JP2000138645A - Multi-carrier transmission circuit and communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a multi-carrier transmission circuit for a mobile communication base station smaller in size by decreasing the instantaneous maximum output power of a broadband signal with a frequency band of several MHz to several tens of MHz so as to reduce the peak factor of a multi-carrier transmission signal. SOLUTION: The multi-carrier transmission circuit generates modulated signals by modulating corresponding carriers with input signals and synthesizes the modulated signals to provide an output of a multiplexed signal, and is provided with carrier generators 3-1-3-n that generate each carrier, modulators 5-1-5-n that modulate each carrier with each input signal to provide an output of the modulated signals, an adder circuit 6 that synthesizes the modulated signals to provide an output of a multiplex signal, variable attenuators 2-1-2-n that adjust the level of each input signal, phase detectors 4-1-4-n that detect the phase of each carrier, and a control circuit 7 that controls the variable attenuators 2-1-2-n according to the phase of each carrier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicarrier transmission circuit mainly for a mobile communication base station.

[0002]

2. Description of the Related Art In recent years, digital mobile communication has rapidly become widespread, and there is an urgent need to install infrastructure including base stations. Particularly in urban areas, small base stations are required for blind areas such as behind buildings and underground shopping malls, and miniaturization of large-scale base station devices has been required.

Hereinafter, a conventional multicarrier transmission circuit will be described with reference to FIG. 6, reference numeral 501 denotes a public telephone network, 502 denotes an exchange, 503-1 to 503-n denotes n baseband processing circuits, 504-1 to 504-n denotes n modulators, 505 denotes an addition circuit, and 506. Is a high-frequency amplifier, and 507 is an antenna.

[0004] From the signals for each user transmitted through the public telephone network 501, only necessary signals are extracted via the exchange 502 and output to each of n channels. The output n signals are used as baseband processing circuits 503-1 to 503-1.
At 503-n, appropriate baseband processing such as band limiting filtering is performed, and modulators 504-1 to 504-n
After the carrier wave is modulated by the above, the signal is analog-added by an adder circuit 505. This output is amplified by the high-frequency amplifier 506 and transmitted from the antenna 507.

[0005] Following the current digital mobile phone,
CDMA (Code) that can secure a larger communication capacity
Division Multiple Accesses
s) The development of mobile phones adopting the system is also progressing. CD
The MA is described in "CDMA System and Next-Generation Mobile Communication System" (Trikes Series; Chapter 1), and a detailed description thereof will be omitted.

[0006] Such a digital mobile phone base station uses linear modulation, and further transmits a signal by carrying a signal on a plurality of carriers (multicarriers). Therefore, a strict linearity and a wide dynamic range are required for a transmission / reception circuit. Is done.

A conventional CDMA multi-carrier transmission circuit will be described with reference to FIG. In FIG. 7, 601- (1
-1) to 601- (nk) are k × n channel input terminals, and 602- (1-1) to 602- (nk) are k
× n code multipliers, 603-1 to 603-n are n digital adders, 604-1 to 604-n are n modulators, 605-1 to 605-n are n carrier waves Circuit, 606 is an addition circuit, 607 is a code selection circuit, 608
Is an output terminal.

The k × n channel signals extracted via the exchange are input to channel input terminals 601- (1-
1) to 601- (nk), and the code selection circuit 6
07, using the code selected at 07.
(1-1) to 602− (nk). The k output signals are used as digital addition circuits 603-1 to 603-6.
03-n are added to one to obtain n outputs. The n outputs and the n carriers generated by the carrier generators 605-1 to 605-n are combined with the modulators 604-1 to 604-
n, and the n outputs are added to an adder circuit 606.
To obtain a multicarrier signal output. This signal is amplified by a high frequency power amplifier circuit and transmitted from an antenna.

In particular, the transmission circuit includes a circuit for handling high power, such as a power amplifier circuit. In order to maintain linearity, the saturation output power can cover the average output power up to the instantaneous maximum output (peak) power. Designed. Moreover,
Since a high transmission rate is required to obtain a large communication capacity, the transmission signal has a bandwidth of several MHz to several tens of MHz.
Extend to For this reason, it is necessary to use a circuit that can follow a signal change of 1/10 microsecond for the transmission circuit.

[0010]

However, when the ratio (peak factor) between the instantaneous maximum output power and the average output power becomes large, the size of the transistor of the power amplifier circuit used becomes large, and the output becomes large from the saturation output power. Must be used at a lower level. As the level is reduced in this way, the ratio (power conversion efficiency) between the DC supply power of the power amplifier and the extracted transmission power decreases.

