JP7174793B2 - Signal analysis device and signal analysis method - Google Patents

Description

The present invention relates to a signal analysis device and a signal analysis method.

Conventionally, under test conditions specified in communication standards such as LTE (Long Term Evolution) and 5G NR (New Radio), devices under test (DUT (Device A transmission test is performed to check the transmission performance of the DUT by receiving and analyzing the signal transmitted from the Under Test).

For example, in OBUE (Operating Band Unwanted Emissions) measurement specified by 3GPP (Third Generation Partnership Project), it is required to measure spurious waves and other unwanted waves over a wide band outside the band including the band of the modulated signal ( e.g. 5G NR 38.104, 38.141-1,2). In such measurements, an FFT (Fast Fourier Transform) type measurement device is more advantageous than a sweep type measurement device from the viewpoint of reliably capturing signals in a short measurement time.

Even when using an FFT-type measuring device, for example, in OBUE measurement, it may be necessary to measure a band wider than the measurement bandwidth supported by the measuring device. In such a case, it is possible to perform wideband spectrum measurement with a wide frequency span by performing multiple captures in the frequency direction (see Patent Document 1, for example).

In Patent Document 1, in order to measure a broadband signal under measurement, the channel width of the signal under measurement is divided into a plurality of divided frequency ranges, and the measurement results of each of the divided frequency ranges are corrected and combined. is disclosed.

Japanese Unexamined Patent Application Publication No. 2014-93738

In the prior art described in Patent Document 1, the channel width of the signal under measurement, which is the entire frequency span, is divided into a plurality of segments (divided frequency ranges), and the spectrum of each segment is obtained from the waveform data of each segment. It is calculated by FFT calculation, and the spectrum of each segment is combined to obtain the entire spectrum. However, the offset of the center frequency of each segment and the coupling position of the spectrum to achieve the appropriate frequency characteristics must be calculated by the operator, and the combination to obtain the final wideband spectrum measurement result must be calculated by the user. Processing, drawing processing, etc. also had to be calculated by oneself.

Also, in spectrum analysis using FFT, FFT processing is normally performed on a signal that has been LPF (Low Pass Filtered) or BPF (Band Pass Filtered) to avoid aliasing. Since the characteristics of the LPF and BPF actually include ripples and transition regions, there is also the problem of deterioration in accuracy at the edges of the spectrum obtained by FFT.

DISCLOSURE OF THE INVENTION The present invention has been made in order to solve the conventional problems. It is an object of the present invention to provide a signal analysis apparatus and a signal analysis method capable of performing wideband spectrum measurement in a wide range of applications.

The signal analysis apparatus of the present invention includes a frequency bandwidth setting unit (24) for setting the frequency bandwidth of each segment obtained by dividing the entire frequency span, and each segment based on the frequency bandwidth of each segment. and a center frequency setting unit (23) for setting the center frequency of each segment, receiving and sampling the signal under measurement in a predetermined frequency bandwidth wider than the frequency bandwidth of each segment based on the center frequency of each segment a waveform data capture unit (10) for capturing waveform data for each segment; a spectrum acquisition unit (51) for subjecting the waveform data of each segment to Fourier transform processing to obtain a spectrum for each segment; a spectrum extraction unit (52) for extracting a spectrum corresponding to the frequency bandwidth of each segment from the spectrum by excluding both end portions of the frequency; a spectrum combiner (53) for obtaining a corresponding overall spectrum , wherein the frequency bandwidth setting unit selects a frequency bandwidth (BW _n,L ) on the lower side of the center frequency of each segment and on the higher side ; The frequency bandwidth (BW _{n, H} ) of each segment is set, and the center frequency setting unit sets the frequency bandwidth (BW _{n, L} ) on the lower side and the higher frequency bandwidth (BW _{n, H} ), the offset (CF _n ) of the center frequency of each segment from the center frequency of the center segment is set.

As described above, in the signal analysis apparatus of the present invention, the frequency bandwidth setting section sets the frequency bandwidth of each segment, and the spectrum extraction section removes both ends of the frequency from the spectrum of each segment. , and the spectrum combining unit combines the extracted spectrums of each segment. This configuration eliminates the need for the operator to calculate the coupling position of the spectrum corresponding to the edge of the frequency bandwidth of each segment, unlike the conventional technique.

Also, the center frequency setting unit sets the center frequency of each segment based on the frequency bandwidth of each segment set by the frequency bandwidth, and the waveform data capture unit uses the set center frequency of each segment as a reference. First, the signal under test is received and sampled at a predetermined frequency bandwidth wider than the frequency bandwidth of each segment to capture waveform data. This configuration eliminates the need for the user to calculate the center frequency of each segment by himself as in the conventional case.

In addition, the spectrum extractor extracts the frequency bandwidth of each segment by excluding both ends of the frequency from the spectrum obtained for each segment, and the spectrum combiner combines the extracted spectrum of each segment to obtain a total to obtain the entire spectrum corresponding to the frequency span of . With this configuration, it is possible to exclude both end portions of the spectrum obtained by the Fourier transform, where the frequency characteristics are deteriorated. In this way, by appropriately selecting the frequency bandwidth of each segment, the Fourier transform result of the band with better frequency characteristics is adopted instead of the Fourier transform result of the band with deteriorated frequency characteristics, and the overall spectrum can be obtained.

Therefore, the signal analysis apparatus of the present invention can perform wideband spectrum measurement with high accuracy and ease even when wideband spectrum measurement is performed by widening the frequency bandwidth by performing capture multiple times in the frequency direction. be able to.
In addition, since the signal analysis apparatus of the present invention can set the frequency bandwidth on the lower side and the higher side than the center frequency in each segment, it is suitable for the frequency characteristics of the waveform data capture section, the spectrum acquisition section, etc. segment configuration can be set.

Also, in the signal analysis apparatus of the present invention, the frequency bandwidth setting unit is configured such that the sum of the frequency bandwidths of the segments is equal to the entire frequency span, and the frequency bandwidth of the segments is equal to the waveform data capture The frequency bandwidth of each segment may be set so as to be narrower than the frequency bandwidth that can be captured by the unit.

With this configuration, the signal analysis apparatus of the present invention can appropriately set the frequency bandwidth of each segment without impairing the frequency characteristics of the signal analysis apparatus.

