JP2018080931A - Measurement apparatus and measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measurement apparatus and a measurement method that are simple in structure and that are capable of measuring a broad band signal.SOLUTION: A spectrum analyzer 10 includes a mixer 12 for frequency-converting a signal under measurement, an ADC 19 for converting an analog signal into a digital signal, a mixer route 25 and a frequency divider route 26 that are provided between the mixer 12 and the ADC 19, a mixer selector switches 13 and 18 for selecting one of the mixer route 25 and the frequency divider route 26, a mixer 15 for frequency-converting an output signal of the mixer 12 in the mixer route 25, and a frequency divider 17 for dividing the frequency of an output signal of the mixer 12 in the frequency divider route 26 in accordance with a predetermined frequency division ratio.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a measuring apparatus and a measuring method capable of measuring a broadband signal.

  For example, a millimeter wave radar is known that measures the distance between vehicles with high accuracy using millimeter wave radio waves. In recent years, the development of 79 GHz band radars that enable wide-angle detection with high resolution compared to 77 GHz band radars that have already been put into practical use is in progress. A chirp signal having a wide frequency bandwidth of a maximum of 4 GHz is used for a 79 GHz band radar adopting an FMCW (Frequency Modulated Continuous Wave) system.

  Conventionally, in order to capture and measure this type of broadband chirp signal, a method of measuring by connecting a broadband oscilloscope to a spectrum analyzer has been proposed (for example, see Non-Patent Document 1).

“Infiniium Oscilloscopes Used for Wideband RF Measurements”, [online], Keysight Technologies, [October 20, 2016 search], Internet <URL: http://www.keysight.com/main/redirector.jspx?action= ref & cname = EDITORIAL & ckey = 2753752 & lc = eng & cc = US & nfr = -11143.0.00>

  However, since the conventional measurement apparatus is configured by combining a spectrum analyzer and an oscilloscope, there has been a problem that the measurement becomes complicated due to a complicated measurement system.

  The present invention has been made to solve the conventional problems, and an object of the present invention is to provide a measuring apparatus and a measuring method capable of measuring a broadband signal with a simple configuration.

  The measuring apparatus according to claim 1 of the present invention includes a first frequency converting means (12) for converting the frequency of a signal under measurement, a signal converting means (19) for converting an analog signal into a digital signal, and the first Route selection means (13) for selecting one of the first and second paths (25, 26) provided between the frequency conversion means and the signal conversion means and the first and second paths. 18), second frequency converting means (15) for converting the frequency of the output signal of the first frequency converting means in the first path, and of the first frequency converting means in the second path. Frequency division means (17) for dividing the output signal into a predetermined frequency division ratio.

  With this configuration, the measuring apparatus according to claim 1 of the present invention can select either the first path that passes through the second frequency conversion means or the second path that passes through the frequency dividing means. When the second path is selected, a wideband signal can be measured by extending the apparent frequency bandwidth of the signal conversion means using the frequency dividing means.

  Therefore, the measuring apparatus according to claim 1 of the present invention can measure a broadband signal with a simple configuration.

  The measuring apparatus according to a second aspect of the present invention has a configuration in which the path selection means selects the second path in measurement that does not require amplitude information of the signal under measurement.

  With this configuration, the measurement apparatus according to claim 2 of the present invention can measure a broadband signal with a simple configuration in measurement that does not require amplitude information of the signal under measurement.

  The measuring apparatus according to claim 3 of the present invention has a configuration in which the first frequency converting means performs frequency conversion of a signal whose frequency continuously changes with time as the signal under measurement.

  With this configuration, the measurement apparatus according to claim 3 of the present invention can measure a broadband signal with a simple configuration with respect to a signal whose frequency continuously changes with time.

  A measurement method according to a fourth aspect of the present invention is a measurement method using the measurement apparatus (10) according to the first aspect, wherein a first signal to be measured is frequency-converted by the first frequency conversion means. Frequency conversion step (S13, S16), signal conversion step (S18) for converting an analog signal into a digital signal by the signal conversion means, and one of the first and second paths by the path selection means A path selection step (S12, S15) to be selected, and a second frequency conversion step (S17) in which the output signal of the first frequency conversion step is frequency-converted in the first path by the second frequency converting means. A frequency dividing step (S14) for dividing the output signal of the first frequency conversion step into a predetermined frequency dividing ratio in the second path by the frequency dividing means; And it has a non-configuration.

  With this configuration, the measurement method according to claim 4 of the present invention can select either the first path that passes through the second frequency converting means or the second path that passes through the frequency dividing means. When the second path is selected, a wideband signal can be measured by extending the apparent frequency bandwidth of the signal conversion means in the frequency division step.

