JP6431570B1 - Frame synchronization apparatus, measurement apparatus including the same, frame synchronization method, and measurement method - Google Patents

Abstract

A frame synchronization apparatus capable of accurately detecting a frame head position even when signal quality is relatively poor.
A frame synchronizer 30 is provided between each data in a head side data area of a reference frame having the same format as an input frame included in a quadrature demodulated signal b and each data in a head side data area of a quadrature demodulated signal b. A start side correlation value calculating unit 42 for calculating the start side correlation value, a start side correlation value integrating unit 44 for calculating the integrated start side correlation value by integrating the start side correlation values, and the end side data area of the reference frame A tail-side correlation value calculating unit 43 that calculates a tail-side correlation value between each data and each data in the tail-side data area of the quadrature demodulated signal b, and summing the tail-side correlation values to calculate an integrated tail-side correlation value And a head position detector 34 for detecting the head position of the input frame based on the complex conjugate product of the integrated head side correlation value and the integrated tail side correlation value.
[Selection] Figure 1

Description

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

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

JP 2001-2111137 A

  However, in the conventional sliding correlation processing, when the signal quality is relatively poor, for example, when the signal-to-noise ratio is relatively small or the frequency error is relatively large, the correlation peak power is reduced and the correlation peak is reduced. However, there is a problem that the frame head position may not be accurately detected.

  The present invention has been made to solve the conventional problems, and is capable of accurately detecting the head position of a frame even when the signal quality is relatively poor, a measurement apparatus including the frame synchronization apparatus, and a frame. An object is to provide a synchronization method and a measurement method.

  A frame synchronizer according to claim 1 of the present invention is a frame synchronizer (30) for detecting a head position (61) of an input frame (60) included in an input signal (b) having a known format, Reference frame storage means (41) for storing a reference frame (50) having the format and reference data to be used as a reference among data included in the input signal, and sequentially shifting the reference data at a predetermined data interval The reference data shift means (32), the first head side data area (53) having a predetermined data length in one direction from the head data of the reference frame, and the direction opposite to the one direction from the tail data of the reference frame A first tail side data area (54) having the predetermined data length in a direction, the predetermined data length in the one direction from the reference data of the input signal; And having the predetermined data length in the opposite direction from the data separated in the one direction by the frame length of the reference frame with reference to the reference data of the input signal. A data area setting means (31) for setting a second tail side data area (64), and each data in the first head side data area and the first data every time the reference data is determined by the reference data shift means. A head side correlation value calculating means (42) for calculating a head side correlation value by performing a correlation calculation with each data in the two head side data areas, and integrating the head side correlation values to obtain an integrated head side correlation value Each time the reference data is determined by the integrated head side correlation value calculating means (44) for calculating the reference data shift means and the second data area in the first tail data area. A tail-side correlation value calculating means (43) for calculating a tail-side correlation value by performing a correlation operation with each piece of data in the tail-side data area, and calculating an integrated tail-side correlation value by integrating the tail-side correlation values. Summing end side correlation value calculating means (45), and frame head position detecting means for detecting the head position of the input frame based on a complex conjugate product of the summing head side correlation value and the summing tail side correlation value ( 34).

  With this configuration, the frame synchronization apparatus according to claim 1 of the present invention detects the leading position of the input frame based on the complex conjugate product of the cumulative leading side correlation value and the cumulative trailing side correlation value. Here, the complex conjugate product of the integration start side correlation value and the integration end side correlation value according to the present invention is not easily affected by the frequency error and has high resistance to noise. Therefore, the frame synchronization apparatus according to claim 1 of the present invention can accurately detect the frame head position even when the signal quality is relatively poor.

  In the frame synchronization apparatus according to claim 2 of the present invention, the reference data shift means sequentially shifts the reference data at the first data interval, and then at a second data interval that is narrower than the first data interval. The reference data is shifted, and the frame head position detecting means estimates a head position area including the head position of the input frame based on the first data interval, and the estimated head position area The first position of the input frame is detected based on the second data interval.

  With this configuration, the frame synchronization apparatus according to claim 2 of the present invention can accurately detect the frame head position while reducing the load of detecting the frame head position.

  A measuring apparatus according to claim 3 of the present invention includes the frame synchronizer (30) according to claim 1 or 2, and measures an input signal (a) including an input frame (60) having a known format. A down-conversion means (21) for down-converting the inputted input signal into a baseband signal, and a head position (61) of the input frame included in the down-converted baseband signal. ) Based on the detection signal (c) detected by the frame synchronizer, demodulating the baseband signal and outputting a demodulated signal (d), and measuring the output demodulated signal Measuring means (12).

