JP2011211393A - Frequency converter, and frequency conversion method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce influence of noise such as spurious, in a frequency converter and a frequency conversion method for converting the frequency of an input analog signal to an intermediate frequency.SOLUTION: The frequency converter includes: a calibration signal generation part 21 for generating calibration signals having boundary frequencies of a plurality of channels having different frequency bands; a phase variation signal generation part 22 for generating a phase variation signal whose phase is randomly changed; a signal combination part 23 for combining the calibration signal from the calibration signal generation part with the phase variation signal from the signal generation part; frequency conversion parts 12-1 to 12-N for converting the frequency of the combination signal from the signal combination part to that of an intermediate frequency signal in accordance with the frequency band of a channel; ADCs 13-1 to 13-N for sampling the intermediate frequency signals from the frequency conversion parts to be converted to digital signals; and an arithmetic processing part 14 for averaging and calculating the phase differences among digital signals of the different ADCs.

Description

  The present invention relates to a frequency conversion device and a frequency conversion method, and more particularly to a frequency conversion device and a frequency conversion method for reducing the influence of noise during phase measurement.

  An apparatus for converting a frequency of a wideband analog signal has been proposed (for example, see Patent Document 1). The apparatus of Patent Document 1 demultiplexes a wideband analog signal into a plurality of channels having different frequency bands, performs frequency conversion for each channel, converts the signal into an intermediate frequency signal, and converts the intermediate frequency signal into a digital signal. The digital signals of the respective channels are synthesized so that the phases of the respective digital signals are matched. In order to adjust the phase of each digital signal, the calibration signal having the frequency at the boundary of each channel is frequency-converted to measure the phase difference between the channels.

JP 2009-246958 A

  In the apparatus of Patent Document 1, the influence of noise such as spurious of the calibration signal is not taken into consideration. For this reason, the phase difference between the channels measured using the calibration signal is affected by noise such as spurious.

  Therefore, an object of the present invention is to provide a frequency conversion device and a frequency conversion method that reduce the influence of noise such as spurious when measuring a phase difference between channels.

  In order to achieve the above object, a frequency conversion device and a frequency conversion method of the present invention synthesize a phase variation signal whose phase varies randomly with an analog signal for measuring a phase difference.

  Specifically, the frequency converter according to the present invention includes a phase fluctuation signal generation unit (22) that generates a phase fluctuation signal whose phase fluctuates randomly, and an analog signal that is input from the phase fluctuation signal generation unit. A signal synthesizer (23) for synthesizing a phase variation signal, a frequency converter (12) for frequency-converting the synthesized signal from the signal synthesizer into an intermediate frequency signal corresponding to the frequency of the input analog signal, Is provided.

  Since the phase variation signal generation unit and the signal synthesis unit are provided, frequency conversion can be performed using a synthesized signal obtained by synthesizing a phase variation signal whose phase varies randomly with the input analog signal. When the frequency conversion unit performs an averaging process on the frequency-converted signal, the influence of noise such as spurious can be reduced. Therefore, the frequency conversion device of the present invention can reduce the influence of noise such as spurious when measuring the phase difference between the channels.

The frequency converter according to the present invention may further include a signal strength adjusting unit (24) that varies the signal strength of the input analog signal or the phase variation signal.
When the amplitude of the phase fluctuation signal is larger than that of noise such as spurious, the influence of noise such as spurious can be reduced. For this reason, even if it is a case where noises, such as a spurious, are large, by further providing a signal intensity adjustment part, the influence of noises, such as a spurious, can be reduced.

  Specifically, the frequency converter according to the present invention includes a calibration signal generator (21) that generates a calibration signal having a boundary frequency between a plurality of channels having different frequency bands, and a phase variation in which the phase varies randomly. A phase variation signal generation unit (22) for generating a signal, a signal synthesis unit (23) for synthesizing a phase variation signal from the signal generation unit with a calibration signal from the calibration signal generation unit, and the signal synthesis A frequency conversion unit (12-1 to 12-N) that converts the synthesized signal from the frequency unit into an intermediate frequency signal corresponding to the frequency band of the channel, and digitally samples the intermediate frequency signal from the frequency conversion unit Each channel calculated from an ADC (Analog Digital Converter) (13-1 to 13-N) to be converted into a signal and a digital signal of a different ADC. And an arithmetic processing unit (14) that calculates the phase difference between the channels by averaging.