  Therefore, the measurement method according to claim 4 of the present invention can measure a broadband signal with a simple configuration.

  The present invention can provide a measuring apparatus and a measuring method having an effect that a broadband signal can be measured with a simple configuration.

It is a block block diagram of the spectrum analyzer in one Embodiment of this invention. It is explanatory drawing of the frequency linearity in the transmission signal of the FMCW system in one Embodiment of this invention. It is a block diagram which shows the main structures when a frequency divider route is selected by the changeover switch in one Embodiment of this invention. It is a figure which shows an example of the input frequency and output frequency of the frequency divider in one Embodiment of this invention. It is a flowchart of the spectrum analyzer in one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. An example in which the measurement apparatus according to the present invention is applied to a spectrum analyzer will be described.

  First, the configuration of the spectrum analyzer in one embodiment of the present invention will be described.

  As shown in FIG. 1, the spectrum analyzer 10 in this embodiment measures the characteristics of the output signal of a DUT (device under test) 1.

  In the present embodiment, the DUT 1 is a device that can be used in, for example, an FMCW radar device mounted on a vehicle and can output a chirp signal having a frequency bandwidth of 4 GHz as a signal under measurement. Hereinafter, an example in which the spectrum analyzer 10 measures the chirp signal will be described.

  The spectrum analyzer 10 includes a local oscillator 11, a mixer 12, a change-over switch 13, a local oscillator 14, a mixer 15, a BPF (bandpass filter) 16, a frequency divider 17, a change-over switch 18, an ADC (analog-to-digital converter) 19, and a measurement. Unit 20, display unit 21, operation unit 22, and control unit 23.

  The local oscillator 11 generates a local oscillation signal having a predetermined frequency and outputs it to the mixer 12.

  The mixer 12 converts the signal under measurement output from the DUT 1 into a predetermined IF (intermediate frequency) signal. Specifically, the mixer 12 mixes the signal under measurement output from the DUT 1 and the local oscillation signal generated by the local oscillator 11 and converts the frequency into an IF signal, and outputs the frequency-converted IF signal to the changeover switch 13. It is supposed to be. The mixer 12 is composed of, for example, a waveguide mixer, and is an example of a first frequency conversion unit.

  The changeover switch 13, together with the changeover switch 18, in accordance with a control signal from the control unit 23, a route via the mixer 15 and the BPF 16 (hereinafter referred to as “mixer route 25”) and a route via the frequency divider 17 (hereinafter referred to as “mixer route 25”) "Divisor route 26"). The mixer route 25 and the divider route 26 are examples of first and second routes, respectively. The changeover switches 13 and 18 are examples of route selection means.

  The local oscillator 14 generates a local oscillation signal having a predetermined frequency and outputs it to the mixer 15.

  The mixer 15 converts the output signal of the changeover switch 13, that is, the output signal of the mixer 12, into a predetermined IF signal. Specifically, the mixer 15 mixes the IF signal (for example, 1875 MHz) output from the mixer 12 and the local oscillation signal (for example, 1800 MHz) generated by the local oscillator 14 and converts the frequency into an IF signal (for example, 75 MHz). The frequency-converted IF signal is output to the BPF 16. The mixer 15 is an example of second frequency conversion means.

  The BPF 16 filters the output signal of the mixer 15, extracts a signal in a predetermined frequency region, and outputs it to the changeover switch 18.

  The frequency divider 17 divides the output signal of the changeover switch 13, that is, the output signal of the mixer 12 into a predetermined frequency division ratio, and outputs the result to the changeover switch 18. The frequency divider 17 is an example of frequency dividing means. In the present embodiment, the frequency divider 17 divides the frequency of the input signal by 1/32.

  The ADC 19 converts an analog signal output from the changeover switch 18 into a digital signal. The ADC 19 is an example of a signal conversion unit.

  The measurement unit 20 includes a waveform memory that stores the output signal of the ADC 19 and performs a predetermined measurement on the stored signal. For example, the measurement unit 20 performs frequency linearity (linearity), amplitude flatness, phase noise, amplitude noise, spurious, Occupied frequency Band Width (OBW), etc. on the chirp signal output from the DUT 1. Measure. Of these measurement items of the chirp signal, in the measurement of frequency linearity, only phase information (frequency information) is necessary, and amplitude information is not necessary.

  The display unit 21 displays the measurement result of the measurement unit 20, measurement conditions, and the like.

  The operation unit 22 is operated by the user to set measurement items, measurement conditions, determination conditions, and the like for measuring the signal under measurement.

  The control unit 23 sets various information input by the operation unit 22 in each unit of the spectrum analyzer 10.

