JP2005116107A - Wobbling signal extracting circuit and optical disk device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wobbling signal extracting circuit extracting a wobbling signal highly accurately even in the band of a high and wide frequency. <P>SOLUTION: This circuit is provided with: a frequency voltage converter 15 for receiving the input of a control clock from a clock input terminal CLK and generating and outputting a bias voltage corresponding to this clock frequency; a gm type adjustment low pass filter 13 constituted of a gm amplifier and a capacitor, which receives the input of the control clock to change a cut-off frequency according to a bias current corresponding to a bias voltage from the frequency voltage converter 15, and adjustment phase comparator 14 for comparing phases between the input and the output of the adjustment low pass filter 13 and outputting its result to the frequency voltage converter 15 to adjust the bias voltage; and gm type signal passage band pass filters 11 and 12 constituted of components substantially similar to those of the adjustment low pass filter 13 and serially connected in two stages to receive the input of an original signal read from an optical disk and to output a wobbling signal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wobble signal extraction circuit that extracts a wobble signal from an original signal read from an optical disc, and an optical disc apparatus using the wobble signal extraction circuit.

  In this type of optical disc apparatus, in order to control the rotation of the optical disc mounted thereon, a wavy (wobbled) guide groove is engraved in the recordable area of the optical disc. The waviness of the guide groove is read from the optical disc as a wobble signal together with the recorded data. Therefore, in addition to data processing, the optical disk apparatus extracts a wobble signal from the original signal, and performs rotation control of the optical disk according to the information. The wobble signal extraction circuit for extracting the wobble signal corresponds to several double speed modes of a CD optical disk (for example, CD-R, CD-RW) and a DVD optical disk (for example, DVD + R, DVD + RW). Is required to be extracted. Note that the DVD optical disk is further classified into a −R / RW system, a + R system, and a −RAM system. In this specification, description will be made using the + R system that has the fastest speed in the double speed mode.

  The wobble signal extraction circuit has a band pass filter (BPF) that passes only the band of the wobble signal from the original signal and blocks the band other than the band of the wobble signal (for example, Patent Document 1). Since the band of the wobble signal changes depending on the double speed mode of the above-described CD-type and DVD-type optical discs, it is necessary to be able to change the cutoff frequency of the band-pass filter.

  Conventionally, there is a wobble signal extraction circuit using a switched capacitor type band-pass filter that can change the cutoff frequency of the band-pass filter. This wobble signal extraction circuit continuously changes the cutoff frequency of the band-pass filter by inputting a control clock synchronized with the rotation of the optical disk from a microcontroller or the like (however, the frequency is high) as a sampling clock. Can do. Such a wobble signal extraction circuit is called a clock follow-up type. The clock-following wobble signal extraction circuit is a method in which a code indicating the rotation speed of the optical disk is input from a microcontroller or the like, the register is rewritten according to the code, and the bandpass filter is switched to one of the preset cutoff frequencies In comparison, since the above-described function can be achieved only by changing the frequency of the control clock, the control can be easily performed.

  FIG. 8 shows a wobble signal extraction circuit using a switched capacitor type bandpass filter. This wobble signal extraction circuit 101 receives a sampling clock from a clock input terminal CLK and switches a switched capacitor filter (SCF) 111 as a sampling circuit that passes a signal of only a band corresponding to the frequency. An anti-aliasing filter (AAF) 112 interposed as a low-pass filter between the signal input terminals PP and a smoothing filter (SMF) 113 interposed as a low-pass filter between the switched capacitor filter 111 and the output terminal WB are configured. . The frequency of the sampling clock included in the original signal is not included in the band where the wobble signal output from the switched capacitor filter 111 exists by the anti-aliasing filter 112 so that the component folded back from the sampling clock frequency (folding noise) is not included. More than half of the components are removed. Further, the smoothing filter 113 removes high frequency components including the aliasing noise generated by the switched capacitor filter 111. For this sampling clock, a frequency that is sufficiently higher than the band in which the wobble signal exists, for example, 1 to 2 digits higher, is usually used.