  A calibration signal generator, a phase variation signal generator, a signal synthesis unit, a frequency conversion unit, and an ADC are provided, so that a synthesized signal obtained by synthesizing the phase variation signal with the calibration signal is used for each channel. The phase difference of the digital signal can be measured. Since the arithmetic processing unit calculates the phase difference calculated from the digital signal by averaging, it is possible to reduce the influence of noise such as spurious. Therefore, the frequency conversion device of the present invention can reduce the influence of noise such as spurious when measuring the phase difference between the channels.

The frequency conversion device according to the present invention may further include a signal strength adjusting unit (24) that varies a signal strength of the calibration signal or the phase variation signal.
When the amplitude of the phase fluctuation signal is larger than that of noise such as spurious, the influence of noise such as spurious can be reduced. For this reason, even if it is a case where noises, such as a spurious, are large, by further providing a signal intensity adjustment part, the influence of noises, such as a spurious, can be reduced.

  Specifically, in the frequency conversion method according to the present invention, a synthesis procedure for synthesizing a phase fluctuation signal whose phase fluctuates randomly with an input analog signal, and a synthesized signal synthesized by the synthesis procedure are inputted. A frequency conversion procedure for converting the frequency into an intermediate frequency signal corresponding to the frequency of the analog signal.

  In order to execute the synthesizing procedure, frequency conversion can be performed using a synthesized signal obtained by synthesizing a phase fluctuation signal whose phase fluctuates randomly with an input analog signal. By performing the averaging process on the signal after frequency conversion, it is possible to reduce the influence of noise such as spurious. Therefore, the frequency conversion method of the present invention can reduce the influence of noise such as spurious when measuring the phase difference between the channels.

In the frequency conversion method of the present invention, signal strength of the input analog signal or the phase variation signal may be varied in the synthesis procedure.
When the amplitude of the phase fluctuation signal is larger than that of noise such as spurious, the influence of noise such as spurious can be reduced. For this reason, according to the present invention, even when the noise such as spurious is large, the influence of the noise such as spurious can be reduced.

  Specifically, the frequency conversion method of the present invention generates a calibration signal having a frequency at the boundary between a plurality of channels having different frequency bands, and generates a phase variation signal whose phase varies randomly, thereby generating the calibration signal. And the phase fluctuation signal are synthesized, the synthesized signal is frequency-converted into an intermediate frequency signal corresponding to the frequency band of the channel and converted into a digital signal, and the phase difference of the digital signal between the channels is averaged. The phase difference measurement procedure for measuring the phase difference between the plurality of channels, the input analog signal is demultiplexed into the frequency band of the channel, and the demultiplexed analog signal is demultiplexed into the frequency band of the channel. Is converted to a digital signal by converting the frequency to an intermediate frequency signal according to the phase difference between the plurality of channels measured by the phase difference measurement procedure. A phase of the digital signal is corrected by using the difference, having an analog signal frequency conversion procedure of synthesizing the digital signal after correcting the phase to correspond to the frequency band of the channel, in this order.

In order to execute the phase difference measurement procedure, it is possible to measure the phase difference of the digital signal of each channel using a synthesized signal obtained by synthesizing the phase variation signal with the calibration signal. Here, since the phase difference of the digital signal is averaged and calculated, the influence of noise such as spurious can be reduced.
Since the analog signal frequency conversion procedure is performed, the phase of the digital signal can be corrected. Here, since the phase difference between channels measured by the phase difference measurement procedure is used, the phase of the digital signal can be corrected using a correction value in which the influence of noise such as spurious is reduced. Therefore, the frequency conversion method of the present invention can reduce the influence of noise such as spurious when measuring the phase difference between the channels.

In the frequency conversion method of the present invention, the signal intensity of the calibration signal or the phase variation signal may be varied in the phase difference measurement procedure.
When the amplitude of the phase fluctuation signal is larger than that of noise such as spurious, the influence of noise such as spurious can be reduced. For this reason, according to the present invention, even when the noise such as spurious is large, the influence of the noise such as spurious can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the frequency converter and frequency conversion method which reduce the influence by noise, such as a spurious, at the time of measuring the phase difference between each channel can be provided.