により、前記中心セグメントの中心周波数からの、前記各セグメントの中心周波数のオフセットを算出し、ここで、ＣＦ_＋ｍは、中心セグメントより周波数が高い側ｍ番目のセグメントにおける、中心セグメントの中心周波数からの、中心周波数のオフセットであり、ＣＦ_－ｍは、中心セグメントより周波数が低い側ｍ番目のセグメントにおける、中心セグメントの中心周波数からの、中心周波数のオフセットであり、ＢＷ_＋ｍ，Ｌは、中心セグメントより周波数が高い側ｍ番目のセグメントのフーリエ変換結果から、該セグメントの中心周波数より低い側で抽出する片側周波数帯域幅であり、ＢＷ_＋ｍ，Ｈは、中心セグメントより周波数が高い側ｍ番目のセグメントのフーリエ変換結果から、該セグメントの中心周波数より高い側で抽出する片側周波数帯域幅であり、ＢＷ_－ｍ，Ｌは、中心セグメントより周波数が低い側ｍ番目のセグメントのフーリエ変換結果から、該セグメントの中心周波数より低い側で抽出する片側周波数帯域幅であり、ＢＷ_－ｍ，Ｈは、中心セグメントより周波数が低い側ｍ番目のセグメントのフーリエ変換結果から、該セグメントの中心周波数より高い側で抽出する片側周波数帯域幅である構成であってもよい。 Further, in the signal analysis device of the present invention, the center frequency setting unit may be:

Calculate the offset of the center frequency of each segment from the center frequency of the center segment by, where CF _+m is the offset from the center frequency of the center segment in the m-th segment on the higher frequency side than the center segment. , is the center frequency offset, CF _−m is the center frequency offset from the center frequency of the center segment in the m-th segment on the lower frequency side than the center segment, and BW _+m,L is the center frequency offset from the center segment From the Fourier transform result of the m-th segment on the high frequency side, the one-side frequency bandwidth extracted on the side lower than the center frequency of the segment, BW _{+ m, H} is the m-th segment on the side where the frequency is higher than the center segment BW-m,L is the one-sided frequency bandwidth extracted on the higher side than the center frequency of the segment from the Fourier transform result, and BW- _m,L is the Fourier transform result of the m-th segment on the lower frequency side than the center segment. BW-m,H is the one-side frequency bandwidth to extract on the side lower than the center frequency, and BW- _m,H is the Fourier transform result of the m-th segment on the side with a lower frequency than the center segment, and extracts on the side higher than the center frequency of the segment. A single-sided frequency bandwidth configuration may also be used.

With this configuration, in the signal analysis apparatus of the present invention, the center frequency setting section can accurately obtain the offset of the center frequency of each segment from the center frequency of the center segment.

Further, in the signal analysis apparatus of the present invention, Fourier transform point number setting for setting, for each segment, the number of Fourier transform points of the Fourier transform processing to be applied to the waveform data of each segment based on the frequency bandwidth of each segment. A section (25) may be further provided, and the spectrum acquisition section (51) may be configured to perform Fourier transform processing based on the number of Fourier transform points set for each of the segments.

With this configuration, the signal analysis apparatus of the present invention can switch the frequency resolution (RBW) for each segment.

Further, in the signal analysis device of the present invention, the Fourier transform point number setting unit may be configured to set the number of Fourier transform points of each segment so that the frequency resolution of trace points in each segment is equal to each other. .

With this configuration, the signal analysis apparatus of the present invention can obtain a spectrum with a constant frequency resolution of trace points over the entire frequency span.

Further, the signal analysis apparatus of the present invention further includes a trace point number setting unit that sets the number of trace points of the spectrum extracted by the spectrum extraction unit for each segment based on the frequency characteristics of the Fourier transform processing in the spectrum acquisition unit. (26), wherein the spectrum extractor extracts the spectrum based on the number of trace points set for each segment, and the spectrum combiner extracts the trace point at the end of each segment to the combining position of the spectrum. The spectrum of each segment may be combined as

With this configuration, in the signal analysis apparatus of the present invention, the spectrum extractor appropriately extracts only portions of the spectrum with good frequency characteristics from the spectrum of each segment, and the spectrum combiner combines the spectra with good frequency characteristics. Since the entire spectrum can be generated by using a high-precision wideband spectrum, a wideband spectrum can be obtained.

Further, the signal analysis apparatus of the present invention includes a storage section (30) for storing the waveform data acquired by the waveform data capture section, and a modulation analysis section for performing modulation analysis using the waveform data stored in the storage section. (40), wherein the spectrum acquisition unit performs Fourier transform processing on the waveform data stored in the storage unit to acquire a spectrum for each segment.

With this configuration, the signal analysis apparatus of the present invention can capture waveform data of all segments in a short period of time in real time, store them in the storage unit, and then perform spectrum analysis. Also, since the same waveform data stored in the storage section can be used for both spectrum analysis and modulation analysis, effective analysis can be performed.

Further, in the signal analysis apparatus of the present invention, the center frequency setting unit sets the center frequency of each segment to a multiple of the frequency resolution of the trace points when the frequency resolution of the trace points of each segment is the same for all segments. It may be configured to

With this configuration, in the signal analysis apparatus of the present invention, the center frequency setting section can efficiently set the center frequency of each segment.

Further, in the signal analysis apparatus of the present invention, the center frequency setting unit may set the frequency resolution of the trace points of each segment to be different in at least one segment, and the sampling rate of the waveform data capture unit to be the same in all segments. In this case, the center frequency of each segment may be set to a common multiple of the frequency resolution of the trace points.

With this configuration, in the signal analysis apparatus of the present invention, the center frequency setting section can efficiently set the center frequency of each segment.

Further, in the signal analysis apparatus of the present invention, the center frequency setting section may set the frequency resolution of the trace points of the segments to be different in at least one segment, and the sampling rate of the waveform data capture section to be set in at least one segment. When the sampling rates are different and the sampling rates are in a power-of-two relationship between the segments, the center frequency of each segment may be set to a multiple of the maximum frequency resolution of the trace points.

With this configuration, in the signal analysis apparatus of the present invention, the center frequency setting section can efficiently set the center frequency of each segment.

In addition, the signal analysis method of the present invention includes the step (S3) of setting the frequency bandwidth of each segment obtained by dividing the entire frequency span; setting a frequency (S4); receiving and sampling the signal under test in a predetermined frequency bandwidth wider than the frequency bandwidth of each segment based on the center frequency of each segment, and generating waveform data for each segment; capturing steps (S5 to S9); performing spectrum acquisition processing on the waveform data of each segment to acquire a spectrum for each segment (S12); The step of extracting the spectrum for the frequency bandwidth of each segment except for (S14), and the step of combining the extracted spectrum of each segment to obtain the entire spectrum corresponding to the entire frequency span (S16 ) and

As described above, in the signal analysis method of the present invention, in the step of setting the frequency bandwidth, the frequency bandwidth of each segment is set, and in the step of extracting the spectrum, both ends of the frequency are extracted from the spectrum of each segment. In the step of extracting the spectrum for the frequency bandwidth of each segment except for the frequency bandwidth and combining the spectrum, the extracted spectrum of each segment is combined. This configuration eliminates the need for the operator to calculate the coupling position of the spectrum corresponding to the edge of the frequency bandwidth of each segment, unlike the conventional technique.

In the step of setting the center frequency, the center frequency of each segment is set based on the frequency bandwidth of each segment, and in the step of capturing the waveform data, the center frequency of each segment is used as a reference for a predetermined frequency bandwidth. It receives and samples the signal under test to capture waveform data. This configuration eliminates the need for the user to calculate the center frequency of each segment by himself as in the conventional case.

Also, in the step of extracting the spectrum, the frequency bandwidth of each segment is extracted by excluding both ends of the frequency from the spectrum of each segment, and in the step of combining the spectra, the extracted spectrum of each segment is combined. to obtain the entire spectrum corresponding to the entire frequency span. With this configuration, it is possible to exclude both end portions of the spectrum obtained by the Fourier transform, where the frequency characteristics are deteriorated. In this way, by appropriately selecting the frequency bandwidth of the segment, the Fourier transform result of the band with the better frequency characteristic is adopted instead of the Fourier transform result of the band with the deteriorated frequency characteristic. A high overall spectrum can be obtained.

