JPH09139679A - Peak power reduction circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the peak power reduction circuit for a multi-carrier signal with low distortion without remarkable reduction in a mean power. SOLUTION: In this circuit, an input multi-carrier signal passes through a directional coupler 11, a 1st delay means 12, a 1st variable attenuation means 13, and a limiter 14 sequentially and is outputted. Then the signal branched by the directional coupler 11 is given to a 1st detection means 15, in which an envelope power level L of the input signal is detected and its detection output is given to a 1st control means 16, which compares the power level L with a threshold level and when the power level exceeds the threshold level, an attenuation of the 1st variable attenuation means 13 is set to a prescribed value for a prescribed time. A delay in the 1st delay means 12 is set based on an operating speed of the 1st detection means 15 and the 1st control means 16. The 1st variable attenuation means 13 and the limiter 14 are used in common, then intermodulation distortion of an out-band output is suppressed in comparison with the case that a peak power is limited by the limiter 14 only.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a multi-carrier transmitter such as a base station for mobile communication or satellite communication, and the multi-carrier signal is added to a multi-carrier signal before inputting it to an amplifier or the like. The present invention relates to a circuit that reduces peak power of a signal.

[0002]

2. Description of the Related Art Since the phases of carriers constituting a multi-carrier signal are variously distributed, the instantaneous phases match and the voltages are combined in phase at a certain moment. As a result, the envelope power increases significantly and the envelope power peak value (PEP) significantly exceeds the average power level of the envelope power.
Occurs. When attempting to amplify such a multi-carrier signal with low distortion by an amplifier, the required saturation output of the amplifier must be set to, for example, a multiple of the average power level of the envelope power so that intermodulation distortion does not occur. I won't. This causes problems such as miniaturization of the amplifier and hindering power saving.

In order to reduce the required saturation output of this amplifier, it is necessary to reduce the peak power of the multi-carrier signal before inputting it to the amplifier. In the circuit of FIG.
The multi-carrier signal input to the input terminal 1 is connected to the output terminal 2 through the attenuator 4. Behind the output terminal 2, for example, a linear amplifier 3 is connected, and a multicarrier signal whose peak power is reduced by the attenuator 4 is input. The attenuation amount of the attenuating means 4 is set so that the distortion in the output signal of the linear amplifier 3 is equal to or less than the specified amount. Also,
Compared to FIG. 13, in FIG. 14, a limiter 5 that limits the signal amplitude to a predetermined value (limit value) is provided instead of the attenuator 4. A PIN diode limiter circuit can be used as the limiter 5.

[0004]

When the input signal is attenuated by a certain amount of attenuation as shown in FIG. 13, not only the peak power is reduced but also the average power of the signal itself is reduced. For example, in order to reduce the peak power of the input signal by 3 dB, it is necessary to set the attenuation amount of the attenuator 4 to 3 dB. At this time, the average power level of the envelope power of the multicarrier signal is also reduced by 3 dB. Further, in the configuration shown in FIG. 14, since the peak power generation time exceeding the limit value of the limiter 5 is short, the average power level of the signal hardly decreases,
When the amplitude is limited by the limiter 5, a remarkable intermodulation distortion is generated, similarly to the influence of the saturation characteristic of the amplifier.

It is an object of the present invention to provide a circuit which has a low distortion and which reduces the peak power of a multicarrier signal without significantly reducing the average power.

[0006]

According to the invention of claim 1, in a peak power reduction circuit for inputting a signal from an input terminal, reducing peak power, and outputting it to an output terminal, a peak power reducing circuit A first delay means, a first variable attenuation means, and a limiter are provided on the path between them. Further, the envelope power of the input signal is detected by the first detection means, and the attenuation amount of the first variable attenuation means is set by the first control means according to the envelope power detected by the first detection means.

According to the invention of claim 2, the first delay means in the invention of claim 1 is replaced by a transmission line.
According to the invention of claim 3, in claim 1, the limiter is a second delay means, a second variable attenuation means provided on the output side of the second delay means, and a signal input to the second delay means. It is replaced by a peak processing section having a second detection means for detecting the envelope power of the above and a second control means for adjusting the attenuation amount of the second variable attenuation means according to the detection signal of the second detection means.

According to the invention of claim 4, in claim 1, the limiter includes a second delay means, a second variable attenuating means provided on the output side of the second delay means, and the first detecting means. It is replaced by a peak processing unit having second control means for adjusting the amount of attenuation of the second variable attenuation means according to the detection signal. According to the invention of claim 5, in claim 3 or 4, the first control means and the second control means are:
The control unit is composed of one control unit, and adjusts the attenuation amounts of the first variable damping unit and the second variable damping unit, respectively.