An example of a system with added noise is shown. 1 shows a configuration example of a frequency conversion device according to a first embodiment. An example of the composite signal x is shown. 1 shows an example of a system of a frequency conversion device according to a first embodiment. It shows a signal vector of the output signal y _2. A comparison of error to C / B is shown. An example of the frequency converter which concerns on Embodiment 2 is shown. An example of the input analog signal Xm is shown. The 1st example of a phase fluctuation signal generation part and a synthetic | combination part is shown. 2 shows a second example of a phase fluctuation signal generation unit and a synthesis unit.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

(Embodiment 1)
FIG. 1 shows an example of a system to which noise is added. An analog signal xo (t) is input from the input terminal. An output signal yo ₁ (t) is output from channel 1. The analog signal xo (t) of the channel 2 is output as an output signal yo ₂ (t) via the circuit 51. It is assumed that xo (t) is represented by Acos (ω ₀ t + θ ₀ ) and the phase shift Δθ in the circuit 51 is θ2. At this time, when noise n (t) = Bcos (ω ₀ t + θ _N ) including frequency components is added to the channel 2, the output signal yo ₁ (t) and the output signal yo ₂ (t) are expressed by the following equations. expressed.

となる。

It becomes.

When the frequency analysis of the output signal yo ₁ (t) and the output signal yo ₂ (t) is performed,

Thus, θ _ε becomes an error. Since the error θ _ε due to θ _N does not decrease even when the averaging process is performed, the phase of the output signal yo ₂ (t) cannot be correctly measured.

FIG. 2 shows a configuration example of the frequency conversion device according to the first embodiment. The frequency conversion device according to the present embodiment includes a phase fluctuation signal generation unit 22, a signal synthesis unit 23, a frequency conversion unit 12, and a signal strength adjustment unit 24, and executes the frequency conversion method according to the present embodiment. To do. The frequency conversion method according to the present embodiment includes a synthesis procedure and a frequency conversion procedure in order.
The

  In the synthesis procedure, the phase variation signal generator 22 generates a phase variation signal γ (t) whose phase varies randomly. Next, the signal synthesis unit 23 synthesizes the phase fluctuation signal γ (t) from the phase fluctuation signal generation unit 22 with the input analog signal xo (t). Here, the composition indicates addition composition. In the frequency conversion procedure, the frequency converter 12 converts the synthesized signal x (t) from the signal synthesizer 23 with a local signal L corresponding to the frequency of the input analog signal xo (t). Thereby, the frequency converter 12 converts the signal into an intermediate frequency signal IF (t) corresponding to the frequency of the analog signal xo (t).

  FIG. 3 shows an example of the composite signal x. The synthesized signal x is composed of an analog signal xo having a frequency fa and a phase variation signal γ including the frequency fa and having a phase that varies randomly within the range of the frequency width Δfa.

FIG. 4 shows an example of a system of the frequency conversion device according to the first embodiment. A synthesized signal x (t) is input instead of the analog signal xo (t) shown in FIG. In this case, the combined signal x (t) is expressed by the following equation.

Here, it is assumed that the phase of γ (t) at the frequency ω ₀ is θ _γ (n) and is randomly distributed in the entire phase region. In this case, the output signal y ₁ (t) and the output signal y ₂ (t) are expressed by the following equations.

となる。 When the frequency analysis of the output signal y ₁ (t) and the output signal y ₂ (t) is performed,

It becomes.

となる。 5 shows a signal vector of the output signal y _2. If the averaging process is performed N times, since γ (t) has a random phase, the phase θ _γ (n) of γ (t) at frequency ω ₀ is

It becomes.

Therefore, if the averaging process is performed N times, the phase ψ ₁ calculated from the output signal y ₁ (t) is expressed by the following equation.

The phase ψ ₂ calculated from the output signal y ₂ (t) is expressed by the following equation.

となる。 Here, when limited to B << C,

It becomes.

となる。このように、アベレージングを行うことで、出力信号ｙ_２（ｔ）の位相ψ_２におけるノイズｎ（ｔ）の影響を減少させることができる。 For this reason,

It becomes. Thus, by performing the averaging, it is possible to reduce the influence of the noise n (t) in the phase ψ ₂ of the output signal y ₂ (t).