  With this configuration, since the measuring apparatus according to claim 3 of the present invention includes the frame synchronization apparatus, even when the signal quality is relatively poor, the frame head position is accurately detected and predetermined measurement is performed. Can do.

A frame synchronization method according to claim 4 of the present invention is a frame synchronization method for detecting a head position (61) of an input frame (60) included in an input signal (60) having a known format, wherein the format is A reference frame storing step (S11) for storing a reference frame (50) having the reference frame, and a reference data shift for sequentially determining the reference data among the data included in the input signal and sequentially shifting the reference data at a predetermined data interval Step (S22), a first head-side data area (53) having a predetermined data length in one direction from the head data of the reference frame, and the direction from the tail data of the reference frame in a direction opposite to the one direction. A first tail side data area (54) having a predetermined data length, a predetermined data in the one direction from the reference data of the input signal. A second head side data area (63) having a data length, and the predetermined data in the opposite direction from the data separated in the one direction by the frame length of the reference frame based on the reference data of the input signal A data area setting step (S12) for setting a second end-side data area (64) having a length, and each data of the first head-side data area for each of the reference data determined in the reference data shift step And a head-side correlation value calculating step (S16) for calculating a head-side correlation value by performing a correlation calculation between the first head-side data area and each data in the second head-side data area, A cumulative top correlation value calculating step (S17) for calculating a side correlation value;
For each of the reference data determined in the reference data shift step, a correlation operation is performed between each data in the first tail data area and each data in the second tail data area to obtain a tail correlation value. End-side correlation value calculating step (S18), calculating the integrated end-side correlation value by integrating the end-side correlation values and calculating the integrated end-side correlation value (S19); A frame head position detecting step (S23) for detecting the head position of the input frame based on a complex conjugate product with the integrated tail-side correlation value.

  With this configuration, the frame synchronization method according to claim 4 of the present invention detects the leading position of the input frame based on the complex conjugate product of the cumulative leading side correlation value and the cumulative trailing side correlation value. Here, the complex conjugate product of the integration start side correlation value and the integration end side correlation value according to the present invention is not easily affected by the frequency error and has high resistance to noise. Therefore, the frame synchronization method according to claim 4 of the present invention can accurately detect the frame head position even when the signal quality is relatively poor.

  A measurement method according to claim 5 of the present invention is a measurement method for measuring an input signal (a) including an input frame (60) having a known format, including the frame synchronization method according to claim 4. A down-conversion step (S13) for down-converting the input signal to a baseband signal, and detection by the frame synchronizer detecting the head position (61) of the input frame included in the down-converted baseband signal A demodulated signal output step (S24) for demodulating the baseband signal based on the signal (c) and outputting a demodulated signal (d); and a measuring step (S25) for measuring the demodulated signal output. It has a configuration.

  With this configuration, the measurement method according to claim 5 of the present invention includes the frame synchronization method, and therefore, even when the signal quality is relatively poor, the frame head position is accurately detected and predetermined measurement is performed. Can do.

  The present invention provides a frame synchronization apparatus, a measurement apparatus including the frame synchronization apparatus, a frame synchronization method, and a measurement method, which have the effect of accurately detecting the frame head position even when the signal quality is relatively poor. It can be done.

It is a block block diagram in one Embodiment of the measuring apparatus which concerns on this invention. It is function explanatory drawing in one Embodiment of the frame synchronizer which concerns on this invention. It is a figure which shows the frame head position detection result by the conventional sliding correlation process. It is a figure which shows the frame head position detection result in one Embodiment of the frame synchronizer which concerns on this invention. It is the graph which compared the conventional sliding correlation process (broken line) and this embodiment (solid line) about the frequency offset estimated value by simulation. It is a flowchart in one Embodiment of the measuring apparatus which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. An example in which the frame synchronization device of the present invention is applied to a measurement device that measures 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 this embodiment includes a receiving unit 20, a frame synchronization apparatus 30, an OFDM demodulating unit 11, a measuring unit 12, and a display unit 13, and measures DUT1. The 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 knows in advance the format of a 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 reception 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 it 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 it to the quadrature demodulator 23.

