JP4847838B2 - Transmitter - Google Patents

Description

  The present invention relates to, for example, a transmitter that transmits a signal of a CDMA (Code Division Multiple Access) method or an OFDM (Orthogonal Frequency Division Multiplexing) method, and particularly suppresses the peak power level of the signal to be transmitted. The present invention relates to a transmitter that effectively performs.

For example, in a transmitter of a mobile communication system that employs a CDMA system and performs wireless communication, a signal to be transmitted (transmission signal) is processed by a digital modulation unit.
FIG. 7 shows a configuration example of the transmitter 3, and N code multiplexed signal generation units B1 to BN corresponding to a plurality of N carriers.
Here, the configuration and operation of the transmitter 3 of this example are generally provided with a carrier number setting unit 15 as compared with the configuration and operation of the transmitter 1 shown in FIG. Not different with respect to points.

The window function generation unit 81 provided in the transmitter 3 of this example will be described. In this example, a window function generation unit 81 that uses a method having values as a table for the window function in advance, instead of a method for directly generating the window function will be described.
FIG. 8 shows a configuration example of the window function generation unit 81.
In the window function generation unit 81 of this example, the comparison result between the level of the threshold power Thr (t) and the level of the instantaneous power Pint (t) is used as an input from the comparison unit 33, and the window function corresponding to the value of the comparison result is obtained. Values are created in advance, and are stored as one window function table 91. The window function table 91 can be configured by a memory or the like using the comparison result as an input address.

  For example, Patent Document 1 is known as a technique for suppressing the peak power by multiplying the intermediate frequency signal after each carrier synthesis by a window function around the peak power (see Patent Document 1).

JP 2005-20505 A

However, in the transmitter 3 as shown in FIGS. 7 and 8, further improvement has been desired for suppressing the peak power level of the signal to be transmitted.
The present invention has been made in view of such conventional circumstances, and an object thereof is to provide a transmitter capable of effectively suppressing the peak power level of a signal to be transmitted. .
Specifically, for example, in the present invention, when transmitting a signal to be transmitted, the peak power of the signal to be transmitted is set by setting an optimal window function according to the number of carriers of the signal to be transmitted. An object of the present invention is to effectively suppress the signal level and improve the signal quality characteristics. Here, as signal quality characteristics, for example, in 3GPP, there are ACLR (Adjacent Channel Leakage Power Ratio), EVM (Error Vector Manufacturer), PCDE (Peak Code Domain Error), and the like.

In order to achieve the above object, the transmitter according to the present invention transmits a signal to be transmitted with the following configuration.
That is, the carrier number specifying means specifies the number of carriers included in the signal to be transmitted. The window function setting means sets a window function corresponding to the number of carriers specified by the carrier number specifying means. Coefficient generation means generates a coefficient for peak level suppression based on the signal to be transmitted and the window function set by the window function setting means. Suppression means suppresses the peak level of the signal to be transmitted using the coefficient generated by the coefficient generation means.

  Therefore, since a coefficient for peak level suppression is generated using a window function corresponding to the number of carriers included in the signal to be transmitted, the signal to be transmitted depends on the number of carriers to be transmitted. The peak power level can be effectively suppressed, and signal quality characteristics (for example, ACLR, EVM, PCDE, etc.) can be improved.

Here, for example, when the signals to be transmitted are configured by combining signals of N carriers 1 to N having a plurality of signals at maximum, the number of carriers included in the signal to be transmitted is 1 It can take any value of ~ N. When the number of carriers included in the signal to be transmitted is 0, there is no signal to be transmitted (that is, no signal). Various numbers may be used as N.
Also, the number of carriers included in the signal to be transmitted can vary depending on, for example, the communication status, but may be set fixedly.

Various modes may be used as a mode for specifying the number of carriers included in a signal to be transmitted. For example, the number of carriers included in a signal to be transmitted is a user or an external device. May be used, and may be specified based on the setting contents, or may be used by detecting the number of carriers at each time point at any time or regularly. May be.
In addition, for example, it is also possible to use an aspect that specifies whether or not each of a plurality of carriers that can be included in a signal to be transmitted is included as a transmission target. It is possible to specify whether or not to be a transmission target, and to specify the number (total number) of carriers to be transmission targets.