Therefore, the signal analysis method of the present invention can perform wideband spectrum measurement with high accuracy and ease even when performing wideband spectrum measurement in which the frequency bandwidth is widened by performing capture multiple times in the frequency direction. be able to.

According to the present invention, even when performing wideband spectrum measurement with a wide frequency span by performing multiple captures in the frequency direction, it is possible to easily perform wideband spectrum measurement with high accuracy. An apparatus and signal analysis method can be provided.

1 is a diagram showing a schematic configuration of a signal analysis device according to one embodiment of the present invention; FIG. FIG. 10 is a diagram showing the overall spectrum obtained by combining the spectrums acquired for each segment, taking the OBUE measurement result as an example; FIG. 4 is a schematic diagram showing an example of a method of combining spectra of segments; Fig. 3 shows a flow chart of a signal analysis method according to an embodiment of the present invention; FIG. 4 is a diagram showing a flowchart of a method for setting the center frequency of each segment in the signal analysis method according to one embodiment of the present invention;

[First Embodiment]
A first embodiment of the present invention will be described with reference to the drawings.

A signal analysis apparatus 1 according to the first embodiment of the present invention analyzes the spectrum of a modulated signal a, which is a signal under test transmitted from a device under test (DUT) 2 . For this purpose, the signal analysis apparatus 1 includes, as shown in FIG. It has

Examples of the DUT 2 include, but are not limited to, an RRH (Remote Radio Head) of a radio base station and a mobile terminal of a mobile station. The modulated signal a transmitted from the DUT 2 is an OFDM modulated signal modulated by, for example, an orthogonal frequency division multiplexing (OFDM) system according to communication standards such as LTE, LTE-Advanced, 5G NR, and wireless LAN. The modulated signal a is also called a signal under measurement. In this embodiment, 5G NR is assumed as the communication standard, and a modulated signal modulated by the OFDM system is received. However, the communication standard and the modulation system are not limited to these. Each component will be described below.

(Waveform data capture part)
The waveform data capture unit 10 receives the modulated signal a, which is the signal under measurement, for each segment obtained by dividing the entire target frequency span, and captures waveform data of a predetermined unit of processing from the modulated signal a. split capture). Here, the processing unit is the amount of data handled at one time in processing such as data capture and frame synchronization, and is represented by time length or data length, and is about 20 ms for two frames, for example. Specifically, the waveform data capture unit 10 receives, for each segment, the modulated signal a transmitted from the DUT 2 via an antenna or by wire, down-converts, samples, and quadrature demodulates to generate quadrature demodulated signals. e (also referred to as waveform data of the signal under measurement) is generated.

More specifically, the waveform data capture unit 10 receives the signal under measurement a in a predetermined frequency bandwidth wider than the frequency bandwidth (BW _n ) of each segment with respect to the set center frequency for each segment. It is designed to capture waveform data by sampling. For this purpose, the waveform data capture section 10 includes a signal level adjustment section 11, a frequency conversion section 12, an analog-digital conversion section (A/D conversion section) 13, and an orthogonal demodulation section .

The signal level adjustment section 11 includes an attenuator, an amplifier, etc., and adjusts the signal level of the modulated signal a input as an analog signal under measurement to the optimum level for the subsequent stage (particularly the mixer for frequency conversion). The level-adjusted modulated signal b is sent to the frequency converter 12 .

The frequency conversion unit 12 includes a mixer and a local oscillator, and inputs the modulated signal b and a local signal generated by the local oscillator to the mixer to down-convert the signals to generate an intermediate frequency (IF) signal c. It's becoming The intermediate frequency signal c is sent to the A/D converter 13 .

The A/D converter 13 samples the intermediate frequency signal c (intermediate frequency OFDM modulated signal) frequency-converted by the frequency converter 12 and converts the signal from an analog signal to a digital signal. The obtained digital baseband signal d is sent to the quadrature demodulator 14 .

The quadrature demodulator 14 quadrature demodulates the digital baseband signal d output from the A/D converter 13 into digital I-phase and Q-phase components. The quadrature demodulator 14 includes, for example, a pair of signal multipliers (phase detectors), a carrier generator that outputs a carrier signal converted to an intermediate frequency (IF), and a π phase shifter that shifts the phase of the carrier signal by 90°. It consists of a /2 phase shifter and a pair of low-pass filters. The obtained quadrature demodulated signal e is sent to the storage section 30 . The quadrature demodulated signal e is a complex signal.

(storage unit)
The storage unit 30 stores the quadrature demodulated signal e (waveform data) acquired by the waveform data capture unit 10 . Specifically, the digital I-phase component and the digital Q-phase component quadrature-demodulated by the quadrature demodulator 14 are sequentially written in the storage unit 30 as measurement data associated with the segment information.

(modulation analysis section)
The modulation analysis unit 40 reads the waveform data stored in the storage unit 30 and performs modulation analysis. Specifically, the modulation analysis section 40 includes a demodulation section 41 and a modulated signal analysis section 42 .

The demodulator 41 demodulates the modulated signal using, for example, the waveform data f of the central segment stored in the storage 30 . Specifically, based on a frame timing signal indicating frame synchronization, the demodulator 41 performs OFDM demodulation processing such as FFT (Fast Fourier Transform) processing and subcarrier demodulation on the waveform data f to generate an OFDM demodulated signal g. It is designed to generate The generated OFDM demodulated signal g is sent to the modulated signal analysis section 42 .

Note that CP (Cyclic Prefix) is removed from each symbol of the waveform data before FFT processing is performed in the demodulator 41, if necessary.

The modulated signal analysis unit 42 measures and analyzes, for example, EVM (Error Vector Magnitude), frequency error, timing error, transmission power, constellation, etc. for the OFDM demodulated signal g output from the demodulation unit 41. It is configured. The measurement and analysis results h by the modulated signal analysis section 42 are sent to the display section 60 and displayed.

The modulation analysis processing by the modulation analysis unit 40 may target the central segment or other segments. However, it is desirable that the segment targeted for modulation analysis processing has a frequency bandwidth wider than the modulation band.

(Spectrum analysis section)
The spectrum analysis unit 50 reads the waveform data i stored in the storage unit 30 and performs Fourier transform processing such as FFT and DFT (Discrete Fourier Transform) on the waveform data i to obtain a spectrum of the entire target frequency span. is designed to generate Also, the spectrum analysis unit 50 is adapted to perform analysis related to measurement, such as OBUE measurement and ACLR (Adjacent Channel Leakage Ratio) measurement, for determining the spectrum of the entire frequency span. For this purpose, the spectrum analysis section 50 has an FFT section 51 , a spectrum extraction section 52 and a spectrum combining section 53 . The FFT section 51 of this embodiment corresponds to the spectrum acquisition section of the present invention.

The FFT unit 51 performs FFT processing on the waveform data i acquired for each segment and stored in the storage unit 30 to acquire the spectrum j for each segment. Specifically, the FFT section 51 performs FFT processing based on the number of FFT points set by the FFT point number setting section 25, which will be described later. Spectrum j of each segment is sent to spectrum extractor 52 .

The spectrum extractor 52 extracts the spectrum k corresponding to the frequency bandwidth of each segment from the spectrum j obtained for each segment by the FFT unit 51 by excluding both end portions of the frequency. Specifically, the spectrum extraction unit 52 extracts the spectrum k based on the number of trace points set by the trace point number setting unit 26, which will be described later. The extracted spectrum k of each segment is sent to the spectrum combiner 53 .

