JP2009253347A - Transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress peak power while maintaining signal quality by monitoring a distortion power/carrier power ratio. <P>SOLUTION: A peak power suppressing means having a peak power suppression function is provided with: a power calculating means 103 for calculating instantaneous power; a peak power detecting means 104 for detecting peak power from the instantaneous power; a peak power suppression ratio calculating means 105 for calculating peak power suppression ratio; a peak power suppression signal generating means 106 for multiplying a peak power suppression function input signal by the peak power suppression ratio to generate a peak power suppression signal; a carrier power measuring means 109 for calculating carrier power of the peak power suppression function input signal; a distortion power measuring means 110 for calculating distortion power from the peak power suppression signal; a distortion power/carrier power ratio calculating means 111 for calculating a ratio of the distortion power to the carrier power; and a threshold power control means 112 for determining an EVM (Error Vector Magnitude) estimated value from the ratio of the distortion power to the carrier power to control threshold power by comparing the EVM estimated value with an EVM standard value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a transmitter of a mobile communication system such as a W-CDMA (Wideband-Code Division Multiple Access) system and an OFDM (Orthogonal Frequency Division Multiplexing) system, and more particularly. The present invention relates to a transmitter capable of suppressing the peak power present in a transmission signal and reducing the PAPR (Peak-to-Average Power Ratio) to increase the power efficiency.

  Conventional transmitters have improved power efficiency by suppressing the peak power present in the transmission signal and lowering the PAPR. In the technique disclosed in Patent Document 1, when transmitting a signal to be transmitted, the transmission target signal level threshold power and the peak power level of the signal to be transmitted are determined in order to determine the peak of the signal to be transmitted. A peak factor is generated according to the ratio, and a result obtained by weighting the generated peak factor with a predetermined window function is generated as a peak suppression coefficient, and the peak power level of the transmission target signal is suppressed by the generated peak suppression coefficient. Thus, the PAPR of the signal to be transmitted is reduced.

JP 2005-20505 A

  With the technique disclosed in Patent Document 1, since it is possible to suppress the peak power of the transmitter and reduce the out-of-band leakage power, the power efficiency can be improved. However, since suppression of peak power degrades signal quality, EVM (Error Vector Magnitude: Error Vector Magnitude), which is a measure representing the modulation accuracy of a transmission signal, for example, the magnitude of an error component that is the difference between an ideal waveform and a measured waveform. It is necessary to monitor a standard value set in advance as a wireless characteristic within a transmission band such as (magnitude). For this reason, if the function for monitoring whether the standard value of the radio characteristics is satisfied is not provided, even if the standard value of the radio characteristics is satisfied with a specific signal, another signal with a different peak power generation pattern of the transmission signal may be used. There is a problem that the standard value of the radio characteristics may not be satisfied, and the signal quality related to the radio characteristics cannot be reliably guaranteed.

  This invention is made | formed in view of such a condition, and it aims at providing the peak power control method in a transmitter and a transmitter which can solve the said problem.

  The transmitter of the present invention detects a peak power present in an input signal, generates a peak power suppression signal, combines with the input signal to generate a transmission signal in which the peak power is suppressed, peak power suppression means, Based on the ratio of the two powers measured by the first power measuring means for measuring the power of the input signal, the second power measuring means for measuring the power of the peak power suppression signal, and the two power measuring means. And a threshold value control means for controlling the peak power detection threshold value.

  The transmitter of the present invention has a function of monitoring whether or not the standard value of the radio characteristics is satisfied, and performs peak power suppression control so as to satisfy the standard value of the radio characteristics, so that signal quality is reliably guaranteed. Can provide a transmitter.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment)
A transmitter that suppresses peak power so as to satisfy the standard value of radio characteristics in the embodiment of the present invention and a peak power control method in the transmitter will be described using the frequency spectrum waveform shown in FIG. The frequency spectrum waveform of FIG. 1 is a graph of the signal waveform with the horizontal axis being the frequency [MHz] and the vertical axis being the level [dB] which is the strength of each component. FIG. 1 shows a frequency spectrum waveform of a peak power suppression unit input signal that is an input signal to a peak power suppression unit having a peak power suppression function, and a peak power suppression component (hereinafter referred to as a distortion component) in which peak power is suppressed. ) And the frequency spectrum waveform of the peak power suppression signal are superimposed and displayed.

