JP2002290164A - Nonlinear compensator and non-linear compensation target monitoring device - Google Patents

Abstract

(57) [Problem] To provide information indicating the degree of deterioration of an amplifier when compensating for nonlinear characteristics of the amplifier. A distortion detector detects a distortion component in the amplifier from an input signal and an output signal of the amplifier, and a distortion compensator obtains a distortion compensation amount based on a distortion component detection result. The distortion compensation of the input signal of the amplifier is performed based on the compensation amount. At this time, the distortion compensation amount used in the distortion compensating unit 17 is registered in the compensation table 20, and the distortion compensation amount registered in the compensation table 20 is registered in the monitoring compensation table 22 in advance.
In operation, the distortion compensation amount registered in the compensation table 20 is compared with the distortion compensation amount registered in the monitoring compensation table 22, and the difference is monitored and output. From this monitoring output, the degree of deterioration of the amplifier can be determined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-linear compensator which is used for a transmission device in a transmission system such as a medium wave, a short wave, a terrestrial wave, a satellite and a cable television, and which compensates for a non-linear characteristic generated in an amplifier of the transmission device. The present invention relates to a non-linear compensation target monitoring device that monitors the degree of deterioration of an internal device of a transmission device using the non-linear compensator.

[0002]

2. Description of the Related Art At present, in a transmitting apparatus used in an analog television broadcasting system, nonlinear compensation is performed by a pre-compensator having characteristics opposite to those produced by an amplifier. In particular, in the transmission device, the nonlinear characteristic of the amplifier changes depending on the operating temperature of the amplifier and the like. Therefore, the compensation characteristic is switched according to the operating condition of the amplifier.

Here, in analog television broadcasting, the signal peak value is almost constant because it is defined by the synchronization peak value. In addition, since the signal is a synchronization signal component near the clip value, there is no need to consider phase distortion generated near the clip level, and only the synchronization amplitude needs to be corrected so that the synchronization length is the same. Further, since the peak factor (peak value / average value) is relatively small, linearity in a low-level signal region is not so required.

On the other hand, in the next-generation digital television broadcasting, the adoption of the OFDM (orthogonal frequency division multiplexing) system has been decided, and various developments have been made for practical use. Here, in the OFDM system, since the peak factor is extremely large compared to the analog system due to the nature of the OFDM signal, linearity is required over a wide range from a low level to a high level. In addition, since the phase of each carrier is the point of information transmission, even a slight disturbance of the phase rotation leads to deterioration of characteristics. As described above, in the OFDM transmission apparatus, the nonlinear characteristic,
Accurate compensation for phase rotation is required.

[0005] Therefore, development of a non-linear compensator for a transmission device has been promoted for realizing digital television broadcasting. However, if the compensator completely compensates for the non-linear characteristic, the output characteristic is maintained irrespective of the deterioration of the internal device of the transmission device, so that it becomes difficult for an administrator to grasp the degree of deterioration of the device. .
That is, in the conventional analog system, the degree of deterioration can be roughly grasped by looking at the output characteristics, and parts can be appropriately replaced, but when the compensation of the nonlinear characteristics is completed in the digital system, the output characteristics deteriorate. It becomes impossible to judge the condition, and confusion is caused in maintenance work such as replacement of parts.

[0006] Accordingly, there is a demand for a method of accurately comprehending the degree of deterioration of an internal device of a transmission apparatus in order to prevent characteristic deterioration when realizing accurate compensation of nonlinear characteristics.

[0007]

As described above, O
In digital signal transmission devices such as the FDM system, accurate compensation of nonlinear characteristics is required. On the other hand, when realizing accurate compensation of nonlinear characteristics,
In order to prevent characteristic deterioration, it is desired to be able to accurately grasp the degree of deterioration of the nonlinear compensation target.

The present invention has been made in consideration of the above circumstances, and has a nonlinear compensator capable of presenting information indicating the degree of deterioration of a non-linear compensation target when compensating for a nonlinear characteristic. It is an object of the present invention to provide a non-linear compensation target monitoring device capable of accurately determining the degree of deterioration of a non-linear compensation target based on information obtained from a device, thereby realizing an efficient maintenance operation.

[0009]

To achieve the above object, a non-linear compensator according to the present invention has the following characteristic configuration.

(1) A distortion detecting section for detecting a distortion component in a device to be compensated from an input signal and an output signal of a device to be compensated for which nonlinear compensation is required, based on the distortion component detected by the distortion detecting section. A distortion compensator for obtaining a distortion compensation amount and performing distortion compensation of an input signal of the compensated device based on the distortion compensation amount; a compensation table for registering the distortion compensation amount used in the distortion compensation unit; A monitoring compensation table for pre-registering the registered distortion compensation amount for monitoring is provided, and in operation, the distortion compensation amount registered in the compensation table is compared with the distortion compensation amount registered in the monitoring compensation table. A compensation monitoring unit that monitors the difference.