The spectrum combiner 53 combines the extracted spectrum k of each segment to obtain the entire spectrum corresponding to the entire target frequency span. The generated spectrum m is sent to the display unit 60 and displayed.

In spectrum analysis using FFT, FFT is performed on a signal subjected to LPF or BPF in order to avoid aliasing. Since the characteristics of the LPF and BPF actually include ripples and transition regions, the frequency characteristics of the signal analysis apparatus deteriorate at the edges of the spectrum obtained by the FFT. That is, it is not possible to obtain an entire spectrum with high accuracy by using all FFT results in each segment.

In this embodiment, by appropriately selecting the frequency bandwidth of each segment, only the FFT results of frequency bands with better frequency characteristics are used instead of the FFT results of frequency bands with deteriorated frequency characteristics. can be employed to refine the overall spectrum.

(Split capture control unit)
The divisional capture control unit 20 controls an operation (divisional capture operation) of capturing waveform data for each segment obtained by dividing the entire frequency span into a plurality of segments. For this purpose, the split capture control unit 20 includes a control unit 21, a segment number setting unit 22, a center frequency setting unit 23, a frequency bandwidth setting unit 24, a resolution bandwidth setting unit 27, an FFT point number setting unit 25, a trace point number A setting unit 26 is provided.

The segment number setting unit 22 sets the number of segments obtained by dividing the entire frequency span. For example, when the frequency span to be measured is 4 GHz and the frequency span supported by the signal analysis device 1 is 1 GHz, the segment number setting unit 22 sets the frequency span to be measured, 4 GHz, to the first to fifth segments (segments 0, segment ±1, segment ±2) (see FIG. 2).

The segment number setting unit 22 may set the number of segments input by the user operating the operation unit 70, for example. Alternatively, the number-of-segments setting unit 22 may be set based on, for example, the measurable frequency span of the signal analysis device 1 and information on the entire frequency span that is the measurement range. The number of segments may be odd or even. Note that "setting" may mean storing a calculated or obtained numerical value (parameter) in a storage unit (not shown) so that it can be used by another component, or storing a calculated or obtained numerical value (parameter) in It may be to send the value to another component that utilizes it.

The number-of-segments setting unit 22 selects the number of segments (=the number of times of capture) so that the number of segments is as small as possible for performing the intended measurement.

The frequency bandwidth setting section 24 sets the frequency bandwidth _BWn of each segment based on the number of segments set by the segment number setting section 22 . Specifically, the frequency bandwidth setting unit 24 determines that the sum of the frequency bandwidths of each segment is equal to the entire frequency span, and that the frequency bandwidth of each segment is a frequency bandwidth that can be captured by the waveform data capture unit 10. The frequency bandwidth of each segment is set to be narrower. With this configuration, it is possible to appropriately set the frequency bandwidth of each segment without impairing the frequency characteristics of the signal analysis device 1 .

More specifically, the frequency bandwidth setting unit 24 sets the frequency bandwidth BW _n,L on the lower side and the frequency bandwidth BW _n,H on the higher side than the center frequency of each segment. . With this configuration, a segment configuration suitable for the frequency characteristics of the waveform data capture section 10, the FFT section 51, and the like can be set.

The frequency bandwidth setting unit 24 may, for example, evenly divide the entire target frequency span so that the frequency characteristics of the signal analysis apparatus 1 fall within a good bandwidth.

For example, when the modulation analysis unit 40 and the spectrum analysis unit 50 perform analysis using the same waveform data, the frequency bandwidth setting unit 24 should set the modulation band to fit within one segment (for example, central segment). In such a case, the frequency bandwidth setting section 24 may allocate segments unevenly according to the measurement conditions.

Depending on the communication standard, the required frequency bandwidth for spectrum analysis may be asymmetrical above and below the modulation band. In that case, the frequency bandwidth of each segment should be adjusted appropriately.

The center frequency setting section 23 sets the center frequency of each segment based on the frequency bandwidth of each segment set by the frequency bandwidth setting section 24 . Specifically, the center frequency setting unit 23 determines the distance from the center frequency of the center segment based on the frequency bandwidth BW _n,L on the lower side and the frequency bandwidth BW _n,H on the higher side than the center frequency of each segment. , offset CF _n of the center frequency of each segment (hereinafter simply referred to as center frequency).

ここで、ＣＦ_＋ｍは、中心セグメントより周波数が高い側ｍ番目のセグメントにおける、中心セグメントの中心周波数からの、中心周波数のオフセットであり、
ＣＦ_－ｍは、中心セグメントより周波数が低い側ｍ番目のセグメントにおける、中心セグメントの中心周波数からの、中心周波数のオフセットであり、
ＢＷ_＋ｍ，Ｌは、中心セグメントより周波数が高い側ｍ番目のセグメントのＦＦＴ結果から、該セグメントの中心周波数より低い側で抽出する片側周波数帯域幅であり、
ＢＷ_＋ｍ，Ｈは、中心セグメントより周波数が高い側ｍ番目のセグメントのＦＦＴ結果から、該セグメントの中心周波数より高い側で抽出する片側周波数帯域幅であり、
ＢＷ_－ｍ，Ｌは、中心セグメントより周波数が低い側ｍ番目のセグメントのＦＦＴ結果から、該セグメントの中心周波数より低い側で抽出する片側周波数帯域幅であり、
ＢＷ_－ｍ，Ｈは、中心セグメントより周波数が低い側ｍ番目のセグメントのＦＦＴ結果から、該セグメントの中心周波数より高い側で抽出する片側周波数帯域幅である。 More specifically, the center frequency setting unit 23 calculates the offset of the center frequency of each segment from the center frequency of the center segment using the following equation.

where CF _+m is the center frequency offset from the center frequency of the center segment in the m-th segment on the higher frequency side than the center segment;
CF _−m is the center frequency offset from the center frequency of the center segment in the m-th segment on the lower frequency side than the center segment;
BW _{+ m,L} is a one-sided frequency bandwidth extracted on the side lower than the center frequency of the segment from the FFT result of the m-th segment on the side higher in frequency than the center segment;
BW _+m,H is a one-sided frequency bandwidth extracted on the side higher than the center frequency of the segment from the FFT result of the m-th segment on the side higher in frequency than the center segment;
BW- _m,L is a one-side frequency bandwidth extracted on the side lower than the center frequency of the segment from the FFT result of the m-th segment on the side of the frequency lower than the center segment,
BW- _m,H is a one-side frequency bandwidth extracted on the side higher than the center frequency of the segment from the FFT result of the m-th segment on the side lower in frequency than the center segment.

Based on the number of segments set by the segment number setting section 22, the resolution bandwidth setting section 27 is configured such that the user or the control section 21, for example, sets the resolution bandwidth (RBW) of each segment.

