JP2002152060A - Transmission power control circuit in wireless transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize more accurate transmission power control for a burst transmission wave than a conventional transmission power control circuit. SOLUTION: The transmission control circuit is provided with a transmission power detection means 15 that detects the amplitude of transmission power, a peak power detection means 16 that detects the maximum amplitude reaching a peak first at the rising of a transmission wave by each burst, a control variable calculation means 17 that compares the maximum amplitude with a predetermined reference amplitude to calculate a control variable of the transmission power. The transmission control circuit controls the transmission power according to the control variable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio transmitter for intermittently transmitting a digitally modulated transmission signal as a burst transmission wave, and more particularly to a transmission power control circuit in the radio transmitter.

[0002]

2. Description of the Related Art As a wireless transmission power control circuit having a function of automatically controlling the transmission power of a digitally modulated transmission signal, a circuit disclosed in, for example, JP-A-8-51372 is known. The configuration of this circuit is shown in FIG. 1 of the publication, and comprises each means as described in claim 1. That is, a modulating means for modulating a signal of a transmission slot sequentially transmitted at a predetermined timing, and output control information and data indicating a deviation of an output level of a transmission slot to be transmitted next are transmitted to a transmission slot earlier than this transmission slot. And a voltage for controlling the output level of the next transmission slot to be transmitted next based on the data from the data generation means. And control means.

[0003] In summary, power control of a burst transmission wave is a transmission power control circuit that uses a power control value calculated from the immediately preceding burst transmission wave.

[0004]

According to the above conventional transmission power control circuit, since the transmission power of the current burst is determined from the immediately preceding burst, the power of the radio transmitter is turned on. It is necessary to use a predetermined initial value as the power control value for the first burst transmission wave transmitted first later.

[0005] For this reason, as for the first burst transmission wave immediately after the start of transmission, there is a problem that it is not possible to guarantee the transmission power with the error minimized unless the initial value is appropriately set. is there. In order to solve this problem, the following methods are conceivable. This means that the last power control value when the power of the wireless transmitter is turned off is stored, and when the power is turned on again, the stored power control value is used to generate the first burst transmission wave. The transmission power is determined.

However, even with such a method,
If the temperature of the wireless transmitter itself changes after power is turned off and before the power is turned on again, or if the impedance of a load such as an antenna connected to the transmission wave output terminal fluctuates. In the above, the stored power control value becomes meaningless, and it cannot be guaranteed that the error of the transmission power of the first burst transmission wave is minimized.

In view of the above problems, it is an object of the present invention to provide a transmission power control circuit that determines transmission power for a current burst without depending on the previous burst. It is. That is, a transmission power control circuit capable of performing complete power control for each burst to be transmitted is provided.

[0008]

FIG. 1 is a block diagram showing the basic configuration of the present invention. In the figure, the wireless transmitter 1
0 comprises blocks 11 to 14 as shown.
Dtx is transmission data, and S is a transmission wave. Among them, the transmission power control circuit 14 to which the present invention is mainly applied is described.

The transmission power control circuit 14 cooperates with the transmission signal generation circuit 11, the transmission power adjustment circuit 12, and the output stage amplification circuit 13 to control the transmission signal digitally modulated in accordance with the transmission data Dtx. As shown in the figure, a transmission power detecting means 15 and a peak power detecting means 16 are transmitted.
And a control amount calculating means 17.

[0010] The transmission power detection means 15 detects the amplitude of the transmission power of the transmission wave S. The peak power detection means 16 includes, among the amplitudes detected by the transmission power detection means 15,
The maximum value of the amplitude that first reaches the peak when the transmission wave S rises is detected for each burst. Control amount calculation means 1
7 compares the maximum value detected by the peak power detection means 16 with a predetermined reference amplitude value Ref,
The transmission power control amount is calculated. Then, the transmission power is controlled in accordance with the control amount calculated by the control amount calculating means 17.

More specifically, radio transmitter 10 includes blocks 11 and 12 as shown. That is, a transmission signal generation circuit 11 that generates a burst transmission signal digitally modulated by the transmission data Dtx, and a power adjustment that controls the transmission power of the transmission wave S in accordance with the control amount calculated by the control amount calculation unit 17. And a circuit 12.