  The quadrature demodulation unit 23 performs quadrature demodulation on the output signal of the ADC 22 into an I (in-phase) signal component and a Q (quadrature) signal component, and outputs the quadrature demodulated signal b to the frame synchronization device 30 and the OFDM demodulation unit 11. It has become.

  The frame synchronization device 30 detects the head position of the frame included in the orthogonal demodulated signal b output from the orthogonal demodulator 23 and outputs a head position detection signal c indicating the detected head position of the frame to the OFDM demodulator 11. It is like that. The detailed configuration of the frame synchronization device 30 will be described later. The quadrature demodulated signal b is an input signal of the frame synchronization device 30.

  The OFDM demodulator 11 receives an orthogonal demodulated signal b from the orthogonal demodulator 23 and a head position detection signal c from the frame synchronizer 30. Then, the OFDM demodulator 11 demodulates the quadrature demodulated signal b from the quadrature demodulator 23 based on the head position detection signal c input from the frame synchronizer 30, generates a demodulated signal d, and outputs it to the measuring unit 12 It is supposed to be. The OFDM demodulator 11 is an example of a demodulated signal output unit.

  The measurement unit 12 is configured to be able to measure, for example, transmission power, EVM (Error Vector Magnitude), constellation, and the like for the demodulated signal d demodulated by the OFDM demodulation unit 11. The measurement unit 12 is an example of a measurement unit.

  The display unit 13 displays data, graphs, and the like of measurement results obtained by the measurement unit 12.

  Next, the configuration of the frame synchronization apparatus 30 will be described. The frame synchronization device 30 includes a correlation processing unit 40, a data area setting unit 31, a reference data shift unit 32, a threshold storage unit 33, and a head position detection unit 34.

  The correlation processing unit 40 includes a reference frame storage unit 41, a head side correlation value calculation unit 42, a tail side correlation value calculation unit 43, a head side correlation value integration unit 44, and a tail side correlation value integration unit 45.

  The reference frame storage unit 41 is a frame having a known OFDM signal format input from the DUT 1, and stores a reference frame including an ideal signal that is not affected by interference or noise. . The reference frame storage unit 41 is an example of a reference frame storage unit.

  Each time the reference data shift unit 32 determines the reference data (described later) of the orthogonal demodulated signal b, the start side correlation value calculation unit 42 sets the start side data area (first start data area) set on the start side of the reference frame 50. Side data area) and each data in the head side data area (second head side data area) set on the head side with reference to the reference data of the orthogonal demodulated signal b. A leading correlation value is calculated. The head side correlation value calculation unit 42 is an example of a head side correlation value calculation unit.

  The tail-side correlation value calculating unit 43 sets the tail-side data region (first tail) set on the tail side of the reference frame 50 every time the reference data shift unit 32 determines the reference data (described later) of the orthogonal demodulated signal b. Side data area) and each piece of data in the tail side data area (second tail data area) set on the tail side with reference to the reference data of the quadrature demodulated signal b. The tail correlation value is calculated. The tail side correlation value calculation unit 43 is an example of a tail side correlation value calculation unit.

  The leading correlation value integrating unit 44 adds the leading correlation values calculated by the leading correlation value calculating unit 42 to calculate an integrated leading correlation value. This head side correlation value integrating unit 44 is an example of a head side correlation value calculating unit.

  The tail-side correlation value integrating unit 45 integrates the tail-side correlation values calculated by the tail-side correlation value calculating unit 43 to calculate an integrated tail-side correlation value. The tail side correlation value integrating unit 45 is an example of a summing tail side correlation value calculating unit.

  The data area setting unit 31 sets a data area in which the head side correlation value calculation unit 42 and the tail side correlation value calculation unit 43 perform correlation calculation. Specifically, the data area setting unit 31 sets a head side data area and a tail side data area of the reference frame and a head side data area and a tail side data area of the orthogonal demodulated signal b. The data area setting unit 31 is an example of a data area setting unit.

  The reference data shift unit 32 determines the reference data in the orthogonal demodulated signal b so that the head side correlation value calculating unit 42 and the tail side correlation value calculating unit 43 perform a correlation operation on the orthogonal demodulated signal b. The reference data is shifted at a predetermined data interval. The reference data shift unit 32 is an example of a reference data shift unit.

  The threshold value storage unit 33 stores a head position detection threshold value for detecting the head position of the input frame included in the orthogonal demodulated signal b. The head position detection threshold value stored in the threshold value storage unit 33 is obtained by, for example, experiments or simulations, and is an amplitude value (power).