FIG. 6 shows a comparison of errors with respect to C / B. The horizontal axis indicates the C / B, the vertical axis represents the error (rad) in the phase at the time of calculating the phase theta _2. The number of averaging processes is 100. If C / B is about 10, the influence of the noise n (t) in the phase ψ ₂ of the output signal y ₂ (t) can be reduced.

  Therefore, it is preferable that the frequency conversion device according to the first embodiment further includes a signal strength adjustment unit 24 that varies the signal strength of the input analog signal xo (t). Thereby, the value of C / B can be made 10 or more. Therefore, the frequency conversion device according to the first embodiment is a spurious component for measuring the phase difference between the channels in the frequency conversion device that converts the frequency of the input analog signal xo (t) into the intermediate frequency IF (t). The influence of noise n (t) such as can be reduced. The signal strength adjusting unit 24 may vary the signal strength of the phase variation signal γ (t).

(Embodiment 2)
FIG. 7 shows an example of a frequency conversion device according to the second embodiment. The frequency conversion device according to the second embodiment includes a distribution unit 11, frequency conversion units 12-1 to 12-N, ADCs 13-1 to 13-N, an arithmetic processing unit 14, a storage unit 18, and a calibration signal. A generation unit 21, a phase fluctuation signal generation unit 22, a signal synthesis unit 23, and a signal intensity adjustment unit 24 are provided.

  FIG. 8 shows an example of the input analog signal Xm. The distribution unit 11 demultiplexes the input analog signal Xm into N (where N is an integer of 2 or more) channels CH1 to CHN. For example, the frequency filter 11-1 extracts the frequency band of the channel CH1, and the frequency filter 11-N extracts the frequency band of the channel CHN.

  The frequency conversion units 12-1 to 12-N illustrated in FIG. 7 perform frequency conversion to intermediate frequency signals IF1 to IFN corresponding to the frequency bands of the channels CH1 to CHN. The ADCs 13-1 to 13-N sample the intermediate frequency signals IF1 to IFN and convert them into digital signals D1 to DN. The arithmetic processing unit 14 combines the digital signals D1 to DN from the ADCs 13-1 to 13-N in correspondence with the frequency bands of the channels CH1 to CHN. Thereby, the frequency conversion device according to the present embodiment can perform frequency conversion of the input analog signal Xm.

The calibration signal generator 21 generates a calibration signal xr having frequencies f _{a2 to} f _aN at the boundaries of the channels CH1 to CHN. The phase variation signal generator 22 generates a phase variation signal γ whose phase varies randomly. The signal strength adjustment unit 24 adjusts the signal strength of the phase variation signal γ so that the signal strength of the phase variation signal γ becomes a predetermined value. Thereby, as explained in FIG. 6, the value of C / B can be kept at a constant value of 10 or more. The signal synthesis unit 23 synthesizes the phase fluctuation signal γ from the phase fluctuation signal generation unit 22 with the calibration signal xr from the calibration signal generation unit 21. Thus, the phase difference between the digital signals D1 to DN is measured using the synthesized signal Xr obtained by synthesizing the calibration signal xr and the phase variation signal γ.

  The frequency conversion device according to the second embodiment executes the frequency conversion method according to the second embodiment. The frequency conversion method according to the second embodiment includes a phase difference measurement procedure and an analog signal frequency conversion procedure in this order.

In the phase difference measurement procedure, a calibration signal xr having a frequency at the boundary between the channels CH1 to CHN is generated, and a phase variation signal γ whose phase varies randomly is generated to synthesize the calibration signal xr and the phase variation signal γ. . For example, the calibration signal xr having the frequency f _a2 at the boundary between the channel CH1 and the channel CH2 is generated, and the phase variation signal γ whose phase varies randomly is generated to synthesize the calibration signal xr and the phase variation signal γ. Thus, the combined signal Xr having a frequency _{f a2} as a frequency fa shown in FIG. 3 is inputted to the distribution section 11. Since the synthesized signal Xr has the frequency f _a2 , the distribution unit 11 extracts and outputs the frequency band of the channel CH1 and the frequency band of the channel CH2.