Referring again to FIG. 1, the peak power detecting means 16 characterizes the present invention in the transmission power control circuit 14 most. This will be explained in more detail. FIG. 2 is a waveform diagram showing an amplitude change of the burst transmission wave. In the figure, the horizontal axis represents time, and the vertical axis represents the amplitude of the burst transmission wave S, and shows one burst wave.

In general, each burst wave is composed of a prefix part and a data main part as shown. Then, under a digital modulation scheme such as π / 4DQPSK or 16QAM, the amplitude of the transmission wave S changes as shown in each burst. The present invention pays particular attention to the front part of such a burst wave. A fixed data pattern for synchronizing on the receiving side is inserted into the first part, ie, the front part, of the burst wave under the digital modulation method. Then, in any burst wave, although the data body part changes every time transmission,
Regarding the preceding part (a fixed data pattern), the form of the amplitude change is almost the same. That is, the amplitude change does not take a different form every time a burst wave is transmitted. The present invention focuses on this fact and has been made by utilizing this fact.

First, the maximum value of the amplitude that first reaches the peak when the burst wave shown in FIG. 2 rises (see the first peak wave A in the figure) is detected. To do this,
This is the peak power detection means 16 described above. Then, an error between the maximum value and the reference amplitude value Ref is obtained, and the first peak wave A
Immediately reflect the error in the burst wave immediately following
Execute power control. This is performed by the control amount adjusting means 17 described above.

After all, according to the present invention, there is no dependence on the power control amount of the immediately preceding burst wave or the power control amount of the burst wave when the power is last turned off before the power is turned on again, unlike the conventional example. In addition, complete power control with only the current burst wave is possible. However, for that purpose, various measures such as speeding up the power control are required.

[0016]

FIG. 3 is a diagram showing an embodiment according to the present invention. Throughout the drawings, the same components are denoted by the same reference numerals or symbols. 3, the output stage amplifier circuit 13 of FIG. 1 is realized as a D / A converter 21 and a transmission amplifier 22. Further, an A / D converter 23 is inserted between the transmission power detection means 15 and the peak power detection means 16 in FIG.

As described above, in realizing the present invention, it is essential to increase the speed of power control. For this purpose, at least the peak power detecting means 16 and the control amount calculating means 17 are programmable devices such as a DSP (Digital Signal P
20). As the transmission power detection means 15, a high-speed type that can sufficiently follow the amplitude change of the burst wave shown in FIG. 2 is employed.

In this embodiment, the transmission signal generation circuit 11
The transmission power adjustment circuit 12 is also realized by being incorporated in the DSP 20 described above. Hereinafter, the operation of the DSP shown in FIG. 3 will be described with reference to a flowchart. FIG. 4 shows the DSP shown in FIG.
20 is a flowchart (No. 1) showing an operation example, FIG. 5 is a flowchart (No. 2), and FIG. 6 is a flowchart (No. 3).

The operations shown in these flowcharts are executed each time each burst wave (transmission wave S) is transmitted. First, the meaning of each symbol appearing in these flowcharts will be clarified. txSig (): transmission wave S (TX · signal) nBst: number of samples i of transmission wave S used in one burst (burst) wave: number of the sample cal: updated correction coefficient (calibration) For example, initial value = 1 CalAlt: correction coefficient used last time (alterna
te) lv (): detected amplitude value (level) lvAdj: amplitude value to be a reference (level adju)
st) This is a fixed value and corresponds to Ref described above. ip: Number of the next (immediate) sample after peak (A) is detected. In FIG. 4, step S11: transmission data in transmission signal generation circuit 11 in FIG. According to Dtx, the transmission wave S
The signals txSig (1) to txSig (nBst) are generated and stored in a memory in the circuit 11.

Step S12: Control amount calculating means 1 in FIG.
At 7, the correction coefficient calAlt of the power adjustment amount is updated to the correction coefficient cal. Step S13: Select the first sample. Step S14: The process proceeds to step S15 every time there is a data input request from the D / A converter 21 in FIG.