  In the frequency spectrum waveform obtained by superimposing the peak power suppression means input signal and the peak power suppression signal in the 10 MHz band OFDM signal shown in the example of FIG. 1, the distortion power and the carrier power calculated by the calculation formula (Equation 5) described later are used. The value of the ratio (hereinafter referred to as distortion power / carrier power ratio) is about −32 [dB].

  In the embodiment of the present invention, the value of EVM is estimated using the distortion power / carrier power ratio. Then, by adjusting the threshold power used when detecting the peak power based on the estimated EVM value, the peak power is suppressed so as to satisfy the EVM standard value.

  When peak power suppression is performed to reduce the PAPR of a signal, the main cause of EMV degradation is suppression of peak power. As long as a peak power suppression signal that intentionally outputs a peak power suppression component of a large level outside the transmission band is not generated, the correspondence between the distortion power / carrier power ratio and the EVM estimated value can be attached. FIG. 2 shows a correspondence table between the distortion power / carrier power ratio and the EVM estimated value. For example, the correspondence table may be created with the distortion power / carrier power set to 1 [dB] steps or the EVM estimated value set to 0.1 [%] steps. As these step sizes are reduced, more accurate control is possible. However, since a memory capacity is required, an optimal step size may be selected.

Next, a procedure for suppressing the peak power so as to satisfy the EVM standard value from the distortion power / carrier power ratio is shown. First, as an example, the EVM standard value is determined in advance to 2.5 [%] (the EVM standard value is selected as the optimum value for the device specifications). Distortion power / carrier power ratio EVM estimation value as shown in FIG. 2 corresponds to _{b n (= 2.5) [%} ] is _{a n (= -32) [dB} ]. Therefore, when the distortion power / carrier power ratio becomes larger than −32 [dB], the EVM estimated value becomes larger than the EVM standard value, and it is determined that the EVM standard is broken. When the threshold power is increased at this time, the distortion power / carrier power ratio is decreased, and the EVM estimated value can be controlled to be smaller than the EVM standard value. For threshold power control, the threshold power may be gradually increased, or the threshold power at which the distortion power / carrier power ratio is −32 [dB] may be calculated and set. Further, when the distortion power / carrier power ratio is smaller than −32 [dB], the EVM estimated value is smaller than the EVM standard value and a margin is generated, so that the threshold power can be reduced. By reducing the threshold power, the PAPR of the transmission signal can be reduced, and the power efficiency can be increased. With the above method, the peak power is suppressed by controlling the threshold power so that the EVM estimated value becomes the EVM standard value.

  A peak power suppression function that can guarantee the EVM standard by controlling the threshold power according to the embodiment of the present invention will be described below with reference to a functional block diagram of the peak power suppression means 200 shown in FIG.

  As shown in FIG. 5, the transmitter peak power suppression means 100 according to the conventional embodiment includes a delay adjustment first means 101, a delay adjustment second means 102, a power calculation means 103, a peak power detection means 104, a peak power. It comprises a suppression rate calculation means 105, a peak power suppression signal generation means 106, an I-phase signal synthesis means 107, and a Q-phase signal synthesis means 108. The transmitter peak power suppression means 200 according to the embodiment of the present invention includes, as shown in FIG. 3, each means of the transmitter peak power suppression means 100 according to the conventional embodiment and carrier power measurement means 109. , Distortion power measuring means 110, distortion power / carrier power ratio calculation means 111, and threshold power control means 112.

