JP2000299652A - Transmission device - Google Patents

Abstract

(57) [Problem] To prevent the influence of linear distortion that a transmission signal receives from a filter and improve the accuracy of pre-distortion distortion compensation processing on the transmission signal. SOLUTION: An equalizer 103 includes a post filter 1.
The transmission signal before being input to the signal receiver 04 is given in advance a distortion that cancels the distortion caused by passing through the post filter 104, thereby removing the influence of the group delay characteristic of the post filter 104, and So that the effect of the pre-distortion due to is not impaired.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a transmitting device,
In particular, the present invention relates to a transmission device used for mobile communication and a distortion compensation method thereof.

[0002]

2. Description of the Related Art In recent transmission apparatuses, high-efficiency transmission amplifiers are often used in order to reduce power consumption. However, if a high-efficiency amplifier is used in the transmission device, it becomes difficult to maintain the linearity of the input power and the output power, and nonlinear distortion is likely to occur.

As described above, when nonlinear distortion occurs in an amplifier, the frequency spectrum of a transmission signal is broadened, and adverse effects such as interference with adjacent channels are caused.

Therefore, the conventional transmitting apparatus employs a distortion compensation technique such as pre-distortion as a technique for improving the efficiency of an amplifier and realizing a low distortion.

Hereinafter, a conventional transmitting apparatus will be described with reference to FIGS. FIG. 5 is a main block diagram illustrating a schematic configuration of a conventional transmission device, and FIG. 6 is a schematic diagram illustrating a function of a predistortion distortion compensation process in the conventional transmission device.

In FIG. 5, a distortion compensator 501 inputs an in-phase component (hereinafter, referred to as “I component”) and a quadrature component (hereinafter, referred to as “Q component”) of a transmission signal into an amplifier 505 described later. A characteristic for canceling and canceling the output characteristic (hereinafter referred to as an inverse characteristic) is given in advance. Details will be described later.

[0007] The D / A converter 502 converts each of the I component and the Q component of the transmission data after distortion compensation into an analog signal.

The post-filter 503 removes unnecessary frequency components from the I and Q components of the transmission data after analog signal conversion, and the quadrature modulator 504 quadrature modulates the input I and Q components. The amplifier 505 amplifies the quadrature-modulated transmission signal.

Next, the function of the pre-distortion distortion compensation processing will be described with reference to FIG.

The input / output characteristics of the amplifier 505 are shown in FIG.
As shown in (1), as the input power increases, the linearity between the input power and the gain, that is, the output power is not maintained. Although the input / output characteristics include an amplitude characteristic and a phase characteristic, only the amplitude characteristic will be described here.

Therefore, the inverse characteristic of the input / output characteristic of the amplifier is
The transmission signal before being input to the amplifier is multiplied in advance. That is, the distortion compensator 501 multiplies the transmission signal by the characteristic shown in FIG.

By such processing, the amplifier 505 can maintain the linearity of the input signal and the gain regardless of the magnitude of the input signal, as shown in FIG. The processing for canceling the distortion in this way is called pre-distortion distortion compensation processing.

As described above, the conventional transmission apparatus performs pre-distortion distortion compensation processing, thereby suppressing the spread of the frequency spectrum of the transmission signal due to the non-linear characteristics of the amplifier, and preventing interference with adjacent channels.

[0014]

However, in the conventional transmitting apparatus, since the post filter has a group delay deviation, a linear distortion occurs when the transmission signal passes through the post filter. There is a problem that the distortion compensation effect is deteriorated.

That is, a post-filter inserted for the purpose of removing unnecessary frequency components usually has a group delay deviation as shown in FIG. For this reason, when a transmission signal is passed through a post filter having such characteristics, a deviation occurs between the waveform of the input signal and the waveform of the output signal within the pass band as shown in FIG. 7B. This is called linear distortion.

Therefore, in the distortion compensating section 501, the amplifier 5
Even if the input / output characteristics are multiplied by the inverse characteristics of the input / output characteristics of 05, a deviation, that is, a phase rotation occurs in the post filter 503, so that the pre-distortion distortion compensation processing cannot be performed accurately.

If this problem is to be solved by increasing the sampling frequency, another problem such as an increase in power consumption in the distortion compensator, the D / A converter, and the like will occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a transmission apparatus that prevents the influence of linear distortion on a transmission signal from a filter and improves the accuracy of predistortion distortion compensation processing on the transmission signal. With the goal.

