JP2010154044A - Peak power suppression circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a peak power suppression circuit capable of executing a peak power suppression process of a transmission signal in a transmitter including a multi-antenna system with a small circuit scale. <P>SOLUTION: This peak power suppression circuit 10 includes a channel selection part 12 for accepting a plurality of input signals respectively corresponding to a plurality of antenna channels in a multi-antenna system, and selecting any one of the input signals within the plurality of input signals, executes a peak power suppression process of suppressing peak power generated in the input signal for the one input signal selected by the channel selection part 12, and outputs an output signal corresponding to the one input signal having been subjected to the peak power suppression process along with other output signals. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a peak power suppression circuit used in a transmitter having a multi-antenna system.

A transmitter used in a wireless communication system such as WiMAX (Worldwide Interoperability for Microwave Access) includes an amplifier for amplifying the power of a transmission signal.
The amplifier is required to have high linearity in order to suppress deterioration of transmission characteristics due to transmission signal distortion.

Here, the input / output power characteristic of the amplifier is a nonlinear region where the relationship between the input signal and the output signal is not linear and the input / output ratio is saturated in the range where the output signal voltage is close to the amplifier power supply voltage.
Therefore, in order to ensure sufficient linearity, it is necessary to supply a sufficiently large current / voltage (= power) to the amplifier as a power supply voltage, and to operate the amplifier in an operation region having a lower linearity than the power supply voltage and high linearity. is there.
For this reason, for example, when a peak power in which a relatively high power level partially appears with respect to the surrounding power level occurs in the transmission signal input to the amplifier, the signal related to the peak power is also included in the linear region of the amplifier. If included, the power supply voltage of the amplifier must be set high accordingly, and the output power ratio (power efficiency) to the power used (power supply power) of the amplifier is lowered.
Therefore, the transmitter includes a circuit for performing processing for suppressing peak power generated in the transmission signal, called CFR (Crest Factor Reduction) or clipping, on the transmission signal (for example, Patent Document 1). reference).

JP 2004-135087 A (FIG. 8 etc.)

A circuit for performing processing such as CFR and clipping can reduce the peak power generated in the transmission signal, thereby reducing the PAPR (Peak to Average Power Ratio) of the transmission signal and improving the power efficiency of the amplifier. it can.
FIG. 9 is a diagram for explaining an example of processing for suppressing peak power. As shown in FIG. 9, the processing performed by the circuit for performing processing for suppressing peak power (hereinafter also referred to as peak power suppressing circuit) is performed for the peak power of a transmission signal generated at a power level higher than a predetermined threshold. Then, a correction signal based on the peak power is generated, and the correction signal is subtracted from the transmission signal to cut out a portion higher than the peak power threshold, thereby determining the power level of the peak power in the transmission signal. It is suppressed below the threshold value.

  By the way, in the transmitter provided with the multi-antenna system, when suppressing the peak power of the transmission signal, the configuration as shown in FIG. 10 is adopted. That is, the conventional transmitter includes the peak power suppression circuit 100 corresponding to each of transmission signals corresponding to a plurality of antenna channels in the multi-antenna system. Each of the peak power suppression circuits 100 includes a correction signal generation unit 101 that generates the correction signal, and performs calculation related to generation and subtraction of the correction signal for the original transmission signal individually for each antenna channel.

  As described above, in a conventional transmitter equipped with a multi-antenna system, in order to suppress peak power of a plurality of transmission signals, a peak power suppression circuit is provided for each of a plurality of antenna channels, and a correction signal is generated and subtracted. Therefore, there is a problem that the amount of calculation becomes large and the circuit scale increases.

  The present invention has been made in view of such circumstances, and provides a peak power suppression circuit capable of performing peak power suppression processing of a transmission signal in a transmitter having a multi-antenna system with a small circuit scale. Objective.

  The present invention for achieving the above object is a peak power suppression circuit used in a transmitter including a multi-antenna system, and accepts a plurality of transmission signals corresponding to a plurality of antenna channels in the multi-antenna system. A selection unit that selects any one of the plurality of transmission signals, and a correction for suppressing the peak power generated in the one transmission signal based on the one transmission signal selected by the selection unit A correction signal generation unit that generates a signal; receives the plurality of transmission signals and the correction signal; performs peak power suppression processing on the one transmission signal to suppress peak power using the correction signal; and Peak power suppression processing unit that outputs the one transmission signal subjected to power suppression processing together with other transmission signals other than the one transmission signal It is characterized in that it comprises a.