  The first delay adjustment means 101 inputs the I-phase component and Q-phase component of the input signal to the peak power suppression means 200, delays the output timing by a predetermined time, and combines the delayed I-phase component signal with the I-phase signal synthesis. The delayed Q-phase component signal is output to the means 107 to the Q-phase signal synthesis means 108.

  The delay adjustment second means 102 inputs the I-phase component and Q-phase component of the input signal to the peak power suppression means 200, delays the output timing for a predetermined time, and outputs the delayed I-phase component signal and Q-phase component signal. This is output to the peak power suppression signal generation means 106.

  The power calculation means 103 inputs the I-phase component and Q-phase component of the input signal to the peak power suppression means 200, calculates the instantaneous power for each sample data, and outputs it to the peak power detection means 104.

  The peak power detection unit 104 compares the instantaneous power calculated by the power calculation unit 103 with the threshold power. If the instantaneous power value is equal to or greater than the threshold power, the peak power detection unit 104 determines that the sample is the peak power. Further, the peak power detection unit 104 outputs the instantaneous power of the sample determined to be the peak power to the peak power suppression rate calculation unit 105.

  The peak power suppression rate calculation unit 105 calculates a coefficient (hereinafter referred to as a peak power suppression rate) for suppressing the peak power to the threshold power level and outputs it to the peak power suppression signal generation unit 106.

  The peak power suppression signal generation means 106 multiplies the I-phase component and Q-phase component of the signal input from the delay adjustment second means 102 by the peak power suppression rate calculated by the peak power suppression rate calculation means 105, and produces a distortion component. A peak power suppression signal is generated. Then, the I-phase component of the generated peak power suppression signal is output to the I-phase signal synthesis unit 107, the Q-phase component is output to the Q-phase signal synthesis unit 108, and the I-phase component and Q-phase component of the generated peak power suppression signal are further output. Is output to the distortion power measuring means 110.

  The I-phase signal synthesis means 107 subtracts the I-phase component output from the peak power suppression signal generation means 106 from the I-phase component output from the delay adjustment first means 101 and outputs the result.

  The Q-phase signal synthesis means 108 subtracts the Q-phase component output from the peak power suppression signal generation means 106 from the Q-phase component output from the delay adjustment first means 101 and outputs the result.

  The carrier power measuring means 109 calculates an average value (hereinafter referred to as carrier power) of the power of the signal input from the delay adjustment first means 101 for a fixed time, and the calculated carrier power is calculated as the distortion power / carrier power ratio calculating means 111. Output to.

  The distortion power measurement unit 110 calculates an average value (hereinafter referred to as distortion power) of the power of the peak power suppression signal input from the peak power suppression signal generation unit 106 for a certain time (hereinafter referred to as distortion power), and uses the calculated distortion power as distortion power / carrier power. It outputs to the ratio calculation means 111.

  The distortion power / carrier power ratio calculation means 111 calculates the distortion power / carrier power ratio, which is the ratio of the distortion power to the carrier power described above, and outputs it to the threshold power control means 112.

  The threshold power control unit 112 refers to the correspondence table between the distortion power / carrier power ratio and the EVM estimated value shown in FIG. 2, and calculates the EVM from the distortion power / carrier power ratio calculated by the distortion power / carrier power ratio calculation unit 111. The estimated value is extracted, it is determined whether the extracted EVM estimated value is larger or smaller than a predetermined EVM standard value, and the threshold power is controlled based on the determination result.

  The flash memory 113 is a rewritable nonvolatile memory that stores data used by each means. The flash memory 113 can be accessed from each means. The initial threshold power and the threshold power rewritten by the threshold power control unit 112 are stored in the flash memory 113. The data shown in the correspondence table between the distortion power / carrier power ratio and the EVM estimated value shown in FIG. 2 is stored in the flash memory 113.

  FIG. 4 is a flowchart showing the flow of peak power suppression processing in the embodiment of the present invention. The peak power suppression process will be described based on the order of steps shown in the flowchart of FIG.