The reason why the peak factor increases in this multicarrier signal will be described. Generally, in a multicarrier signal, as shown in FIG. 2A, a plurality of carriers exist at a certain frequency interval at the same time. The phase relationship between these carriers changes over time. During this change, as shown in FIG. 2B, when two or more carriers out of a plurality of carriers approach the same phase, the total power instantaneously increases. In particular, as the number of carrier waves having the same phase increases, the peak output power instantaneously becomes larger than the average output power as shown in FIG. 2C. For such a signal having a large ratio of the peak output power to the average output power (peak factor), the size of the transistor of the power amplifier used increases, and the ratio of the DC supply power of the power amplifier to the extracted transmission power ( Power conversion efficiency) is reduced.

In particular, the peak factor of the CDMA system is twice as large as that of the conventional TDMA system. Further C
By multiplexing codes, which is a feature of DMA, the peak factor is further increased.
It has a peak factor of dB. If this is further multiplexed on a multicarrier, the peak factor becomes larger. For this reason, a transmission circuit such as a power amplifier circuit is required to have considerably strict linearity as compared with the related art, and it is necessary to use an element capable of outputting power 10 times or more larger than the actually used power. As a result, the circuit scale of the transmission circuit increases, and it is difficult to reduce the size of the base station device.

As measures to reduce the peak factor, Japanese Patent Application Laid-Open Nos. 8-274732 and 8-8182.
A multicarrier transmission circuit using feedback control as shown in FIG. 49 has been proposed. However, since this circuit employs a feedback configuration, when transmitting a signal in a narrow band (several kHz to several hundred kHz), the fluctuation speed of the signal is several tens of microseconds or more, and the circuit can follow. However, the circuit cannot follow the fluctuation speed of a wide band signal of several MHz to several tens of MHz, and is difficult to apply.

In view of the above-mentioned problems of the conventional multi-carrier transmission circuit, the present invention considers several MHz.
To provide a multicarrier transmission circuit capable of miniaturizing a circuit by suppressing instantaneous maximum output power to a small value and reducing a peak factor of a multicarrier transmission signal even for a wideband signal of up to several tens of MHz. With the goal.

[0015]

According to the present invention, n (n is 2)
A multicarrier transmission circuit that generates n modulated signals by modulating the corresponding carrier with the input signal of the above (integer) and combines the n modulated signals to output a multiplexed signal. N carrier generating means for generating each carrier, n modulating means for modulating each carrier with each of the input signals and outputting the modulated signal, and synthesizing the n modulated signals. Synthesizing means for outputting the multiplexed signal, level varying means for directly or indirectly adjusting the level of each modulated signal, and n carrier phase detecting means for detecting the phase of each carrier, Control means for controlling the level varying means according to the phase of each carrier detected by each carrier phase detecting means.

According to the present invention, even for a wideband signal of several MHz to several tens of MHz, the instantaneous maximum output power is suppressed to a small value, the peak factor of a multicarrier transmission signal is reduced, and the transmission circuit is downsized. It becomes possible.

That is, the multi-carrier transmission circuit of the present invention detects the phase of each modulated signal of the multi-carrier transmission signal in advance and predicts the phase relationship of each modulated signal which shows instantaneous maximum power. By directly or indirectly adjusting the level of each of the modulated signals in accordance with the phase relationship, the level of each of the modulated signals having the same or near-phase relationship is lowered to reduce the peak factor of the multicarrier transmission signal. To reduce. As a result, the saturation output power of the power amplifier can be reduced, so that the element size can be reduced. As a result, the size of the transmission circuit including the power amplifier can be reduced.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) First, the first embodiment of the present invention will be described.
The embodiment will be described with reference to FIGS.

FIG. 1 is a block diagram showing a multicarrier transmission circuit according to the first embodiment of the present invention. In FIG. 1, 1-1 to 1-n denote n input terminals and 2-1.
２−2-n are n variable attenuators (corresponding to the level varying means of the present invention), 3-1 to 3-n are n carrier generators (corresponding to the carrier generating means of the present invention), 4-1 4-n are n phase detectors (corresponding to the carrier phase detecting means of the present invention);
-1 to 5-n are n modulators (corresponding to the modulating means of the present invention), 6 is an adder circuit (corresponding to the synthesizing means of the present invention), 7 is a control circuit (corresponding to the controlling means of the present invention), 8 is an output terminal.

