JP2019102925A - Frame synchronizer and measuring apparatus including the same and frame synchronization method and method for measurement - Google Patents

Abstract

To provide a frame synchronizer capable of shortening the processing time of frame synchronization processing.SOLUTION: A frame synchronizer generates a frame trigger 70 including frame triggers 71, 74 with a time period of frame length, captures a capture signal 81 including a frame 2 from an input signal 60 with reference to the frame trigger 71, detects the head position 62 of the frame 2 included in the capture signal 81, detects the time from the frame trigger 71, as the reference, to the head position 62 of the frame 2, as a reference time Ts, captures a capture signal 82 including a frame 12 from the input signal 60 with reference to a frame trigger 74 after the reference time Ts is detected, and then detects the head position 64 of the frame 12 on the basis of the reference time Ts.SELECTED DRAWING: Figure 2

Description

  The present invention relates to, for example, a frame synchronization apparatus that detects the start position of a frame, a measurement apparatus including the same, and a frame synchronization method and measurement method.

  Conventionally, this type of device prepares in advance a reference frame having the same format as the frame to be received, and performs so-called sliding correlation processing in which correlation processing is performed by sequentially shifting symbols of the reference frame with respect to symbols of the received signal. A correlation peak is determined by execution, and the start position of the frame is detected based on the correlation peak (see, for example, Patent Document 1).

JP 2001-211137 A

  However, in the conventional sliding correlation processing, sliding correlation processing is performed each time a capture signal is captured from a received signal to obtain the head position of a frame included in the capture signal, so the processing time for frame synchronization processing is relatively long. There was a problem that it takes a long time.

  The present invention has been made to solve the conventional problems, and a frame synchronization apparatus capable of shortening the processing time of frame synchronization processing, a measurement apparatus including the same, and a frame synchronization method and measurement method. Intended to be provided.

  A frame synchronization apparatus according to a first aspect of the present invention is a frame synchronization apparatus (30) for detecting a head position of a captured frame from an input signal (b) including a plurality of frames whose frame lengths are known, A frame trigger generating means (31) for generating a frame trigger (70) including the first and second frame triggers at a frame length time interval; and a first frame including the first frame based on the first frame trigger First capture means (41) for capturing a capture signal of the first signal from the input signal, and detecting a head position of the first frame included in the first capture signal captured and detecting the detection signal (c) externally First frame start position detecting means (42) for outputting to the first frame, and the first frame trie as a reference by the first capturing means Reference time detection means (43) for detecting the time from the first frame start position detection means to the first position of the first frame detected as the reference time, and the reference time by the reference time detection means A second capture means (51) for capturing from the input signal a second capture signal including a second frame based on the second frame trigger after the detection; and the second capture captured A second frame head position detecting means (53) for detecting the head position of the second frame included in the signal based on the reference time and outputting the detection signal (c) to the outside doing.

  With this configuration, the frame synchronization apparatus according to claim 1 of the present invention detects the reference time from the first frame trigger to the head position of the first frame, and then detects the reference time of the second frame based on the reference time. The start position can be detected.

  Therefore, in the frame synchronization apparatus according to claim 1 of the present invention, the processing time of the frame synchronization processing is longer than that of the prior art in which sliding correlation processing etc. is performed every time a capture signal is captured from an input signal The shortening can be achieved.

  The frame synchronization apparatus according to claim 2 of the present invention further comprises detection window setting means (52) for setting a detection window (W) for detecting the start position of the second frame based on the reference time, The second frame head position detecting means is configured to detect the head position of the second frame in the detection window set by the detection window setting means.

  With this configuration, the frame synchronization apparatus according to claim 2 of the present invention detects the start position of the second frame in the detection window, so that the processing time of the frame synchronization processing can be shortened.

  A measuring apparatus according to a third aspect of the present invention is a measuring apparatus (10) including the frame synchronization apparatus (30) according to the first or second aspect, wherein the input signal is downconverted to a baseband signal. Down conversion means (21) for converting and demodulation signal output means (13) for demodulating the baseband signal based on the detection signal (c) outputted from the frame synchronization device and outputting a demodulation signal (d) And measuring means (14) for measuring the output demodulated signal.

  According to this configuration, the measurement apparatus according to claim 3 of the present invention includes the frame synchronization apparatus capable of shortening the processing time of the frame synchronization process, so that the measurement time can be shortened.