According to the invention of claim 6, claims 3 to 5
In any of the above, the second delay means is replaced with a transmission line.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the embodiment of FIG. In FIG. 1, parts corresponding to those in FIG. 13 are designated by the same reference numerals. In the present invention, a directional coupler 11 is inserted after the input terminal 1, and one output path of the directional coupler 11 has a first delay means 12 for delaying an input multicarrier signal and a first variable attenuation. Means 13 and limiter 14 are provided, through which the multicarrier signal is output to output terminal 2.
The path branched to the other side by the directional coupler 11 is provided with a first detection means 15 for detecting the envelope power level of the multicarrier signal, and the detection signal of the first detection means 15 is the first control means 16 Entered in.

The first control means 16 compares the envelope power level of the multicarrier signal detected by the first detection means 15 with a threshold value, and when the threshold power value is exceeded, the first variable attenuation means 13 is provided. Is set to a predetermined amount for a predetermined time.
The delay amount of the first delay means 12 is set based on the operating speeds of the first detection means 15 and the first control means 16. The first delay means 12 can be configured using a delay line. The first variable attenuator 13 can be easily configured by using a PIN diode or the like, and a commercially available product can also be used. Further, the limiter 14 can be configured by using a PIN diode limiter circuit. The first detecting means 15 can be configured by using a diode and a capacitor, the parameter of the element is determined so as to follow the fluctuation of the envelope power of the multi-carrier signal, and the signal according to the envelope power level is changed to the first control means. Output to 16.

The first control means 16 is, for example, an A / D converter, a microprocessor, a ROM, an RA as a basic circuit.
The first variable attenuator 1 is composed of an M, D / A converter and the like, and monitors the detection signal input from the first detector 15.
It has a function of setting and adjusting the attenuation amount of 3. The control operation of the first control means 16 will be described in detail below. Figure 2A
FIG. 6 is a flowchart showing the control operation of the first control means 16. First, the envelope detection power level L of the multicarrier signal is detected by the first detection means 15 (step S
1), it is determined whether the level exceeds the threshold value Lth1 (S2). When the power level L exceeds Lth1, the attenuation amount D1 of the first variable attenuation means 13 is adjusted according to a predetermined attenuation operation (S).
3). A time chart of the operation of the first variable attenuation means 13 is shown in FIG. 2B. After this damping operation, the process returns to step S1 of detecting the envelope power level L again.

Here, the spectrum of the distortion generated by adjusting the power level of the multi-carrier signal by the first variable attenuator 13 is the time that defines the attenuation operation time ΔT of the first variable attenuator 13 and the attenuation amount D1. It depends on the function. Distortion within the band of the input multi-carrier signal is set by setting ΔT to a modulation period of each carrier of the multi-carrier signal and defining the attenuation amount D1 by a gradual change so as to follow the Blackman-Harris window function. It is possible to suppress. The maximum value of the attenuation amount D1 is set to about 3 dB, for example. Further, by defining the attenuation amount by the window function, the decrease in the average power due to the attenuation is small during ΔT, as compared with the case where the attenuation amount is fixed at 3 dB, for example.

Since the rising of the Blackman-Harris window function is gradual as shown in FIG. 2B, the effect of reducing the peak power is small immediately after the start of the damping operation defined according to this window function. However, by appropriately setting the delay amount of the first delay unit 12, it is possible to adjust the temporal rising position of the attenuation amount defined by the window function. For example, the first delay is performed so that the time at which the attenuation amount of the first variable attenuating unit 13 is maximized matches the timing at which the envelope power level L exceeds Lth1 in the signal input to the first variable attenuating unit 13. Means 1
Set a delay amount of 2.

The attenuation amount D1 of the first variable attenuation means 13
Is not limited to the Blackman-Harris window function, and other window functions such as a Hamming window function and a Hanning window function can be used. By operating the first variable attenuator 13 as described above, it is possible to suppress the distortion caused by the change in the attenuation amount within the band of the input signal and reduce the peak power. By using the first variable attenuator 13 and the limiter 14 together, the intermodulation distortion generated outside the band of the output signal is suppressed to a low level as compared with the case where the peak power is limited only by the limiter 14 as shown in FIG. be able to.
The limiter limit value Lth2 is set equal to, for example, Lth1, and the peak power of the multicarrier signal output by the peak power reduction circuit of the present invention is Lth1 (= Lth.
2).

By continuously or intermittently executing the above series of controls, it is possible to reduce the peak power of the multicarrier signal with low distortion and without significantly reducing the average power. 3 to 5 show another embodiment of the invention of claim 1. In these embodiments, the order of the directional coupler 11, the first delay means 12, the first variable attenuation means 13, and the limiter 14 is changed in various ways as compared with FIG. Is similar to the description of FIG.