According to the peak power suppression circuit configured as described above, the correction signal generation unit and the peak power suppression processing unit generate a correction signal for one transmission signal selected by the selection unit and perform peak power suppression processing. Therefore, as compared with the case where correction signal generation and peak power suppression processing are performed for each antenna channel as in the above-described conventional example, the amount of calculation required in correction signal generation and peak power suppression processing can be suppressed. As a result, the circuit scale of the peak power suppression circuit can be further reduced. That is, the peak power suppression circuit of the present invention receives a plurality of transmission signals corresponding to each of a plurality of antenna channels, selectively performs peak power suppression processing only on one of the transmission signals, and is subjected to peak power suppression processing. A plurality of antenna channels including one transmission signal subjected to peak power suppression processing by outputting one transmission signal together with other transmission signals other than the one transmission signal among the plurality of transmission signals. A plurality of transmission signals corresponding to each are output.
Thus, according to the peak power suppression circuit of the present invention, it is possible to perform peak power suppression processing of a transmission signal in a transmitter having a multi-antenna system with a small circuit scale.

The selection unit may select a transmission signal having the highest power among the plurality of transmission signals.
In this case, it is because there is a possibility that the peak power is generated at the timing of the transmission signal having the highest power, and thus it is possible to select a transmission signal having a high possibility that the peak power is generated.

Since the peak power suppression process suppresses the peak power of the transmission signal in a predetermined time width including the timing at which the peak power suppression process is performed, the suppression effect is continuously applied to the transmission signal immediately after the peak power suppression process. Less need to perform peak power suppression processing. For this reason, when one transmission signal is selected by the selection unit, the selection unit restricts selection of the transmission signal of the antenna channel corresponding to the selected transmission signal for a predetermined time thereafter. A selection restriction unit may be provided.
In this case, by setting the predetermined time to a range in which the suppression effect by the peak power suppression process reaches, it is possible to prevent the peak power suppression process from being performed in the overlapping range in the transmission signal of one antenna channel, By selecting another transmission signal corresponding to another antenna channel other than the antenna channel corresponding to the selected one transmission signal, and causing the peak power suppression processing unit to perform peak power suppression processing on the other transmission signal. The peak power suppression process can be performed efficiently.

In a multi-antenna system, particularly when beamforming is performed, a plurality of transmission signals corresponding to each antenna channel have a large correlation between the signals between the channels, so that a peak is generated between the plurality of transmission signals corresponding to each antenna channel. There is a high possibility that electric power is generated at the same timing.
Therefore, in the peak power suppression circuit, the plurality of transmission signals are subjected to delay processing for adding different delay times to the plurality of transmission signals, and the plurality of transmission signals subjected to the delay processing are selected. It is preferable to further include a delay processing unit.
In this case, different delay times are added to the plurality of transmission signals before the selection unit accepts the plurality of transmission signals, so that it is possible to avoid the peak powers generated in the transmission signals from overlapping at the same timing.
This prevents the peak power generated in each transmission signal from being received at the same timing when the selection unit selects any one transmission signal for each of the plurality of transmission signals received at the same timing. The peak power generated in each transmission signal can be received at different timings. As a result, it is possible to select all the peak power generated in each transmission signal.

  As described above, according to the peak power suppression circuit of the present invention, the peak power suppression process of the transmission signal in the transmitter including the multi-antenna system can be performed with a small circuit scale.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a block diagram illustrating a configuration of a main part of a transmission device used in a base station device of a wireless communication system. The transmission apparatus 1 is, for example, a base station apparatus that adopts a scheme based on “WiMAX” defined in IEEE 802.16 that supports an orthogonal frequency division multiple access (OFDMA) scheme in order to realize broadband wireless communication. A multi-antenna system including a plurality (M in the illustrated example) of antennas 2 is used.
The transmitter 1 includes a plurality of amplifiers 3, a plurality of D / A converters 4, and a plurality of modulators 5 connected to a plurality of antennas 2, respectively, and a peak according to an embodiment of the present invention in which these are connected. And a power suppression circuit 10.
The modulator 5 performs quadrature modulation of a transmission signal to be transmitted from the antenna 2. The D / A converter 4 converts the transmission signal after quadrature modulation from a digital signal to an analog signal. The amplifier 3 amplifies the transmission signal analog-converted by the D / A converter 4. The transmission signal amplified by the amplifier 3 is radiated and transmitted from the antenna 2 to the space. The peak power suppression circuit 10 performs peak power suppression processing on the transmission signal supplied to the antenna 2 to suppress peak power generated in the transmission signal.