  Various modes may be used as a mode for setting the window function according to the number of carriers included in the signal to be transmitted. For example, a window function suitable for each possible number of carriers. May be used in which the value of the window function is stored in advance in the memory and the value of the window function corresponding to the number of carriers is read from the memory and set, or for each possible number of carriers. Information such as mathematical formulas for generating (calculating, etc.) window function values suitable for the memory is stored in advance in the memory, mathematical formulas corresponding to the number of carriers are read from the memory, and the read mathematical formulas are A mode of setting the value of the window function generated by using may be used.

Various modes may be used as a coefficient for suppressing a peak level for a signal to be transmitted and a mode for suppressing a peak level for a signal to be transmitted using the coefficient. As an example, a peak level is suppressed by performing a predetermined calculation on a signal to be transmitted using a coefficient for peak level suppression, and a coefficient for realizing such peak level suppression is a predetermined coefficient. A mode of generating by calculation can be used.
Note that various signal levels such as a power level or a voltage level may be used.

  As described above, according to the transmitter according to the present invention, since the coefficient for peak level suppression is generated using the window function according to the number of carriers included in the signal to be transmitted, Depending on the number of carriers to be suppressed, it is possible to effectively suppress the peak power level of the signal to be transmitted.

Embodiments according to the present invention will be described with reference to the drawings.
In the present embodiment, a case where the present invention is applied to a transmission apparatus provided in a base station apparatus or the like of a wireless communication system employing a CDMA system is shown. In such a transmission apparatus, generally, a high power signal is amplified by an amplifier.
In addition to the CDMA system, the present invention may be applied to an OFDM system or the like.

A first embodiment of the present invention will be described.
FIG. 1 shows a configuration example of the transmitter 1 of this example, and also shows N code multiplexed signal generation units B1 to BN corresponding to a plurality of N carriers 1 to N.
In the transmitter 1 of this example, N code multiplexed signal generation units B1 to BN are connected to N carriers 1 to N, respectively. In addition, a plurality of (n + 1) pieces of transmission data are input to each of the code multiplexed signal generation units B1 to BN for each of the carriers 1 to N.

The transmitter 1 of this example includes a digital modulation unit 11, a peak power suppression unit 12, a frequency conversion unit 13, and a carrier number setting unit 15.
The digital modulation unit 11 includes N waveform shaping filters C1 to CN and N digital quadrature modulation units E1 to EN corresponding to the N carriers 1 to N, and an I-phase component (I Two adders 21 and 22 are provided corresponding to the component) and the Q-phase component (Q component).

The peak power suppression unit 12 includes two delay units 23 and 24 and two multipliers 25 and 26 corresponding to the I component and the Q component, and the peak power suppression coefficient calculation unit 14 includes Is provided.
The peak power suppression coefficient calculation unit 14 includes an instantaneous power calculation unit 31, a threshold value generation unit 32, a comparison unit 33, a suppression rate generation unit 34, a window function generation unit 35, and a suppression coefficient calculation unit 36. ing.
The frequency conversion unit 13 includes two D / A (Digital to Analog) converters 27 and 28 corresponding to the I component and the Q component, and also includes an analog quadrature modulation unit 29.

  Here, each of the code multiplex signal generation units B1 to BN performs spread modulation by multiplying the input transmission data D (0) to D (n) by the code multiplex signal sequence, and performs each of the carriers 1 to N. (N + 1) spread modulation signals are combined, and the resulting I component DI and Q component DQ are output to the waveform shaping filters C1 to CN of the transmitter 1. For example, a spread code is used as the code multiplexed signal sequence.

An example of the operation performed by the transmitter 1 of this example will be shown. Note that t represents the sampling time.
Each of the waveform shaping filters C1 to CN inputs the signals of the carriers 1 to N, which are spread and modulated by the code multiplexed signal generators B1 to BN, for each of the I component and the Q component, and occupies the input signals. Spectrum shaping is performed so that the band falls within a preset value, and the I component and Q component of the spectrum shaping result are output to the digital quadrature modulation units E1 to EN.
Each of the digital quadrature modulation units E1 to EN performs digital quadrature modulation on the signals of the respective carriers 1 to N input from the respective waveform shaping filters C1 to CN, and sends the I component of the digital quadrature modulation result to one adder 21. The Q component of the digital quadrature modulation result is output to the other adder 22.
Here, in this example, the waveform shaping filters C1 to CN and the digital quadrature modulation units E1 to EN are controlled by the carrier number setting unit 15 described later. This will be described later.