FIG. 6 shows an embodiment of the invention of claim 2. In this embodiment, the first delay means 12 is replaced by a transmission line 17 as compared with FIG. 1, and the other points are the same as in FIG. When the operations of the first detection means 15 and the first control means 16 are sufficiently high speed as compared with the fluctuation of the envelope power level of the multicarrier signal, the first delay means 12 is not always necessary and the transmission with a small delay is performed. Track 17
Can be replaced with. The same applies to the embodiments of FIGS. 3, 4 and 5.

When the inventions of claims 1 and 2 are carried out, a harmonic component is generated in the first variable attenuation means 13 or the limiter 14. FIG. 7 is a diagram showing an embodiment provided with a means for removing this harmonic component, and is different from FIG. 1 in that a band pass filter 18 is provided in the preceding stage of the output terminal 2. FIG. 8 shows an embodiment of the invention of claim 3. In this embodiment, the part constituted by the limiter 14 in FIG. 1 is constituted by the directional coupler 21, the second delay means 22, the second variable attenuation means 23, the second detection means 25 and the second control means 26. It is replaced by the peak processing unit 30. Others are the same as those in FIG. 1 and are denoted by the same reference numerals as those in FIG. The operation of the peak processing section 30 will be described below.

The output signal of the first variable attenuation means 13 is input to the directional coupler 21. A second delay means 22 for delaying a signal and a second variable attenuating means 23 are provided on one output path of the directional coupler 21 and are connected to the output terminal 2. Second detection means 2 for detecting the envelope power level of the signal is provided on the path branched to the other side by the directional coupler 21.
5 is provided, and the detection signal of the second detection means 25 is input to the second control means 26. When the envelope power level of the signal detected by the second detection means 25 exceeds the threshold value, the second control means 26 reduces the attenuation amount of the second variable attenuation means 23 by a predetermined amount, for example, of the signal. Set the envelope power to be limited to a threshold. The delay amount of the second delay means 22 is set according to the operating speeds of the second detection means 25 and the second control means 26.

The control operation of the second control means 26 is shown in a flow chart form in FIG. 9A, and the envelope power waveform of the signal and the attenuation operation of the second variable attenuation means 23 are shown in correspondence with each other in FIG. 9B. As shown in FIG. 9A, the envelope power level L2 of the signal input to the peak processing unit 30 is detected (S4), L
It is determined whether 2 exceeds the threshold value Lth2 (S5). If L2 exceeds Lth2, the attenuation amount D2 of the second variable attenuation means 23 is adjusted (S6), and the process returns to step S4 for detecting the envelope power level L2 again. If L2 does not exceed Lth2 in step S5, the attenuation is 0 dB.
(S7), the process returns to step S4 for detecting the envelope power level L2. Envelope power level L shown in FIG. 9B (a)
9B shows an example of changes in the attenuation amount D2 with respect to changes in FIG.
(B). The attenuation amount D2 is adjusted so that the envelope power L2 of the signal is limited by Lth2, and the envelope power waveform shown in 9B (c) is obtained as the output signal of the second variable attenuation means 23. However, in FIG. 9B, the peak processing unit 30
The gain between the input and output of is assumed to be 1.

The limiter 14 shown in FIGS. 3 to 7 can be similarly constructed by the peak processing section 30. As described above, by configuring the limiter in claim 1 with the peak processing unit 30, generation of harmonic components is suppressed. In the above description, the attenuation amount D2 is L while the second variable damping means 23 is operating.
Although it has been described that it changes according to 2, it is also possible to predefine a window function like the attenuation amount D1 set in the first variable attenuation means 13 or to fix the attenuation amount to a certain constant value. Is.

The peak power of the multi-carrier signal can be reduced to a low distortion by constantly or intermittently executing the above series of controls. FIG. 10 shows an embodiment of the invention of claim 4. The circuit of this embodiment is obtained by removing the directional coupler 21 and the second detection means 25 from the peak processing section 30 of the circuit shown in FIG. 8, and the second control means outputs the detection signal of the first detection means 15. Therefore, the feature is that the amount of attenuation of the second variable attenuation means 23 is controlled. Others are the same as those in FIG. 8 and are denoted by the same reference numerals as those in FIG. If the control operation of the first control means 16 is predetermined, the second detection means 2 in the embodiment of FIG.
5 is not always necessary, and the amount of attenuation of the second variable attenuation means 23 can be adjusted using the detection signal of the first detection means 15.

FIG. 11 shows an embodiment of the invention of claim 5.
Compared with the embodiment of FIG. 8, the first control means 16 and the second
The control means 26 is replaced by one control means 28. Here, the detection signals of the first detection means 15 and the second detection means 25 are input to the control means 28, and the attenuation amounts of the first variable attenuation means 13 and the second variable attenuation means 23 are set and adjusted by the control means 28. It Inside the control means 28, the same operation as the control operation described in FIGS. 2 and 9 is executed in parallel.

