JP2011040880A - Radio communication device and transmission output control method there of - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication device which controls transmission power corresponding to modulation methods or algorithms of modulated waves, and detects more stable and accurate transmission power. <P>SOLUTION: Corresponding to modulation methods or algorithms of modulated waves, time positions for transmission level calculation are prestored into a memory 6, and the difference between the transmission level at a time position read by a controller 5 and a reference signal level determined by the controller 5 is calculated. A correction value corresponding to the error, which is stored in the memory 6, is added to a reference control voltage Cref, and the gain of a gain variable amplifier 1 is controlled. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radio communication apparatus and a transmission output control method in the radio communication apparatus.

Currently, data communication by a wireless local area network (LAN) represented by the IEEE 802.11 standard is widely used. For example, personal computers (PCs), PC peripheral devices such as printers, hard disks, broadband routers, FAX, It is adopted as a signal transmission means that replaces wired communication in electronic devices such as cameras, videos, mobile phones, etc., automobiles and airplanes, and wireless data transmission is performed between the electronic devices.
As a wireless LAN standard, IEEE802.11a supports high-speed data communication of a maximum of 54 Mbps using an OFDM (Orthogonal Frequency Division Multiples) modulation method, and the frequency band uses the 5 GHz band. Is done.
IEEE802.11b is a DSSS (Direct Sequence Spread Spectrum) system that supports high-speed communication of 5.5 Mbps and 11 Mbps, and can be used freely without a radio license. The 4 GHz ISM (Industrial, Scientific and Medical) band is used.
IEEE802.11g supports high-speed data communication up to 54 Mbps using the OFDM modulation method, and uses the 2.4 GHz band as in the case of IEEE802.11b.
On the other hand, there is IEEE 802.11h as a communication system for enabling wireless LAN to be used in Europe, and a TPC (Transmission Power Control) function has been newly demanded. Here, the TPC function is a specification in which, for example, when the terminal and the base station are close to each other, the transmission power is suppressed when good communication is possible even if the transmission power is suppressed. Compared with a conventional wireless LAN, the TPC function is more accurate. There is a need to control the output power well.

  In preparation for such communication standards and radio wave standards, a transmission apparatus shown in the circuit diagram of FIG. 1 has been proposed (see Patent Document 1). In this transmission apparatus, the power of each transmission burst signal is fetched from the output of the coupler 3 and the power detector 4 to the controller 5 at the timing (predetermined time position) for each burst signal, and the fetched transmission power is predetermined. The error of the predetermined power is calculated by the controller 5. On the other hand, a correction value for each error is stored in the memory 6 in advance, the calculated correction value corresponding to the error is read, and the gain added to the reference control voltage is used as a control voltage to control the gain of the variable gain amplifier 1 Use the control method. This makes it possible to reliably and rapidly control output control of transmission waves that change in a burst manner as in the time division multiplex communication system.

  However, in the transmission device described in Patent Document 1, the time level for repeatedly calculating the transmission level at a predetermined time position of the burst signal and detecting the transmission power is fixed. Although it is useful for other signals, if a burst signal in other modulation schemes or a different control command (algorithm) is used, detection of the transmission power may be accurate. Absent.

  The present invention has been made in view of the above-described conventional problems, and its purpose is to control transmission power according to a modulation method and a use algorithm of a modulated wave, thereby achieving stable and accurate transmission power. It is to provide a transmission output control method to be detected and a wireless communication apparatus using the transmission output control method.

The present invention is a wireless communication apparatus that controls a variable gain amplifier to control the power of an input signal of the variable gain amplifier to a predetermined output power of an output signal, the output power detecting means for detecting the output power; A controller that controls the variable gain amplifier with a control signal based on a correction value according to an error between the output power detected by the output power detection means and a predetermined output power, and the controller Deciding the detection timing of the output power detection means according to the modulation method or algorithm used of the transmission signal, and performing operation control to repeat a control cycle from detection of the output power to control of the variable gain amplifier A wireless communication device.
Another invention relates to a transmission output control method for controlling a variable gain amplifier in a radio communication apparatus to control a power of an input signal of the variable gain amplifier to a predetermined output power of an output signal, wherein the output power is detected. An output power detection step, a control step of controlling the variable gain amplifier with a control signal based on a correction value according to an error between the output power detected in the output power detection step and a predetermined output power; Determining a detection timing of the output power detection step according to a modulation method of a transmission signal or an algorithm used by the controller, and repeating a control cycle from the detection of the output power to the control of the variable gain amplifier This is a transmission output control method in a wireless communication apparatus.