When the transmission apparatus 1 forms a beam with a plurality of antennas 2 and transmits a transmission signal, the transmission apparatus 1 corresponds to each of the plurality of antennas 2 (each antenna channel) with respect to one baseband signal. Thus, the phase and amplitude are weighted to generate a plurality (M) of transmission signals (x _m (n) in the figure) corresponding to each antenna channel. Here, m is a value (1 ≦ m ≦ M) corresponding to each antenna channel, and n indicates a certain time (timing).
The plurality of generated transmission signals are output to the peak power suppression circuit 10. The peak power suppression circuit 10 performs a peak power suppression process on a plurality of given transmission signals, and then performs a plurality of corresponding transmission signals (z _m (n) in the figure) after the peak power suppression process. Is output to the modulator 5. The plurality of transmission signals x _m (n) and the plurality of transmission signals z _m (n) after the peak power suppression processing are complex signals, and are D / A after being orthogonally modulated by the modulator 5. It is output to the converter 4.
Thereafter, the plurality of transmission signals are processed by the D / A converter 4 and the amplifier 3 and supplied to the antenna 2 for transmission.

As described above, the peak power suppression circuit 10 receives the plurality of transmission signals generated by the transmission device 1 and outputs the plurality of transmission signals subjected to the peak power suppression processing. In the following description, a plurality of transmission signals received by the peak power suppression circuit 10 are expressed as “a plurality of input signals x _m (n)” or “input signal X _m (n) (vector expression of a plurality of input signals x _m (n)”. ) ”And“ a plurality of output signals z _m (n) ”or“ output signals Z _m (n) ”(a plurality of output signals z) that have been subjected to the peak power suppression processing output from the peak power suppression circuit 10. _m (n) vector representation) ".

FIG. 2 is a block diagram illustrating a functional configuration of the peak power suppression circuit 10.
In the figure, the peak power suppression circuit 10 includes a first delay processing unit 11 that performs a delay process to be described later on the received input signal X _m (n), and an input signal X _m (delayed by the first delay processing unit 11). n) given to the channel selection unit 12 and the second delay processing unit 13, the correction signal generation unit 14 connected to the channel selection unit 12, and the signal output from the correction signal generation unit 14 and the second delay processing unit 13, respectively. And a third delay processing unit 17 that performs processing corresponding to the delay processing performed by the first delay processing unit 11.

The first delay processing unit 11, to the plurality of input signals x _m (n) each of which is each element of the input signal X _m (n), the plurality of input signals x _m (n) different delay times for each Add delay processing. As a result, each of the plurality of input signals x _m (n) ′ subjected to this delay processing is given a “shift” of relative timing (for each antenna channel).
The first delay processing unit 11 outputs a plurality of input signals x _m (n) ′ (X _m (n) ′) subjected to the delay processing to the channel selection unit 12 and the second delay processing unit 13, respectively.

The correction signal generator 14 calculates a correction signal Y _m (n) for suppressing peak power generated in the input signal X _m (n). The correction signal Y _m (n) is a vector representation of a plurality of correction signals y _m (n) corresponding to each antenna channel.

The second delay processing unit 13 delays the input signal X _m (n) ′ by a time necessary for the channel selection unit 12 and the correction signal generation unit 14 to calculate the correction signal Y _m (n).
The calculation unit 16 subtracts the correction signal Y _m (n) from the input signal X _m (n) ′ delayed by the second delay processing unit 13 and outputs the obtained output signal Z _m (n) ′ to the third signal. Output to the delay processing unit 17. At this time, the input signal X _m (n) ′ is delayed by the time required for the calculation of the correction signal Y _m (n) by the second delay processing unit 13, so the relative timings of both signals coincide. .

The arithmetic unit 16 receives the input signal X _m (n) ′ and the correction signal Y _m (n), and subtracts the correction signal Y _m (n) from the input signal X _m (n) ′, whereby the input signal An output signal Z _m (n) ′ in which peak power generated in X _m (n) ′ is suppressed is output. As described above, the peak power suppression circuit 10 subtracts the correction signal Y _m (n) from the input signal X _m (n) ′ output from the second delay processing unit 13 to thereby obtain the input signal X _m (n) ′. The peak power suppression process is performed to suppress the peak power generated in

The output signal Z _m (n) ′ has a relative timing “deviation” given to each antenna channel by the first delay processing unit 11.
Therefore, the third delay processing unit 17 performs a delay process for eliminating the “deviation”, and outputs an output signal Z _m (n) in which the relative timing of each antenna channel is restored and matched. To do.
The plurality of input signal delay processing by the first delay processing unit 11 is made x _m (n) ', in addition to the delay processing a plurality of input signals x _m before delay processing (n) is performed Since they are substantially the same, in the following description, they are also simply referred to as “a plurality of input signals x _m (n)” without distinguishing between them.