[0019]

The gist of the present invention is that an equalizer preliminarily applies a distortion to a transmission signal before input of the filter so as to cancel out a linear distortion given by the filter, so that the filter is grouped. It is an object of the present invention to remove the influence of having a delay deviation so that the effect of the pre-distortion distortion compensation processing is not impaired.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A transmitting apparatus according to a first aspect of the present invention includes a nonlinear distortion compensating means for providing a distortion to a transmission signal in advance for canceling the nonlinear distortion generated when amplifying the transmission signal; And a linear distortion compensating means for preliminarily applying, to the transmission signal, distortion for canceling the linear distortion given to the transmission signal by the frequency extraction means.

According to this configuration, since a distortion that cancels the linear distortion caused by the filter passing through the transmission signal is given to the transmission signal before the filter is input, the filter has a group delay deviation. The influence of linear distortion can be removed, and the accuracy of the pre-distortion distortion compensation processing can be improved.

[0022] The transmission apparatus according to a second aspect of the present invention, in the first aspect, employs a configuration in which the linear distortion compensating means is formed by digital signal processing.

According to this configuration, since the linear distortion compensation is performed by digital signal processing, the hardware scale can be made smaller than in the case of analog signal processing of the same function and purpose, and the compensation operation can be stabilized. Can be achieved.

[0024] In a transmission apparatus according to a third aspect of the present invention, in the second aspect, the linear distortion compensating means may be a linear distortion compensating means according to an individual difference of a group delay deviation of the frequency extracting means. A configuration is employed in which the linear distortion given in advance to the transmission signal is changed by changing the group delay characteristic.

According to this configuration, the linear distortion given to the signal before input to the filter can be changed in accordance with the individual difference of the group delay characteristic of the filter. , Nonlinear compensation can be appropriately compensated.

According to a fourth aspect of the present invention, in the transmission apparatus according to the second aspect or the third aspect, the linear distortion compensating means changes a group delay characteristic in accordance with an operation environment of the apparatus to thereby transmit a transmission signal. Is adapted to adaptively change the linear distortion given in advance to.

According to this configuration, since the linear distortion given to the signal before the filter input can be adaptively changed according to the operating environment, the linear distortion caused by passing through the filter is appropriately removed, and the nonlinear distortion caused by the amplifier is reduced. Compensation can be made appropriately.

A communication terminal device according to a fifth aspect of the present invention employs a configuration including the transmission device according to any one of the first to fourth aspects.

[0029] The base station apparatus according to the sixth aspect of the present invention comprises:
A configuration for performing communication with the communication terminal device according to the fifth aspect is employed.

[0030] A base station apparatus according to a seventh aspect of the present invention comprises:
A configuration including the transmitting device according to any one of the first to fourth aspects is employed.

A communication terminal apparatus according to an eighth aspect of the present invention employs a configuration for performing communication with the base station apparatus according to the seventh aspect.

According to these configurations, since appropriate distortion compensation is performed on the transmission signal, the spread of the frequency spectrum of the transmission signal can be suppressed, and interference with an adjacent channel can be prevented.

The predistortion distortion compensating method according to a ninth aspect of the present invention provides a distortion to a transmission signal in advance to cancel nonlinear distortion generated when amplifying the transmission signal, and removes unnecessary frequency components from the transmission signal. Distortion for canceling the linear distortion generated when the transmission is performed is given to the transmission signal in advance, unnecessary frequency components are removed from the transmission signal, and the transmission signal is amplified.

According to this method, since a distortion that cancels the linear distortion caused by passing through the filter is given to the transmission signal before the input of the filter, the filter has a group delay deviation. The influence of linear distortion can be removed, and the accuracy of the pre-distortion distortion compensation processing can be improved.

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

(Embodiment 1) The transmitting apparatus according to the present embodiment transmits a distortion that cancels linear distortion given to a signal passing through a filter due to a filter having a group delay deviation before input to the filter. It has an equalizer that gives a signal in advance.

Hereinafter, the transmitting apparatus according to the present embodiment will be described using FIG. 1 and FIG. FIG. 1 is a main block diagram illustrating a schematic configuration of a transmitting apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a schematic diagram illustrating a function of an equalizer of the transmitting apparatus according to Embodiment 1 of the present invention. It is.

In FIG. 1, a distortion compensating section 101 gives the I component and the Q component of the transmission signal the inverse characteristics of the input / output characteristics of the amplifier 106 described later. D / A
The converter 102 calculates the I component and Q of the transmission data after the distortion compensation.
Each component is converted to an analog signal.