  According to the present invention, there is provided a transmission output control method for detecting stable and accurate transmission power by controlling transmission power in accordance with a modulation scheme and algorithm of a modulated wave, and a radio communication apparatus having the transmission output control method. Can be provided.

It is a transmission power control block diagram in this embodiment. It is a flowchart of the transmission output control operation by a controller. It is a timing chart of transmission power detection in this embodiment. 4A is a diagram illustrating an example of a waveform in OFDM, and FIG. 4B is a diagram illustrating an example of a waveform in the DSSS system. It is a figure which shows the time position for detecting the transmission level at the time of taking an OFDM waveform for an example. FIG. 6A is a table showing time positions for each packet size in OFDM and FIG. 6B in DSSS. FIG. 7A is a table of correction voltage values corresponding to error voltages in OFDM, and FIG. 7B is a DSSS modulation method. It is a table showing the time position with respect to the random number in an OFDM modulation system. It is the figure which displayed the random time position of the OFDM waveform.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings.
The wireless communication apparatus according to this embodiment basically uses the conventional transmission apparatus shown in FIG. 1, except that the transmission power voltage detection timing by the transmission power detection means is fixed for the conventional one. It differs from the conventional transmitter in that the time position is changed dynamically instead of the time position.
That is, in the transmission apparatus shown in FIG. 1, the modulated wave is amplified by the amplifier 1 and the power amplifier 2 whose gain can be variably controlled, and transmitted through the coupler 3. The controller 5 receives the voltage V indicating the transmission power detected by the power detector 4 and controls the amplification factor of the amplifier 1 so as to keep the transmission power at a predetermined value. Here, the controller 5 is composed of a digital microprocessor, and an A / D converter for digitizing the output voltage V (analog) of the power detector 4 and a control voltage C (analog) of the amplifier 1. A D / A converter for outputting is incorporated. The memory 6 is provided for storing in advance data for determining the control voltage C corresponding to the input voltage V.

FIG. 2 is a flowchart showing the transmission output control operation by the controller 5.
In FIG. 2, first, at the start of operation, the control voltage C is output from the controller 5 as a predetermined reference value Cref (S201), and the gain of the amplifier 1 is controlled. Here, the reference value Cref is a control voltage of the amplifier 1 when the transmission output becomes a predetermined value Pref in a steady state. Next, transmission power P (represented voltage V) is detected at detection timing synchronized with the transmission signal (S202).
The detection timing of the transmission power P is set, for example, at a time position corresponding to the modulated wave, and this can be easily obtained from a transmission circuit control system (not shown).
When the voltage V of the transmission power P is detected, this voltage V and a predetermined reference control voltage Vref
And a transmission output error (voltage) a (a = V−Vref) is calculated (S203), and a correction value b corresponding to the transmission output error (voltage) a is read from the memory 6 (204). Then, the control voltage C obtained by adding the correction value b to the reference value Cref is output (S205).

Here, the reference control voltage Vref is an output voltage value of the power detector 4 when the transmission power P becomes the predetermined value Pref. Further, if the transmission output error (voltage) a is used as it is as the correction value (voltage) b, the transient response greatly overshoots, so that the correction output (voltage) b is within a range of about 50 to 80% of the transmission output error (voltage) a. It has established. For example, it can be obtained by the following (Equation 1).
(Equation 1)
b = a / 2, a> a0
b = 0, a <a0
Here, the voltage a0 is determined as a sufficiently small value with respect to the reference value Cref. This is to prevent a fine change in the control voltage C when the output level has converged to the predetermined value Pref. Then, the value of the correction value b determined as in (Equation 1) is stored in the memory 6 for each value of the transmission output error (voltage) a (at an appropriate step).
Note that an operation like (Equation 1) may be directly calculated by the processor in the controller 5 without using the memory 6. However, using the memory has an advantage that the program does not have to be changed when the correction value is changed.

As described above, when the control cycle up to step S205 (FIG. 2) is executed by the controller 5, the power detection and correction value calculation in steps S202 to S205 and the control voltage update are performed again from the next transmission power detection timing. The process is repeated. In that case, the processing of steps S203 to S205 in each control cycle is executed in the correction processing section shown in the operation timing chart of FIG.
As shown in FIG. 3, transmission power (outputs) P1, P2,... Are controlled so that errors a1, a2,. By performing in synchronization with the transmission signal, it is possible to obtain a stable control voltage for each control cycle, and to perform reliable and high-speed transmission output control.