FIG. 3 is a block diagram showing the configuration of the correction signal generation unit 14 together with the channel selection unit 12.
The correction signal generation unit 14 includes one input signal x _l (n) (where l is one corresponding to one antenna channel) selected by the channel selection unit 12 from the plurality of input signals x _m (n). An element signal V _k (n), which is an integer and is a signal necessary for obtaining a correction signal for 1 ≦ l ≦ M), is calculated, and based on this element signal V _k (n), the input signal X and it outputs the _m correction signals for suppressing peak power occurring in the _{(n) Y m (n)} .

The channel selection unit 12 sequentially receives a plurality of input signals x _m (n) continuously given from the first delay processing unit 11. FIG. 4 is a diagram illustrating an input / output mode in the channel selection unit 12.
The channel selection unit 12 selects one input signal x _l (n) from among the plurality of input signals x _m (n) for each of the plurality of input signals x _m (n) received at the same timing. And output to the correction signal generator 14.
The channel selection unit 12 acquires and compares the power levels of the received plurality of input signals x _m (n). Then, among the plurality of input signal received at the same timing x _m (n), selects the highest power of the input signal x _m (n) is as one of the input signals x _l (n).

Here, as will be described later, the one input signal x _l (n) is an object of calculation for obtaining the clipping amount u _l (n) in the correction signal generation unit 14, so that a signal having peak power is generated. Preferably it is selected. This is because the highest power input signal x _m (n) may have a peak power at that timing, and thus the peak power among the plurality of input signals x _m (n). It is possible to select an input signal that is highly likely to occur.

In addition, the channel selection unit 12 selects one input signal x _l (n) from among a plurality of input signals x _m (n) corresponding to each antenna channel, so that it becomes a signal to be subjected to the subsequent calculation. It can be said that the corresponding antenna channel is selected. The channel selection unit 12 outputs control information W (n) indicating that the one input signal x _l (n) (the corresponding antenna channel) has been selected to the correction signal generation unit 14.
This control information W (n) is represented by a vector composed of M elements w _m (n) corresponding to each antenna channel, as shown in the following equation (1). The channel selection unit 12 sets “1” to only the value corresponding to the antenna channel corresponding to the selected input signal x _l (n) among the elements w _m (n) constituting the control information W (n). And other values are set to “0” to indicate that one input signal x _l (n) is selected.
W (n) = [w ₁ (n) (= 0), w ₂ (n) (= 0), ... w _l (n) (= 1), ... w _M (n) (= 0 ] ... (1)

In addition, the channel selection unit 12 includes a selection restriction unit 12 a that restricts the selection of antenna channels performed by the channel selection unit 12. When the channel selection unit 12 selects one input signal x _l (n) from among the plurality of input signals x _m (n) at a certain timing, the selection limiting unit 12a thereafter The selection of the input signal of the antenna channel corresponding to the selected one input signal x _l (n) is restricted. Therefore, the channel selection unit 12 does not continuously select input signals corresponding to the same antenna channel, but selects input signals corresponding to other antenna channels.
Note that the predetermined time during which the selection restriction unit 12a restricts the selection is set in a range in which the suppression effect by the peak power suppression process reaches, as will be described later.

Returning to FIG. 3, the correction signal generation unit 14 receives a single input signal x _l (n) selected by the channel selection unit 12 and calculates a clipping amount calculation unit 18 that calculates a clipping amount necessary for the peak power suppression processing. A band limiting unit 19 that limits the band of the calculated clipping amount, and a channel separation unit 20 that outputs a correction signal Y _m (n).