  A frame synchronization method according to a fourth aspect of the present invention is a frame synchronization method for detecting the start position of a captured frame from an input signal (b) including a plurality of frames whose frame lengths are known, A frame trigger generating step (S13) of generating a frame trigger including the first and second frame triggers at time intervals; and inputting the first capture signal including the first frame based on the first frame trigger A first capture step (S15) of capturing from a signal, and a first position of detecting a head position of the first frame included in the captured first capture signal and outputting a detection signal (c) to the outside A frame head position detection step (S16); and the first frame referred to in the first capture step. A reference time detection step (S17) for detecting a time from a trigger to the start position of the first frame detected in the first frame start position detection step as a reference time; and the reference time in the reference time detection step A second capture step (S19) of capturing from the input signal a second capture signal including a second frame on the basis of the second frame trigger after the second frame trigger is detected; And a second frame head position detection step (S22) of detecting the head position of the second frame included in the capture signal based on the reference time and outputting the detection signal (c) to the outside. doing.

  According to this configuration, in the frame synchronization method according to claim 4 of the present invention, after detecting the reference time from the first frame trigger to the start position of the first frame, the frame synchronization method of the second frame is performed based on the reference time. The start position can be detected.

  Therefore, in the frame synchronization method according to claim 4 of the present invention, the processing time of the frame synchronization processing is longer than that of the prior art in which sliding correlation processing etc. is performed every time a capture signal is captured from an input signal The shortening can be achieved.

  The frame synchronization method according to claim 5 of the present invention further includes a detection window setting step (S21) for setting a detection window (W) for detecting the start position of the second frame based on the reference time, The second frame head position detection step is configured to detect the head position of the second frame in the detection window set in the detection window setting step.

  With this configuration, in the frame synchronization method according to claim 5 of the present invention, the start position of the second frame is detected in the detection window, so that the processing time of the frame synchronization processing can be shortened.

  A measuring method according to claim 6 of the present invention is the measuring method including the frame synchronization method according to claim 4 or claim 5, and a down-converting step of down-converting the input signal into a baseband signal S11), a demodulation signal output step (S24) of demodulating the baseband signal based on the detection signal (c) output in the frame synchronization method and outputting a demodulation signal (d); And a measurement step of measuring the demodulated signal (S25).

  According to this configuration, since the measurement method according to claim 6 of the present invention includes the frame synchronization method capable of shortening the processing time of the frame synchronization processing, the measurement time can be shortened.

  The present invention can provide a frame synchronization apparatus having an effect that processing time of frame synchronization processing can be shortened, a measurement apparatus including the same, and a frame synchronization method and measurement method.

It is a block block diagram in one embodiment of the measuring device concerning the present invention. It is function explanatory drawing of the flame | frame synchronizer based on this invention. FIG. 8 is a conceptual explanatory view comparing a frame head position detection method according to an embodiment of the frame synchronization apparatus of the present invention with a frame head position detection method according to the related art. It is a flowchart in one embodiment of the measuring device concerning the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. An example in which the frame synchronization apparatus of the present invention is applied to a measurement apparatus for measuring a device under test (DUT) that outputs an OFDM (Orthogonal Frequency Division Multiplexing) signal will be described.

  First, the configuration of an embodiment of the measuring apparatus according to the present invention will be described.

  As shown in FIG. 1, the measuring apparatus 10 in the present embodiment includes a receiving unit 20, a frame synchronization apparatus 30, an OFDM demodulation unit 13, a measuring unit 14, and a display unit 15, and measures the DUT 1. An input signal a input from the DUT 1 includes an input frame having a known format, and has a signal component of a data symbol and a reference signal component. That is, the measuring apparatus 10 grasps in advance the format of the frame included in the OFDM signal (input signal a) input from the DUT 1, and the position of the reference signal component in the input frame is known.

  The receiving unit 20 includes a down converter 21, an ADC (analog / digital converter) 22, and an orthogonal demodulation unit 23.

  The down converter 21 converts the frequency of the input signal a input from the DUT 1 into a baseband signal, and outputs the baseband signal to the ADC 22. The down converter 21 is an example of down conversion means.

  The ADC 22 converts the signal frequency-converted by the down converter 21 from an analog value to a digital value, and outputs the converted signal to the quadrature demodulation unit 23.