FIG. 12 shows an embodiment of the invention of claim 6.
Compared to FIG. 8, the first delay means 12 and the second delay means 22 are replaced with a transmission line 17 and a transmission line 27, respectively, and the other points are the same as in FIG. When the operations of the first detecting means 15, the first controlling means 16, the second detecting means 25 and the second controlling means 26 are sufficiently fast as compared with the fluctuation of the envelope power level of the multi-carrier signal, the first delay. The means 12 and the second delay means 22 are not always necessary and can be replaced with a transmission line with a small delay. Further, in this embodiment, the case where both the first delay means 12 and the second delay means 22 are replaced by the transmission line is shown, but the first detection means 15, the first control means 16,
Depending on the operating speeds of the second detection means 25 and the second control means 26, either the first delay means 12 or the second delay means 22 may be replaced with a transmission line.

Although the directional couplers 11 or 11 and 21 have been provided in the above description, they may be omitted. Although the input signal is a multi-carrier signal, other signals may be used.

[0026]

As described above, according to the present invention, the peak power of the multi-carrier signal can be reduced without significantly reducing the average power, as compared with the case of the conventional attenuator of FIG. It will be possible. Therefore, for example, by providing the peak power reduction circuit of the present invention in the preceding stage of the amplifier in a base station device for mobile communication, a multicarrier transmission device for satellite communication, etc., the required saturation power of the amplifier can be significantly reduced.

According to the present invention, the modulation cycle is controlled by the first delay means 12, the first variable attenuation means 13, the first detection means 15, the first control means 16 and the like except for the limiter 14 or the peak processing section 30. By gently changing the amount of attenuation of the first variable attenuator 13 within a certain time width, it is possible to suppress the noise generated by the attenuating operation within its own band and reduce the peak. Therefore, the limiter 1
4 or limiting the peak power of out-of-band noise associated with peak suppression performed by the peak processing unit 30 with only a limiter.
It can be reduced considerably compared to the conventional case.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

2A is a flow chart showing an example of a control operation of a control means 16 in FIG. 1, and FIG. 2B is a diagram showing a change of an attenuation amount of a variable attenuation means 13 in FIG. 1 with time.

FIG. 3 is a block diagram showing another embodiment of the invention of claim 1;

FIG. 4 is a block diagram showing still another embodiment of the invention of claim 1;

FIG. 5 is a block diagram showing another embodiment of the invention of claim 1;

FIG. 6 is a block diagram showing an embodiment of the invention of claim 2;

FIG. 7 is a block diagram showing still another embodiment of the invention of claim 1;

FIG. 8 is a block diagram showing an embodiment of the invention of claim 3;

9A is a flow chart showing an example of control operation of the second control means 26 in FIG. 8, and B is an operation waveform chart of a main part in the peak processing section 30 in FIG.

FIG. 10 is a block diagram showing an embodiment of the invention of claim 4;

FIG. 11 is a block diagram showing an embodiment of the invention of claim 5;

FIG. 12 is a block diagram showing an embodiment of the invention of claim 6;

FIG. 13 is a block diagram showing a peak power reduction circuit using a conventional attenuator.

FIG. 14 is a block diagram showing a peak power reduction circuit using a conventional limiter.

Claims (6)

[Claims] 1. A peak power reduction circuit for inputting a signal from an input terminal, reducing peak power and outputting the peak power to an output terminal, wherein first variable attenuating means inserted in a path between the input terminal and the output terminal. A limiter inserted in a path between the input terminal and the output terminal for limiting the amplitude of an input signal to a predetermined level for output, and a path between the input terminal and the first variable attenuation means A first delay means inserted in the first delay means, a first detecting means for detecting the envelope power of the input signal, and a first adjusting means for adjusting the attenuation amount of the first variable attenuating means in accordance with the detection signal of the first detecting means. 1. A peak power reduction circuit comprising: 2. The peak power reduction circuit according to claim 1, wherein the first delay means is replaced with a transmission line. 3. The limiter according to claim 1, further comprising: a second delay means, a second variable attenuating means provided on an output side of the second delay means, and a signal input to the second delay means. And a second processing means for detecting the envelope power, and a second control means for adjusting the attenuation amount of the second variable attenuation means according to the detection signal of the second detection means. Peak power reduction circuit characterized by. 4. The limiter according to claim 1, wherein the limiter is a second delaying means, a second variable attenuating means provided on the output side of the second delaying means, and a detection signal of the first detecting means. A peak power reduction circuit characterized in that it is replaced by a peak processing section comprising: second control means for adjusting the amount of attenuation of the second variable attenuation means. 5. The control means according to claim 3 or 4, wherein the first control means and the second control means are one control means for adjusting the attenuation amounts of the first variable damping means and the second variable damping means, respectively. A peak power reduction circuit characterized by being configured. 6. A peak power reduction circuit according to claim 3, wherein the second delay means is replaced with a transmission line.