JP 2001-143404 A

  Currently, CD optical discs are standardized from 22.05 KHz 1 × speed to 1.235 MHz 56 × speed, and DVD + R optical discs are standardized from 816.4 KHz 1 × speed to 6.53 MHz 8 × speed. In the future, DVD-type optical discs are expected to have higher speed standards. As described above, the wobble signal extraction circuit is required to be able to extract the wobble signal corresponding to some of these types.

  However, when the above-described switched capacitor type bandpass filter is used for the wobble signal extraction circuit, the sampling clock needs to have a very high frequency at about 4 × speed of 3.27 MHz of a DVD + R optical disk. It is extremely difficult to generate and control the clock. Further, when the amplifier constituting the internal circuit of the switched capacitor filter is operated with the sampling clock having such a high frequency as described above, a characteristic shift occurs. As a result, the accuracy of the switched capacitor filter, that is, the switching capacitor type bandpass filter Accuracy is reduced.

  By the way, as a band pass filter capable of continuously changing the cutoff frequency, a gm type band pass filter constituted by a gm (mutual conductance) filter is conceivable. This gm filter includes an amplifier (gm amplifier) and a capacitor whose gm (mutual conductance) is determined according to a bias current. By adjusting this bias current, the time constant determined by gm and the value of the capacitor can be changed, so that the cut-off frequency of the gm-type bandpass filter composed of the gm filter can be continuously changed.

  In order to configure the wobble signal extraction circuit using the gm type band pass filter and to achieve the clock follow-up type, a bias current is supplied to the gm amplifier in accordance with the frequency of the control clock corresponding to the rotation speed of the optical disk. Therefore, a frequency voltage (fV) converter that outputs a bias voltage corresponding to the bias current is required. An example of a wobble signal extraction circuit including this frequency voltage converter and using a gm type band pass filter is shown in FIG. The wobble signal extraction circuit 201 inputs a source signal from the original signal input terminal PP and outputs a wobble signal to the output terminal WB, and a control clock from the clock input terminal CLK. And a frequency voltage (f-V) converter 213 that outputs a bias voltage. Since the control clock does not have to be higher than the cutoff frequency, it is not difficult to obtain it, and the gm amplifier is not required to operate at a speed higher than the cutoff frequency.

  However, the wobble signal extraction circuit 201 maintains a proportional or inverse proportional relationship between the frequency and voltage in the frequency voltage converter 213 in a wide range of double speed modes of the optical disc, and further, the bias voltage (or bias current) in the bandpass filter 211. ) And gm are difficult to maintain because of the influence of parasitic components (such as parasitic capacitance and parasitic resistance) inside the frequency-voltage converter 213 and the band-pass filter 211.

  The present invention has been made in view of the above-mentioned reasons, and an object of the present invention is to provide a wobble signal extraction circuit capable of extracting a wobble signal with high accuracy even at a high frequency and in a wide band, and using the same. It is another object of the present invention to provide an optical disc apparatus that supports a wide range of double speed modes.

  In order to solve the above-described problem, a wobble signal extraction circuit according to claim 1 is a wobble signal extraction circuit that extracts a wobble signal from an original signal input from an optical disc. A frequency / voltage converter for generating and outputting a voltage, a gm amplifier and a capacitor as components, an adjustment low-pass filter that receives the control clock and changes a cutoff frequency according to a bias current corresponding to the bias voltage, and this adjustment Comparing the phase of the input and output of the low-pass filter for adjustment, the phase comparator for adjustment that adjusts the bias voltage output to the frequency-voltage converter, and substantially the same components as the adjustment low-pass filter, A band-pass filter that inputs the original signal and the bias voltage and outputs a wobble signal; Characterized in that the Ete made.

  A wobble signal extraction circuit according to a second aspect is the wobble signal extraction circuit according to the first aspect, wherein the wobble signal extraction circuit includes substantially the same components as the switched capacitor filter and the adjustment low-pass filter, and the original signal and the bias The anti-aliasing filter that inputs voltage and outputs it to the switched capacitor filter, and the smoothing that consists of substantially the same components as the low-pass filter for adjustment, and outputs the wobble signal by inputting the output of the switched capacitor filter and the bias voltage A second bandpass filter provided in parallel with the bandpass filter, and a selection switch for selecting an output of the bandpass filter and the second bandpass filter. It is characterized by becoming.