One adder 21 adds (combines) the digital quadrature modulation results input from the N digital quadrature modulation units E1 to EN to the I component, and adds the signal AI (t) of the addition result to one delay unit. 23 and the instantaneous power calculation unit 31.
The other adder 22 adds (synthesizes) the digital quadrature modulation results input from the N digital quadrature modulation units E1 to EN with respect to the Q component, and adds the signal AQ (t) of the addition result to the other delay unit. 24 and the instantaneous power calculation unit 31.

  Based on the I component AI (t) and the Q component AQ (t) of the addition result signal input from the two adders 21 and 22, the instantaneous power calculation unit 31 determines the instantaneous power Pint (t ) And outputs the calculation result to the threshold generation unit 32, the comparison unit 33, and the suppression rate generation unit 34. Here, as an example, the instantaneous power Pint (t) is expressed as (Equation 1).

The threshold generation unit 32 sets a threshold power Thr (t) for performing peak suppression based on the instantaneous power Pint (t) input from the instantaneous power calculation unit 31, and the setting result is compared with the comparison unit 33 and the suppression. Output to the rate generator 34.
Here, various values may be set as the threshold power Thr (t). For example, the threshold power Thr (t) is a value larger than the instantaneous power Pint (t) by a predetermined value, or the instantaneous power Pint (t) in a predetermined period. A value that is larger than the average value by a predetermined value can be used.

  The comparison unit 33 compares the level of the threshold power Thr (t) input from the threshold generation unit 32 with the level of the instantaneous power Pint (t) input from the instantaneous power calculation unit 31, and suppresses the comparison result. The data is output to the rate generator 34 and the window function generator 35. Here, in this example, the portion where the instantaneous power Pint (t) exceeds the threshold power Thr (t) is detected as the peak power portion of the addition result signal described above.

Based on the input from the instantaneous power calculator 31 and the input from the comparator 33, the suppression rate generator 34 detects the peak power by the comparator 33 when the instantaneous power Pint (t) exceeds the threshold power Thr (t). If it is, the ratio between the threshold power Thr (t) and the instantaneous power Pint (t) is calculated to calculate a predetermined peak factor Gain (t), and the calculation result is output to the suppression coefficient calculation unit 36. .
Further, the suppression rate generation unit 34 determines that the instantaneous power Pint (t) is less than or equal to the threshold power Thr (t) based on the input from the instantaneous power calculation unit 31 and the input from the comparison unit 33, and the peak power Is not detected (that is, not detected), a value of 1 is set as the peak factor Gain (t), and the setting result is output to the suppression coefficient calculation unit 36.

  Here, in this example, the peak factor Gain (t) is expressed as (Equation 2). In this example, since the instantaneous power Pint (t) and the threshold power Thr (t) are represented by power dimensions, the square root (sqrt) is calculated in order to suppress the peak level in the voltage domain. ing.

Based on the input from the comparison unit 33, the window function generation unit 35 determines a predetermined window when the instantaneous power Pint (t) exceeds the threshold power Thr (t) and the comparison unit 33 detects the peak power. The function Weight (s) is generated, and the generation result is output to the suppression coefficient calculation unit 36. In other cases (that is, when the peak power is not detected), the window function generation unit 35 outputs, for example, a value of 1 to the suppression coefficient calculation unit 36.
Here, in this example, the window function generation unit 35 is controlled by the carrier number setting unit 15 described later. This will be described later.

When the Hanning window is used as the window function, an example of the window function Weight (s) is expressed as (Equation 3).
M is an integer representing the number of samples. Further, the number of samples M is set by being optimized according to the standard bandwidth of the transmission spectrum, for example.
In addition, s corresponds to a section from time (T−M / 2) to time (T + M / 2) with respect to time T when the peak power is generated, from (−M / 2) to (+ M / 2). Take a value in the interval (−M / 2 ≦ s ≦ + M / 2). Thereby, M peak power suppression coefficients Exp_Gain (t) are generated around one time T when the peak power exists.

The suppression coefficient calculation unit 36, for example, a peak factor Gain input from the suppression rate generation unit 34 in a section from time (T−M / 2) to time (T + M / 2) centered on time T at which peak power exists. A weight is given to the window (t) by the window function Weight (s) input from the window function generator 35, and the result of giving the weight is a peak power suppression coefficient Exp_Gain (t). Output to.
As an example, the peak power suppression coefficient Exp_Gain (t) is expressed as (Equation 4). T represents the time when peak power occurs.

As described above, the peak power suppression coefficient calculation unit 14 sets the peak power suppression coefficient Exp_Gain (t) for realizing necessary peak power level suppression for the instantaneous power Pint (t) of the addition result signal described above. To do.
In this example, the Hanning window is used, but other arbitrary window functions may be used.
The purpose of multiplying the window function is to keep the frequency band of distortion generated when suppressing the peak power level in the vicinity of the carrier. Since various studies have been tried on the window function and it is generally known, the detailed description is omitted in this specification.