Hereinafter, an operation performed by the correction signal generation unit 14 to obtain the correction signal Y _m (n) from one input signal x _l (n) will be described.
First, when the clipping amount calculation unit 18 receives one input signal x _l (n), the clipping amount calculation unit 18 should suppress the peak power to be equal to or lower than a predetermined threshold based on the following formulas (2) and (3). A clipping amount u _l (n), which is a quantity, is obtained.
Note that one input signal x _l (n) is a complex signal as described above, and the clipping amount u _l (n) is also a complex signal.
u _l (n) = f (| x _l (n) |) x _l (n) (2)

In the above equation (3), the threshold value P is a value for determining whether or not the power is peak power, and is set in advance to a predetermined value based on the characteristics of the amplifier 3 and the like.
In the above formula (3), the absolute value of the input signal x _l (n) is greater than the threshold value _{P, f (| x l (} n) |) by the absolute value and the threshold value of the input signal x _l (n) An operation is performed to divide the difference from P by the absolute value of the input signal x _l (n). Further, as in Expression (2), by multiplying f (| x _l (n) |) by the input signal x _l (n), the difference between the input signal x _l (n) and the threshold value P is obtained as a complex signal. The clipping amount u _l (n) expressed by
On the other hand, when the absolute value of the input signal x _l (n) is not greater than the threshold value P (threshold value P or less), f (| x _l (n) |) is “0”. Accordingly, the clipping amount u _l (n) is “0”.
As described above, when the absolute value of the input signal x _l (n) is larger than the threshold value P, the clipping amount calculation unit 18 determines that the peak power is generated, and the clipping amount u _l (n). Is output as the difference between the input signal x _l (n) and the threshold value P, and if the absolute value of the input signal x _l (n) is equal to or less than the threshold value P, it is determined that no peak power is generated, and clipping “0” is output as the quantity u _l (n).

Next, the clipping amount calculation unit 18 outputs the obtained clipping amount u _l (n) to the band limiting unit 19.
FIG. 5 is a block diagram showing the configuration of the band limiting unit 19. The band limiting unit 19 constitutes a digital filter having K taps, and limits the band of the clipping amount u _l (n) obtained by the clipping amount calculation unit 18. The band limiting unit 19 includes K multipliers 19a that multiply the clipping amount u _l (n) by a predetermined weighting coefficient a _k (0 ≦ k ≦ K), and a clipping amount u _l (n). Are sequentially delayed every unit time and provided to each multiplication unit 19a. Note that “k” is a value corresponding to each tap, and corresponds to a tap located in a direction in which the delay amount increases as the value increases.

When the clipping amount u _l (n) is given from the clipping amount calculation unit 18, the band limiting unit 19 generates a unit in the time axis direction from each of the multiplying units 19 a in each tap based on the clipping amount u _l (n). A plurality of element signals v ₀ (n) to v _K (n) delayed for each time are output. That is, as shown in the following formula (4), the band limiting unit 19 responds to the past timing from the current timing n according to the increase of the value k, and corresponds to a plurality of element signals v ₀ (n) to v _K. (N) is obtained.
v _k (n) = a _k u (n−k) (where 0 ≦ k ≦ K) (4)

It should be noted that the weighting coefficient of each multiplier 19a is set to a value that can suitably obtain an element signal necessary for obtaining a correction signal from the clipping amount u _l (n).
The band limiting unit 19 outputs the element signal V _k (n) (vector display of the plurality of element signals v ₀ (n) to v _K (n)) to the channel separation unit 20.
As described above, the band limiting unit 19 obtains the element signal V _k (n) from one input signal x _l (n).

The channel separation unit 20 is provided with the element signal V _k (n) from the band limiting unit 19 and the control information W (n) from the channel selection unit 12, and based on these, the input signal X _m (n) A correction signal Y _m (n) for suppressing the generated peak power is output.
FIG. 6 is a block diagram showing the configuration of the channel separation unit 20. The channel separation unit 20 includes M separation / combination units 20a corresponding to the respective antenna channels.
Element signals V _k (n) (a plurality of element signals v ₀ (n) to v _K (n)) are given to the separation / combination units 20a. Further, each demultiplexing / combining unit 20a is provided with an element w _m (n) corresponding to the corresponding antenna channel among the demultiplexing / combining unit 20a in the control information W (n).
Each separation combiner 20a, respectively, when the element signals V _k (n) and the element w _m (n) is given, the correction signal y _m for correcting the input signal of the corresponding antenna channel (n) Output To do.