Step S15: Steps S11 and S
According to the values obtained in step 12, txSig (i) ×
calAlt is input to the D / A converter 21 as data. However, i = 1. Step S16: The level output from the A / D converter 23 in FIG.
(I). However, i = 1.

Thus, the initial setting of the power adjustment process is completed using the first sample. In FIG. 5, step S21: advance the sample to the next sample. Step S22: Same as step S14 (FIG. 4). Step S23: Same as step S15 (FIG. 4).

Step S24: Step S16 (FIG. 4)
the same as. Step S25: The control amount calculating means 17 in FIG. 3 determines whether or not the current level lv (i) is smaller than the previous level lv (i-1). This is to determine whether or not the first peak wave A in FIG. 2 has been exceeded. In FIG. 2, for example, if the amplitude of the eleventh sample (the amplitude increases monotonically from the first to the eleventh) drops below the amplitude of the tenth sample, the maximum value is reached at the tenth sample. You can see that

Step S26: i when the passage of the maximum value is detected is set as ip. Therefore, it is (ip-1) that the maximum value actually appeared. Step S27: According to the ip, the correction coefficient cal
Is calculated based on the equation shown in S27 of FIG. That is, the previous correction coefficient calAlt is multiplied by the ratio between the reference amplitude value lvAdj and the local maximum value lv (ip-1) to obtain the updated correction coefficient cal at the time of peak detection.

In FIG. 6, step S31: advance the sample further than ip. Step S32: Same as step S14 (FIG. 4). Step S33: txSig (i) × cal is calculated using the correction coefficient cal updated in step S27 (FIG. 5), and the calculated value is transmitted from the transmission power adjustment circuit 12 of FIG. 3 to the D / A converter 21. Output. Thereafter, within one burst, the transmission power of the transmission wave S is controlled to be constant using the updated correction coefficient cal.

Looking at the above-mentioned flowchart,
In the first flowchart (FIG. 4), since the previous correction coefficient calAlt must be used, the transmission power controlled to be constant includes an error. However, the error has no effect on normal transmission. This is shown in FIG. FIG. 7 is a diagram for explaining an error in transmission power.

In this figure, the horizontal axis represents time, and the vertical axis represents correction coefficients (cal, calAlt). The scale on the horizontal axis is the sample number (i). Sample number 1 to i
Up to p (see step S26 in FIG. 5) is a part where the flowchart in FIG. 4 and the flowchart in FIG. 5 are executed, and the above-described error is inevitably generated. The period of the sample numbers ip to nBst is a period during which the transmission wave S is transmitted with a predetermined constant transmission power.

The above error occurs in the period of sample numbers 1 to ip, and this is represented as an area ΔS in the figure.
On the other hand, the area of the expected transmission power after ip is shown as S. Usually, since ip << nBst, S is so large as to be incomparable to ΔS. Generally, the transmission power is represented by the average power of the burst wave, and this average power is substantially equal to the above S. Therefore, the error ΔS hardly affects the average power.

In addition, since the error ΔS occurs only for a short time at the head of one burst wave, the transmission power is completely controlled to a predetermined constant when transmitting the data body. Regarding FIG. 7, there is a point to be noted other than the error ΔS. This is the previous correction coefficient ca
This is a transition portion from 1 Alt to the updated correction coefficient cal.

As described above, the control amount of the transmission power is changed by the correction coefficient set by the control amount calculating means 14, but as can be seen from FIG.
Initial correction coefficient (calAl) used at the beginning of burst
t) and a steady-state correction coefficient (cal) used after the beginning of the burst. In this case, when the transition from the initial correction coefficient (correction coefficient used last time) to the steady-state correction coefficient is performed abruptly (in a stepwise manner) as shown in FIG. Will interfere with other stations.

Therefore, a transition period of the correction coefficient is provided between the initial period using the initial correction coefficient and the steady period using the steady correction coefficient. In the transition period, the correction coefficient is changed along the ramp shape. This will be described with reference to FIG. FIG. 8 is a diagram illustrating a preferable transition of the correction coefficient. This figure corresponds to FIG.