Each delay unit 23, 24 is an addition result signal input from each adder 21, 22 corresponding to the time required for the processing for calculating the peak power suppression coefficient Exp_Gain (t) by the peak power suppression coefficient calculation unit 14. The delays of AI (t) and AQ (t) are adjusted, and the delayed signals are output to the multipliers 25 and 26.
The multipliers 25 and 26 use the addition result signals AI (t) and AQ (t) input from the delay units 23 and 24 and the peak power suppression coefficient Exp_Gain (t) input from the suppression coefficient calculation unit 36, respectively. Multiplication is performed to suppress the peak power and the surrounding signal levels, and the multiplication results A′I (t) and A′Q (t) are output to the D / A converters 27 and 28. Here, the multiplication results A′I (t) and A′Q (t) are expressed as (Equation 5).

Each D / A converter 27, 28 converts the digital signal input from each multiplier 25, 26 into an analog signal, and outputs the D / A conversion result to the analog quadrature modulation unit 29.
The analog quadrature modulation unit 29 performs analog quadrature modulation on the analog signal composed of the I component and the Q component input from the two D / A converters 27 and 28, thereby converting the signal into a signal in a radio frequency band. Output.
The signal output from the analog quadrature modulation unit 29 is then subjected to processing such as amplification as necessary, and is wirelessly transmitted by an antenna (not shown).

The carrier number setting unit 15 determines the carrier transmission state based on the carrier on / off information (On / Off information) set in advance or based on the detection result of carrier detection. The information on the carrier to be processed by the transmitter is stored in a memory or the like.
Here, as the carrier on / off information, for example, it is specified whether each of the plurality of carriers 1 to N is in a transmission state (on state) or not in a transmission state (off state). Information is used.
In the carrier detection, for example, the plurality of carriers 1 to N are transmitted by detecting a carrier to be transmitted (on-state carrier) or by detecting another carrier (off-state carrier). A carrier in a state (on state) and a carrier in a state of not transmitting (off state) are identified.

The carrier number setting unit 15 outputs the setting information of the transmission carrier specified as described above to each waveform shaping filter C1 to CN and each digital quadrature modulation unit E1 to EN. Here, in the transmission carrier setting information, for example, it is specified whether each of the carriers 1 to N is in an on state or an off state.
Each of the waveform shaping filters C1 to CN and each of the digital quadrature modulation units E1 to EN controls operation on / off based on transmission carrier setting information input from the carrier number setting unit 15. In this example, in the block (each waveform shaping filter C1 to CN and each digital quadrature modulation unit E1 to EN) corresponding to the carrier in which the transmission state (ON state) is set, the operation is performed and the operation is executed. In the block (each waveform shaping filter C1 to CN and each digital quadrature modulation unit E1 to EN) corresponding to the carrier in which no transmission (off state) is set, the operation is turned off and the operation is stopped.

The carrier number setting unit 15 outputs the transmission carrier setting information specified as described above to the window function generating unit 35.
The window function generation unit 35 generates a window function Weight (s) corresponding to the transmission carrier setting information based on the transmission carrier setting information input from the carrier number setting unit 15 and outputs the window function Weight (s) to the suppression coefficient calculation unit 36. To do. In this example, the window function generation unit 35 generates a window function Weight (s) corresponding to the number of transmission carriers specified based on the transmission carrier setting information (the number of carriers in the on state). Thus, the window function Weight (s) is switched according to the number of transmission carriers.

Here, the window function generation unit 35 of this example will be described in detail.
In this example, the window function generation unit 35 that uses a method having a value as a table in advance for the window function will be described. However, as another configuration example, a configuration using a method that directly generates a window function may be used. Good.
FIG. 2 shows a configuration example of a window function generation unit 35a, which is a first configuration example of the window function generation unit 35, and also shows a comparison unit 33, a suppression coefficient calculation unit 36, and a carrier number setting unit 15. is there.
The window function generation unit 35a of this example includes N window function tables F1 to FN that are the same as the total number N of carriers, and a selector 41.