The FFT point number setting unit 25 sets the number of FFT points of the FFT processing applied to the waveform data of each segment by the FFT unit 51 based on the frequency bandwidth and resolution bandwidth of each segment. ing. With this configuration, it is possible to switch the frequency resolution (RBW) in each segment. Note that the FFT point number setting unit 25 of the present embodiment corresponds to the Fourier transform point number setting unit of the present invention, and the number of FFT points representing the number of points to be subjected to FFT processing of the present embodiment is the Fourier transform of the present invention. corresponds to the number of Fourier transform points representing the number of points at which

The FFT point number setting unit 25 may be configured to set the number of FFT points of each segment so that the frequency resolution of trace points in each segment is equal to each other. With this configuration, it is possible to obtain a spectrum with a constant frequency resolution of trace points over the entire frequency span.

The trace point number setting section 26 sets the number of trace points of the spectrum extracted by the spectrum extraction section 52 for each segment based on the frequency characteristics of the FFT processing in the FFT section 51 . With this configuration, the spectrum extraction unit 52 appropriately extracts only the portion with good frequency characteristics from the spectrum of each segment, and the spectrum combining unit 53 combines the spectra with good frequency characteristics to generate the entire spectrum. Therefore, a highly accurate broadband spectrum can be obtained.

The control unit 21 receives an operation input from the operation unit 70, acquires various parameters, and stores them in a storage unit (not shown). Further, the control section 21 controls the divisional capture control section 20 as well as the waveform data capture section 10 and the spectrum analysis section 50 .

(display unit, operation unit)
The display unit 60 includes a display device such as a liquid crystal display, and displays the analysis result h of the modulated signal sent from the modulated signal analysis unit 42 and the spectrum m sent from the spectrum coupling unit 53 using graphs, tables, and the like. is displayed on the display device.

The operation unit 70 is operated by the user to set various parameters in addition to measurement items, measurement conditions, and determination conditions when testing the DUT 2 . Specifically, the operation unit 70 includes, for example, input devices such as a touch panel, a keyboard, a mouse, and a dial, and a control circuit for controlling the input devices.

<Split Capture and Combining Spectrum>
Next, when measuring a frequency span wider than the measurable frequency bandwidth of the signal analysis device 1 (that is, the frequency bandwidth supported by the signal analysis device 1), the entire frequency span is divided and each A method of capturing segment waveform data (divided capture) and combining spectra obtained from each segment waveform data to obtain a spectrum of the entire frequency span will be described.

FIG. 2 shows the measurement result of OBUE, and shows the entire spectrum obtained by combining the spectrum acquired for each segment. In the example of FIG. 2, the frequency span to be measured is approximately 4 GHz, and the frequency span of 4 GHz is divided into five segments, each segment being approximately 800 MHz. In one capture, the range is slightly wider than 800 MHZ, and the so-called margin for coupling is included. The segments are segment- ₂ , segment- ₁ , segment ₀ , segment +1, and segment +2 in order from the left in FIG. ₊₁ and CF ₊₂ .

In FIG. 2, the main frequency components of the modulated signal are present within the frequency bandwidth of segment 0, and almost no frequency components of the modulated signal are present in the other segments ±1 and ±2. That is, it is confirmed that unnecessary spurious is not generated.

Next, a method for setting the center frequency of each segment will be described.

In the following description, the segment number n is n=0, ±1, ±2, . is represented by a + (plus) number, and the lower side is represented by a - (minus) number.

The center frequency CF _n [Hz] of segment n is represented by an offset from the center frequency of segment 0 . Since the center frequency of segment 0 is the same as the target center frequency, the absolute value of the center frequency of each segment can be obtained from the absolute value of the target center frequency and the offset CF _n from this absolute value. The user normally only sets the absolute value of the center frequency of center segment 0 and the entire frequency span. The center frequency CF _n of the remaining segments is calculated and set by the center frequency setting unit 23 .

The frequency resolution of the trace points of the spectrum obtained by FFT processing is
It is determined from the sampling rate and the number of FFT points according to the relational expression of frequency resolution=sampling rate/number of FFT points.

Therefore, the one-sided frequency bandwidth BW _n,L , BW _n,H [Hz] extracted from the FFT (or DFT) result of each segment can be calculated by the following equation.

Here, each parameter is as follows.
S _n : the sampling rate of each segment. The sampling rate S _n of each segment n is determined by the control unit 21 depending on the hardware of the signal analysis device 1 , but may be set by the user using the operation unit 70 .

N _n : the number of FFT points (or the number of DFT points) of each segment. The number of FFT points N _n (or the number of DFT points) of each segment n is determined by the FFT point number setting unit 25 depending on the hardware of the signal analysis device 1. good too.

N _n,L ,N _n,H : The number of one-side trace points cut out from the FFT (DFT) result of each segment, and the number of one-side trace points N _{n,L on the low frequency side and N n,L} on the high side There are one-sided trace points _Nn,H . These trace point numbers are determined by the trace point number setting unit 26 depending on the hardware of the signal analysis apparatus 1 . However, depending on the purpose and situation of the measurement, the user may set it using the operation unit 70 in consideration of the error tolerance due to the FFT filter, the bandwidth of the modulation analysis, and the like.

BW _n,L , BW _n,H : One-side frequency bandwidth [Hz] extracted from the FFT (DFT) result of each segment. There is a one-sided frequency bandwidth BW _n,L on the low frequency side and a one-sided frequency bandwidth BW _n,H on the high frequency side. These frequency bandwidths are determined by the frequency bandwidth setting unit 24 depending on the hardware of the signal analysis apparatus 1, but may be set by the user using the operation unit 70. FIG. For example, if it is desired to perform modulation analysis on segment +10, the user may be allowed to make settings such that only the frequency bandwidth of that segment is widened.

Also, from the definition of the center frequency, CF ₀ =±0.

The center frequency CF _n of each segment n is determined as follows by the center frequency setting section 23 on the higher frequency side.

In the same way, the m-th segment is determined by the center frequency setting unit 23 as follows.

The center frequency CFn of each segment _n is similarly determined by the center frequency setting section 23 as follows for the lower frequency side.

中心周波数設定部２３は、上記方法に基づいて、中心周波数のオフセット位置を決定するようになっている。 In the same way, the m-th segment in the negative direction is determined by the center frequency setting unit 23 as follows.

The center frequency setting unit 23 determines the offset position of the center frequency based on the above method.

FIG. 3 is a schematic diagram showing a method of combining the spectrum of each segment. FIG. 3 shows an example of dividing the entire frequency span of interest into five segments n (n=-2, -1, 0, +1, +2). First, various conditions of this example will be described.

In this example, all segments n have the same sampling rate S _n , for example, S _n =S _fft =128 [MHz] (see reference numeral 81). The number of FFT points Nn of each segment _n is also equal, for example, _Nn = _Nfft =128 [pts] (see reference numeral 82). Therefore, the frequency resolution of the trace points is S _n /N _n =128 [MHz]/128 [pt]=1 [MHz/pt].

In the FFT result of each segment (see reference numeral 83), the value of the FFT operation result corresponding to the FFT point corresponding to the center frequency CF ₀ of the center segment is represented by "C", and the FFT on the side of the frequency higher than the center frequency CF ₀ The value of the calculation result is indicated by "H", and the value of the FFT calculation result on the lower frequency side is indicated by "L".