In FIG. 1, each of the input terminals 1-1 to 1-n
N input signals (corresponding to the input signal of the present invention) input with equal power are attenuated by the respective attenuation amounts through the respective variable attenuators 2-1 to 2-n. -N. Each of the modulators 5-1 to 5-n includes a carrier generator 3-1 to
The carrier generated at 3-n (corresponding to the carrier of the present invention) is modulated by n input signals. The outputs of the modulators 5-1 to 5-n (corresponding to the modulated signal of the present invention) are added by the adding circuit 6 and output to the output terminal 8 (corresponding to the multiplexed signal of the present invention).

Here, the procedure in which each of the variable attenuators 2-1 to 2-n attenuates each input signal will be described. Each phase detector 4
-1 to 4-n detect in advance the phases of the carrier waves output from the carrier wave generators 3-1 to 3-n, for example, using a warm-up period before actual transmission. The phase relationship changes according to the elapsed time from when the phase detection is performed, but if the frequency of each carrier is known, the phase relationship at that time can be predicted. Based on the detected phase information, the control circuit 7 predicts the phase relationship of each carrier, and controls the attenuation of each of the variable attenuators 2-1 to 2-n accordingly.

The control of the amount of attenuation will be described in detail below with reference to FIGS. 2A and 2B are diagrams showing a conventional general multicarrier transmission signal, FIG. 2A is a diagram showing a frequency spectrum of a general multicarrier transmission signal, and FIG. 2B is a diagram showing a general multicarrier transmission signal. FIG. 2C is a diagram showing a temporal change of the total power of a general multicarrier transmission signal.

FIG. 3 is a diagram showing a multicarrier transmission signal according to the first embodiment of the present invention, and FIG.
FIG. 3B is a diagram showing the phase relationship of the multicarrier transmission signal of the present embodiment in which the attenuation of the variable attenuator is controlled under the same conditions as in FIG. 2B, and FIG. 3B is the same condition as in FIG. It is a figure showing the time change of the total electric power in the multicarrier transmission signal in this Embodiment which controlled the attenuation of the variable attenuator below. Note that the frequency spectrum of the multicarrier transmission signal in the present embodiment is the same as that in FIG.

As described in the prior art, a multicarrier signal generally has a plurality of carriers at certain frequency intervals. The phase relationship between these carriers changes over time. During this change, when two or more carriers out of the plurality of carriers approach the same phase, the total power instantaneously increases. Particularly, the peak output power instantaneously increases as the number of carriers in phase increases. For such a signal having a large peak factor, the size of the transistor of the power amplifier used increases, and the ratio (power conversion efficiency) between the DC supply power of the power amplifier and the extracted transmission power decreases.

Therefore, in the phase relationship as shown in FIG. 2B, while maintaining the phase relationship as shown in FIG.
By suppressing the amplitudes of 1 and f2 and increasing the amplitudes of the other frequencies, the peak of the total power can be suppressed as shown in FIG. The reason why the amplitudes of other frequencies are increased is to balance as a whole.

The control circuit 7 controls the attenuation of each of the variable attenuators 2-1 to 2-n so as to correspond to the amplitude of each frequency shown in FIG. By suppressing the peak output power of the total power to be lower than the average output power, the size of the transistor used in the power amplifier circuit can be reduced, and the power conversion efficiency of the power amplifier can be improved.

In the present embodiment, the level varying means of the present invention is connected to the input side of the modulator as a variable attenuator, and adjusts the level of each input signal of the present invention to thereby achieve the present invention. Although the level of each modulated signal has been described as being indirectly adjusted, the present invention is not limited to this. For example, the level of each modulated signal of the present invention may be directly connected to the output side of a modulator. Alternatively, the same effect can be obtained even if the level of each modulated signal of the present invention is indirectly adjusted by adjusting the level of each carrier of the present invention by being connected to the output side of the carrier generator.

In short, the same effect can be obtained if the level of each modulated signal of the present invention is adjusted directly or indirectly. The same effect can be obtained even in combination with a variable gain amplifier.

In this embodiment, each of the input terminals 1-1 to 1-n is connected to each of the digital addition circuits 603 to 603 in FIG.
1 to 603-n are connected one to one, the CD
This is applied to a multicarrier transmission circuit of the MA system. That is, an example is shown in FIG.

(Second Embodiment) Next, a second embodiment of the present invention will be described.
An embodiment will be described with reference to the drawings.
This embodiment is different from the above-described first embodiment in that a code modulation unit, a code selection unit, a preprocessing combining unit, and the like of the present invention are provided. Therefore,
In the present embodiment, components that are not particularly described are the same as those in the first embodiment, and components that are assigned the same reference numerals as those in the first embodiment are the same as those in the first embodiment unless otherwise described. It has the same function as that of the first embodiment.