  An optical disk device according to a third aspect includes the wobble signal extraction circuit according to the first or second aspect, wherein the wobble signal is extracted from an original signal read from the optical disk, and rotation control of the optical disk is performed. .

  The wobble signal extraction circuit of the present invention uses a band pass filter composed of substantially the same components as the adjustment low pass filter for signal passing, so that a wobble signal can be extracted with high accuracy even at a high frequency and in a wide band. Can do. In addition, an optical disk device provided with the optical disk apparatus can support high-speed and wide-range double-speed modes of the optical disk.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, the best embodiment of the invention will be described with reference to the drawings. FIG. 1 is a block diagram of a wobble signal extraction circuit that extracts a wobble signal from an original signal read from an optical disc according to an embodiment of the present invention. The wobble signal extraction circuit 1 inputs, as an input / output unit, a clock input terminal CLK for inputting a control clock synchronized with the rotation of the optical disk (corresponding to the rotation speed) from a microcontroller or the like, and an original signal read from the optical disk. It has an original signal input terminal PP and a wobble signal output terminal WB for outputting the extracted wobble signal. When a control clock is input from the clock input terminal CLK, a frequency voltage (f-V) converter 15 that generates and outputs a bias voltage corresponding to the frequency, and a gm amplifier and a capacitor as will be described later. As a component, a control clock is input from the clock input terminal CLK, a bias voltage from the frequency voltage converter 15 is input, and a cutoff frequency is changed according to a bias current corresponding to the bias voltage. And the phase of the input (that is, the control clock) and the output (that is, the control clock whose phase has been changed) of the adjustment low-pass filter 13 are compared, and a voltage corresponding to the phase difference is output to the frequency voltage converter 15. An adjustment phase comparator 14 for adjusting the bias voltage output from the frequency voltage converter 15; Consists of substantially the same components as the pass filter 13 and receives the original signal read from the optical disc and is connected in series to two stages that receive the bias voltage from the frequency voltage converter 15 and output the wobble signal. And gm-type band pass filters 11 and 12 for signal passage.

  The wobble signal extraction circuit 1 operates as follows. The control clock input to the clock input terminal CLK is input to the frequency voltage converter 15 and the adjustment low-pass filter 13. The frequency voltage converter 15 generates a bias voltage corresponding to the frequency and outputs the bias voltage to the adjustment low pass filter 13 and the signal pass band pass filters 11 and 12. The adjustment low-pass filter 13 is a secondary low-pass filter as will be described later. When the frequency of the control clock matches the cut-off frequency, the phase is rotated by 90 degrees and output. When the phase of the output signal of the adjustment low-pass filter 13 is rotated 90 degrees with respect to the input signal, the adjustment phase comparator 14 outputs a voltage ½ of the adjustment reference voltage VREF to the frequency voltage converter 15. If the phase is shifted, a voltage higher or lower than ½ of the adjustment reference voltage VREF is output to the frequency voltage converter 15 according to the shift. In other words, the adjustment phase comparator 14 detects a deviation from the phase difference of 90 degrees with respect to the phase between the input and output of the adjustment low-pass filter 13. Thus, the feedback adjusts the bias voltage output from the frequency voltage converter 15 so that the phase difference between the input and output of the adjustment low-pass filter 13 is 90 degrees.

  As described above, the bias voltage from the frequency voltage converter 15 is input to the band pass filters 11 and 12 for passing signals, which are configured by substantially the same components as the adjustment low pass filter 13. The cutoff frequency is substantially equal to that of the adjustment low-pass filter 13. Therefore, since the band pass filters 11 and 12 for passing signals with the frequency of the control clock from the clock input terminal CLK as the cut-off frequency can be obtained, a high-accuracy band pass filter can be realized even at a high frequency and a wide band. By inputting a control clock synchronized with the rotation of the optical disc in accordance with the double speed mode, a wobble signal corresponding to a wide range of double speed modes can be extracted.

  In the wobble signal extraction circuit 1, the control clock is directly input to the adjustment low-pass filter 13 from the clock input terminal CLK. However, another filter, for example, a low-pass filter may be interposed. What is important is that the phase of the input and output of the adjustment low-pass filter 13 is compared by the adjustment phase comparator 14 to detect a deviation from the phase difference of 90 degrees. Furthermore, the adjustment low-pass filter 13 may be two stages or more, and the adjustment phase comparator 14 may perform comparison with a phase difference of 180 degrees or more as a center.