An equalizer (EQ) 103 gives a transmission signal passing through a distortion having a characteristic opposite to the distortion given by a post filter 104 described later. Post filter 1
Reference numeral 04 removes unnecessary frequency components from the I component and the Q component of the transmission data after the analog signal conversion. Since the post filter 104 has a group delay characteristic as shown in FIG. 2, the equalizer 103 has a group delay characteristic as shown in FIG. 2, that is, a group that gives a distortion that cancels the distortion given by the post filter 104. Delay characteristics.

The quadrature modulator 105 quadrature-modulates the input I and Q components, and the amplifier 106 amplifies the quadrature-modulated transmission signal.

Next, the operation of the transmitting apparatus having the above configuration will be described.

The I component and the Q component of the transmission signal are first given distortion by the distortion compensator 101, and later the amplifier 106
The signal is converted into a signal having distortion corresponding to being canceled by the application of nonlinear distortion.

Next, the transmission signal converted into an analog signal by the D / A converter 102 is passed through an equalizer 103. The I component and the Q component of the transmission signal are each given a linear distortion under the influence of the group delay deviation of the equalizer 103, and become a signal having a distortion corresponding to being canceled by the linear distortion given later by the post filter 104.

Next, the I and Q components of the transmission signal are
It is passed through a post filter 104. Post filter 10
4 removes unnecessary frequency components and gives linear distortion. Here, the post-filter 10 is included in the transmission signal.
Since the distortion that cancels out with the linear distortion given by 4 is given in advance by the equalizer 103, the output of the post filter 104 has been subjected to ideal unnecessary frequency component removal as shown in FIG. State, and a signal that does not include linear distortion can be obtained.

Next, the transmission signal is quadrature-modulated by quadrature modulator 105 and amplified by amplifier 106. The non-linear distortion given to the transmission signal by this amplification is canceled by the distortion given in advance by the distortion compensating section 101.

As described above, according to the present embodiment, since the equalizer preliminarily applies a distortion that cancels the linear distortion caused by passing through the filter to the transmission signal before the filter input, the post filter has a group delay deviation. , The effect of linear distortion can be eliminated, and the accuracy of the pre-distortion distortion compensation processing can be improved.

Further, according to the present embodiment, the power consumption of the distortion compensator, D / A converter, etc. increases without increasing the sampling frequency in order to remove the linear distortion given by the post filter. Not even.

(Embodiment 2) The transmitting apparatus according to the present embodiment has the same configuration as that of Embodiment 1 except that a digital equalizer is used as an equalizer.

Hereinafter, the transmitting apparatus according to the present embodiment will be described with reference to FIG. FIG. 3 is a main part block diagram showing a schematic configuration of the transmitting apparatus according to Embodiment 2 of the present invention. In FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and the detailed description is omitted.

An equalizer (EQ) 301 is a digital equalizer, which differs from the first embodiment in that the D / A
It is provided before the converter 102. However, the function of the equalizer 301 is the same as that of the equalizer 103 of the first embodiment.
And has a group delay characteristic that can be given to a signal passing through a distortion that cancels the linear distortion given by the post filter 104.

As described above, according to the present embodiment, a digital equalizer is used as an equalizer, and the equalizer process is performed by digital signal processing. Therefore, the hardware scale is smaller than that of analog signal processing having the same function and purpose. The size can be reduced, and the group delay characteristics of the equalizer can be stabilized.

(Embodiment 3) The transmitting apparatus according to the present embodiment is different from the transmitting apparatus according to the present invention except that an equalizer varies a linear distortion given to a transmission signal before input of a filter according to an individual difference of a group delay characteristic of the filter. It has a configuration similar to that of the second embodiment.

Hereinafter, the transmitting apparatus according to the present embodiment will be described with reference to FIG. FIG. 4 is a main block diagram showing a schematic configuration of the transmitting apparatus according to Embodiment 3 of the present invention. In FIG. 4, the same components as those in FIG. 3 are denoted by the same reference numerals, and detailed description will be omitted.

An equalizer (EQ) 401 is a digital equalizer similar to the equalizer 301 of the second embodiment, but adopts a configuration in which the group delay characteristic can be set from the outside.

The equalizer (EQ) characteristic setting unit 402
A plurality of group delay characteristics are held, and the group delay characteristics of the equalizer 401 are set from outside the equalizer. The control unit 403
An equalizer characteristic setting unit 402 is instructed which group delay characteristic is to be set in the equalizer 401 in accordance with the individual difference in the group delay characteristic of a post filter which is a device that performs analog signal processing.

The control unit 403 selects an appropriate group delay characteristic according to the individual difference of the group delay characteristic of the post-filter found by, for example, a test at the time of shipping the device, and instructs the equalizer characteristic setting unit 402.