  The start position detection unit 34 calculates a complex conjugate product (amplitude) of the integration start side correlation value and the integration end side correlation value, and calculates the calculated complex conjugate product and the start position detection threshold value stored in the threshold value storage unit 33. Are to be compared. When the calculated complex conjugate product exceeds the head position detection threshold, the head position detector 34 outputs a head position detection signal c indicating that the head position of the input frame has been detected to the OFDM demodulator 11. It is like that. That is, the head position detector 34 is an example of a frame head position detector. The complex conjugate product indicates a result obtained by multiplying one of the integrated head-side correlation value and the integrated tail-side correlation value with the other as a complex conjugate.

  Next, the function of the frame synchronization apparatus 30 will be specifically described with reference to FIG.

  FIG. 2 shows the reference frame 50 and the orthogonal demodulated signal b with the horizontal axis as the time axis. First, the reference frame 50 will be described. The reference frame 50 is composed of N symbols including a head symbol (head data) at the head position 51 and a tail symbol (tail data) at the tail position 52. That is, the frame length of the reference frame 50 is N symbols.

  The reference frame 50 has a data length 53 in the direction from the head position 51 toward the tail position 52 and a data length in the direction from the tail position 52 toward the head position 51. And (N−L) end-side data areas 54. That is, in the reference frame 50, the end of the head side data area 53 is the (N-L-1) th symbol, and the head of the tail side data area 54 is the Lth symbol. For example, N = 256 and L = 64.

  Next, the quadrature demodulated signal b will be described. The quadrature demodulated signal b includes an input frame 60. The input frame 60 has a head position 61 and a tail position 62.

  In order to detect the start position 61 of the input frame 60, the reference data shift unit 32 sequentially shifts the position of the reference data of the orthogonal demodulated signal b to be compared with the start symbol of the reference frame 50 as symbols S0, S1, S2,. To do. In the present embodiment, the reference data shift unit 32 shifts the position of the reference data one symbol at a time.

  In the orthogonal demodulated signal b, a frame length equal to the frame length of the reference frame 50 from the symbol S0 is set. The end of this frame length is the symbol S3.

  In the quadrature demodulated signal b, similarly to the reference frame 50, the head side data area 63 having a data length of (N−L) in the direction from the symbol S0 toward the end position 62 is set with reference to the symbol S0. Yes.

  On the other hand, with the symbol S0 as a reference, similarly to the reference frame 50, a tail-side data region 64 having (N−L) data lengths in the direction from the symbol S3 to the symbol S0 is set.

  Each time the reference data shift unit 32 shifts the reference data of the orthogonal demodulated signal b to the symbols S0, S1, S2,..., The start side correlation value calculation unit 42 stores each data in the start side data area 53 of the reference frame 50. And a head-side correlation value is calculated by performing a correlation operation between each data in the head-side data area 63 set in the orthogonal demodulated signal b.

  The tail-side correlation value calculation unit 43 stores each data in the tail-side data area 54 of the reference frame 50 each time the reference data shift unit 32 shifts the reference data of the quadrature demodulated signal b to symbols S0, S1, S2,. And the end-side correlation value is calculated by performing a correlation operation with each piece of data in the end-side data area 64 set in the orthogonal demodulated signal b.

  The start side correlation value integrating unit 44 adds up the start side correlation values calculated by the start side correlation value calculating unit 42 to calculate an integrated start side correlation value R1 (k). Here, k = 0, 1,..., (N−1).

  The tail-side correlation value integrating unit 45 integrates the tail-side correlation values calculated by the tail-side correlation value calculating unit 43 to calculate an integrated tail-side correlation value R2 (k).

For example, the head position detection unit 34 obtains a complex conjugate product by multiplying the complex conjugate R1 ^* (k) of the integrated leading correlation value R1 (k) by the integrated trailing correlation value R2 (k). The absolute value | R2 (k) · R1 ^* (k) | of the complex conjugate product is compared with the head position detection threshold value.

When the value of | R2 (k) · R1 ^* (k) | exceeds the head position detection threshold value, the head position detector 34 receives a symbol as reference data of the orthogonal demodulated signal b at that time. The head position 61 of the frame 60 is determined, and the head position detection signal c is output to the OFDM demodulator 11. In the example shown in FIG. 2, when the reference frame 50 is at the position indicated by A, the value of | R2 (k) · R1 ^* (k) | exceeds the head position detection threshold value.