  Further, the signal pass bandpass filters 11 and 12 are not limited to two stages according to the characteristics of other circuits constituting the optical disc apparatus, and the number of stages is further increased. Conversely, the bandpass filters 12 are omitted. A single stage is also possible.

  Next, the adjustment low-pass filter 13 constituting the wobble signal extraction circuit 1 will be described in detail with reference to FIG. The adjustment low-pass filter 13 has an input terminal IN that receives a control clock, and an output terminal OUT, and includes a differential amplifier 35, four gm amplifiers 31, 32, 33, 34, and four capacitors 36, 37, 38, 39. Each gm amplifier has a non-inverting input terminal and an inverting input terminal, a non-inverting output terminal and an inverting output terminal, and further has a bias voltage input terminal BIAS for inputting a bias voltage. The parts other than the differential amplifier 35 are a gm filter 30a composed of gm amplifiers 31 and 32 and capacitors 36 and 37, and a gm filter composed of gm amplifiers 33 and 34 and capacitors 38 and 39 having substantially the same circuit configuration. 30b.

  The differential amplifier 35 receives the voltage of the input terminal IN and generates a differential voltage signal with the signal reference voltage Vref as a reference. The differential voltage signal is input to the non-inverting input terminal and the inverting input terminal of the gm amplifier 31 through the differential input terminals (IN +, IN−) of the gm filter 30a. The non-inverting output terminal and the inverting output terminal of the gm amplifier 31 and the gm amplifier 32 connected to each other are grounded via capacitors 36 and 37, respectively, and the differential output terminals (OUT +, OUT−) of the gm filter 30a. The differential input terminals (IN +, IN−) of the gm filter 30b are connected to the non-inverting input terminal and the inverting input terminal of the gm amplifier 33, respectively. The non-inverting output terminal and the inverting output terminal of each of the gm amplifier 33 and the gm amplifier 34 connected to each other are grounded via capacitors 38 and 39, and also passed through the differential output terminals (OUT + and OUT−) of the gm filter 30b. The polarity is reversed, and the non-inverting input terminals of the gm amplifiers 32 and 34 through the feedback differential input terminals (FB + and FB−) of the gm filter 30a and the feedback differential input terminals (FB + and FB−) of the gm filter 30b. And inverting input terminals, respectively. One (OUT +) of the differential output terminals (OUT +, OUT−) of the gm filter 30b becomes the output terminal OUT of the adjustment low-pass filter 13. Thus, by being constituted by a two-stage gm filter, it is possible to obtain the characteristics of a second-order low-pass filter as shown by the LPF curve in FIG.

  FIG. 4 is a detailed circuit diagram of the gm filter 30a (and 30b). The gm filter 30a has a bias voltage input terminal BIAS for inputting a bias voltage, differential input terminals IN + and IN−, feedback differential input terminals FB + and FB−, and differential output terminals OUT + and OUT−. P-type MOS transistors 41 and 42 whose gates are connected to the bias voltage input terminal BIAS, NPN-type differential pair bipolar transistors 43 and 44 whose bases are connected to the differential input terminals IN + and IN−, respectively, and a feedback difference The NPN type differential pair bipolar transistors 45 and 46 whose bases are connected to the dynamic input terminals FB + and FB−, respectively, and the capacitors 36 and 37 are configured. The P-type MOS transistors 41 and 42 generate a bias current according to the bias voltage input from the bias voltage input terminal BIAS, and the differential pair bipolar transistors 43 and 44 and the differential pair bipolar transistors 45 and 46 are generated according to the bias current. The value of gm (mutual conductance) changes. As a result, the cut-off frequency of the gm filter 30a is determined by the gm value and the capacitance values of the capacitors 36 and 37. The drawing-side current generation circuit 50 and the NPN-type bipolar transistors 51 to 53 are circuits that flow current to the drawing side in accordance with the bias current.