(2) In the configuration of (1), the compensation monitoring unit updates at least the compensation amount table in an initial operation start state and the compensation table in an operation state as the monitoring compensation table. A table for registering the compensation amount immediately before the operation is performed, and the table is switched and used according to a temporal change.

(3) In the configuration of (1), when the difference result obtained by the comparison exceeds a reference range, the compensation monitoring unit judges that the abnormality is abnormal and notifies the outside.

(4) A distortion detecting section for detecting a distortion component in the compensated device from an input signal and an output signal of the compensated device for which nonlinear compensation is required, and based on the distortion component detected by the distortion detecting section. A distortion compensating amount is obtained, a distortion compensating unit for compensating for a distortion of an input signal of the compensated device based on the distortion compensating amount, and a change in a distortion component detected by the distortion detecting unit is constantly or periodically monitored. And a compensation monitoring unit that monitors the compensation state.

(5) In the configuration of (4), the compensation monitoring section compares the distortion component detection result with a reference value and accumulates a history of the difference.

The monitoring apparatus for non-linear compensation according to the present invention has the following characteristic configuration.

(6) A monitoring state monitor for monitoring the deterioration state of the non-linear compensation target by taking out and monitoring the monitoring result from the compensation monitoring section of the nonlinear compensator of (1).

(7) A monitoring state monitoring means for monitoring a deterioration state of a non-linear compensation target by taking out and monitoring a monitoring result from a compensation monitoring section of the nonlinear compensator of (4).

(8) In the configuration of (6) or (7), the monitoring state monitoring means extracts a monitoring result from the compensation monitoring unit by remote control.

[0019]

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

FIG. 1 shows the configuration of an OFDM transmitting apparatus to which the present invention is applied. A baseband OFDM signal input to the present apparatus is converted by a modulator 1 into an OFDM signal in an IF frequency band. Through such a nonlinear compensator 2,
The signal is converted into an RF frequency by the up-converter 3, is power-amplified by the RF amplifier 4, and is output as a transmission signal. R
The output of the F amplifier 4 is partially distributed by a distributor (for example, a directional coupler) 5, converted to an IF frequency by a down converter 6, and monitored for a transmission output (PA) monitor signal (hereinafter referred to as “PA”).
The signal is supplied to the nonlinear compensator 2 as a PA signal). The non-linear compensator 2 obtains a non-linear characteristic of the PA signal by comparing the transmission signal from the modulator 1 with the PA signal, and compensates for the characteristic to be within an allowable range. The non-linear compensator 2 is connected to a monitoring state monitor 7 for monitoring the compensation result.

FIG. 2 is a block diagram showing a configuration of the nonlinear compensator 2.

In FIG. 2, an IF signal from the modulator 1 is supplied to an IF input terminal. This IF signal is quadrature-demodulated by the IF input demodulation unit 11 to become digital baseband signals I1 and Q1 in a complex format. On the other hand, the output from the RF amplifier 4 to the PA input terminal
A PA signal converted to the F frequency is supplied. This PA
The signal is quadrature-demodulated by the PA input demodulation unit 12, and becomes digital baseband signals I2 and Q2 in a complex format.

The digital baseband signals I1 and Q1 output from the IF input demodulation unit 11 are
And supplied to the Pythagoras converter 16. The delay adjuster 13 delays the digital baseband signals I1 and Q1 from the IF input demodulator 11 by a predetermined time, respectively, to obtain digital baseband signals I3 and Q3. The digital baseband signals I3 and Q3 are supplied to the delay detector 14 and the distortion detector 15 together with the digital baseband signals I2 and Q2 from the PA input demodulator 12.

In the delay detecting section 14, the delay adjusting section 13
And the digital baseband signals I2 and Q3 from the PA input demodulation unit 12.
2 by complex multiplication to obtain a complex correlation between the two and R
An EAL (real part) signal and an IMAG (imaginary part) signal are obtained, and delay information is obtained from a peak position in a correlation output. This delay information is supplied to the delay adjusting unit 13 and is used for adjusting the delay time.