  The orthogonal demodulation unit 23 orthogonally demodulates the output signal of the ADC 22 into an I (in-phase) signal component and a Q (orthogonal) signal component, and outputs the orthogonally demodulated signal b orthogonally demodulated to the frame synchronization unit 30 and the OFDM demodulation unit 13 It has become.

  The frame synchronization device 30 performs frame synchronization processing by detecting the start position of a frame included in the input signal. Specifically, the frame synchronization device 30 detects the start position of the frame included in the quadrature demodulation signal b output from the orthogonal demodulation unit 23, and detects the start position detection signal c indicating the start position of the detected frame outside the device. It is output to the OFDM demodulator 13 of FIG. The detailed configuration of this frame synchronization device 30 will be described later. The orthogonal demodulation signal b is an input signal of the frame synchronization device 30.

  The OFDM demodulation unit 13 is configured to receive the orthogonal demodulation signal b from the orthogonal demodulation unit 23 and the head position detection signal c from the frame synchronization device 30. Then, the OFDM demodulation unit 13 demodulates the orthogonal demodulation signal b from the orthogonal demodulation unit 23 based on the head position detection signal c input from the frame synchronization device 30 to generate a demodulation signal d, and outputs it to the measurement unit 14 It is supposed to The OFDM demodulator 13 is an example of a demodulated signal output unit.

  The measurement unit 14 is configured to be able to measure, for example, transmission power, EVM (Error Vector Magnitude), constellation, and the like with respect to the demodulated signal d demodulated by the OFDM demodulation unit 13. The measurement unit 14 is an example of a measurement unit.

  The display unit 15 is configured to display data, a graph, and the like of the measurement result obtained by the measurement unit 14.

  Next, the configuration of the frame synchronization device 30 will be described. The frame synchronization apparatus 30 includes a first synchronization processing unit 40, a second synchronization processing unit 50, a frame trigger generation unit 31, a reference time storage unit 32, and a synchronization state detection unit 33.

  The first synchronization processing unit 40 includes a first capture unit 41, a first head position detection unit 42, and a reference time detection unit 43. The second synchronization processing unit 50 includes a second capture unit 51, a detection window setting unit 52, and a second head position detection unit 53.

  Hereinafter, the detailed configuration of the frame synchronization device 30 will be described with reference to FIG. FIG. 2 is a diagram for explaining the function of the frame synchronization device 30. As shown in FIG.

  In FIG. 2, the input signal 60 of the frame synchronizer 30, the frame trigger 70, the capture signal 80, and the reference frame 90 are shown.

  The input signal 60 includes a plurality of frames such as frames 1 and 2 whose frame length is known. Although the head position 61 of frame 1 and the head position 62 of frame 2 are shown, when the frame synchronization device 30 inputs the input signal 60, the head positions of these are unknown.

  The frame trigger generation unit 31 generates a frame trigger 70 and outputs the frame trigger 70 to the first synchronization processing unit 40 and the second synchronization processing unit 50. The frame trigger 70 includes frame triggers 71-76. The time interval of each frame trigger is equal to the frame length of each frame included in the input signal 60. The frame trigger generation unit 31 is an example of a frame trigger generation unit.

  The first capture unit 41 captures a capture signal 81 having a length including at least one frame based on the frame trigger 71 (first frame trigger) as a first capture process for the input signal 60. It is supposed to be. In the illustrated example, the capture signal 81 has a length of two frames and includes frame 2 (hatched portion). The frame 2 corresponds to the first frame, and the data included in the frame 2 is to be measured by the measuring unit 14. The first capture unit 41 is an example of a first capture unit.

  The first head position detection unit 42 uses the previously prepared reference frame 90 having the same format as that of the input frame, for example, the head position 62 of the frame included in the capture signal 81 by sliding correlation processing. Is to detect. The illustrated example shows a state in which the reference frame 90 slides for time Ta during the sliding correlation process. As a result of the sliding correlation process, the first head position detection unit 42 can detect the head position 62 of the frame 2. The start position 62 of the frame 2 corresponds to the start position of the first frame. The first head position detection unit 42 is an example of a first frame head position detection unit.

  The reference time detection unit 43 detects the time from the frame trigger 71 referenced by the first capture unit 41 to the start position 62 of the frame 2 detected by the first start position detection unit 42 as a reference time Ts. It is supposed to be. The reference time detection unit 43 is an example of a reference time detection unit.