In this figure, T0 is an initial correction coefficient cal.
Alt is the initial period, where T1 is the steady-state correction coefficient c
This is a stationary period using al. And these periods T0
A transition period Tt of the correction coefficient is provided between and T1. Preferably, the correction coefficient (calAlt → ca) in the period Tt is used.
1) is varied along a ramp shape R. Thus, the spread of the spectrum described above is suppressed.

FIG. 9 is a flowchart (No. 1) showing an operation example of the DSP 20 in a mode in which the correction coefficient is changed along the ramp shape, and FIG. 10 is a flowchart (No. 2). Step S41 in FIG. 9 is the same as step S41 in FIG.
It is a continuation from 27. Also, all steps S51 in FIG.
The contents of steps S54 to S54 are the same as the contents of steps S31 to S34 in FIG.

In FIG. 9, step S41: similar to step S21 (FIG. 5). Step S42: Same as step S22 (FIG. 5). Step S43: calRmp is generated in the control amount calculating means 17 in FIG. calRmp is a correction coefficient that changes along the ramp shape R during the transition period Tt in FIG. In the present embodiment, a cosine-shaped window function w (i) is adopted as the ramp shape R, and is applied from sample numbers ip to ip + nRmp. nRmp is the total number of samples in the transition period Tt. The correction coefficient calRmp at this time is expressed by the following equation.

[0035]

(Equation 1)

Is calculated. Thereby, the spread of the spectrum can be prevented. In the present invention,
In addition to being able to prevent the above-mentioned spread of the spectrum, it is also devised that more accurate power control can be performed. This will be described below.

FIG. 11 is an enlarged view showing a waveform of an undesired head portion of a burst wave. When the amplitude value of the first peak wave of the burst (A in FIG. 2) is small, for example, as shown in FIG. 11B, accurate power control becomes difficult. This is because, referring to FIG.
When fed back to the SP 20, a detection error unavoidably included in the transmission power detection means 15, a calculation error of the correction coefficient (cal) included in the control amount calculation means 17, or a non-linearity in the transmission amplifier 22. This is because various error factors such as distortion due to the above-mentioned error accumulate, and the small-amplitude peak wave B is buried therein.

Therefore, in the present invention, a device is added so that the amplitude of the first peak at the head of the burst wave does not decrease as shown in FIG. 11B. Specifically, in the transmission signal generation circuit 11 of FIG. 3, the amplitude of the leading portion (1 to ip in FIG. 7) of the burst transmission wave S corresponds to a predetermined average power of the transmission power in the burst. A data pattern larger than the amplitude is set at the head of the transmission signal.

For this purpose, a preamble signal for synchronizing symbols, a synchronization symbol for recognizing the start of information in a burst, and a correction coefficient for changing the control amount by the control amount calculating means 17 are set as initial correction coefficients. The above data pattern is obtained by adjusting at least one of window functions (w (i) in FIG. 8) which determine the transition shape when transitioning from.

As a result, it is possible to make the initial peak wave A exceed the intended average transmission power. Such a data pattern is determined once in the programming stage and does not need to be changed thereafter. However, in order to determine such a data pattern, first prepare a variety of data patterns, test them one by one,
It is necessary to select a desired one in an AND-trial manner.

As described above, the first peak wave A can be made to always exceed the above average power. However, this is not enough, and it is desired that such an initial peak wave A appears even earlier. This will be described with reference to FIG.
FIG. 12 is an enlarged view showing another example of the waveform of the head portion of the undesired burst wave.

If the first peak wave of the burst is delayed behind C shown in FIG. 12D as shown in FIG. 12D, the detection of the peak wave (peak detection) is also delayed, so that the processing load on the DSP 20 increases accordingly. . Usually, the DSP 20 performs various processes in parallel, as is clear from FIG. For this reason, it is required that the above-mentioned peak detection be completed as early as one sample.

Therefore, when the control coefficient for changing the control amount of the synchronization symbol and the transmission power for recognizing the start of the information in the burst by the control amount calculating means 17 is changed from the initial correction coefficient to the steady-state correction coefficient. In a state where both window functions (w (i) in FIG. 8) that determine the transition shape of the signal are fixed, the pattern of the preamble in the burst is changed to the head portion of the burst-like transmission wave S (1 to ip in FIG. 7). Is set so that the amplitude is the earliest that is larger than the amplitude corresponding to the predetermined average power for the transmission power in the burst.