As described above, according to the present embodiment, the linear distortion given to the signal before the filter is input by the equalizer can be changed according to the individual difference of the group delay characteristic of the post-filter. The linear distortion can be appropriately removed, and the nonlinear distortion due to the amplifier can be appropriately compensated.

(Embodiment 4) The transmitting apparatus according to the present embodiment is different from Embodiment 3 in that the linear distortion given to the transmission signal before the filter input by the equalizer can be adaptively changed during operation of the apparatus. Has the same configuration as

In the transmitting apparatus according to the present embodiment, in FIG. 4, control section 403 monitors various parameters, for example, apparatus temperature, apparatus power supply voltage and the like during apparatus operation, and determines any group delay characteristic. It is determined whether or not it is appropriate to use, and an instruction is given to the equalizer characteristic setting unit 402.

As described above, according to the present embodiment, the linear distortion given to the signal before the filter is input by the equalizer can be adaptively changed according to the operating environment. Thus, the nonlinear distortion due to the amplifier can be appropriately compensated.

It should be noted that the first to fourth embodiments are used.
In the above, a case where an equalizer is used has been described, but a configuration other than the equalizer may be employed as long as the configuration has an effect of canceling out linear distortion generated in a transmission signal by passing through a filter. Further, the application of the present invention is not limited to a transmission device that performs quadrature modulation.

[0062]

As described above, according to the present invention,
By applying a distortion that cancels out the linear distortion given by the filter to the transmission signal before the filter input by the equalizer in advance, it is possible to prevent the influence of the linear distortion that the transmission signal receives from the filter. The accuracy of the pre-distortion distortion compensation processing for a signal can be improved.

Further, the sampling frequency is not increased in order to remove the linear distortion given by the post filter, and the power consumption in the distortion compensator, D / A converter and the like does not increase.

[Brief description of the drawings]

FIG. 1 is a main block diagram showing a schematic configuration of a transmitting apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a schematic diagram showing a function of an equalizer of the transmitting apparatus according to Embodiment 1 of the present invention.

FIG. 3 is a main block diagram showing a schematic configuration of a transmitting apparatus according to Embodiment 2 of the present invention.

FIG. 4 is a main block diagram showing a schematic configuration of a transmitting apparatus according to Embodiments 3 and 4 of the present invention.

FIG. 5 is a main block diagram showing a schematic configuration of a conventional transmission device.

FIG. 6 is a schematic diagram showing a function of pre-distortion in a conventional transmission device.

FIG. 7A is a schematic diagram showing a group delay characteristic of a post filter. FIG. 7B is a schematic diagram showing a deviation between input and output waveforms of the post filter.

[Explanation of symbols]

 Reference Signs List 101 distortion compensation unit 102 D / A converter 103 equalizer 104 post filter 105 quadrature modulator 106 amplifier 301 equalizer 401 equalizer 402 equalizer characteristic setting unit 403 control unit

Claims (9)

[Claims] A non-linear distortion compensating means for providing a distortion to a transmission signal in advance for canceling a non-linear distortion generated when amplifying the transmission signal, a frequency extracting means for removing unnecessary frequency components from the transmission signal, A linear distortion compensating means for preliminarily applying a distortion to the transmission signal for canceling the linear distortion applied to the transmission signal by the means. 2. The transmitting apparatus according to claim 1, wherein said linear distortion compensating means comprises digital signal processing. 3. The linear distortion compensating means changes a group delay characteristic of the linear distortion compensating means in accordance with an individual difference of a group delay deviation of the frequency extracting means, thereby providing a linear distortion given to a transmission signal in advance. 3. The transmitting device according to claim 2, wherein: 4. The apparatus according to claim 2, wherein the linear distortion compensator adaptively changes a linear distortion given to a transmission signal in advance by changing a group delay characteristic according to an operation environment of the apparatus. Item 4. The transmitting device according to Item 3. 5. A communication terminal device comprising the transmission device according to claim 1. Description: 6. A base station apparatus for performing communication with the communication terminal apparatus according to claim 5. 7. A base station apparatus comprising the transmission apparatus according to claim 1. Description: 8. A communication terminal device for performing communication with the base station device according to claim 7. 9. A transmission signal is preliminarily provided with a distortion for canceling non-linear distortion generated when amplifying the transmission signal, and a distortion for canceling linear distortion generated when removing unnecessary frequency components from the transmission signal is transmitted. A pre-distortion distortion compensating method characterized by providing a signal in advance, removing unnecessary frequency components from a transmission signal, and amplifying the transmission signal.