FIG. 7 is a block diagram showing a configuration of the separation / synthesis unit 20a. The separation / combination unit 20a includes K multiplication units 20a1 for multiplying each of the plurality of element signals v ₀ (n) to v _K (n) by the element w _m (n), and the elements given to the multiplication units 20a1. It has K−1 delay elements 20a2 for sequentially delaying w _m (n) per unit time, and a combining unit 20a3 for combining outputs from the multiplying units 20a1.
The synthesizer 20a3 synthesizes a value obtained by multiplying each of the plurality of element signals v ₀ (n) to v _K (n) by the element w _m (n). As a correction signal y _m (n) for correction so as to suppress the peak power of the input signal of the antenna channel.

Here, for example, when the value m ≠ 1, that is, when the element w _m (n) is other than the one corresponding to the antenna channel of one input signal selected by the channel selection unit 12, the element w _m ( Since n) is set to “0”, “0” is given to each multiplier 20a1.
Therefore, the multiplication results of the multiplication units 20a1 are all “0”, and the synthesis unit 20a3 sets the correction signal y _m (n) (value m ≠ l) to “0” without substantially performing the calculation. Output.

On the other hand, in the case of m = 1, that is, in the case of the element w _l (n) corresponding to the antenna channel of one input signal selected by the channel selection unit 12, the element w _l (n) is set to “1”. Therefore, “1” is given to each multiplier 20a1.
Therefore, a plurality of element signals v ₀ (n) to v _K (n) are reflected in the multiplication results of the multiplication units 20a1. The plurality of element signals v ₀ (n) to v _K (n) are temporally changed from the current timing to the past timing according to each value k as shown in the above equation (4). The values are sequentially delayed so as to correspond retroactively.

Therefore, the separation / combination unit 20a sequentially delays the element w _m (n) to each multiplication unit 20a1, thereby giving the value k of each element signal v ₀ (n) to v _K (n). A corresponding delay amount is assigned to each, and the element signals v ₀ (n) to v _K (n) are combined by the combining unit 20a3.
As described above, when the value m = 1, the synthesizer 20a3 outputs the result of synthesizing the element signals v ₀ (n) to v _K (n) as the correction signal y _l (n). The correction signal y _l (n) includes the element signals v ₀ (n) to v _K (n) corresponding to the past timing from the current timing according to the value k. As in the correction signal shown in FIG.
As described above, the separation / combination unit 20a outputs a plurality of correction signals y _m (n) based on the element signals v ₀ (n) to v _K (n).
The calculation of the channel separation unit 20 can be expressed as the following equation (5).

The channel separation unit 20 performs only the calculation for the antenna channel corresponding to one input signal x _l (n) selected by the channel selection unit 12 at a certain timing n, that is, when the value m = 1. ), And the calculation regarding the other antenna channel is substantially not performed because the element w _m (n) in the above equation (5) is “0”.
That is, the peak power suppression circuit 10 of the present embodiment calculates the clipping amount for only one input signal x _l (n) selected by the channel selection unit 12 when calculating the correction signal Y _m (n) at a certain timing n. u _l (n) and the correction signal y _l (n) are calculated, and the correction signal is not substantially calculated for the other input signals.

On the other hand, like the transmitter shown in the conventional example, the same as the clipping amount calculating unit 18 and the band limiting unit 19 of the present embodiment corresponding to each of the transmission signals corresponding to a plurality of antenna channels. When adopting a configuration including a peak power suppression circuit having a functional unit, at a certain timing n, it is necessary to cause the peak power suppression circuit for each antenna channel to perform the calculation shown in the following equation (6).
In the following formula (6), u _m (n−k) represents a clipping amount calculated for each antenna channel.

That is, in the conventional example, at a certain timing n, the clipping amount and the correction signal y _m (n) based on the clipping amount are calculated for all the input signals of each antenna channel.
Therefore, in the peak power suppression circuit 10 of the present embodiment that performs the calculation for only one selected input signal x _l (n), the calculation amount is almost equivalent to the calculation amount for one antenna channel in the transmitter of the conventional example. Therefore, the clipping amount and the correction signal for all the antenna channels can be calculated, and the amount of calculation can be effectively suppressed as compared with the conventional example.

In this embodiment, since a plurality of antennas 2 form a beam and transmit a transmission signal, a plurality of transmission signals corresponding to each antenna channel have a large correlation of signals between the channels and correspond to each antenna channel. There is a high possibility that peak power will occur at the same timing among a plurality of transmission signals.
In this regard, the peak power suppression circuit 10 of the present embodiment includes the first delay processing unit 11 so that the peak power generated in each transmission signal (a plurality of input signals x _m (n)) overlaps at the same timing. Can be avoided.