The plurality of window function tables F1 to FN store the correspondence between the comparison result value from the comparison unit 33 and the corresponding window function value in the memory for each number of carriers. That is, each of the window function tables F1 to FN stores the correspondence between the input value from the comparison unit 33 and the output value of the window function corresponding to the number of carriers (1 to N in this example). Here, the information stored in each of the window function tables F1 to FN is created and set in advance, for example.
In this example, when the peak power is not detected, the window function generation unit 35a outputs, for example, a value of 1 to the suppression coefficient calculation unit 36. Therefore, the output value corresponding to this case is also output. Stored in the window function tables F1 to FN.

The selector 41 receives the transmission carrier setting information from the carrier number setting unit 15 and corresponds to the number of transmission carriers specified by the input transmission carrier setting information (any one of the window function tables F1 to FN). ) And the output terminal of the selected window function table is connected to the input terminal of the suppression coefficient calculation unit 36. Thereby, based on the window function table selected by the selector 41, an output value corresponding to the input value from the comparison unit 33 is output to the suppression coefficient calculation unit 36.
As described above, in this example, by having the window function tables F1 to FN for the number of transmission carriers, the window function suitable for the number of transmission carriers is used to obtain the peak power suppression effect suitable for the number of transmission carriers. Can do.

FIG. 3 shows a configuration example of a window function generation unit 35b, which is a second configuration example of the window function generation unit 35, and also shows a comparison unit 33, a suppression coefficient calculation unit 36, and a carrier number setting unit 15. is there.
In the configuration of this example, a control unit 53 is provided.
The window function generation unit 35b of this example includes two window function tables 51a and 51b and a selector 52.

Each of the two window function tables 51 a and 51 b has a memory for storing the correspondence between the input value from the comparison unit 33 and the output value of the window function, and the storage contents are rewritten by the control unit 53.
In this example, when the peak power is not detected, the window function generation unit 35b outputs, for example, a value of 1 to the suppression coefficient calculation unit 36. Therefore, the output value corresponding to this case is also output. It is stored in the window function tables 51a and 51b.

The control unit 53 receives the transmission carrier setting information from the carrier number setting unit 15 and displays information on the value of the window function corresponding to the number of transmission carriers specified by the input transmission carrier setting information in one window function table. (A surface) 51a or the other window function table (B surface) 51b is set.
The selector 52 selects the window function table (one of the two window function tables 51a and 51b) in which the window function value information is set by the control unit 53, and sets the output end of the selected window function table as the suppression coefficient. Connected to the input end of the calculation unit 36. Thereby, based on the window function table selected by the selector 52, an output value corresponding to the input value from the comparison unit 33 is output to the suppression coefficient calculation unit 36.

  Here, various configurations may be used as the configuration for controlling the selector 52. As one configuration example, the window function table initially selected by the selector 52 and the control unit 53 are initially set to match the window function table for setting the window function value information. Each time the selector 52 and the control unit 53 change the number of transmission carriers specified by the transmission carrier setting information input from the carrier number setting unit 15, the selector 52 and the control unit 53 select a window function table opposite to the current one. Any configuration can be used. As another configuration example, the control unit 53 outputs information specifying the window function table (one of the two window function tables 51a and 51b) in which the window function value information is set to the carrier number setting unit 15, A configuration in which the carrier number setting unit 15 outputs the information to the selector 52 and the selector 52 selects the window function table based on the information can be used.

In addition, the control unit 53 constantly or periodically monitors the transmission carrier setting information input from the carrier number setting unit 15, and when the number of transmission carriers changes, the control unit 53 currently selects the transmission carrier. The window function value information corresponding to the number of transmission carriers is set in the window function table opposite to the window function table. When the setting by the controller 53 is completed (or after that), the selector 52 selects the window function table on the surface opposite to the current one.
By performing such control, even when the number of transmission carriers changes, window function value information is set in a window function table that is not currently used, and this is switched to the currently used window function table. Thus, a peak power suppression effect suitable for the number of transmission carriers can be obtained using a window function suitable for the number of transmission carriers.

Here, in this example, the window function tables 51a and 51b having a two-surface configuration are shown, but a configuration having three or more surfaces can be used, or a one-surface configuration can be used.
For example, in a configuration including a window function table for only one surface, the window function table is reset by the control unit 53 when the number of transmission carriers changes. In this configuration, the peak power suppression operation during the resetting of the window function table does not operate normally strictly, but a normal peak power suppression operation is realized after the resetting.