(Step S0)
First, the I-phase component signal and the Q-phase component signal input to the peak power suppression unit 200 are processed in step S1, a delay adjustment first unit 101 that performs processing in step S1, a delay adjustment second unit 102 that performs processing in step S3, and step S4. Is output to the power calculation means 103 that performs the process.

(Step S1)
The first delay adjustment unit 101 performs delay adjustment of the I-phase component and the Q-phase component of the input signal to the peak power suppression unit 200. The I-phase component and Q-phase component of the signal output from the delay adjustment first means 101 are output to the carrier power measuring means 109 that calculates the average power value of the peak power suppression means input signal in step S2. In addition, the I-phase component and Q-phase component of the signal output from the first delay adjustment unit 101 are output to the I-phase signal combining unit 107 and the Q-phase signal combining unit 108 which perform the process of subtracting the peak power suppression signal in step 8. Is done.

(Step S2)
The carrier power measuring means 109 calculates the carrier power, which is the average power value in a certain section of the peak power suppression means input signal input from the delay adjustment first means in step S1, for example, by the following (Equation 1). The carrier power measurement means 109 outputs the calculated carrier power to the distortion power / carrier power ratio calculation means 111 that calculates the distortion power / carrier power ratio in step S10.
An example of a calculation formula for calculating the carrier power is shown in (Equation 1).

(Step S3)
The delay adjustment second means 102 performs delay adjustment of the I-phase component and Q-phase component of the input signal to the peak power suppression means 200. The I-phase component and Q-phase component of the signal output from the delay adjustment second means 102 are output to the peak power suppression signal generation means 106 that generates the peak power suppression signal in step S7.

(Step S4)
The power calculation means 103 calculates the instantaneous power for each sample from, for example, the following (Equation 2) from the I-phase component and Q-phase component of the peak power suppression means input signal. The instantaneous power calculated by the power calculation unit 103 is output to the peak power detection unit 104 that determines whether the instantaneous power is equal to or higher than the threshold power in step S5.
An example of the formula for calculating the instantaneous power is shown in (Equation 2).

(Step S5)
The peak power detection unit 104 takes out the threshold power from the flash memory 113. Then, the peak power detection unit 104 determines whether or not the instantaneous power input from the power calculation unit 103 in step S4 is equal to or greater than the extracted threshold power. When the peak power detection unit 104 determines that the instantaneous power is greater than or equal to the threshold power, the instantaneous power becomes the peak power. Therefore, in step S6, the peak power suppression rate calculation unit 105 that calculates the peak power suppression rate Outputs instantaneous power.

(Step S16)
When the peak power detection unit 104 determines in step S5 that the instantaneous power is smaller than the threshold power, the process proceeds to step S16, and since the instantaneous power does not become the peak power, it is not necessary to suppress the peak power. In step S7, the suppression rate is set to 0, and the peak power suppression signal generation unit 106 that generates a peak power suppression signal is output.

(Step S6)
The peak power suppression rate calculation means 105 proceeds to step S6 when the instantaneous power is equal to or higher than the threshold power in step S5, and inputs the peak power from the peak power detection means 104. Further, the peak power suppression rate calculation unit 105 takes out the threshold power from the flash memory 113. The peak power suppression rate calculation means 105 calculates the peak power suppression rate from the peak power and the threshold power by, for example, the following (Equation 3), and outputs it to the peak power suppression signal generation means 106 that generates the peak power suppression signal in step S7. .
An example of the calculation formula for the peak power suppression rate is shown in (Equation 3).

(Step S7)
The peak power suppression signal generating means 106 multiplies the I-phase component and Q-phase component of the peak power suppression means input signal by the peak power suppression rate, and generates an I-phase component and a Q-phase component of the peak power suppression signal, which is a distortion component. In step S8, the I-phase signal combining means 107 and Q-phase signal combining means 108 for subtracting the peak power suppression signal and the distortion power measuring means 110 for calculating the average power value in step S9 are output.