FIG. 4 is a block diagram showing a multicarrier transmission circuit according to the second embodiment of the present invention. 4, 10-1 to 10-m are m channel input terminals, 20-1 to 20-m are m code multiplication circuits (corresponding to the code modulation means of the present invention), and 9 is each code multiplication circuit A code selection circuit (corresponding to the code selection means of the present invention) for selecting a signal according to the specification of the control circuit; Are digitally added (corresponding to the preprocessing synthesis means of the present invention).

In FIG. 4, each channel input terminal 10
The channel signals (corresponding to the pre-processing input signal of the present invention) input with equal amplitudes of -1 to 10-m are multiplied by the codes specified by the code selection circuit 9 in the code multiplication circuits 20-1 to 20-m. Is done. Each of the channel signals multiplied by the code (corresponding to the encoded signal for preprocessing of the present invention) is input to digital addition circuits A1 to An designated by the control circuit 7, where they are digitally added and multiplexed. Each of the multiplexed channel signals (corresponding to the input signal of the present invention) is applied to modulators 5-1 to 5-
n. The operation after the modulators 5-1 to 5-n is as follows.
According to the first embodiment.

Here, the control circuit 7 is a digital addition circuit A
A procedure for specifying a channel signal to be input for each of 1 to An will be described. The phase detectors 4-1 to 4-n detect the phases of the carrier waves output from the carrier generators 3-1 to 3-n in advance using, for example, a warm-up period before actual transmission. The phase relationship changes according to the elapsed time from the time of performing the phase detection, but if the frequency of each carrier is known,
It is possible to predict the phase relationship of the time. Based on the detected phase information, the control circuit 7 predicts the phase relationship between the carrier waves, and causes the code selection circuit 9 to select a code to be assigned to each channel signal in accordance with the phase relationship. 1 to 20-m.
Further, the control circuit 7 designates the number of channel signals to be added to the n digital addition circuits A-1 to An in accordance with the predicted phase relationship between the carrier waves. The control circuit 7
This number is determined so as to correspond to the amplitude of each frequency in FIG. 3B described in the first embodiment.
Accordingly, the amplitude of the input signal of each of the multiplexed modulators 5-1 to 5-n is determined by the number of multiplexed channel signals, and this number is determined by the phase relationship of the carrier wave.
The same effect as that of the embodiment can be obtained.

The codes are selected such that the codes do not match between channel inputs connected to the same digital adder circuit A.

As a method of adjusting the level of the modulated signal, in addition to the above-described method, a method of adjusting the level of the coded signal after being coded by the code in FIG. is there.

As another adjustment method, a method of adjusting the level of the modulated signal by adjusting the code selected by the code selection circuit 9 is also possible.

In the present embodiment, m is a multiple of n, and in the initial state, each digital adder A-
If the lines are connected so that 1 to An combine the m / n channel signals into one multiplexed signal, the circuit is applied to the CDMA multicarrier transmission circuit. .

Further, the control means of the present invention comprises the first
In the second embodiment, when the relationship between the phases of two or more carriers is a predetermined relationship including the same phase, the level of the multiplexed signal is higher than when the adjustment by the level varying means is not performed. As described above, it has been described that the level of each modulated signal is determined and the level varying means is controlled so as to be the determined level.However, when an allowable maximum value of peak power or the like is set, Further, control may be performed to determine the level of each of the modulated signals so that the level of the multiplexed signal does not exceed a predetermined value. Conversely, if there is a demand not to drop the output below a certain level, control may be performed to determine the level of each modulated signal so that the level of the multiplexed signal increases. . In short, the control means of the present invention
What is necessary is just to control the level varying means according to the phase of each carrier detected by each carrier phase detecting means.

The present invention is not limited to the CDMA system,
Other multi-carrier systems such as the FDMA system and the TDMA system are also applicable.

Further, in addition to the above-described multi-carrier transmission circuit, the transmission apparatus of the present invention includes the following:
It comprises a high-frequency amplifier circuit for amplifying the output of the multicarrier transmission circuit, and an antenna for transmitting the amplified signal to the outside.

[0042]

As is apparent from the above description, the present invention suppresses the instantaneous maximum output power to a small value even for a wide band signal of several MHz to several tens of MHz, and reduces the peak of the multicarrier transmission signal. By reducing the factor, it is possible to provide a multicarrier transmission circuit in which the circuit can be downsized.

That is, the multicarrier transmission circuit of the present invention detects the phase of each carrier of the multicarrier transmission signal in advance, and when the phase relationship indicates the instantaneous maximum power (2
(The phases of two or more carriers are in-phase), and the level of each carrier is controlled. As a result, even for a wideband signal of several MHz to several tens of MHz, the instantaneous maximum output power can be suppressed to a small value, the peak factor of the multicarrier transmission signal can be reduced, and the transmission circuit can be downsized. .