The number of trace points cut out (extracted) from each segment is determined symmetrically on the higher and lower frequencies than the center frequency _CF0 (see reference numeral 84). Only the number of trace points of the central segment differs from the other segments, for example N _0,L =N _0,H =N _c =60, and for the rest, for example, N _m,L =N _m,H =N _s =56. It's becoming

Similarly, for the frequency bandwidth cut (extracted) from each segment, for example, BW _0,L =BW _0,H =S _c =60 [MHz], otherwise, for example, BW _m,L =BW _m,H =S _s = 56 [MHz] (see reference numeral 85). Thus, in this embodiment, the number of trace points and the frequency bandwidth of the central segment are wider than those of the other segments in order to perform modulation analysis using the waveform data of the central segment.

The portion of the value of the FFT calculation result corresponding to the trace point of each segment or the edge of the frequency bandwidth becomes the overlapping portion (or margin) with the adjacent segment. That is, in the trace points of each segment, the trace point at the end becomes the joint position (spectrum joint position) with the adjacent segment. Which of the trace point at the end of one adjacent segment and the trace point at the end of the other segment is adopted is determined according to which segment has the superior FFT operation result at the connection position. good too.

The overall spectrum (see reference numeral 86) is obtained by combining the spectrum of each segment at the combining point. In FIG. 3, in the entire spectrum (reference numeral 86), the number of trace points in each segment (reference numeral 87), the number of trace points on the higher and lower sides than the center frequency CF ₀ (reference numeral 88), and the frequency bandwidth (reference numeral 88) 89) and the offset of the center frequency (see 90) respectively.

In FIG. 3, for the sake of simplicity, reference numerals 81 to 85 are assigned only to segment-1, but the same applies to other segments.

The signal analysis apparatus 1 according to the first embodiment includes, for example, a computer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input/output interface, and a storage device such as a hard disk. Provided individually or as a whole. As a result, for example, some or all of the functions of the waveform data capture unit 10, the divisional capture control unit 20, the modulation analysis unit 40, the spectrum analysis unit 50, etc. can store various processing programs stored in the ROM or storage device in the RAM. It can be realized by reading and executing by CPU.

(Signal analysis method)
Next, a signal analysis method according to this embodiment will be described with reference to FIG.

First, the user operates, for example, the operation unit 70 to input the absolute value of the center frequency and the entire frequency span to be analyzed (step S1).

Next, the segment number setting unit 22 sets the number of segments obtained by dividing the entire frequency span (step S2). The user may set the number of segments.

The frequency bandwidth setting unit 24 sets the frequency bandwidth _BWn of each segment (step S3). Specifically, the frequency bandwidth setting unit 24 sets a frequency bandwidth BW _n,L on the lower side and a frequency bandwidth BW _n,H on the higher side than the center frequency of each segment.

The center frequency setting unit 23 sets the center frequency of each segment based on the frequency bandwidth of each segment set by the frequency bandwidth setting unit 24 (step S4). Specifically, the center frequency setting unit 23, based on the frequency bandwidth BW _{n, L} on the lower side and the frequency bandwidth BW _{n, H} on the higher side than the center frequency of each segment, uses the following equations (1) and (2 ) Calculate and set the offset _CFn of the center frequency of each segment from the center frequency of the center segment 0 by the equation.

Next, the waveform data capture section 10 adjusts the center frequency of the measurement frequency band so as to match the center frequency of each segment set by the center frequency setting section 23 under the control of the control section 21 (step S5). Specifically, the waveform data capture unit 10 adjusts the center frequency of the captureable frequency band by adjusting the frequency of the local signal of the frequency conversion unit 12 .

Next, the frequency converter 12 down-converts the modulated signal b attenuated to an appropriate level by the signal level adjuster 11 to generate an intermediate frequency (IF) signal c (step S6).

The A/D converter 13 samples the intermediate frequency signal c frequency-converted by the frequency converter 12 and converts it from an analog signal to a digital signal (step S7). The A/D converter 13 sends the obtained digital baseband signal d to the quadrature demodulator 14 .

The quadrature demodulator 14 quadrature demodulates the digital baseband signal d output from the A/D converter 13 into an I-phase component and a Q-phase component (step S8).

Next, the storage unit 30 stores the quadrature demodulated signal e (waveform data) captured by the waveform data capture unit 10 (step S9). Specifically, the storage unit 30 sequentially stores the digital I-phase component and Q-phase component quadrature-demodulated by the quadrature demodulator 14 in association with the segment information.

The control unit 21 determines whether or not waveform data capture has been completed for all segments (step S10). If waveform data capture has not been completed for all segments (NO in step S10), the process returns to step S5. If waveform data capture has been completed for all segments (YES in step S10), the process proceeds to step S11.

In step S11, the FFT point number setting unit 25 performs FFT processing applied to the waveform data of each segment based on the frequency bandwidth of each segment and the resolution bandwidth of each segment set by the resolution bandwidth setting unit 27. The number of FFT points is set (step S11).

Next, the FFT unit 51 reads the waveform data acquired for each segment and stored in the storage unit 30, performs FFT processing, and acquires the spectrum for each segment (step S12).

The trace point number setting unit 26 sets the number of trace points of the spectrum extracted by the spectrum extraction unit 52 based on the frequency characteristics of the FFT processing in the FFT unit 51 (step S13).

Next, based on the number of trace points set by the number of trace points setting section 26, the spectrum extraction section 52 extracts the spectrum for the frequency bandwidth of each segment by excluding both end portions of the frequency from the acquired spectrum for each segment. Extract (step S14).

The control unit 21 determines whether or not spectrum acquisition has been completed for all segments (step S15). If spectrum acquisition has not been completed for all segments (NO in step S15), the process returns to step S11. If spectrum acquisition has been completed for all segments (YES in step S15), the process proceeds to step S16.

In step S16, the spectrum combiner 53 combines the extracted spectrums for each segment to generate the entire spectrum corresponding to the entire target frequency span.

The display unit 60 displays the spectrum m sent from the spectrum coupling unit 53 on the display device using a graph, table, or the like (step S17).

The setting of the number of FFT points in step S11 and the setting of the number of trace points in step S13 may be performed in advance, for example, after step S4.

When performing modulation analysis, the demodulation unit 41 reads the waveform data of the target segment stored in the storage unit 30, and performs OFDM demodulation processing such as FFT processing and subcarrier demodulation on the waveform data to perform OFDM demodulation. A signal g is generated and output to the modulated signal analysis unit 42 .

The modulated signal analysis unit 42 measures and analyzes, for example, EVM, frequency error, timing error, transmission power, constellation, etc. for the OFDM demodulated signal g output from the demodulation unit 41 .

The display unit 60 displays the analysis result h sent from the modulated signal analysis unit 42 on a display device using graphs, tables, and the like.

(action/effect)
As described above, in the signal analysis apparatus 1 according to the present embodiment, the frequency bandwidth setting unit 24 sets the frequency bandwidth of each segment, and the spectrum extraction unit 52 extracts both ends of the frequency from the spectrum of each segment. The spectrum for the frequency bandwidth of each segment is extracted except for , and the spectrum combiner 53 combines the extracted spectrum of each segment. This configuration eliminates the need for the operator to calculate the coupling position of the spectrum corresponding to the edge of the frequency bandwidth of each segment.

Further, the center frequency setting unit 23 sets the center frequency of each segment based on the frequency bandwidth of each segment set by the frequency bandwidth setting unit 24, and the waveform data capture unit 10 sets each segment The signal under measurement is received and sampled in a predetermined frequency bandwidth wider than the frequency bandwidth of each segment based on the center frequency of the segment, and waveform data is captured. This configuration eliminates the need for the operator to calculate the center frequency of each segment by himself.