(Step S8)
The I-phase signal combining unit 107 subtracts the I-phase component of the peak power suppression signal from the I-phase component of the delay adjustment first unit and outputs the result. The Q-phase signal combining unit 108 subtracts the Q-phase component of the peak power suppression signal from the Q-phase component of the delay adjustment first unit and outputs the result.

(Step S9)
The distorted power measuring means 110 calculates the distorted power, which is the average power value in the certain section, from the peak power suppression signal generated in step S7, for example, by the following (Equation 4). The distortion power measurement means 110 outputs the calculated distortion power to the distortion power / carrier power ratio calculation means 111 that calculates the distortion power / carrier power ratio in step S10.
An example of a calculation formula for calculating the distortion power is shown in (Expression 4).

(Step S10)
The distortion power / carrier power ratio calculation means 111 calculates a distortion power / carrier power ratio from the input carrier power and the input distortion power by, for example, the following (Equation 5), and a threshold value for determining the EVM estimated value in step S11 It outputs to the power control means 112. Since the distortion power is a very small value compared to the carrier power, the calculation result is easy to control when converted to the dB value.
An example of a calculation formula for calculating the distortion power / carrier power ratio is shown in (Formula 5).

(Step S11)
The threshold power control unit 112 extracts the distortion power / carrier power ratio and EVM estimated value correspondence table data shown in FIG. 2 from the flash memory 113 and refers to the EVM estimated value correspondence table data to input the distortion power / An EVM estimate corresponding to the carrier power ratio is determined. For example, if the distortion power / carrier power ratio is an _{+ 1} , the EVM corresponding to the distortion power / carrier power ratio an _{+ 1} in the correspondence table data of the distortion power / carrier power ratio and the EVM estimation value shown in FIG. Since the estimated value is b _{n + 1} , the EVM estimated value is determined to be b _{n + 1} .

(Step S12)
Next, the threshold power control unit 112 determines whether or not the EVM estimated value determined in step S11 is larger than a predetermined EVM standard value. When the threshold power control unit 112 determines that the EVM estimated value is larger than the EVM standard value, the process proceeds to step S13 for controlling the threshold power. When the threshold power control unit 112 determines that the EVM estimated value is equal to or less than the EVM standard value, the threshold power control unit 112 proceeds to step S14 to return the threshold power to the initial value.

(Step S13)
Since it is determined in step S12 that the EVM estimated value is greater than the EVM standard value, the threshold power control unit 112 adds a predetermined value to the threshold power to obtain the threshold power.

(Step S14)
When it is determined in step S12 that the EVM estimated value is equal to or less than the EVM standard value, the threshold power control unit 112 takes out the initial value of the threshold power from the flash memory 113, and sets the extracted initial value of the threshold power as the threshold power. To do.

(Step S15)
The threshold power control means 112 stores the threshold power determined in step S13 or step S14 in the flash memory 113. The threshold power stored in the flash memory 113 is extracted for calculation by the peak power detection means 104 in step S5 and the peak power suppression rate calculation means 105 in step S6 that generate the next peak power suppression signal. Thereafter, the input signal is continuously processed by repeatedly executing from step S0.

  According to such an embodiment, since the distortion power / carrier power ratio can be associated with the EVM, the EVM estimated value corresponding to the distortion power / carrier power ratio is determined in advance based on data measured in the past. be able to. Then, the distortion power / carrier power ratio is determined conversely from the EVM standard value that maintains the signal quality. By controlling the threshold power of the peak power so as to have this determined distortion power / carrier power ratio, it is possible to provide a transmitter capable of maintaining the EVM standard value and a peak power control method in the transmitter.

  The peak power suppression means 200 described in the above embodiment can be applied to a communication apparatus such as a transmitter, a transmission amplifier, and the like.