The head position detection unit 34 compares | R1 (k) · R2 ^* (k) | with the head position detection threshold instead of the absolute value | R2 (k) · R1 ^* (k) |. Also good. In the case of comparison with the latter, compared with the case of comparison with the former, the amplitude is the same and the phase is reversed. However, since the head position detection threshold is the amplitude, there is no problem in detecting the head position 61 of the input frame 60. Absent.

  Next, the function of the frame synchronization apparatus 30 will be described using mathematical expressions.

When the reference frame 50 shown in FIG. 2 is represented by s (k) and the orthogonal demodulated signal b input at t ₀ is represented by r (k), r (k) is represented by [Equation 1]. Δf is a frequency error (frequency shift), T is a sampling period, k = 0, 1,..., N−1.

ここで、ω_ｋは雑音（ノイズ）を示している。

Here, ω _k represents noise (noise).

  When noise is not considered, the data r1 (k ′) of the head side data area 63 of the orthogonal demodulated signal b is expressed by [Equation 2].

ただし、ｋ'＝０，１，・・・、Ｎ−Ｌ−１

Where k ′ = 0, 1,..., N−L−1.

  Similarly, data r2 (k ′) in the tail side data area 64 of the orthogonal demodulated signal b is expressed by [Equation 3].

The head side correlation value calculation unit 42 causes each data (r1 (k ′)) of the head side data area 63 of the orthogonal demodulated signal b and each data (s1 (k ′)) of the head side data area 53 of the reference frame 50. Is multiplied for each sample to obtain the leading correlation value. Specifically, for example, the head side correlation value calculating unit 42 multiplies r1 (k ′) and the complex conjugate s1 ^* (k ′) of s1 (k ′), and sets r1 (k) as the head side correlation value. ') · S1 ^* (k') is obtained.

  An integrated leading correlation value R1 (k) obtained by integrating these leading correlation values is expressed by [Equation 4] and is calculated by the leading correlation value integrating unit 44.

Similarly, the tail-side correlation value calculation unit 43 causes each data (r2 (k ′)) in the tail-side data area 64 of the orthogonal demodulated signal b and each data (s2 (k) in the tail-side data area 54 of the reference frame 50 to be stored. Multiply the complex conjugate of ')) for each sample to obtain the tail correlation value. Specifically, for example, the tail-side correlation value calculation unit 43 multiplies r2 (k ′) and the complex conjugate s2 ^* (k ′) of s2 (k ′) to obtain r1 (k ') · S2 ^* (k') is obtained.

  An integrated tail correlation value R2 (k) obtained by integrating these tail correlation values is represented by [Equation 5] and is calculated by the tail correlation value integration unit 45.

When the complex conjugate R1 ^* (k) of the integration start side correlation value R1 (k) is multiplied by the integration end side correlation value R2 (k), the complex conjugate product is expressed by [Equation 6]. The calculation shown in [Equation 6] is executed by the head position detector 34.

The absolute value of the complex conjugate product ^{R2 (k) · R1 * (} k) | R2 (k) · R1 * (k) | is expressed by [Equation 7]. The calculation shown in [Equation 7] is executed by the head position detector 34.

As is clear from [Equation 7], the absolute value | R2 (k) · R1 ^* (k) | of the complex conjugate product is not affected by the frequency error because it does not include a frequency element.

  Therefore, since the frame synchronization apparatus 30 in the present embodiment has a configuration for detecting the head position of the frame based on the correlation result that is not affected by the frequency error, even when the frequency error is relatively large, The power of the correlation peak is not reduced and the correlation peak is not obscured.

  Further, in the conventional sliding correlation processing, the correlation is performed once for N frames for one frame. On the other hand, the frame synchronizer 30 in this embodiment calculates (N−L) frames at the head side and the tail side. It is the structure which performs a correlation calculation twice. Therefore, assuming that the noise is additive white Gaussian noise (AWGN), there is no correlation between the noise and the input signal. Therefore, the embodiment in which the correlation is performed twice by the averaging theory is more than the conventional one. Noise immunity can be improved.

  Therefore, the frame synchronization apparatus 30 according to the present embodiment accurately sets the frame head position even when the signal quality is relatively poor, such as when the signal-to-noise ratio is relatively small or the frequency error is relatively large. Can be detected.