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a multicarrier transmission circuit according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a conventional general multicarrier transmission signal.

FIG. 3 is a diagram illustrating a multicarrier transmission signal according to the first embodiment of the present invention.

FIG. 4 is a block diagram illustrating a multicarrier transmission circuit according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing a multicarrier transmission circuit according to another embodiment of the present invention.

FIG. 6 is a basic configuration diagram of a conventional multicarrier transmission circuit.

FIG. 7 is a configuration diagram of a conventional multicarrier transmission circuit.

[Explanation of symbols]

 1-1 to 1-n input terminal 2-1 to 2-n variable attenuator 3-1 to 3-n carrier generator 4-1 to 4-n phase detector 5-1 to 5-n modulator 6 addition Circuit 7 Control circuit 8 Output terminal 9 Code selection circuit 10-1 to 10-m Channel input terminal 20-1 to 20-m Code multiplication circuit A1 to An Digital addition circuit

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroaki Kosugi 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Shinichi Kugo 4-3-1 Tsunashima Higashi, Kohoku-ku, Yokohama, Kanagawa Prefecture Communication Industry Co., Ltd.

Claims (11)

[Claims] An n number of modulated signals are generated by modulating respective carrier waves with n (n is an integer of 2 or more) input signals, and the n modulated signals are combined. In a multi-carrier transmission circuit that outputs a multiplexed signal, n carrier wave generating means for generating each carrier wave, and n modulation means for modulating each carrier wave with each of the input signals and outputting the modulated signal Synthesizing means for synthesizing the n modulated signals and outputting the multiplexed signal; level varying means for directly or indirectly adjusting the level of each of the modulated signals; and adjusting the phase of each of the carrier waves. And n control means for controlling the level varying means according to the phase of each of the carrier waves detected by each of the carrier wave phase detecting means. Chi-carrier transmission circuit. 2. Codes for generating m pre-processing coded signals by encoding m (m is an integer equal to or more than n) pre-processing input signals with corresponding codes. Modulating means; code selecting means for selecting the code for each of the preprocessing input signals; and n preprocessing for combining the m preprocessing encoded signals to generate n input signals. 2. The multicarrier transmission circuit according to claim 1, further comprising: a use combining unit. 3. The level varying means indirectly adjusts the level of each of the modulated signals by adjusting the level of each of the input signals or by adjusting the level of each of the carrier waves. Claim 1 characterized by the following:
Or the multicarrier transmission circuit according to 2. 4. The level varying means indirectly changes the level of each of the modulated signals by switching connection of a line to which each of the preprocessing coded signals is input to each of the preprocessing synthesizing means. Adjusting the number of the pre-processing coded signals to be synthesized by the respective pre-processing synthesizing units according to the phase of each of the carrier waves detected by the respective carrier phase detecting means. Determined for each means, controls the level variable means, The code selection means, based on the switching of the connection,
3. The multicarrier transmission circuit according to claim 2, wherein the code is selected. 5. The apparatus according to claim 1, wherein the level varying unit adjusts the level of each of the modulated signals by adjusting the levels of the m preprocessing input signals before being encoded. Item 3. The multicarrier transmission circuit according to Item 2. 6. The multicarrier transmission circuit according to claim 2, wherein said level varying means adjusts the level of each of said modulated signals by adjusting said code. 7. The m is a multiple of n, and in the initial state, each of the preprocessing synthesizing units synthesizes m / n preprocessing encoded signals to form one preprocessing multiplex signal. 5. The multicarrier transmission circuit according to claim 4, wherein a line is connected so as to generate an encoded signal. 8. The apparatus according to claim 2, wherein the level varying unit indirectly adjusts the level of each of the modulated signals by adjusting the level of each of the pre-encoded signals. Multi-carrier transmission circuit. 9. The multiplexing apparatus according to claim 1, wherein when the phase relationship between the two or more carrier waves is a predetermined relationship including the same phase, the control unit performs the multiplexing more than when the adjustment by the level varying unit is not performed. The level of each of the modulated signals is determined so that the level of the signal is reduced, and the level varying means is controlled so that the level becomes the determined level. A multicarrier transmission circuit as described. 10. The multicarrier transmission according to claim 9, wherein said control means determines the level of each of said modulated signals so that the level of said multiplexed signal does not exceed a predetermined value. circuit. 11. A multi-carrier transmission circuit according to claim 1, comprising: a high-frequency amplification circuit for amplifying an output of the multi-carrier transmission circuit; and an antenna for transmitting an output of the high-frequency amplification circuit. A communication device for performing communication.