However, in the above modulated wave input, transmission power detection by a modulation method such as the conventional time division multiplex communication method has a fixed transmission power detection timing. For example, a frequency band such as OFDM is equally spaced. If the transmission power detection timing (time position) synchronized with the burst signal is applied to a modulation method such as a modulation method that transmits the signal divided into two, it may be difficult to obtain a stable and accurate correction value b.
Therefore, in this embodiment, the setting of the time position, which is the transmission power detection timing, is more stable by dynamically setting in accordance with the modulation method of the modulated wave and, for example, the algorithm executed by the controller shown in FIG. In addition, the transmission power can be accurately controlled.

Hereinafter, OFDM and DSSS modulation schemes will be described in detail as an example of this embodiment.
First Embodiment The OFDM system belongs to multicarrier modulation because data is carried on a large number of subcarriers. Since these subcarriers are orthogonal to each other, they usually have the advantage of not interfering with each other even though the data are arranged so densely that they overlap, using the Fast Fourier Transform (FFT) algorithm. Can be distinguished efficiently.
In addition, the DSSS modulation method is a spread spectrum method in which transmission data is multiplied using a signal having a much wider band than the transmission data, and energy is spread over a wide frequency range for communication. On the other hand, the calculation by the spread code is performed, and the energy is spread and transmitted in a wider band than the transmission data.
The OFDM modulated wave and the DSSS modulated wave are different in data size, amplitude level, and waveform.

  4A is a diagram illustrating an example of a waveform in OFDM, and FIG. 4B is a diagram illustrating an example of a waveform in the DSSS system. As shown in FIG. 4, the waveform can be explained by packetized data. In general, the waveform is composed of a preamble part (control signal for establishing packet synchronization) for identifying the head of the packet and a payload part as a data body, and is transmitted. Level detection is performed in the payload portion of the data body. Also, modulation waves with different modulation schemes such as OFDM and DSSS have different data sizes, amplitude levels, waveforms, etc., so the time position that is the timing for detecting an appropriate transmission level for each modulation scheme is set. It is necessary to set in advance.

  FIG. 5 is a diagram showing a time position for detecting a transmission level when an OFDM waveform is taken as an example. As shown in FIG. 5, the time position is, for example, the power peak position of the payload portion of each packet, It can be set at the center frequency position. This can be easily obtained from a transmission circuit control system (not shown).

In order to predetermine the time position according to the modulation method, the time position can be stored in the memory according to the packet size of each modulated wave as follows.
FIG. 6 is an example of a table diagram showing time positions for each packet size stored for each modulation method. For example, for the OFDM scheme of FIG. 6A, the time position of a signal with a packet size of 0 to 100 bytes is 100 ns (ns: one billionth of a second), and the time position of a packet signal of 100 to 500 bytes is 500 ns. , The time position of the packet signal of 500 to 1000 bytes is 700 ns, the time position of the packet signal of 1000 to 1500 bytes is 1000 ns. Similarly, in the DSSS system, as shown in FIG. The time position can be stored in advance.

That is, the time position for detecting the transmission power is held in the memory 6 (FIG. 1), the controller 5 reads the information from the memory 6, and the voltage V representing the transmission power (output) P synchronized with the transmission signal packet is obtained. The transmission output error (voltage) a is calculated by comparison with the reference control voltage Vref (S203), and a correction value b corresponding to the transmission output error (voltage) a is obtained from the memory 6. Read (S204). Then, the correction value b is added to the reference value Vref to output a control voltage (S205), and these steps are repeated to control the transmission level.
Here, the signal level at the time of determining the reference control voltage Vref includes, for example, a transmission level at a certain time position or a level obtained by taking an average of signal levels at a plurality of time positions synchronized with a packet. . The reference control voltage Vref is determined by the controller 5.
The correction value (voltage) b is stored in a table on the memory 6 as a predetermined correction voltage value according to the modulation method of the modulation wave, and the controller 5 determines the transmission output error (voltage) a. It can be read from the memory 6.

  FIG. 7 is a table of the correction voltage value (voltage) b corresponding to the transmission output error (voltage) according to the modulation method. As shown in FIG. 6, the correction voltage b is determined in a range of about 50 to 80% of the transmission output error (voltage) a based on the above (Formula 1). For example, in the case of the OFDM modulation scheme of FIG. 6A, 10% of 50% is used as a correction voltage for an error of 20 mV, and in the case of the DSSS modulation scheme of FIG. 6B, 80 mV of 8 mV is used for an error of 10 mV. The correction voltage is stored in the memory.