Also, the spectrum extractor 52 extracts the frequency bandwidth of each segment by excluding both ends of the frequency from the spectrum acquired for each segment, and the spectrum combiner 53 combines the extracted spectrum of each segment. to obtain the entire spectrum corresponding to the entire frequency span. With this configuration, it is possible to exclude both ends of the spectrum obtained by FFT, where the frequency characteristics are deteriorated. In this way, by appropriately selecting the frequency bandwidth of each segment, the FFT result of the band with the worse frequency characteristic is not used, and the FFT result of the band with the better frequency characteristic is adopted to achieve high accuracy. You can get the whole spectrum.

Therefore, the signal analysis apparatus 1 of the present embodiment can perform wideband spectrum measurement with high accuracy and ease even when performing wideband spectrum measurement in which the frequency bandwidth is widened by performing capture multiple times in the frequency direction. can be done.

Further, the signal analysis apparatus 1 according to this embodiment performs spectrum analysis using the waveform data of each segment stored in the storage unit 30, and performs modulation analysis using the same waveform data. . Since the same waveform data can be used for both spectrum analysis and modulation analysis in this way, it is efficient in terms of data storage and transfer, and the same waveform data can be effectively analyzed by different methods. can do

[Second embodiment]
Next, a signal analysis device 1 according to a second embodiment of the invention will be described.

The center frequency and the like of each segment have the following characteristics.

A) When the frequency resolution of the trace points is the same for all segments:
The center frequency of the segment will be a multiple of the frequency resolution of the trace points. The frequency corresponding to the combined position of the spectrum will be the position that hits the trace point on both segments of the combination.

B) When the frequency resolution of trace points is different between segments:
B-1) When the sampling rate is the same for all segments:
If the common multiple of the frequency resolution of the trace points of each segment is the center frequency of the segment, then the frequency corresponding to the joint position of the spectrum will be the position of the trace point in both of the joint segments.

B-2) When the sampling rate is in a power-of-two relationship between segments:
As a more special example of the above B-1), by setting a multiple of "the maximum frequency resolution of the trace points of each segment" as the center frequency of the segment, the frequency corresponding to the coupling position of the spectrum is , at whichever of both segments it joins will hit the tracepoint.

B-3) Otherwise:
In this case, the center frequency of each segment cannot be determined using special properties, and the center frequency of each segment is determined according to the above equations (1) and (2).

A specific example of the properties in the above case A) will be shown. For example, when capturing is performed at a sampling rate of 128 MHz and the number of FFT points is 128, it is assumed that this is the number of FFT points (minimum number of FFT points) at which the frequency resolution is the coarsest in the signal analysis apparatus 1 . Calculation of the frequency resolution of the trace points in this case yields 128 [MHz]/128 [pt]=1 [MHz/pt].

Consider the case of measuring with finer frequency resolution under the same sampling rate condition. That is, consider measuring with 128 (n=7) or more FFT points. Since the number of general FFT points is nth power of 2, the frequency resolution of trace points is always a value that divides 1 MHz (for example, 0.5 MHz (when n=8), 0.25 MHz (when n=9), 0.125 MHz (when n=10), . . . ).

Therefore, "the offset of the center frequency of each segment from the center frequency of the center segment" is the "multiple of the frequency resolution". In this embodiment, the center frequency for each capture is determined so that the center frequency interval for each of five captures, for example, is a multiple of 1 MHz.

FIG. 5 is a diagram showing a flowchart of a method for setting the center frequency of each segment in the signal analysis device 1 according to the second embodiment of the present invention. As shown in FIG. 5, when the frequency resolution of the trace points is the same for all segments (YES in step S41), the center frequency setting unit 23 sets the center frequency of each segment to a multiple of the frequency resolution of the trace points ( step S42).

If the frequency resolution of trace points is different in at least one segment (NO in step S41) and the sampling rate is the same in all segments (YES in step S43), the center frequency setting unit 23 sets the center frequency of each segment. A frequency is set to a common multiple of the frequency resolution of the trace points (step S44).

In addition, the center frequency setting unit 23 sets the frequency resolution of trace points to be different in at least one segment (NO in step S41), the sampling rate is different in at least one segment (NO in step S43), and the sampling rate is in a power-of-two relationship between segments (YES in step S45), the center frequency of each segment is set to a multiple of the maximum frequency resolution of the trace points (step S46). With such a configuration, the center frequency setting unit 23 can efficiently set the center frequency of each segment.

Further, if the sampling rate does not have a power-of-two relationship between the segments in step S45 (NO in step S45), the center frequency setting unit 23 sets each Sets the center frequency of the segment.

INDUSTRIAL APPLICABILITY As described above, the present invention can perform wideband spectrum measurement with high accuracy and ease even when performing wideband spectrum measurement with a wide frequency span by performing multiple captures in the frequency direction. and is useful for the overall signal analysis apparatus and signal analysis method.

1 signal analyzer 2 DUT (device under test)
REFERENCE SIGNS LIST 10 waveform data capture unit 11 signal level adjustment unit 12 frequency conversion unit 13 A/D conversion unit 14 quadrature demodulation unit 20 split capture control unit 21 control unit 22 segment number setting unit 23 center frequency setting unit 24 frequency bandwidth setting unit 25 FFT Point number setting section (Fourier transform point number setting section)
26 trace point number setting unit 27 resolution bandwidth setting unit 30 storage unit 40 modulation analysis unit 41 demodulation unit 42 modulation signal analysis unit 50 spectrum analysis unit 51 FFT unit (spectrum acquisition unit)
52 spectrum extraction unit 53 spectrum coupling unit 60 display unit 70 operation unit a modulated signal (signal under measurement)
b modulated signal c intermediate frequency signal d digital baseband signal e quadrature demodulated signal (waveform data)
f, i waveform data g OFDM demodulated signal h analysis result j, k, m spectrum

Claims (11)

a frequency bandwidth setting unit (24) for setting the frequency bandwidth of each segment obtained by dividing the entire frequency span;
a center frequency setting unit (23) for setting the center frequency of each segment based on the frequency bandwidth of each segment;
a waveform data capture section (10) for receiving and sampling a signal under measurement in a predetermined frequency bandwidth wider than the frequency bandwidth of each segment with reference to the center frequency of each segment, and capturing waveform data for each segment; ,
a spectrum acquisition unit (51) that performs Fourier transform processing on the waveform data of each segment and acquires a spectrum for each segment;
a spectrum extraction unit (52) for extracting a spectrum corresponding to the frequency bandwidth of each segment from the spectrum of each segment, excluding both ends of the frequency;
a spectrum combiner (53) for combining the extracted spectrum of each segment to obtain the entire spectrum corresponding to the entire frequency span ;
The frequency bandwidth setting unit sets a frequency bandwidth (BW _n,L ) on the lower side and a frequency bandwidth (BW _n,H ) on the higher side than the center frequency of each segment,
The center frequency setting unit, based on the frequency bandwidth (BW _n,L ) on the lower side and the frequency bandwidth (BW _n,H ) on the higher side than the center frequency of each segment, from the center frequency of the center segment , for setting the center frequency offset (CF _n ) of each of said segments . The frequency bandwidth setting unit is configured such that the sum of the frequency bandwidths of the segments is equal to the entire frequency span, and the frequency bandwidth of the segments is narrower than the frequency bandwidth that can be captured by the waveform data capture unit. 2. The signal analysis apparatus according to claim 1, wherein the frequency bandwidth of each segment is set such that The center frequency setting unit is expressed by the following equation