Next, the composite signal Xr is frequency-converted to intermediate frequency signals IF1 to IFN corresponding to the frequency bands of the channels CH1 to CHN and converted to digital signals D1 to DN, and the digital signals D1 to DN between the channels CH1 to CHN are converted. The phase differences between a plurality of channels are measured by averaging and calculating the phase differences Δφ _{2 to} Δφ _n . For example, the frequency converter 12-1 converts the composite signal Xr into an intermediate frequency signal IF1 corresponding to the frequency band of the channel CH1, and the ADC 13-1 converts the intermediate frequency signal IF1 into a digital signal D1. The frequency converter 12-2 converts the composite signal Xr into an intermediate frequency signal IF2 corresponding to the frequency band of the channel CH2, and the ADC 13-2 converts the intermediate frequency signal IF2 into a digital signal D2. The arithmetic processing unit 14 calculates the phase difference Δφ ₂ between the digital signal D1 and the digital signal D2 between the channels. Thereby, the frequency converter according to the second embodiment can measure a coefficient for correcting the phase difference Δφ ₂ between the digital signal D1 and the digital signal D2.

In the phase difference measurement procedure, the above procedure is repeated to average the phase difference between the digital signal D1 and the digital signal D2. Thus, definitive when measuring the phase difference [Delta] [phi ₂ of the digital signal D1 and the digital signal D2, it is possible to reduce the noise due to the influence of spurious or the like included in the digital signal D1 and the digital signal D2.

The phase differences Δφ _{3 to} Δφ _n of the digital signals between other channels such as the phase difference between the digital signal D2 and the digital signal D3 can be measured in the same manner. Then, the measured phase differences Δφ _{2 to} Δφ _n are stored in the storage unit 18.

In the analog signal frequency conversion procedure, the input analog signal Xm is demultiplexed into the frequency bands of channels CH1 to CHN, and the demultiplexed analog signal Xm is converted into intermediate frequency signals IF1 to IFN corresponding to the frequency bands of channels CH1 to CHN. Frequency conversion is performed to convert the signals into digital signals D1 to DN. Next, the arithmetic processing unit 14 reads out the phase correction coefficient from the storage unit 18, and uses the phase differences Δφ _{2 to} Δφ _n of the plurality of channels CH 1 to CHN measured by the phase difference measurement procedure to output the digital signals D ₁ to DN. The phase differences Δφ _{2 to} Δφ _n are corrected. Next, the arithmetic processing unit 14 synthesizes the digital signals D1 to DN whose phases have been corrected in correspondence with the frequency bands of the channels CH1 to CHN.

The frequency conversion device according to the second embodiment uses the combined signal Xr in which the phase variation signal γ is combined with the calibration signal xr when the phase differences Δφ _{2 to} Δφ _n of the digital signals D _{1 to} DN are measured. Each of the DN phase differences Δφ _{2 to} Δφ _n is averaged. For this reason, it is possible to reduce the influence of noise n (t) such as spurious on the phase differences Δφ ₂ to Δφ _{n of} the measured digital signals D ₁ to DN.

  The signal strength adjusting unit 24 may adjust the signal strength of the calibration signal xr so that the signal strength of the calibration signal xr becomes a predetermined value.

  For example, the phase fluctuation signal generation unit and the synthesis unit may be configured as shown in FIG. In the first example of the phase fluctuation signal generation unit and the synthesis unit illustrated in FIG. 9, the phase fluctuation signal generation unit 22 includes a noise generator 31 and a BPF (Band-pass filter) 32. The noise generator 31 is, for example, a PRBS (Pseudo-Random Bit Sequence) or PN (Pseudo Random Noise) oscillator. The BPF 32 extracts a frequency band having a frequency width Δfa centered on the frequency of the calibration signal xr from the signal from the noise generator 31. As a result, the phase fluctuation signal generator 22 outputs a phase fluctuation signal γ whose phase fluctuates randomly.

  The frequency width Δfa is arbitrary. For example, when the frequency of the calibration signal xr is 900 MHz and the difference in signal strength between the calibration signal xr and the phase variation signal γ is 60 dB, the frequency width Δfa is about 1 MHz. is there.