  The reference time storage unit 32 is configured to store data of the reference time Ts detected by the reference time detection unit 43.

  The synchronization state detection unit 33 is in the head position synchronization state indicating the state in which the data of the reference time Ts is stored in the reference time storage unit 32 (the state in which the reference time Ts is detected), or the data of the reference time Ts is It is configured to detect any one of the head position asynchronous states, which indicates a state not stored in the reference time storage unit 32 (a state in which the reference time Ts is not detected). Then, the synchronization state detection unit 33 outputs the input signal 60 to the first synchronization processing unit 40 when the start position asynchronous state is detected, and the second synchronization process when the start position synchronization state is detected. It is output to the unit 50.

  The second capture unit 51 uses the frame trigger 74 (second frame trigger) as a reference after the reference time detection unit 43 detects the reference time Ts, that is, as a second or subsequent capture process for the input signal 60. , And is adapted to capture a capture signal 82 having a length that includes at least one frame. In the illustrated example, the capture signal 82 has a length of two frames and includes a frame 12 (hatched portion). The frame 12 corresponds to the second frame, and the data included in the frame 12 is to be measured by the measuring unit 14. The second capture unit 51 is an example of a second capture unit.

  The detection window setting unit 52 reads the data of the reference time Ts stored in the reference time storage unit 32, and sets the detection window (window) W having a relatively narrow time width with reference to the frame trigger 74. There is. The detection window setting unit 52 is an example of a detection window setting unit.

  The second head position detection unit 53 uses the reference frame 90 prepared in advance in the detection window W set by the detection window setting unit 52, for example, a frame included in the capture signal 82 by sliding correlation processing, that is, The head position 64 of the frame 12 is detected. The start position 64 of the frame 12 corresponds to the start position of the second frame. The second head position detection unit 53 is an example of a second frame head position detection unit.

  In the example shown in FIG. 2, the capture signal 81 starts capturing at the same time as the frame trigger 71 and the capture signal 82 starts capturing at the same time as the frame trigger 74, but the present invention is limited to this. Instead, it may be configured to start capture at a certain time away from the frame trigger.

  Next, the effect of the frame synchronization device 30 in the present embodiment will be described based on FIG. 3 in comparison with the prior art. FIG. 3A conceptually shows a method for detecting the head position of a frame according to the prior art. FIG. 3B conceptually shows a method of detecting the head position of a frame by the frame synchronization device 30 in the present embodiment.

  As shown in FIG. 3A, in the related art, with respect to each capture signal 100 captured from the input signal 60, the detection time of the head position of the frame by the sliding correlation process is different for each capture process. Specifically, in the illustrated example, the detection time Ta is for the first capture signal 101, the detection time Tb for the second capture signal 102, and the detection time Tc for the third capture signal 103.

  On the other hand, as shown in FIG. 3B, the frame synchronization device 30 in the present embodiment has the detection time Ta for the first capture signal 81 as in the prior art, but the second and subsequent capture signals 82 , 83 differs from the prior art. In order to simplify the description, in FIG. 3B, the capture start time of the capture signal 81 is made to coincide with the capture start time of the capture signal 101.

  Specifically, since the frame synchronization device 30 is configured to detect the head position of the frame by sliding correlation processing in the detection window W set based on the reference time Ts at the second time and thereafter, the second time and later Becomes the detection time Tw, and it is possible to greatly reduce the time as compared with the prior art.

  The frame 22 (hatched portion) included in the third capture signal 83 corresponds to the second frame, and the data included in the frame 22 is to be measured by the measuring unit 14. The start position 66 of the frame 22 corresponds to the start position of the second frame. Also, the frame trigger 77 corresponds to the second frame trigger.

  Next, the operation of the measuring apparatus 10 in the present embodiment will be described based on FIG. 4 and with reference to FIG. FIG. 4 is a flowchart for explaining a frame synchronization method and a measurement method in the present embodiment.

  The downconverter 21 downconverts the input signal a input from the DUT 1 into a baseband signal (step S11). The down-converted signal is converted from an analog value to a digital value by the ADC 22 and output to the quadrature demodulation unit 23.