That is, the first delay processing unit 11 performs, for each of the plurality of input signals x _m (n) (transmission signal), delay processing for adding a different delay time to each of the plurality of input signals x _m (n), A plurality of input signals x _m (n) (a plurality of input signals x _m (n) ′) subjected to the delay processing are supplied to the channel selection unit 12.
FIG. 8 is a graph showing an example of a change over time in the power levels of two input signals corresponding to different antenna channels. FIG. 8A shows a state before delay processing by the first delay processing unit 11. A state (b) shows a state after the delay processing by the first delay processing unit 11. Further, the input signals shown in FIG. 8 each indicate a state where peak power is generated.

In FIG. 8A, the timing of the peak power of the input signal corresponding to one antenna channel shown in the upper stage and the timing of the peak power of the input signal corresponding to the other antenna channels shown in the lower stage are almost the same. The case where it has done is shown.
When the input signal shown in FIG. 8A is given to the first delay processing unit 11, the first delay processing unit 11 applies the plurality of input signals x _{m to} each of the plurality of input signals x _m (n). (N) Since different delay times are added to each, as shown in FIG. 8B, the peak power of the input signal corresponding to one antenna channel and the peak power of the input signal corresponding to another antenna channel, as shown in FIG. There is a relative timing shift between
As shown in FIG. 8 (b), the first delay processing unit 11 gives a “shift” of relative timing to each of the plurality of input signals x _m (n) for each antenna channel. Output to. The channel selection unit 12 receives a plurality of input signals x _m (n) to which a “deviation” of relative timing is given for each antenna channel.

Thus, before the channel selection unit 12 receives a plurality of input signals x _m (n), different delay times at a plurality of input signals x _m (n), respectively is added, relative timing to each other for each antenna channel Therefore, it is possible to avoid the peak power generated in each input signal x _m (n) from overlapping at the same timing.
Thus, when the channel selection unit 12 selects any one input signal x _l (n) for each of the plurality of input signals x _m (n) received at the same timing, each input signal x _m ( The peak power generated in n) can be prevented from being received at the same timing, and the peak power generated in each input signal x _m (n) is received at different timings. As a result, the peak power generated in each input signal x _m (n) can be selected without exception.

In the present embodiment, the calculation of the clipping amount and the correction signal y _m (n) based on the clipping amount is basically performed only for the input signal selected by the channel selection unit 12. Therefore, as described above, by receiving and calculating so that the peak powers are at different timings, it is possible to prevent the calculations for each antenna channel from overlapping at the same timing, and the calculation of the peak power suppression circuit 10 is performed. Resources can be used effectively.

As described above, the correction signal generation unit 14 obtains and outputs the correction signal Y _m (n) based on the control information W (n) and the one input signal x _l (n).

Returning to FIG. 2, the correction signal Y _m (n), as described above, used for the subtraction to the input signal X _m (n) by given to the arithmetic unit 16, the input signal X _m (n) A peak power suppression process for suppressing the generated peak power is performed.
Here, the correction signal Y _m (n) includes the correction signal y _l (n) corresponding to one input signal x _l (n) and the correction signal y _m (n) corresponding to another input signal. (M ≠ l) is “0”. For this reason, the peak power suppression circuit 10 of this embodiment performs the peak power suppression process on only one input signal x _l (n) selected by the channel selection unit 12 at a certain timing n, and the other input signals The peak power suppression process is not performed.
That is, the arithmetic unit 16 receives the input signal X _m (n) and the correction signal Y _m (n), and performs the peak power suppression process for suppressing the peak power using the correction signal Y _m (n) as one input signal x. _l performed for (n), one input signal x _l, which is processed peak power suppressing the output signal z _l corresponding to (n) (n), the other output signal corresponding to the other input signal z _m ( n) A peak power suppression processing unit configured to output together with (m ≠ l) is configured.

As described above, the output signal Z _m (n) ′ output from the calculation unit 16 has a relative timing “shift” given to each antenna channel by the first delay processing unit 11. .
The third delay processing unit 17 to which the output signal Z _m (n) ′ is given from the calculation unit 16 performs delay processing for eliminating the “deviation”, and outputs in which the relative timings of the respective antenna channels coincide with each other. The signal Z _m (n) is output.

As described above, the peak power suppression circuit 10 of the present embodiment receives the input signal X _m (n) generated by the transmission device 1 and outputs the output signal Z _m (n) subjected to the peak power suppression process.