  Next, the signal pass bandpass filters 11 and 12 will be described in detail. FIG. 5 shows an internal circuit of the bandpass filter 11 (and 12). As described above, the band-pass filter 11 includes substantially the same components as the adjustment low-pass filter 13. That is, it has an input terminal IN and an output terminal OUT, and is composed of a differential amplifier 35, four gm amplifiers 31, 32, 33, and 34, and four capacitors 36, 37, 38, and 39. The connection of these components is almost the same as that of the adjustment low-pass filter 13, but the differential voltage output of the differential amplifier 35 is connected to one end of each of the capacitors 36 and 37 in place of the ground potential, and the gm amplifier 31 is connected. The non-inverting input terminal and the inverting input terminal are both connected to the signal reference voltage Vref. With this configuration, it is possible to obtain the characteristics of the second-order bandpass filter as shown by the BPF curve in FIG. 3, and the cutoff frequency is determined according to the bias voltage input from the bias voltage input terminal BIAS. Thus, the adjustment low-pass filter 13 and the band-pass filter 11 have substantially the same cutoff frequency (f0) as shown in FIG. 3, and the filter characteristics change in conjunction with the input bias voltage. Of course, the Q value (steepness) of the BPF and LPF curves in FIG. 3 can be arbitrarily changed by changing the constants of the constituent elements.

  Next, the frequency voltage converter 15 will be described in detail with reference to FIG. 6 which is an internal circuit diagram thereof. When the control clock input from the clock input terminal CLK changes from the high level to the low level, the N-type MOS transistor 61 is turned off, and the capacitor 62 is charged by the current Iadj from the P-type MOS transistor 72. Until the voltage of the capacitor 62 reaches the voltage VREF / 2 generated by dividing the adjustment reference voltage VREF by the resistors 73 and 74, the output of the comparator 63 is at a low level, and the charge / discharge circuit 70 is charged. . When the voltage of the capacitor 62 exceeds the voltage VREF / 2, the output of the comparator 63 becomes high level, and the charge / discharge circuit 70 is discharged at a rate equal to that at the time of charging. When the control clock changes from a low level to a high level, the voltage is held, converted into a current, and output. From this current, the current Iadj of the P-type MOS transistor 72 is generated via the P-type MOS transistor 71. Therefore, the time until the voltage of the capacitor 62 reaches the voltage VREF / 2 is inversely proportional to the current Iadj. If the time is ½ of the low level period of the control clock, that is, ¼ of the period of the control clock, the charging is performed. The charging time and discharging time of the discharging circuit 70 become equal, and the current Iadj is kept constant. Thus, a current Iadj corresponding to the frequency of the control clock can be obtained.

  Also, the adjustment voltage from the adjustment phase comparator 14 is received at the input terminal FB, and the voltage VREF / 2 is adjusted via the resistor 75. As a result, the current Iadj is adjusted. As described above, this adjustment voltage fluctuates around the voltage VREF / 2 when the phase difference between the input and output of the adjustment low-pass filter 13 is 90 degrees.

  The bias voltage output terminal BIAS is connected to the gates of the P-type MOS transistors 71 and 72. As described above, in the adjustment low-pass filter 13 and the signal passing band-pass filters 11 and 12, this bias voltage is supplied to the P-type MOS. A bias current proportional to the current Iadj can be obtained by receiving the transistor.

  Next, a wobble signal extraction circuit according to another embodiment of the present invention will be described. FIG. 7 is a block diagram thereof. The wobble signal extraction circuit 2 is suitable for extracting a wobble signal in a wider band than the wobble signal extraction circuit 1. That is, in the wobble signal extraction circuit 1 described above, the gm-type signal passing bandpass filters 11 and 12 change the cutoff frequency by changing the gm of the gm amplifier, and the capacitance value of the capacitor is fixed. Therefore, the fluctuation range of the cut-off frequency is restricted by the capacitance value of the capacitor. In order to cope with a low speed (low frequency) of about 1 × that of a CD optical disk, an excessively small current that is difficult to control as a bias current of the gm amplifier is required. In some cases, a capacitor with a large capacitance is required. The wobble signal extraction circuit 2 includes a switched capacitor type second bandpass filter 20 that is highly effective at a low frequency and is very effective, and is provided in parallel with gm type bandpass filters 11 and 12 by a selection switch 19. The output is switched and the gm-type bandpass filters 11 and 12 are used for high frequencies, so that wobble signals in a wider range are extracted.