That is, the synchronization symbol and the window function w (i)
Is determined, and the preamble pattern is brute-forced so that the first peak wave A at the head portion exceeds the above average power earliest. For example, in a system using the π / 4 DQPSK modulation method, this preamble is often used by repeating a 4-bit pattern. In this case, 16 kinds of patterns (0000,000,000
1,0010... 1111), the pattern in which the peak wave exceeds the average power earliest is selected. This selection is also made by the cut and try described above.

Thus, the processing load of the DSP 20 can be reduced even a little. In the embodiment described with reference to FIG. 11, it is assumed that there is only one type of synchronization symbol. However, in an actual system, a plurality of types of synchronization symbols (for example, 2
Seeds) exist and are used depending on the application. For example, in the transmission of a certain signal, a burst is transmitted by adding a first synchronization symbol, and in the transmission of another signal, a burst is transmitted by adding a second synchronization symbol.
Such a system.

In such a system, the initial peak wave A needs to exceed the above-mentioned average power, regardless of which pattern of the synchronization symbol is added, whereby the power control error must be minimized. . Therefore, the present invention is configured as follows so as to cope with the above system.

First, a premise is a system in which a plurality of types of synchronization symbols exist for recognizing the start of information in a burst and one of them is added to a burst and transmitted. Here, the transmission signal generation circuit 11 shown in FIG. 3 determines, for all the synchronization symbols among the preamble patterns that are larger than the amplitude corresponding to the predetermined average power of the transmission power in the burst, the A preamble pattern that minimizes the transmission power deviation is set at the beginning of the transmission signal.

As a method for dealing with a system in which a plurality of types of synchronization symbols exist as described above, there is a better method other than the above-described configuration. This better method is a method that can make the power control error almost zero. In short, this means that a reference amplitude value Ref (corresponding to lvAdj described above) is individually provided for each synchronization symbol. Ref1, Ref2, etc.

First, it is assumed that there is a plurality of synchronization symbols for recognizing the start of information in a burst, and that the transmission power control circuit is used in a system in which any one of them is added to the burst and transmitted. . Here, the control amount calculating means 17 in FIG. 3 calculates a predetermined reference amplitude value (Ref),
A plurality of reference amplitude values suitable for each of the plurality of types of synchronization symbols are set.

Thus, no matter which synchronization symbol is added, the power control error can be made substantially zero.

[0051]

As described above, according to the present invention, more accurate transmission power control can be realized as compared with the prior art.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of the present invention.

FIG. 2 is a waveform diagram showing an amplitude change of a burst transmission wave.

FIG. 3 is a diagram showing an embodiment according to the present invention.

FIG. 4 is a flowchart (part 1) illustrating an operation example of the DSP 20 illustrated in FIG. 3;

FIG. 5 is a flowchart (part 2) illustrating an operation example of the DSP 20 illustrated in FIG. 3;

FIG. 6 is a flowchart (part 3) illustrating an operation example of the DSP 20 illustrated in FIG. 3;

FIG. 7 is a diagram for explaining an error in transmission power.

FIG. 8 is a diagram illustrating a preferable transition of a correction coefficient.

FIG. 9 is a flowchart (part 1) illustrating an operation example of the DSP 20 in a mode in which the correction coefficient is changed along the lamp shape.

FIG. 10 is a flowchart (part 2) illustrating an operation example of the DSP 20 in a mode in which the correction coefficient is changed along the lamp shape.

FIG. 11 is an enlarged view showing a waveform of a head portion of an undesired burst wave.