  Next, the conventional sliding correlation process and the correlation process in the present embodiment are compared, and the effect of the frame synchronization apparatus 30 will be described with reference to FIGS.

  FIG. 3 shows a frame head position detection result (for one frame) by the conventional sliding correlation processing. FIG. 4 shows a frame head position detection result (for one frame) by the frame synchronization apparatus 30 in the present embodiment. The horizontal axis indicates the number of samples, and the vertical axis indicates the amplitude (power). This correlation result is when the signal-to-noise ratio (SNR) is 10 dB and the frequency error is ½ of the subcarrier spacing in the frequency direction.

  As shown in FIG. 3, in the conventional sliding correlation processing, the peak level indicating the frame head position is about 0.6, while the peak level of noise is 0.3 to 0.4. The difference is relatively small.

  On the other hand, as shown in FIG. 4, in the frame synchronization apparatus 30 according to the present embodiment, the peak level of noise is reduced to 0.1 to 0.2 from the conventional level, and the peak level indicating the frame head position is shown. The difference from the noise level is relatively large.

  As described above, in the conventional sliding correlation processing, the correlation is performed once for N frames for one frame, whereas in the present embodiment, (N−L) head side and tail side are performed. This is because it is configured to perform the correlation calculation twice in total.

  On the other hand, FIG. 5 shows an example of a graph comparing the conventional sliding correlation processing (broken line) and the present embodiment (solid line) when the frequency offset estimated value by simulation is 75 kHz in the frequency direction subcarrier interval. It is.

  As shown in FIG. 5, the range of frequency errors that can be synchronized is about ± 45 kHz in the conventional sliding correlation process (broken line), but is expanded to a range of about ± 70 kHz in the present embodiment (solid line). ing.

  Next, operation | movement of the measuring apparatus 10 in this embodiment is demonstrated using FIG. FIG. 6 is a flowchart for explaining a frame synchronization method and a measurement method in the present embodiment.

  When the user operates an operation unit (not shown), the reference frame 50 is stored in the reference frame storage unit 41, the data of each correlation region is stored in the data region setting unit 31, and the head position detection threshold is stored in the threshold storage unit 33. (Step S11).

  The data area setting unit 31 outputs data indicating the area to be correlated to the correlation processing unit 40, and sets each data area (step S12). Specifically, the data area setting unit 31 sets a head side data area 53 and a tail side data area 54 of the reference frame, and a head side data area 63 and a tail side data area 64 of the orthogonal demodulated signal b.

  The down converter 21 down-converts the input signal a input from the DUT 1 into a baseband signal (step S13). The down-converted signal is converted from an analog value to a digital value by the ADC 22 and output to the quadrature demodulator 23.

  The orthogonal demodulator 23 performs orthogonal demodulation on the output signal of the ADC 22 into the I signal component and the Q signal component, and outputs the orthogonal demodulated signal b to the frame synchronizer 30 and the OFDM demodulator 11 (step S14).

  The reference data shift unit 32 sets reference data in the orthogonal demodulated signal b so that the head side correlation value calculating unit 42 and the tail side correlation value calculating unit 43 perform correlation operations on the orthogonal demodulated signal b ( Step S15). For example, the reference data shift unit 32 determines the symbol S0 in the orthogonal demodulated signal b shown in FIG. 2 as the reference data.

  The leading correlation value calculation unit 42 performs a correlation operation between each data in the leading data area 53 of the reference frame 50 and each data in the leading data area 63 of the orthogonal demodulated signal b to obtain a leading correlation value. Calculate (step S16).

  The start side correlation value integration unit 44 integrates the start side correlation values calculated by the start side correlation value calculation unit 42 according to the above [Equation 4] to calculate the integration start side correlation value R1 (k) (step S17). ).

  The tail-side correlation value calculation unit 43 performs a correlation operation between each piece of data in the tail-side data area 54 of the reference frame 50 and each piece of data in the tail-side data area 64 of the orthogonal demodulated signal b to obtain a tail-side correlation value. Calculate (step S18).

  The tail-side correlation value integration unit 45 integrates the tail-side correlation values calculated by the tail-side correlation value calculation unit 43 according to the above [Equation 5] to calculate the integration tail-side correlation value R2 (k) (step S19). ).

The head position detector 34 obtains the absolute value | R2 (k) · R1 ^* (k) | of the complex conjugate product from the above [Equation 7], and | R2 (k) · R1 ^* (k) | The position detection threshold value is compared (step S20).