  The orthogonal demodulation unit 23 orthogonally demodulates the output signal of the ADC 22 into an I signal component and a Q signal component, and outputs the orthogonally demodulated signal b subjected to orthogonal demodulation to the frame synchronization unit 30 and the OFDM demodulation unit 13 (step S12).

  The frame trigger generation unit 31 generates the frame trigger 70 at a time interval of the frame length of each frame included in the input signal 60 and outputs the frame trigger 70 to the first synchronization processing unit 40 and the second synchronization processing unit 50 (step S13). ).

  The synchronization state detection unit 33 detects that the data of the reference time Ts is not in the start position asynchronous state when it is not stored in the reference time storage unit 32, and when it is stored in the reference time storage unit 32, the head position The synchronization state is detected (step S14). Then, when detecting the head position asynchronous state, the synchronization state detection unit 33 outputs the input signal b (the input signal 60 in FIG. 2) input from the reception unit 20 to the first synchronization processing unit 40. On the other hand, when detecting the leading position synchronization state, the synchronization state detection unit 33 outputs the input signal b to the second synchronization processing unit 50.

  If it is detected in step S14 that the head position is asynchronous, the first synchronization processing unit 40 operates as follows.

  The first capture unit 41 captures the capture signal 81 (first capture signal) with reference to the frame trigger 71 (first frame trigger) (step S15).

  The first start position detection unit 42 detects the start position 62 (the start position of the first frame) of the frame 2 included in the capture signal 81 by, for example, sliding correlation processing using the reference frame 90 prepared in advance. (Step S16).

  The reference time detection unit 43 detects the time from the frame trigger 71 referenced by the first capture unit 41 to the start position 62 of the frame 2 detected by the first start position detection unit 42 as a reference time Ts. (Step S17).

  The reference time storage unit 32 stores data of the reference time Ts detected by the reference time detection unit 43 (step S18).

  On the other hand, when the head position synchronization state is detected in step S14, the second synchronization processing unit 50 operates as follows.

  The second capture unit 51 captures the capture signal 82 (second capture signal) with reference to the frame trigger 74 (step S19).

  The detection window setting unit 52 reads the data of the reference time Ts stored in the reference time storage unit 32 (step S20), and sets the detection window W based on the frame trigger 74 (second frame trigger) (step S21). ). For example, the detection window setting unit 52 sets the detection window W such that the distance from the frame trigger 74 to the center of the detection window W is the reference time Ts.

  The second head position detection unit 53 uses the reference frame 90 prepared in advance in the detection window W set by the detection window setting unit 52, for example, in the frame 12 included in the capture signal 81 by sliding correlation processing. The start position 64 (the start position of the second frame) is detected (step S22).

  The first head position detection unit 42 and the second head position detection unit 53 output the head position detection signal c to the OFDM demodulation unit 13 (step S23).

  The OFDM demodulation unit 13 demodulates the quadrature demodulation signal b from the quadrature demodulation unit 23 based on the head position detection signal c to generate a demodulation signal d, and outputs the demodulation signal d to the measurement unit 14 (step S24).

  The measurement unit 14 performs predetermined measurement on the demodulated signal d from the OFDM demodulation unit 13 (step S25).

  In addition, when continuing measurement after step S25, the measuring apparatus 10 performs the process after step S14, captures a new capture signal, and measures the capture signal.

  In addition, when the measuring apparatus 10 needs to newly detect the reference time Ts after detection of the reference time Ts, for example, when the signal from the DUT 1 is interrupted after detection of the reference time Ts, the head position synchronization state The first synchronous processing unit 40 newly performs processing of detecting the reference time Ts.

  As described above, after detecting the reference time Ts from the first frame trigger 71 to the head position 62 of the frame 2, the frame synchronization device 30 in the present embodiment determines the frames 12, 22 and so on based on the reference time Ts. The head position 64, 66, etc. of the frame is detected, so that processing time for frame synchronization processing is longer than that of the prior art in which sliding correlation processing etc. is performed to capture the head position of the frame every time a capture signal is captured from the input signal. The shortening can be achieved.

  In addition, since the measuring apparatus 10 according to the present embodiment includes the frame synchronization device 30 capable of shortening the processing time of the frame synchronization process, the measurement time can be shortened.