In the distortion detecting section 15, the delay adjusting section 13
And the digital baseband signals I2 and Q3 from the PA input demodulation unit 12.
2 and the polar coordinates (R3, θ) from the Cartesian coordinates (I3, Q3) (I2, Q2) by Pythagoras transformation, respectively.
3) Convert to (R2, θ2), and obtain the amplitude error ΔR and the phase error Δθ of both from the following equation. ΔR = R3-R2 Δθ = θ3-θ2 The obtained amplitude error ΔR and phase error Δθ are supplied to the distortion compensator 17. In the distortion compensating section 17, the amplitude error ΔR and the phase error Δθ from the distortion detecting section 15 are respectively integrated in sections, and the integration results are registered in the compensation table 20 as distortion compensation amounts R4 and θ4. Distortion compensation amount R4
θ4 is also supplied to the compensation monitoring unit 21.

On the other hand, the digital baseband signals I1 and Q1 output from the IF input demodulation unit 11 are converted from Cartesian coordinates (I1, Q1) to polar coordinates (R1, θ1) by the Pythagoras converter 16, and then subjected to distortion compensation. It is supplied to the unit 17. The distortion compensating section 17 reads the distortion compensation amount corresponding to the input level R1 from the compensation table 20 and adds the distortion compensation amount to R1 and θ1, thereby compensating for nonlinear characteristics and phase rotation. Result R1 ', θ
1 ′ is returned to the original Cartesian coordinates (I4, Q4) by the inverse Pythagoras converter 18 and supplied to the IF output modulator 19.

The IF output modulating section 19 quadrature-modulates the input digital baseband signals (I4, Q4), and outputs them as distortion-compensated analog IF signals.

The compensation monitoring unit 21 includes a monitoring compensation table 22. When the power is turned on or after the RF amplifier 4 is repaired, the compensation amount stored in the compensation table 20 is initially stored in the monitoring compensation table 22. Register as a value. An example is shown in FIGS. FIG. 3 shows the compensation table 2
FIG. 4 is a characteristic diagram of compensation amounts R4 and θ4 stored in 0, and FIG. 4 shows compensation amounts R5 and θ5 initially registered in monitoring compensation table 22.
FIG.

At the time of operation, the compensation monitoring unit 21 calculates the compensation amounts R4 and θ4 according to the input level R1 from the compensation table 20 and R5 and θ5 according to the input level R1 from the monitoring compensation table 22. In comparison, the operation state of the RF amplifier 4 is monitored. This monitoring content can be monitored by the monitoring status monitor 7 (see FIG. 1) connected externally.

As the monitoring compensation table 22,
In addition to the table in which the compensation amount in the initial state is registered, a table in which the compensation amount immediately before the compensation table 20 is updated is prepared. By switching and using the table in accordance with this, it is possible to accurately monitor a change in the operating state of the RF amplifier 4.

Here, in the compensation monitoring unit 21, a compensation amount R4 corresponding to the input level R1 from the compensation table 20 is set.
If the result of comparing θ4 with R5 and θ5 according to the input level R1 from the monitoring compensation table exceeds a preset reference value, it is determined that an abnormality has occurred and a warning is issued. It is possible to quickly notify the administrator of a failure of the amplifier 4 or the like.

The result of comparing the compensation amounts R4 and θ4 according to the input level R1 from the compensation table 20 with R5 and θ5 according to the input level R1 from the monitoring compensation table 22 is based on a preset reference value. Even when the value is not exceeded,
It is possible to monitor the non-linear characteristics and phase rotation of the RF amplifier 4 that change with season, weather, and time.

FIG. 5 is a block diagram showing another embodiment of the nonlinear compensator according to the present invention. In FIG. 5, the same parts as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will not be repeated.

The feature of this non-linear compensator is that the compensation amount is not monitored in the compensation table 20 but the distortion detection results ΔR and Δθ obtained by the distortion detection unit 15 are constantly or periodically monitored by the compensation monitoring unit 24. The point is to monitor the situation. That is, the distortion monitoring values ΔR, Δθ
Is compared with a reference value, and a history of the difference is taken to monitor the state of each change. According to this configuration, since the change in the amount of distortion generated in the transmission output remains as a history, it is possible to determine from which point the transmission output has started to become abnormal, and to facilitate maintenance work on the RF amplifier 4. Can be increased.

In this case, the monitoring state monitoring device 7 can confirm the occurrence of an abnormality that has occurred in the past by extracting the history information accumulated in the compensation monitoring unit 24 as necessary, such as during maintenance and inspection. It can be used to determine the replacement time.

In the above embodiment, the case of the nonlinear compensator used for the transmission apparatus of the OFDM signal, which is a digital signal, has been described.
8 of C (Advanced Television System Committee) system
It can also be used for a VSB (vestigial sideband) analog transmission device.

The monitoring state monitoring device 7 need not always be arranged near the non-linear compensator, but may be arranged, for example, in a central control room or the like in the station of a broadcasting station, and compensated by wired or wireless remote control. It is more effective to extract information from the monitoring unit.

