristic is directly reflected on the transmission output.

SUMMARY OF THE INVENTION An object of the present invention is to provide a power amplifying circuit capable of always keeping a transmission output constant accurately even when a high-frequency signal is turned on and off, and when the frequency of the high-frequency signal changes, and a transmission output thereof. It is to provide a control method.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a power amplifying device having a variable attenuator for controlling the level of a high-frequency signal, the attenuation factor of which can be variably controlled, and a power amplifier for power-amplifying the high-frequency signal. In the circuit, a table in which a control signal value of a variable attenuator such that a power amplifier output level for the frequency and temperature becomes a predetermined value for each set of frequency and temperature values, and a temperature of the power amplifier are detected. Temperature detecting means for outputting a temperature signal; a frequency signal indicating a frequency of the high-frequency signal when a high-frequency signal is input; and a temperature signal detected by the temperature detecting means, and a set of the frequency and the temperature. Control means for reading a control signal value corresponding to the variable attenuator from the table and outputting the control signal value to the variable attenuator. It discloses the width circuit.

Further, the present invention provides a transmission output control method for a power amplifier circuit comprising a variable attenuator for controlling the level of a high-frequency signal, the attenuation factor of which can be variably controlled, and a power amplifier for power-amplifying the high-frequency signal. A table storing control signal values of the variable attenuator such that an output level with respect to the frequency and the temperature becomes a predetermined value for each set of the frequency and the temperature, and a temperature detection value of the power amplifier and an input high-frequency signal. A control signal value corresponding to the frequency of the variable attenuator is read from the table to control the attenuation factor of the variable attenuator.

[0008]

Embodiments of the present invention will be described below. FIG. 1 is a block diagram showing an example of the configuration of a power amplifier circuit according to the present invention, in which feed-forward control is performed using a CPU 10, a frequency / temperature table, etc., without performing feedback control as in the related art. It is a feature. The temperature detector 12 detects the internal temperature of the power amplifier 3, and the detected temperature t is digitized by the A / D converter 14 and input to the CPU 10. The frequency signal F is a signal given from the system side and is a signal indicating the frequency of the high-frequency signal transmitted in each time slot.
The frequency / temperature table 11 measures in advance the frequency characteristics of the whole of the preamplifier 1, the variable attenuator 2, the power amplifier 3, and the directional coupler 4, and furthermore, the frequency characteristics of the input high-frequency signal level. A power control signal CP determined for each frequency is stored so that the fluctuation is corrected by the attenuation control of the variable attenuator 2. The power control signal CP needs to be changed by a temperature change. Table 1 as values for each temperature
1 is stored. However, since the influence of the temperature fluctuation is mostly at the power amplifier 3, the temperature t of the power amplifier 3 is used here as the temperature data as described above.

The CPU 10 accesses the table 11 using the input frequency signal F and the detected temperature t, reads out the corresponding power control signal CP, converts the power control signal CP into an analog signal by the D / A converter 16, and attenuates the variable attenuator 2. Control.
By using this feedforward configuration control method,
Since the detector 5 and the directional coupler 4 do not enter the control loop, even if the high-frequency signal is turned on or off or the frequency is switched, a control error due to their excessive response or frequency characteristics can be eliminated.

Here, the frequency / temperature table 11 will be described using a specific example. The target system now covers a frequency range of 225-399.975 MHz by 25k.
It is assumed that switching is performed in Hz steps. Then, the number of used frequencies is (399.975-225) M
Hz / 25 kHz + 1 = 7000 waves. Further, the temperature inside the power amplifier is set to a fluctuation range of 10 to 70 ° C. In order to prepare the data in the table 11 in, for example, 2 ° C. steps, 31 temperature numbers of 10, 12,. Become. Therefore, if you try to prepare data for each of the above 25 kHz frequency and 2 ° C temperature,

## EQU1 ## It is necessary to prepare 7000 × 31 = 217,000 data in the table 11. In this case, only discrete values for every 25 kHz are input for the frequency, but the temperature changes continuously. Therefore, when the temperature is between 2 ° C., the temperature is approximated by the closest temperature or, if necessary, is interpolated using an interpolation method.

The stored data is, for example, 2B in one data.
Even if (bytes) are used, the total is 434 kB, which is feasible, but can be greatly reduced from the viewpoint of economy and the like. In this method, for example, only data at 2 MHz intervals for the number of used frequencies 7000 is prepared in the frequency / temperature table 11. In this case, the number of frequencies is 225, 227,..., 399, and 89 MHz of 401 MHz, and the total number of data to be prepared in the table 11 is assuming that the temperature remains at 2 ° C. intervals.

## EQU2 ## The number may be 89 × 31 = 2759. This is about 1/80 of the data amount in the case of (Equation 1). When the frequency does not match any of the 89 values, the power control signal CP is obtained by interpolation using the values on both sides of the frequency. Since the operation of this interpolation is extremely simple, the operation time is the control signal CP.
It does not cause output delay.

The directional coupler 4 and the detector 5 shown in FIG.
Detects the transmission power level Pf and the level Pr of the reflected wave from the antenna as in the prior art, and these are digitized by the A / D converter 13 and input to the CPU 10.
These detection levels are not used for the feedback loop and are not used for controlling the transmission power. The detection levels are monitored by the CPU, and if there is an abnormality, the system is notified as a monitor signal M. Thereby, for example, the transmission request signal T is turned off, and the CPU 10
The signal is output as a transmission control signal T 'to each amplifier via the corresponding device, and measures such as stopping transmission are taken.

[0013]

According to the present invention, it is easy to control the transmission power level to be always the target value even in a system in which the frequency is switched on / off for each transmission time slot. effective.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration example of a power amplifier circuit according to the present invention.

FIG. 2 is a block diagram illustrating a configuration example of a conventional power amplifier circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Preamplifier 2 Variable attenuator 3 Power amplifier 10 CPU 11 Frequency / temperature table 12 Temperature detector

Claims (3)

[Claims] 1. A power amplifying circuit comprising a variable attenuator for controlling the level of a high-frequency signal and having a variable controllable attenuation factor, and a power amplifier for power-amplifying the high-frequency signal, comprising: A table in which a control signal value of the variable attenuator such that the output level of the power amplifier with respect to the frequency and the temperature becomes a predetermined value for each set, and a temperature for detecting the temperature of the power amplifier and outputting a temperature signal Detecting means, when a high-frequency signal is input, a frequency signal indicating the frequency of the high-frequency signal and a temperature signal detected by the temperature detecting means are input, and a control signal value corresponding to a set of the frequency and the temperature is inputted. Control means for reading out from a table and outputting to the variable attenuator. 2. When the frequency indicated by the frequency signal of the input high-frequency signal does not match any frequency of a set of frequency and temperature prepared in the table, the table including the frequency indicated by the frequency signal therebetween. The power according to claim 1, wherein the control means calculates a control signal value for the frequency by interpolation using control signal values corresponding to the above two adjacent frequencies and outputs the control signal value to the variable attenuator. Amplifier circuit. 3. A transmission output control method for a power amplifier circuit comprising: a variable attenuator for controlling the level of a high-frequency signal, the attenuation factor of which can be variably controlled; and a power amplifier for power-amplifying the high-frequency signal. A table is provided in which a control signal value of the variable attenuator is previously stored such that the output level of the power amplifier with respect to the frequency and the temperature becomes a predetermined value for each set of the value of the frequency and the temperature. A control signal value corresponding to the frequency of the variable attenuator is read from the table to control an attenuation factor of the variable attenuator.