As described above, in the transmitter 1 of this example, for example, when transmission is performed using a plurality or a single carrier frequency, the instantaneous power Pint (t) of the digital modulation results AI (t) and AQ (t) to be transmitted ) And the threshold power Thr (t) is calculated as a peak factor Gain (t), and the peak factor Gain (t) is weighted by the window function Weight (s) to suppress the peak power. The coefficient Exp_Gain (t) is calculated, and the voltage level of the peak power of the digital modulation results AI (t) and AQ (t) and the voltage level around the peak power are determined by the peak power suppression coefficient Exp_Gain (t). Control.
Therefore, in the transmitter 1 of this example, both reduction of peak power and limitation of out-of-band leakage power can be achieved, and peak power can be effectively reduced.

Further, in the transmitter 1 of this example, when transmitting a signal to be transmitted, an optimal window function is set according to the number of carriers of the signal to be transmitted.
Therefore, in the transmitter 1 of this example, it is possible to effectively suppress the peak power level of the signal to be transmitted, and to improve the signal quality characteristics (for example, 3LRP, ACLR, EVM, PCDE, etc.). Can be improved.
Further, in the transmitter 1 of this example, the waveform shaping filters C1 to CN and the digital quadrature modulation units E1 to EN are turned on / off according to whether or not the signals of the carriers 1 to N are to be transmitted. Control.
Therefore, in the transmitter 1 of this example, it is possible to improve efficiency by turning on only the processing block corresponding to the carrier to be transmitted.

  Note that the peak power suppression process as in this example is a non-linear process, which may affect a system using a linear modulation method. For this reason, there is a trade-off relationship between reducing the peak power and increasing the power efficiency of the amplifier and the communication quality. For this reason, specific numerical values used for the peak power suppression processing as in this example may be determined variously depending on, for example, the system operator that employs the present invention.

The structural example of the transmitter 1 of this example is shown.
In the transmitter 1 that transmits a signal to be transmitted,
In order to suppress the peak power of the signal to be transmitted, a peak power suppression rate (in this example, a peak factor Gain (t) in accordance with the ratio between the transmission target signal level threshold and the peak power level of the signal to be transmitted )) To generate a peak power suppression rate generator 34;
A window function generator 35 that outputs a predetermined window function Weight (t);
A peak power suppression coefficient calculation unit 36 that generates a peak power suppression coefficient Exp_Gain (t) obtained by weighting the peak power suppression rate generated by the peak power suppression rate generation unit 34 with a predetermined window function;
Multipliers 25 and 26 for suppressing the peak power level of the signal to be transmitted by the peak power suppression coefficient generated by the peak power suppression coefficient calculator 36;
A carrier number setting unit 15 for setting information on the number of carriers to be transmitted to the window function generation unit 35;
The peak power suppression rate generator 34 is based on the input from the instantaneous power calculator 31 that detects the level of the signal to be transmitted (in this example, instantaneous power), and the transmission target signal level threshold and the instantaneous power calculator 31 sets a peak power suppression rate according to the ratio to the level of the signal to be transmitted detected by 31;
The peak power suppression coefficient calculation unit 36 sets the peak power suppression rate set by the peak power suppression rate generation unit 34 using a window function in which an optimal one is selected from a plurality of window functions according to the number of carriers. Generate the weighted result as the peak power suppression coefficient,
The multipliers 25 and 26 multiply the signal to be transmitted by the peak power suppression coefficient generated by the peak power suppression coefficient calculator 36 to suppress the level of the signal to be transmitted.

  In the transmitter 1 of the present example, the carrier number specifying unit is configured by the function of the carrier number setting unit 15 specifying the number of carriers included in the signal to be transmitted, and the window function generating unit 35 A window function setting unit is configured by a function of setting a window function according to the number of carriers based on transmission carrier setting information input from the setting unit 15, and includes an instantaneous power calculation unit 31, a threshold generation unit 32, and a comparison A coefficient for peak level suppression (in this example, peak power suppression) based on a signal to be transmitted by the unit 33, suppression rate generation unit 34, and suppression coefficient calculation unit 36 or a window function set by the window function generation unit 35. Coefficient generating means is configured by the function of generating the coefficient Exp_Gain (t)), and the multipliers 25 and 26 use the coefficient to set the peak level for the signal to be transmitted. Functions by suppressing means for pressurizing is configured.

A second embodiment of the present invention will be described.
FIG. 4 shows a configuration example of the transmitter 2 of this example, and also shows N code multiplexed signal generators B1 to BN corresponding to a plurality of N carriers 1 to N.
The configuration and operation of the transmitter 2 of this example are compared with the configuration and operation of the transmitter 1 shown in FIG. 1. Multipliers 61 and 62 and a subtracter are provided in the subsequent stage of the delay units 23 and 24 of the peak power suppression unit 16. The difference is that 63 and 64 are provided, and that a subtractor 37 is provided between the suppression rate generator 34 and the suppression coefficient calculator 36 in the peak power suppression coefficient calculator 17.
In FIG. 4, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and in this example, differences from the first embodiment with reference to FIG. 1 will be described in detail.