The head position detector 34 determines whether or not | R2 (k) · R1 ^* (k) | exceeds the head position detection threshold (step S21).

If it is not determined in step S21 that | R2 (k) · R1 ^* (k) | exceeds the head position detection threshold, the reference data shift unit 32 shifts the reference data by one symbol (step S22). The process returns to step S16. For example, the reference data shift unit 32 shifts from the symbol S0 to S1 in the orthogonal demodulated signal b shown in FIG. 2, and the correlation processing unit 40 executes a new correlation process using the symbol S1 as reference data.

On the other hand, when it is determined in step S21 that | R2 (k) · R1 ^* (k) | exceeds the head position detection threshold, the head position detector 34 converts the head position detection signal c into the OFDM demodulator 11. (Step S23).

  The OFDM demodulator 11 demodulates the quadrature demodulated signal b from the quadrature demodulator 23 based on the head position detection signal c, generates a demodulated signal d, and outputs it to the measuring unit 12 (step S24).

  The measuring unit 12 performs a predetermined measurement on the demodulated signal d from the OFDM demodulating unit 11 (step S25).

  As described above, the frame synchronization apparatus 30 in the present embodiment has a configuration for detecting the leading position of the input frame based on the complex conjugate product of the cumulative leading side correlation value and the cumulative trailing side correlation value. As described above, the complex conjugate product of the integration start side correlation value and the integration end side correlation value in this embodiment is not easily affected by the frequency error, and has high resistance to noise. Therefore, the frame synchronization apparatus 30 in the present embodiment can accurately detect the frame head position even when the signal quality is relatively poor.

  In addition, since the measuring apparatus 10 according to the present embodiment includes the frame synchronization apparatus 30, it is possible to accurately detect the frame head position and perform a predetermined measurement even when the signal quality is relatively poor.

(Modification)
In the above-described embodiment, the reference data shift unit 32 has been described as shifting the position of the reference data one symbol at a time, but the present invention is not limited to this.

  For example, after the reference data shift unit 32 shifts the position of the reference data by the first data interval (data pitch) and the head position detection unit 34 estimates the approximate head position area of the frame, It is also possible to adopt a configuration in which the approximate head position area is shifted at a second data interval that is smaller than the data interval.

  Specifically, for example, the reference data shift unit 32 first shifts the position of the reference data by 8 symbols, and the head position detection unit 34 estimates a rough head position area of the frame. Next, the reference data shift unit 32 shifts the position of the reference data one symbol at a time, and the head position detection unit 34 accurately obtains the frame head position.

  With this configuration, the measurement apparatus 10 and the frame synchronization apparatus 30 according to the present embodiment can accurately detect the frame head position while reducing the detection processing load of the frame head position.

  As described above, the frame synchronization apparatus according to the present invention, the measurement apparatus including the frame synchronization method, and the frame synchronization method and measurement method can accurately detect the frame start position even when the signal quality is relatively poor. And is useful as a frame synchronization apparatus, a measurement apparatus including the same, a frame synchronization method, and a measurement method.

1 DUT
10 measuring apparatus 11 OFDM demodulator (demodulated signal output means)
12 Measuring unit (measuring means)
21 Down-converter (Down-converting means)
30 frame synchronizer 31 data area setting unit (data area setting means)
32 Reference data shift unit (reference data shift means)
33 threshold storage unit 34 head position detection unit (frame head position detection means)
41 Reference frame storage unit (reference frame storage means)
42 Leading correlation value calculating unit (leading correlation value calculating means)
43 Tail-side correlation value calculation unit (Tail-side correlation value calculation means)
44 Leading correlation value integrating unit (Integrating leading correlation value calculating means)
45 Tail-side correlation value integration unit (integration end-side correlation value calculation means)
50 Reference frame 51 Reference frame start position 52 Reference frame end position 53 Reference frame start side data area 54 Reference frame end side data area 60 Input frame 61 Orthogonal demodulation signal start position 62 Orthogonal demodulation signal end position 63 Orthogonal Demodulated signal start side data area 64 Orthogonal demodulated signal end side data area a Input signal (measurement device input signal)
b Quadrature demodulated signal (input signal of frame synchronizer)
c Detection signal d Demodulation signal

Claims (5)