  The selection switch 19 selects the gm-type bandpass filters 11 and 12 when the optical disk is high-speed, for example, at a quadruple speed or higher of a DVD + R optical disk, and the switched-capacitor-type second bandpass when the speed is lower than that. The filter 20 is selected.

  The second band-pass filter 20 includes a switched capacitor filter (SCF) 16 that inputs a control clock from the clock input terminal CLK as a sampling clock, and substantially the same components as the adjustment low-pass filter 13. The anti-aliasing filter 17 that is a low-pass filter that inputs an original signal from the input terminal PP and outputs the original signal to the switched capacitor filter 16 and substantially the same components as the adjustment low-pass filter 13 are configured, and the output of the switched capacitor filter 16 is input. And a smoothing filter 18 which is a low-pass filter for outputting a wobble signal.

  The anti-aliasing filter 17 and the smoothing filter 18 receive the bias voltage output from the frequency voltage converter 15 as in the case of the adjustment low-pass filter 13 and the gm-type band-pass filters 11 and 12. Therefore, when the second bandpass filter 20 is selected, the cutoff frequencies of the antialiasing filter 17 and the smoothing filter 18 are determined in conjunction with the cutoff frequency of the adjustment lowpass filter 14.

  Further, since the sampling clock input to the switched capacitor filter 16 must have a higher frequency than the cutoff frequency, the frequency of the control clock input to the clock input terminal CLK must be increased. Therefore, when the second band-pass filter 20 is selected as a control clock input to the adjustment low-pass filter 13 and the frequency-voltage converter 15, the frequency is reduced by dividing by the frequency divider (DIV) 21. A switch 22 is provided so that a clock can be used.

  As described above, the wobble signal extraction circuits 1 and 2 according to the embodiment of the present invention can extract a wobble signal with high accuracy even at a high frequency and a wide band. Therefore, the optical disc apparatus provided with such wobble signal extraction circuits 1 and 2 can cope with a high-speed and wide-range double speed mode of the optical disc.

The block diagram of the wobble signal extraction circuit which concerns on embodiment of this invention. The circuit diagram of the adjustment low-pass filter same as the above. The characteristic view of the adjustment low-pass filter and the band pass filter for signal passage same as the above. The circuit diagram of a gm filter same as the above. The circuit diagram of the band pass filter for signal passage same as the above. The circuit diagram of a frequency voltage converter same as the above. The block diagram of the wobble signal extraction circuit which concerns on another embodiment of this invention. The circuit diagram of the wobble signal extraction circuit of background art. The circuit diagram of the wobble signal extraction circuit of related technology.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Wobble signal extraction circuit 11, 12 Band pass filter 13 Low pass filter for adjustment 14 Phase comparator for adjustment 15 Frequency voltage converter 16 Switched capacitor filter 17 Antialias filter 18 Smoothing filter 19 Selection switch 20 2nd band pass filter

Claims (3)

In a wobble signal extraction circuit that extracts a wobble signal from an original signal input from an optical disc,
A frequency voltage converter that inputs a control clock and generates and outputs a bias voltage corresponding to the frequency; and
an adjustment low-pass filter that includes a gm amplifier and a capacitor, inputs the control clock, and changes a cutoff frequency according to a bias current according to the bias voltage;
An adjustment phase comparator that compares the phase of the input and output of the low pass filter for adjustment, and outputs the frequency voltage converter to adjust the bias voltage;
A band-pass filter that is composed of substantially the same components as the adjustment low-pass filter and that inputs the original signal and the bias voltage and outputs a wobble signal;
A wobble signal extraction circuit comprising: The wobble signal extraction circuit according to claim 1,
A switched capacitor filter and an anti-alias filter configured to include substantially the same components as the adjustment low-pass filter, input the original signal and the bias voltage, and output to the switched capacitor filter, and substantially the adjustment low-pass filter And a smoothing filter that outputs the wobble signal by inputting the output of the switched capacitor filter and the bias voltage, and is provided in parallel with the bandpass filter. When,
A selection switch for selecting outputs of the bandpass filter and the second bandpass filter;
And a wobble signal extraction circuit. An optical disc apparatus comprising the wobble signal extraction circuit according to claim 1, wherein a wobble signal is extracted from an original signal read from the optical disc, and rotation control of the optical disc is performed.

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