  As described above, the frame synchronization apparatus according to the present invention, the measurement apparatus provided with the same, the frame synchronization method, and the measurement method have an effect that processing time of frame synchronization processing can be shortened, and The present invention is useful as a frame synchronization apparatus for detecting a head position, a measurement apparatus including the same, and a frame synchronization method and measurement method.

1 DUT (device under test)
2 frames (first frame)
10 Measurement apparatus 13 OFDM demodulator (demodulated signal output means)
12, 22 frames (second frame)
14 Measuring section (measuring means)
21 Down converter (down conversion means)
30 Frame Synchronizer 31 Frame Trigger Generator (Frame Trigger Generator)
40 first synchronization processing unit 41 first capture unit (first capture means)
42 First head position detection unit (first frame head position detection means)
43 Reference time detection unit (reference time detection means)
50 second synchronization processing unit 51 second capture unit (second capture means)
52 Detection window setting unit (detection window setting means)
53 Second head position detection unit (second frame head position detection means)
60 input signal 62 start position of first frame 64, 66 start position of second frame 70 frame trigger 71 first frame trigger 74, 77 second frame trigger 80 capture signal 81 first capture signal 82, 83 Second capture signal 90 Reference frame Tb Detection time W Detection window

Claims (6)

A frame synchronizer (30) for detecting the start position of a captured frame from an input signal (b) including a plurality of frames whose frame lengths are known,
Frame trigger generating means (31) for generating a frame trigger (70) including first and second frame triggers at a time interval of the frame length;
First capture means (41) for capturing from the input signal a first capture signal including a first frame based on the first frame trigger;
First frame head position detection means (42) for detecting the head position of the first frame included in the captured first capture signal and outputting the detection signal (c) to the outside;
Reference time to detect time from the first frame trigger referenced by the first capture means to the start position of the first frame detected by the first frame start position detection means as a reference time Detection means (43),
Second capture means (51) for capturing a second capture signal including a second frame from the input signal based on the second frame trigger after the reference time is detected by the reference time detection means When,
Second frame head position detection means (53) for detecting the head position of the second frame included in the captured second capture signal based on the reference time and outputting a detection signal (c) to the outside When,
A frame synchronization apparatus comprising: It further comprises detection window setting means (52) for setting a detection window (W) for detecting the head position of the second frame based on the reference time.
The frame according to claim 1, wherein the second frame head position detecting means detects the head position of the second frame in the detection window set by the detection window setting means. Sync device. A measuring device (10) comprising a frame synchronization device (30) according to claim 1 or claim 2;
Down-converting means (21) for down-converting the input signal to baseband signals;
Demodulation signal output means (13) for demodulating the baseband signal based on the detection signal (c) output from the frame synchronization device and outputting a demodulation signal (d);
Measuring means (14) for measuring the output demodulated signal;
The measuring apparatus characterized by having. A frame synchronization method for detecting the start position of a captured frame from an input signal (b) including a plurality of frames whose frame lengths are known,
A frame trigger generating step (S13) of generating a frame trigger including the first and second frame triggers at a time interval of the frame length;
A first capture step (S15) of capturing a first capture signal including a first frame from the input signal based on the first frame trigger;
A first frame head position detection step (S16) of detecting a head position of the first frame included in the captured first capture signal and outputting a detection signal (c) to the outside;
A reference time for detecting a time from the first frame trigger referenced in the first capture step to the head position of the first frame detected in the first frame head position detection step as a reference time Detection step (S17),
A second capture step of capturing a second capture signal including a second frame from the input signal based on the second frame trigger after the reference time is detected in the reference time detection step (S19) When,
A second frame head position detection step (S22) for detecting a head position of the second frame included in the captured second capture signal based on the reference time and outputting a detection signal (c) to the outside When,
A frame synchronization method comprising: The method further includes a detection window setting step (S21) of setting a detection window (W) for detecting a head position of the second frame based on the reference time.
5. The frame synchronization method according to claim 4, wherein the second frame head position detection step detects the head position of the second frame in the detection window set in the detection window setting step. A measurement method comprising the frame synchronization method according to claim 4 or 5,
A down-converting step (S11) of down-converting the input signal into a baseband signal;
A demodulation signal output step (S24) for demodulating the baseband signal based on the detection signal (c) output in the frame synchronization method and outputting a demodulation signal (d);
Measuring (S25) measuring the output demodulated signal;
Measurement method characterized by including.

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