FIG. 12 is an enlarged view showing another example of a waveform at the head of an undesired burst wave.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Wireless transmitter 11 ... Transmission signal generation circuit 12 ... Transmission power adjustment circuit 13 ... Output stage amplifier circuit 14 ... Transmission power control circuit 15 ... Transmission power detection means 16 ... Peak power detection means 17 ... Control amount calculation means 20 ... DSP 21: D / A converter 22: Transmission amplifier 23: A / D converter

Claims (13)

[Claims] 1. A transmission power control circuit in a radio transmitter for transmitting a digitally modulated transmission signal as a transmission power-controlled burst transmission wave, comprising: a transmission power detection means for detecting an amplitude of transmission power of the transmission wave. A peak power detection unit that detects, for each burst, a maximum value of an amplitude that first reaches a peak when the transmission wave rises, among the amplitudes detected by the transmission power detection unit; and the peak power detection unit. Control amount calculation means for calculating the control amount of the transmission power by comparing the local maximum value detected by the control value and a predetermined reference amplitude value, according to the control amount calculated by the control amount calculation means A transmission power control circuit in the wireless transmitter, wherein the transmission power is controlled. 2. A transmission signal generation circuit for generating the burst transmission signal digitally modulated by transmission data, a power adjustment circuit for controlling the transmission power according to the control amount calculated by the control amount calculation means, The transmission power control circuit in the wireless transmitter according to claim 1, further comprising: 3. The transmission wave according to claim 1, wherein the burst-shaped transmission wave comprises a prefix part and a data body part, and a fixed data pattern is inserted in the prefix part. 3. A transmission power control circuit in the wireless transmitter according to 2. 4. The control amount calculating means calculates an error between the maximum value of the amplitude and a predetermined reference amplitude value, and calculates the error as the transmission wave immediately following the first peak wave forming the maximum value. The transmission power control circuit in the wireless transmitter according to any one of claims 1 to 3, wherein 5. The transmission power control circuit according to claim 1, wherein the control amount is changed by a correction coefficient set by the control amount calculating unit. . 6. The radio transmitter according to claim 5, wherein the correction coefficient comprises an initial correction coefficient used at the head of the burst and a steady-state correction coefficient used after the head of the burst. Transmission power control circuit. 7. The transmission in the wireless transmitter according to claim 6, wherein a transition period of the correction coefficient is provided between an initial period using the initial correction coefficient and a stationary period using the stationary correction coefficient. Power control circuit. 8. The transmission power control circuit according to claim 7, wherein the correction coefficient is changed along a ramp shape during the transition period. 9. The transmission signal generation circuit generates a data pattern such that an amplitude of a leading portion of the burst transmission wave is larger than an amplitude corresponding to a predetermined average power of transmission power in the burst. The transmission power control circuit in the wireless transmitter according to any one of claims 2 to 7, wherein the transmission power control is set at a head of a transmission signal. 10. The control amount calculating means calculates (i) a preamble signal for synchronizing symbols, (ii) a synchronization symbol for recognizing the start of information in the burst, and (iii) the control amount. 10. The data pattern is obtained by adjusting at least one of a window function that determines a transition shape when a correction coefficient for changing the initial correction coefficient and the steady correction coefficient is changed. Transmission power control circuit in the wireless transmitter of FIG. 11. A method for changing a synchronization symbol for recognizing the start of information in the burst and a correction coefficient for changing the control amount by the control amount calculating means from an initial correction coefficient to a steady-state correction coefficient. In a state where both window functions that determine the transition shape are fixed, the preamble pattern in the burst is set to have the earliest amplitude of the leading portion of the burst-like transmission wave, the predetermined average of the transmission power in the burst. 10. A pattern which is set to be larger than an amplitude corresponding to electric power.
A transmission power control circuit in the wireless transmitter according to 1. 12. A system in which a plurality of types of synchronization symbols exist for recognizing the start of information in the burst and any one of them is added to the burst and transmitted.
The transmission signal generation circuit includes a transmission power between the synchronization symbols for all the synchronization symbols in a preamble pattern that is larger than an amplitude corresponding to a predetermined average power for the transmission power in the burst. 10. The transmission power control circuit in a wireless transmitter according to claim 9, wherein the transmission power control circuit is set at a head portion of a transmission signal of a preamble pattern that minimizes the deviation. 13. A transmission power control circuit used in a system for transmitting a plurality of synchronization symbols for recognizing the start of information in the burst, wherein one of the synchronization symbols is alternatively added to the burst and transmitted. 10. The transmission power control circuit according to claim 9, wherein the predetermined reference amplitude value is a plurality of reference amplitude values suitable for each of the plurality of types of synchronization symbols.