The suppression rate generator 34 of the peak power suppression coefficient calculator 17 outputs a predetermined peak factor Gain (t) to the subtractor 37. The peak factor Gain (t) is expressed as, for example, (Equation 2).
The subtractor 37 subtracts the peak factor Gain (t) input from the suppression rate generation unit 34 from 1, that is, calculates {1-Gain (t)}, and outputs the result to the suppression coefficient calculation unit 36. To do.
The suppression coefficient calculation unit 36 gives a weight to the value {1-Gain (t)} input from the subtractor 37 by the window function Weight (t) input from the window function generation unit 35, and the weight is calculated. The given result is output to the two multipliers 61 and 62 as the peak power suppression coefficient Exp_Gain (t).
As an example, the peak power suppression coefficient Exp_Gain (t) is expressed as (Equation 6). T represents the time when the peak occurred.

Each of the multipliers 61 and 62 uses the addition result signals AI (t) and AQ (t) input from the delay units 23 and 24 and the peak power suppression coefficient Exp_Gain (t) input from the suppression coefficient calculation unit 36. The peak power suppression level is calculated by multiplication, and the calculation result is output to the subtracters 63 and 64.
The subtracters 63 and 64 suppress peak power input from the multipliers 61 and 62 from the addition result signals (main line signals) AI (t) and AQ (t) input from the delay units 23 and 24, respectively. The level is subtracted, and signals A ″ I (t) and A ″ Q (t) as the subtraction results are output to the D / A converters 27 and 28, respectively.
Here, the signals A ″ I (t) and A ″ Q (t) are expressed as (Equation 7).

The structural example of the transmitter 2 of this example is shown.
In the transmitter 2 that transmits a signal to be transmitted,
In order to suppress the peak power of the signal to be transmitted, a peak power suppression rate (in this example, a peak factor Gain (t) in accordance with the ratio between the transmission target signal level threshold and the peak power level of the signal to be transmitted )) To generate a peak power suppression rate generator 34;
A window function generator 35 that outputs a predetermined window function Weight (t);
A peak power suppression coefficient calculation unit 36 that generates a result obtained by weighting a value obtained from the peak power suppression rate generated by the peak power suppression rate generation unit 34 with a predetermined window function as a peak power suppression coefficient Exp_Gain (t); ,
Multipliers 61 and 62 and subtractors 63 and 64 for suppressing the peak power level of the signal to be transmitted by the peak power suppression coefficient generated by the peak power suppression coefficient calculator 36;
A carrier number setting unit 15 for setting information on the number of carriers to be transmitted to the window function generation unit 35;
The peak power suppression rate generator 34 is based on the input from the instantaneous power calculator 31 that detects the level of the signal to be transmitted (in this example, instantaneous power), and the transmission target signal level threshold and the instantaneous power calculator The peak power suppression rate corresponding to the ratio of the signal to be transmitted detected by 31 is determined, and a value obtained by subtracting the peak power suppression rate from 1 by the subtractor 37 is generated.
The peak power suppression coefficient calculation unit 36 optimizes the value (1-peak power suppression rate) set by the peak power suppression rate generation unit 34 and the subtractor 37 from a plurality of window functions according to the number of carriers. The result weighted by the selected window function is generated as the peak power suppression coefficient,
The multipliers 61 and 62 and the subtractors 63 and 64 use the value obtained by multiplying the signal to be transmitted and the peak power suppression coefficient generated by the peak power suppression coefficient calculator 36 as a suppression level, and The level of the signal to be transmitted is suppressed by subtracting the suppression level from the level of the signal to be.

  In the transmitter 2 of this example, the multipliers 61 and 62 and the subtractors 63 and 64 are transmission targets using a peak level suppression coefficient (in this example, a peak power suppression coefficient Exp_Gain (t)). Suppression means is configured by the function of suppressing the peak level of the signal.

As a third embodiment of the present invention, a specific example of the effect obtained by the transmitter of this example as shown in FIGS. 1 and 4 will be described.
As a problem of peak power suppression processing in a multicarrier transmitter, there is a phenomenon that the probability of occurrence of peak power varies depending on the number of carriers, and the optimum value of the parameter for peak power suppression varies depending on the number of transmission carriers. One such parameter is the value of the window function.
Therefore, in the transmitter of this example, the window function used for peak power suppression processing is switched according to the number of carriers to be transmitted.