Calculate the offset of the center frequency of each said segment from the center frequency of said center segment by, where:
CF _+m is the center frequency offset from the center frequency of the center segment in the m-th segment on the higher frequency side than the center segment;
CF _−m is the center frequency offset from the center frequency of the center segment in the m-th segment on the lower frequency side than the center segment;
BW _+m,L is a one-side frequency bandwidth extracted on the side lower than the center frequency of the segment from the Fourier transform result of the m-th segment on the side of the frequency higher than the center segment,
BW _{+ m,H} is a one-sided frequency bandwidth extracted on the side higher than the center frequency of the segment from the Fourier transform result of the m-th segment on the side of the frequency higher than the center segment;
BW- _m,L is a one-side frequency bandwidth extracted on the side lower than the center frequency of the segment from the Fourier transform result of the m-th segment on the side of the frequency lower than the center segment,
BW- _m,H is a one-side frequency bandwidth extracted on the side higher than the center frequency of the segment from the Fourier transform result of the m-th segment on the side of the frequency lower than the center segment, according to claim 1 or 2 Signal analyzer. Further comprising a Fourier transform point number setting unit (25) for setting, for each segment, the number of Fourier transform points of the Fourier transform process to be applied to the waveform data of each segment, based on the frequency bandwidth of each segment;
The signal analysis apparatus according to any one of claims 1 to 3 , wherein said spectrum acquisition section (51) performs Fourier transform processing based on the number of Fourier transform points set for each segment. 5. The signal analysis apparatus according to claim 4 , wherein said Fourier transform point number setting unit sets the number of Fourier transform points of each segment such that the frequency resolutions of trace points in each segment are equal to each other. further comprising a trace point number setting unit (26) for setting, for each segment, the number of trace points of the spectrum extracted by the spectrum extraction unit based on the frequency characteristics of the Fourier transform processing in the spectrum acquisition unit;
The spectrum extraction unit extracts a spectrum based on the number of trace points set for each segment,
The signal analysis apparatus according to any one of claims 1 to 5 , wherein said spectrum combiner combines the spectrums of said segments using the trace points at the ends of said segments as spectrum combining positions. further comprising: a storage unit (30) for storing waveform data acquired by the waveform data capture unit; and a modulation analysis unit (40) for performing modulation analysis using the waveform data stored in the storage unit; The signal analysis apparatus according to any one of claims 1 to 6 , wherein the acquisition section applies Fourier transform processing to the waveform data stored in the storage section and acquires a spectrum for each segment. a frequency bandwidth setting unit (24) for setting the frequency bandwidth of each segment obtained by dividing the entire frequency span;
a center frequency setting unit (23) for setting the center frequency of each segment based on the frequency bandwidth of each segment;
a waveform data capture section (10) for receiving and sampling a signal under measurement in a predetermined frequency bandwidth wider than the frequency bandwidth of each segment with reference to the center frequency of each segment, and capturing waveform data for each segment; ,
a spectrum acquisition unit (51) that performs Fourier transform processing on the waveform data of each segment and acquires a spectrum for each segment;
a spectrum extraction unit (52) for extracting a spectrum corresponding to the frequency bandwidth of each segment from the spectrum of each segment, excluding both ends of the frequency;
a spectrum combiner (53) for combining the extracted spectrum of each segment to obtain the entire spectrum corresponding to the entire frequency span;
The signal analysis device, wherein the center frequency setting unit sets the center frequency of each segment to a multiple of the frequency resolution of the trace points when the frequency resolution of the trace points of each segment is the same for all segments. a frequency bandwidth setting unit (24) for setting the frequency bandwidth of each segment obtained by dividing the entire frequency span;
a center frequency setting unit (23) for setting the center frequency of each segment based on the frequency bandwidth of each segment;
a waveform data capture section (10) for receiving and sampling a signal under measurement in a predetermined frequency bandwidth wider than the frequency bandwidth of each segment with reference to the center frequency of each segment, and capturing waveform data for each segment; ,
a spectrum acquisition unit (51) that performs Fourier transform processing on the waveform data of each segment and acquires a spectrum for each segment;
a spectrum extraction unit (52) for extracting a spectrum corresponding to the frequency bandwidth of each segment from the spectrum of each segment, excluding both ends of the frequency;
a spectrum combiner (53) for combining the extracted spectrum of each segment to obtain the entire spectrum corresponding to the entire frequency span;
The center frequency setting unit sets the center frequency of each segment to the trace when the frequency resolution of the trace points of each segment is different in at least one segment and the sampling rate of the waveform data capture unit is the same for all segments. Signal analyzer set to common multiple of frequency resolution of points. a frequency bandwidth setting unit (24) for setting the frequency bandwidth of each segment obtained by dividing the entire frequency span;
a center frequency setting unit (23) for setting the center frequency of each segment based on the frequency bandwidth of each segment;
a waveform data capture section (10) for receiving and sampling a signal under measurement in a predetermined frequency bandwidth wider than the frequency bandwidth of each segment with reference to the center frequency of each segment, and capturing waveform data for each segment; ,
a spectrum acquisition unit (51) that performs Fourier transform processing on the waveform data of each segment and acquires a spectrum for each segment;
a spectrum extraction unit (52) for extracting a spectrum corresponding to the frequency bandwidth of each segment from the spectrum of each segment, excluding both ends of the frequency;
a spectrum combiner (53) for combining the extracted spectrum of each segment to obtain the entire spectrum corresponding to the entire frequency span;
The center frequency setting unit is arranged such that the frequency resolution of the trace points of each segment is different in at least one segment, the sampling rate of the waveform data capture unit is different in at least one segment, and the sampling rate is different between segments. , the center frequency of each segment is set to a multiple of the largest of the frequency resolutions of the trace points, if the relation is a power of two. setting the frequency bandwidth of each segment obtained by dividing the entire frequency span (S3);
setting the center frequency of each segment based on the frequency bandwidth of each segment (S4);
receiving and sampling the signal under measurement in a predetermined frequency bandwidth wider than the frequency bandwidth of each segment with reference to the center frequency of each segment, and capturing waveform data for each segment (S5 to S9);
a step of subjecting the waveform data of each segment to Fourier transform processing to obtain a spectrum for each segment (S12);
a step of extracting a spectrum for the frequency bandwidth of each segment by excluding both ends of the frequency from the spectrum of each segment (S14);
a step of combining the extracted spectrums of the respective segments to obtain an entire spectrum corresponding to the entire frequency span (S16);
including
In the step of setting the frequency bandwidth, setting a frequency bandwidth (BW _n,L ) on the lower side and a frequency bandwidth (BW _n,H ) on the higher side than the center frequency of each segment;
In the step of setting the center frequency, based on the frequency bandwidth (BW _n,L ) on the lower side and the frequency bandwidth (BW _n,H ) on the higher side than the center frequency of each segment, the center of the center segment A signal analysis method of setting the center frequency offset (CF _n ) of each said segment from frequency.

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