In summary, the present embodiment has the following characteristics.
(1) The peak power control apparatus according to the present invention detects peak power present in an input signal, generates a peak power suppression signal, combines with the input signal, and generates a transmission signal in which the peak power is suppressed. Suppression means, first power measurement means for measuring the power of the input signal, second power measurement means for measuring the power of the peak power suppression signal, and two measured by the two power measurement means Threshold control means for controlling the peak power detection threshold based on the power ratio is provided.
(2) The peak power control apparatus according to the present invention includes carrier power measurement means for measuring carrier power of an input signal, and distortion for measuring distortion power that is power of the peak power suppression signal generated by the peak power suppression signal generation means. A power measurement means, a distortion power / carrier power ratio calculation means for calculating a ratio of the carrier power and the distortion power, and a ratio of the carrier power and the distortion power calculated by the distortion power / carrier power ratio calculation means. Threshold control means for controlling the threshold power based on this, and peak power suppression means for generating a signal in which the peak power of the input signal is suppressed is provided.
(3) The threshold value control means in the peak power control apparatus of the present invention is configured such that when the EVM value of the input signal falls outside the standard range, the EVM value of the input signal falls within the standard range. Thus, the threshold power is controlled as described above.
(4) A transmitter including the peak power suppression unit according to any one of (1) to (3).
(5) A transmission amplifier including the peak power suppression unit according to any one of (1) to (3).
(6) The peak power control method of the invention detects peak power present in an input signal, generates a peak power suppression signal, and combines it with the input signal to generate a transmission signal in which the peak power is suppressed. A first power measurement step for measuring the power of the input signal, a second power measurement step for measuring the power of the peak power suppression signal, and two powers measured by the two power measurement steps And a threshold value control step for controlling the peak power detection threshold value based on the ratio.
(7) The peak power control method of the present invention includes a carrier power measurement step for measuring the carrier power of an input signal, and a distortion for measuring distortion power that is the power of the peak power suppression signal generated by the peak power suppression signal generation step. A power measurement step, a distortion power / carrier power ratio calculation step for calculating a ratio of the carrier power and the distortion power, and a ratio of the carrier power and the distortion power calculated in the distortion power / carrier power ratio calculation step. And a threshold power control step for controlling the threshold power based on the threshold power and a peak power suppression step for generating a signal in which the peak power of the input signal is suppressed.
(8) In the peak power control method of the present invention, when the EVM value of the input signal is out of the standard range, the threshold power is set so that the EVM value of the input signal is within the standard range. It is characterized by control.
Note that the present invention is not limited to the above-described embodiment, and is generally applicable to the case of controlling power.

  The present invention is suitable for the peak power control method in the transmitter and the transmitter, but is not limited to the peak power control method in the transmitter and the transmitter, and can be applied to general communication apparatuses using signals.

It is a figure explaining the frequency spectrum waveform in the peak power suppression function which concerns on embodiment of this invention. It is a table | surface which shows an example of a response | compatibility of the distortion electric power / carrier electric power ratio which concerns on embodiment of this invention, and an EVM estimated value. It is a block diagram which shows the peak power suppression means of the transmitter concerning embodiment of this invention. It is a flowchart which shows the peak power suppression process concerning embodiment of this invention. It is a block diagram which shows the peak power suppression means of the transmitter concerning the conventional embodiment.

Explanation of symbols

100, 200... Peak power suppression means 101... Delay adjustment first means 102... Delay adjustment second means 103... Power calculation means 104. Peak power detection means 105... Peak power suppression rate calculation means 106... Peak power suppression signal generation means 107... I phase signal synthesis means 108. Phase signal combining means 109... Carrier power measuring means 110... Distorted power measuring means 111... Distorted power / carrier power ratio calculating means 112. Control means

Claims (1)

A peak power suppression unit that detects a peak power present in the input signal to generate a peak power suppression signal, generates a transmission signal in which the peak power is suppressed by combining with the input signal; and
First power measuring means for measuring the power of the input signal;
Second power measuring means for measuring the power of the peak power suppression signal;
Threshold control means for controlling a peak power detection threshold based on a ratio of the two powers measured by the two power measuring means;
A transmitter characterized by comprising:

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