According to the peak power suppression circuit 10 of the present embodiment configured as described above, the correction signal generation unit 14 and the calculation unit 16 perform one input signal x _l (n) selected by the channel selection unit 12. Thus, the correction signal y _l (n) is applied to the peak power suppression process, so that the correction signal generation and the peak power suppression process are performed in comparison with the case where the correction signal generation and the peak power suppression process are performed for each antenna channel as in the conventional example. The amount of calculation required in the peak power suppression process can be suppressed. As a result, the circuit scale of the peak power suppression circuit 10 can be further reduced.
As described above, according to the peak power suppression circuit 10 of the present invention, the peak power suppression process of the input signal X _m (n) in the transmitter including the multi-antenna system can be performed with a small circuit scale. .

In the above embodiment, the peak power suppression process is performed by, for example, subtracting the correction signal y _l (n) having a temporal width as shown in FIG. 9 from the input signal x _l (n). Since it is performed, the suppression effect of the process reaches a predetermined time width including the timing at which the peak power suppression process is performed. For this reason, since the suppression effect also reaches the input signal immediately after the peak power suppression process, there is little need to perform the peak power suppression process continuously.
In this regard, in the present embodiment, the channel selection section 12, at a certain timing, any one of the input signals x _l of the plurality of input signals x _m (n) (n) is selected by the channel selection section 12 And a selection restriction unit 12a for restricting selection of the input signal of the antenna channel corresponding to the selected one input signal x _l (n) for a predetermined time thereafter, the channel selection unit 12 Does not continuously select input signals corresponding to the same antenna channel, and the peak power suppression processing is not continuously performed for input signals corresponding to the same antenna channel.

  In the above case, by setting the predetermined time to a range in which the suppression effect by the peak power suppression process reaches, it is possible to prevent the peak power suppression process from being performed in an overlapping range in the input signal of one antenna channel, By selecting an input signal corresponding to another antenna channel and performing the peak power suppression process for the other input signal, the peak power suppression process can be performed efficiently.

The present invention is not limited to the above embodiment. For example, when the transmission apparatus 1 transmits a transmission signal without forming a beam, such as transmitting different data from a plurality of antennas 2, a plurality of transmission signals corresponding to each antenna channel are transmitted between channels. Therefore, the first delay processing unit 11 and the third delay processing unit 17 may be omitted.
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a block diagram which shows the structure of the principal part of the transmitter used for the base station apparatus of a radio | wireless communications system. It is a block diagram which shows the functional structure of a peak power suppression circuit. It is the block diagram which showed the structure of the correction signal production | generation part with the channel selection part and the channel separation part. It is a figure which shows the mode of input / output in a channel selection part. It is a block diagram which shows the structure of a band limitation part. It is a block diagram which shows the structure of a channel separation part. It is a block diagram which shows the structure of a isolation | separation synthetic | combination part. 6 is a graph showing an example of a change with time of power levels of two input signals corresponding to different antenna channels, wherein (a) is a state before delay processing by the first delay processing unit; (b) Indicates a state after the delay processing by the first delay processing unit. It is a figure for demonstrating a peak electric power suppression process. It is the figure which showed the aspect of the peak power suppression circuit which the conventional transmitter has.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Peak power suppression circuit 11 First delay processing part 12 Channel selection part 14 Correction signal generation part 16 Calculation part

Claims (4)

A peak power suppression circuit used in a transmitter equipped with a multi-antenna system,
A selection unit that receives a plurality of transmission signals corresponding to each of a plurality of antenna channels in the multi-antenna system and selects any one of the plurality of transmission signals;
A correction signal generation unit that generates a correction signal for suppressing peak power generated in the one transmission signal based on the one transmission signal selected by the selection unit;
The one transmission signal that has received the plurality of transmission signals and the correction signal, performs peak power suppression processing on the one transmission signal to suppress peak power using the correction signal, and is subjected to the peak power suppression processing. And a peak power suppression processing unit that outputs together with other transmission signals other than the one transmission signal.   The peak power suppression circuit according to claim 1, wherein the selection unit selects a transmission signal having the highest power among the plurality of transmission signals.   The selection unit restricts selection of a transmission signal of an antenna channel corresponding to the selected one transmission signal for a predetermined time after the selection unit selects one transmission signal. The peak power suppression circuit according to claim 1, further comprising a unit.   The apparatus further includes a delay processing unit that performs a delay process for adding a different delay time to each of the plurality of transmission signals, and provides the selection unit with the plurality of transmission signals subjected to the delay process. The peak electric power suppression circuit as described in any one of Claims 1-3.

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