FIG. 5 shows an example of frequency characteristics at the time of one-carrier transmission.
FIG. 6 shows an example of frequency characteristics at the time of 4-carrier transmission.
5 and 6, the horizontal axis of the graph indicates the frequency, and the vertical axis indicates the signal level. In addition, the characteristics when the Hanning window is used and the characteristics when the Kaiser window is used are shown.

When the total transmission power is set to be equal, in 4-carrier transmission, the CNR (Carrier to Noise Ratio) is 12 dB worse than in 1-carrier transmission, and the probability of occurrence of peak power is high. For this reason, when the same peak power detection threshold is used, the ACLR characteristics are worse in the 4-carrier transmission than in the 1-carrier transmission.
In peak power suppression using windowing, there is a trade-off relationship between ACLR and PCDE. For example, when transmitting 1 carrier, use a Kaiser window with good EVM and PCDE characteristics, and when transmitting 4 carriers. By using a Hanning window with good ACLR characteristics, it is possible to output a transmission signal with little signal quality degradation.

Here, the configuration of the system and apparatus according to the present invention is not necessarily limited to the configuration described above, and various configurations may be used. The present invention can also be provided as, for example, a method or method for executing the processing according to the present invention, a program for realizing such a method or method, or a recording medium for recording the program. It is also possible to provide various systems and devices.
The application field of the present invention is not necessarily limited to the above-described fields, and the present invention can be applied to various fields.
In addition, as various processes performed in the system and apparatus according to the present invention, for example, the processor executes a control program stored in a ROM (Read Only Memory) in hardware resources including a processor and a memory. A controlled configuration may be used, and for example, each functional unit for executing the processing may be configured as an independent hardware circuit.
The present invention can also be understood as a computer-readable recording medium such as a floppy (registered trademark) disk or a CD (Compact Disc) -ROM storing the control program, and the program (itself). The processing according to the present invention can be performed by inputting the program from the recording medium to the computer and causing the processor to execute the program.

It is a figure which shows the structural example of the transmitting apparatus which concerns on 1st Example of this invention. It is a figure which shows the 1st structural example of a window function production | generation part. It is a figure which shows the 2nd structural example of a window function production | generation part. It is a figure which shows the structural example of the transmitter which concerns on 2nd Example of this invention. It is a figure which shows an example of the frequency characteristic at the time of 1 carrier transmission. It is a figure which shows an example of the frequency characteristic at the time of 4 carrier transmission. It is a figure which shows the structural example of a transmitter. It is a figure which shows the structural example of a window function production | generation part.

Explanation of symbols

1, 2, 3 ... Transmitter 11, 71 ... Digital modulation unit 12, 16, 72 ... Peak power suppression unit 13, Frequency conversion unit 14, 17, 73 ... Peak power suppression coefficient calculation , 15... Carrier number setting unit, 21, 22... Adder, 23, 24.. Delay unit, 25, 26, 61, 62. A converter), 29 .. Analog quadrature modulation unit, 31.. Instantaneous power calculation unit, 32... Threshold generation unit, 33 .. Comparison unit, 34 .. Suppression rate generation unit, 35, 35 a, 35 b, 81 -Window function generation unit, 36-Suppression coefficient calculation unit, 37, 63, 64-Subtractor, 41, 52-Selector, 51a, 51b, 91-Window function table, 53-Control unit,
B1 to BN, code multiplexed signal generator, C1 to CN, G1 to GN, waveform shaping filter, E1 to EN, H1 to HN, digital quadrature modulator, F1 to FN, window function table,

Claims (1)

In a transmitter for transmitting a digital signal sampled in the time domain ,
Carrier number specifying means for specifying the number of carriers included in the signal to be transmitted;
Window function setting means for setting a window function according to the number of carriers specified by the carrier number specifying means;
Suppression rate generation means for generating a peak level suppression rate according to the ratio of the peak power level of the signal to be transmitted and the transmission target signal level threshold;
Coefficient generation means for generating, as a peak level suppression coefficient, a result obtained by weighting the peak level suppression rate generated by the suppression rate generation means with the window function set by the window function setting means ;
Suppression means for suppressing a peak level for the signal to be transmitted using the coefficient generated by the coefficient generation means;
A transmitter characterized by comprising:

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