A frame synchronizer (30) for detecting a head position (61) of an input frame (60) included in an input signal (b) having a known format,
Reference frame storage means (41) for storing a reference frame (50) having the format;
Reference data shift means (32) for determining reference data to be used as a reference among data included in the input signal and sequentially shifting the reference data at a predetermined data interval;
A first head side data area (53) having a predetermined data length in one direction from the head data of the reference frame, and a first data area having the predetermined data length in a direction opposite to the one direction from the tail data of the reference frame. 1 end side data area (54), a second start side data area (63) having a predetermined data length in the one direction from the reference data of the input signal, and the reference data of the input signal A data area setting means (31) for setting a second tail side data area (64) having the predetermined data length in the opposite direction from data separated in the one direction by the frame length of the reference frame;
Each time the reference data is determined by the reference data shift means, a correlation operation is performed between each data in the first head data area and each data in the second head data area, so that a head correlation value is obtained. Starting side correlation value calculating means (42) for calculating
Integrated head-side correlation value calculating means (44) for calculating the integrated head-side correlation value by integrating the head-side correlation values;
Each time the reference data is determined by the reference data shift means, a correlation calculation is performed between each data in the first tail data area and each data in the second tail data area, and the tail correlation value is obtained. End side correlation value calculating means (43) for calculating
Integration end side correlation value calculating means (45) for calculating the integration end side correlation value by integrating the end side correlation values;
Frame start position detection means (34) for detecting the start position of the input frame based on a complex conjugate product of the integration start side correlation value and the integration end side correlation value;
A frame synchronization apparatus comprising: The reference data shift means shifts the reference data at a second data interval narrower than the first data interval after sequentially shifting the reference data at a first data interval.
The frame head position detecting means estimates a head position area including the head position of the input frame based on the first data interval, and based on the second data interval in the estimated head position area. Detecting the head position of the input frame;
The frame synchronizer according to claim 1. A measuring device (10) comprising a frame synchronizer (30) according to claim 1 or 2, and measuring an input signal (a) comprising an input frame (60) having a known format,
Down-converting means (21) for down-converting the inputted input signal into a baseband signal;
The demodulated signal (d) is demodulated by demodulating the baseband signal based on the detection signal (c) detected by the frame synchronizer at the head position (61) of the input frame included in the downconverted baseband signal. Demodulated signal output means (11) for outputting;
Measuring means (12) for measuring the output demodulated signal;
A measuring apparatus comprising: A frame synchronization method for detecting a leading position (61) of an input frame (60) included in an input signal (60) having a known format,
A reference frame storing step (S11) for storing a reference frame (50) having the format;
A reference data shift step (S22) for determining reference data to be used as a reference among the data included in the input signal and sequentially shifting the reference data at a predetermined data interval;
A first head side data area (53) having a predetermined data length in one direction from the head data of the reference frame, and a first data area having the predetermined data length in a direction opposite to the one direction from the tail data of the reference frame. 1 end side data area (54), a second start side data area (63) having a predetermined data length in the one direction from the reference data of the input signal, and the reference data of the input signal A data area setting step (S12) for setting a second tail data area (64) having the predetermined data length in the opposite direction from data separated in the one direction by the frame length of the reference frame,
For each reference data determined in the reference data shift step, a correlation calculation is performed between each data in the first leading data area and each data in the second leading data area to obtain a leading correlation value Starting side correlation value calculating step (S16) for calculating
An integrated leading correlation value calculating step (S17) for calculating the integrated leading correlation value by integrating the leading correlation values;
For each of the reference data determined in the reference data shift step, a correlation operation is performed between each data in the first tail data area and each data in the second tail data area to obtain a tail correlation value. A tail-side correlation value calculating step (S18) for calculating
An integration end side correlation value calculating step (S19) for calculating the integration end side correlation value by integrating the end side correlation values;
A frame head position detecting step (S23) for detecting the head position of the input frame based on a complex conjugate product of the integrated head side correlation value and the integrated tail side correlation value;
Including a frame synchronization method. A method for measuring an input signal (a) comprising an input frame (60) having a known format, comprising the frame synchronization method of claim 4.
A down-conversion step (S13) for down-converting the inputted input signal into a baseband signal;
The demodulated signal (d) is demodulated by demodulating the baseband signal based on the detection signal (c) detected by the frame synchronizer at the head position (61) of the input frame included in the downconverted baseband signal. A demodulated signal output step (S24) for outputting;
A measurement step (S25) for measuring the output demodulated signal;
A measurement method comprising:

Images