  For example, the phase fluctuation signal generation unit and the synthesis unit may be configured as shown in FIG. In the second example of the phase variation signal generation unit and the synthesis unit shown in FIG. 10, the phase variation signal generation unit 22 includes two PN oscillators 33a and 33b, a signal synthesis unit 25a and a signal synthesis unit 25b, and an adder 34. . The PN oscillator 33a and the PN oscillator 33b each output a signal whose phase varies randomly. The signal synthesizer 25a and the signal synthesizer 25b respectively multiply and synthesize the calibration signal xr whose phases are shifted by π / 2 with the output signal of the PN oscillator 33a and the output signal of the PN oscillator 33b. The adder 34 adds and synthesizes the signals from the signal synthesizer 25a and the signal synthesizer 25b. As a result, the phase fluctuation signal γ is output from the adder 34.

  The present invention can be applied to the information communication industry.

11: Distribution unit 11-1, 11-2, 11-N: Frequency filter 12-1, 12-2, 12-N: Frequency conversion unit 13-1, 13-2, 13-N: ADC
14: arithmetic processing unit 18: storage unit 21: calibration signal generation unit 22: phase fluctuation signal generation unit 23: signal synthesis unit 24: signal intensity adjustment unit 25a, 25b: signal synthesis unit 31: noise generator 32: BPF
33a, 33b: PN oscillator 34: Adder 51: Circuit

Claims (8)

A phase fluctuation signal generator (22) for generating a phase fluctuation signal whose phase fluctuates randomly;
A signal synthesizer (23) that synthesizes the phase fluctuation signal from the phase fluctuation signal generator with the input analog signal;
A frequency converter (12) that converts the synthesized signal from the signal synthesizer to an intermediate frequency signal according to the frequency of the input analog signal;
A frequency conversion device comprising:   The frequency converter according to claim 1, further comprising a signal strength adjusting unit (24) configured to vary a signal strength of the input analog signal or the phase variation signal. A calibration signal generator (21) for generating a calibration signal having a boundary frequency of a plurality of channels having different frequency bands;
A phase fluctuation signal generator (22) for generating a phase fluctuation signal whose phase fluctuates randomly;
A signal synthesizer (23) for synthesizing the phase variation signal from the signal generator with the calibration signal from the calibration signal generator;
A frequency converter (12-1 to 12-N) that converts the synthesized signal from the signal synthesizer to an intermediate frequency signal corresponding to the frequency band of the channel;
ADC (Analog Digital Converter) (13-1 to 13-N) that samples the intermediate frequency signal from the frequency conversion unit and converts it into a digital signal;
An arithmetic processing unit (14) for averaging and calculating a phase difference between channels calculated from digital signals of different ADCs;
A frequency conversion device comprising:   The frequency converter according to claim 3, further comprising a signal strength adjustment unit (24) that varies a signal strength of the calibration signal or the phase variation signal. A synthesis procedure for synthesizing a phase fluctuation signal whose phase fluctuates randomly to the input analog signal,
A frequency conversion procedure for frequency-converting the synthesized signal synthesized by the synthesis procedure into an intermediate frequency signal corresponding to the frequency of the input analog signal;
The frequency conversion method which has these in order.   6. The frequency conversion method according to claim 5, wherein, in the synthesis procedure, the signal strength of the input analog signal or the phase fluctuation signal is varied. A calibration signal having a frequency at a boundary between a plurality of channels having different frequency bands is generated, a phase variation signal whose phase is randomly varied is generated, and the calibration signal and the phase variation signal are synthesized. By converting the frequency into an intermediate frequency signal corresponding to the frequency band of the channel and converting it to a digital signal, and averaging and calculating the phase difference of the digital signal between the channels, the level between the plurality of channels is calculated. A phase difference measurement procedure for measuring the phase difference;
The input analog signal is demultiplexed into the frequency band of the channel, the demultiplexed analog signal is converted into an intermediate frequency signal corresponding to the frequency band of the channel and converted into a digital signal, and the phase difference measurement procedure An analog signal frequency conversion procedure for correcting the phase of the digital signal using the measured phase difference between the plurality of channels, and synthesizing the digital signal after correcting the phase corresponding to the frequency band of the channel;
The frequency conversion method which has these in order.   The frequency conversion method according to claim 7, wherein in the phase difference measurement procedure, a signal intensity of the calibration signal or the phase fluctuation signal is varied.

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