  As described above, the wireless communication apparatus according to the first embodiment, as shown in FIGS. 1 and 2, gain-amplifier 1 for signal amplification and the output of the gain-variable amplifier is amplified and transmitted. Power amplifier 2, a modulation method for the packet size and signal, a transmission power detection means for detecting transmission power P from a transmission level at a time position for detecting transmission power corresponding to the modulation method, and the transmission Correction voltage output means for outputting a correction voltage b corresponding to a transmission output error (voltage) a between the transmission power P detected by the power detection means and a predetermined reference value (predetermined output power) Cref; and The sum or difference between the correction voltage b output from the correction voltage output means and a predetermined reference control voltage Vref is obtained, and the gain of the variable gain amplifier 1 is controlled by the obtained control voltage. As an apparatus provided with a gain control means, stability, and allows for accurate control of transmission power.

Second Embodiment In the wireless communication apparatus according to the first embodiment, the power peak position or center frequency position is stored as a table on the memory 6 according to the packet size, and transmitted from the transmission level at the time position. Although transmission power detection means for detecting power is used, in the second embodiment, transmission power detection means for detecting transmission power from transmission levels at random time positions is used.

  FIG. 8 is a table of time positions with respect to random number numbers in the OFDM modulation scheme. As shown in FIG. 8, the controller 5 (FIG. 1) determines an arbitrary random number and detects transmission power at the time position stored corresponding to the random number. FIG. 9 is a diagram showing a time-to-power level displaying a random time position of the OFDM waveform. As shown in FIG. 9, the reference control voltage Vref is determined by the controller 5 by detecting a transmission level at a random time position and taking an average of a specific signal level or a plurality of signal levels.

  As described above, the wireless communication apparatus according to the second embodiment, as shown in FIGS. 1 and 2, gain variable amplifier 1 for signal amplification and power amplification of the output of the variable gain amplifier is transmitted. A power amplifier 2 for transmitting, a transmission power detection means for detecting a voltage V of transmission power (output) P from the transmission level at the random time position, and a transmission power P detected by the transmission power detection means A correction voltage b corresponding to a transmission output error (voltage) a between the voltage V of V and a predetermined reference value (predetermined output power) Cref is output, and the output correction voltage b and a predetermined reference control voltage Vref are output. And a controller 5 (FIG. 1) for controlling the gain of the variable gain amplifier 1 using the control voltage of the obtained sum, thereby enabling stable and accurate control of transmission power. To become.

  DESCRIPTION OF SYMBOLS 1 ... Amplifier, 2 ... Power amplifier, 3 ... Coupler, 4 ... Power detector, 5 ... Controller, 6 ... Memory.

Japanese Patent Laid-Open No. 11-4132

Claims (5)

A wireless communication device that controls a variable gain amplifier to control the power of an input signal of the variable gain amplifier to a predetermined output power of an output signal,
Output power detection means for detecting the output power;
A controller that controls the variable gain amplifier with a control signal based on a correction value according to an error between the output power detected by the output power detection means and a predetermined output power;
The controller determines a detection timing of the output power detection means according to a modulation method or a use algorithm of a transmission signal, and performs operation control that repeats a control cycle from detection of the output power to control of the variable gain amplifier. A wireless communication device. The wireless communication device according to claim 1,
The controller obtains a correction value according to the error based on a correspondence table between the error and a correction value according to an error between the output power and a predetermined output power, and the correction value is A radio communication apparatus, wherein the variable gain amplifier is controlled by a control voltage obtained by adding or subtracting to a predetermined reference control voltage of the variable gain amplifier. The wireless communication device according to claim 2,
A table storing the detection timing of the output power based on the packet size of the signal in the signal modulation method;
The controller determines a detection timing of the output power based on a packet size of the signal based on a modulation scheme of the table, and generates the control voltage based on the output power detected at the timing. Communication device. The wireless communication device according to claim 2,
The controller stores a random number and a time position corresponding to the random number as a table on a memory for each signal modulation method, and changes the time position for detecting transmission power at random by the controller. A wireless communication device that generates the control voltage. A transmission output control method for controlling a variable gain amplifier in a wireless communication device to control power of an input signal of the variable gain amplifier to a predetermined output power of an output signal,
An output power detection step of detecting the output power;
A control step of controlling the variable gain amplifier with a control signal based on a correction value according to an error between the output power detected in the output power detection step and a predetermined output power;
Determining the detection timing of the output power detection step according to the modulation method or use algorithm of the transmission signal,
A transmission output control method in a radio communication apparatus, wherein a control cycle from detection of the output power to control of the variable gain amplifier is repeated.

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