[0038]

As described above, according to the present invention, a nonlinear compensator capable of presenting information indicating the degree of deterioration of a non-linear compensation target when compensating for nonlinear characteristics, and a nonlinear compensator obtained from the nonlinear compensator It is possible to accurately determine the degree of deterioration of the non-linear compensation target based on the information, thereby providing a non-linear compensation target monitoring device capable of realizing an efficient maintenance operation.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a transmission device to which a nonlinear compensator according to the present invention is applied.

FIG. 2 is a block diagram showing an embodiment of a non-linear compensator used in the transmission device of FIG.

FIG. 3 is a characteristic diagram of a compensation amount stored in a compensation table of FIG. 2;

FIG. 4 is a characteristic diagram of a compensation amount initially registered in the monitoring compensation table of FIG. 2;

FIG. 5 is a block diagram showing another embodiment of the nonlinear compensator used in the transmission device of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Modulator 2 ... Nonlinear compensator 3 ... Up converter 4 ... RF amplifier 5 ... Distributor (directional coupler) 6 ... Down converter 7 ... Monitoring state monitor 11 ... IF input demodulation unit 12 ... PA input demodulation unit 13 ... Delay adjusting unit 14 ... Delay detecting unit 15 ... Distortion detecting unit 16 ... Pythagoras converter 17 ... Distortion compensating unit 18 ... Inverse Pythagoras converter 19 ... IF output modulating unit 20 ... Compensation table 21 ... Compensation monitoring unit 22 ... Monitoring compensation Table 24: Compensation monitoring unit

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Seiji Isobe 1 Kosuka Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa F-term in the Toshiba Komukai Plant (reference) 5C025 AA09 5J090 AA01 AA41 CA00 CA21 FA20 GN02 GN05 KA00 KA15 KA53 KA55 KA67 MA20 SA14 TA01 TA02 5J091 AA01 AA41 CA00 CA21 FA20 KA00 KA15 KA53 KA55 KA67 MA20 SA14 TA01 TA02 5K004 AA01 BA02 BB02 BD01 5K046 BB03 EE37 EE51 EE65 EF01 EF23 EF34 Z

Claims (8)

[Claims] 1. A distortion detector for detecting a distortion component in a device to be compensated from an input signal and an output signal of a device to be compensated for which nonlinear compensation is required, and a distortion based on the distortion component detected by the distortion detector. A distortion compensator for obtaining a compensation amount and compensating for a distortion of an input signal of the compensated device based on the distortion compensation amount; a compensation table for registering a distortion compensation amount used in the distortion compensation unit; and a compensation table registered in the compensation table. A monitoring compensation table for pre-registering the distortion compensation amount to be monitored for monitoring, and comparing the distortion compensation amount registered in the compensation table with the distortion compensation amount registered in the monitoring compensation table during operation. A non-linear compensator comprising: a compensation monitoring unit that monitors a difference. 2. The compensation monitoring unit registers, as the monitoring compensation table, at least a table for registering a compensation amount in an initial operation start state and a compensation amount immediately before the compensation table is updated in an operation state. 2. The non-linear compensator according to claim 1, further comprising a table that switches between the tables according to a temporal change. 3. The non-linear compensator according to claim 1, wherein the compensation monitoring unit determines that the difference is outside the reference range and determines that the difference is abnormal, and notifies the outside of the difference. 4. A distortion detecting section for detecting a distortion component in the compensated device from an input signal and an output signal of the compensated device for which nonlinear compensation is required, and a distortion based on the distortion component detected by the distortion detecting portion. A distortion compensating unit for obtaining a compensation amount and compensating for a distortion of an input signal of the compensated device based on the distortion compensation amount; and constantly or periodically monitoring a change in a distortion component detected by the distortion detecting unit. And a compensation monitoring unit for monitoring a compensation state. 5. The nonlinear compensator according to claim 4, wherein the compensation monitoring unit compares the distortion component detection result with a reference value and accumulates a history of the difference. 6. A non-linear compensation target characterized by comprising monitoring state monitoring means for monitoring a deterioration state of the non-linear compensation target by taking out and monitoring a monitoring result from the compensation monitoring part of the non-linear compensator according to claim 1. Monitoring device. 7. A non-linear compensation target characterized by comprising a monitoring state monitoring means for monitoring a deterioration state of the non-linear compensation target by taking out and monitoring a monitoring result from the compensation monitoring part of the non-linear compensator according to claim 4. Monitoring device. 8. The non-linear compensation target monitoring apparatus according to claim 6, wherein the monitoring state monitoring means retrieves a monitoring result from the compensation monitoring unit by remote control.