  The control unit 23 determines whether or not the amplitude information of the signal under measurement is necessary for the measurement item set by the operation unit 22. For example, in the measurement item of the chirp signal described above, information that amplitude information is necessary for measurement of amplitude flatness, phase noise, amplitude noise, spurious, and occupied frequency bandwidth, and information that amplitude information is unnecessary for measurement of frequency linearity is stored in memory ( The control unit 23 determines whether or not the amplitude information of the signal under measurement is necessary for the measurement item set by the operation unit 22 based on the stored information. It is.

  Next, measurement of the frequency linearity of the chirp signal will be described with reference to FIG. FIG. 2 is a schematic diagram for explaining frequency linearity in an FMCW transmission signal (chirp signal). In FIG. 2, the horizontal axis represents a time axis and the vertical axis represents a frequency axis, and an ideal transmission signal 31 (broken line) and a transmission signal 32 to be measured (solid line) are shown. The transmission signals 31 and 32 are signals (chirp signals) whose frequencies change continuously with time, and have a frequency bandwidth of 4 GHz.

  In the FMCW radar device, a frequency-modulated transmission signal as indicated by a broken line in FIG. 2 is radiated as a millimeter-wave band radar wave. Then, the reflected wave returned from the radar wave reflected by the target is received by the receiving antenna, and the received signal and the transmitted signal are used to measure the target such as the distance to the target and the relative speed of the target. The target information regarding is detected.

  Therefore, in order to detect the target information with high accuracy in the FMCW radar device, it is desirable that the frequency linearity of the transmission signal is higher. Therefore, the frequency linearity of the transmission signal 32 to be measured is measured.

  Next, the function of the frequency divider 17 in this embodiment will be described with reference to FIGS. FIG. 3 shows a main configuration when the frequency divider route 26 is selected by the changeover switches 13 and 18. FIG. 4 is a diagram illustrating an example of an input frequency and an output frequency of the frequency divider 17. The case where the frequency divider route 26 is selected is a case where only the phase information (frequency information) of the signal under measurement is required and the amplitude information is unnecessary, for example, the measurement of the frequency linearity of the chirp signal. .

  As shown in FIG. 3, the frequency divider 17 in this embodiment receives an IF signal from the mixer 12, divides the frequency of the input IF signal by 1/32, and outputs it to the ADC 19.

  The mixer 12 is assumed to receive a signal under measurement of 78.2 GHz to 82.2 GHz from the DUT 1. In addition, the mixer 12 is assumed to receive a signal having a local oscillation frequency of 77 GHz from the local oscillator 11. In this configuration, the mixer 12 outputs a signal under measurement of 1.2 GHz to 5.2 GHz (center frequency 3.2 GHz).

  The ADC 19 has a frequency bandwidth of 125 MHz and can sample at 400 MHz.

  In this configuration, frequencies that can be input / output by the frequency divider 17 are as shown in FIG. That is, the input frequency of the IF signal input by the frequency divider 17 is 1.2 GHz to 5.2 GHz (center frequency 3.2 GHz), and the frequency bandwidth is 4 GHz.

  Since the frequency divider 17 divides the frequency of the input IF signal by 1/32, the output frequency of the IF signal output from the frequency divider 17 is 37.5 MHz to 162.5 MHz (as shown in FIG. The center frequency is 100 MHz) and the frequency bandwidth is 125 MHz.

  Therefore, when the frequency divider route 26 is selected, the spectrum analyzer 10 in this embodiment can apparently expand the frequency bandwidth 125 MHz of the ADC 19 to 4000 MHz (4 GHz).

  Moreover, since the spectrum analyzer 10 in the present embodiment is configured to divide by the frequency divider 17 in the frequency divider route 26, the phase information is not lost.

  Furthermore, since the spectrum analyzer 10 according to the present embodiment has a configuration in which the frequency divider 17 is used without performing the down-conversion process in order to convert the IF signal to a lower frequency, it is an unnecessary signal generated in the down-conversion process. There is no problem with image signals.

  Next, the operation of the spectrum analyzer 10 in the present embodiment will be described with reference to FIG.

  The control unit 23 determines whether or not the amplitude information of the signal under measurement is necessary for the measurement item set by the operation unit 22 (step S11). Specifically, for example, when the measurement item set by the operation unit 22 is frequency linearity, the control unit 23 determines that the amplitude information is unnecessary, and amplitude flatness, phase noise, amplitude noise, spurious, occupation If it is a frequency bandwidth, it is determined that amplitude information is necessary.

  In step S11, when the control unit 23 determines that the amplitude information is unnecessary (No), the control unit 23 controls the changeover switches 13 and 18 to select the frequency divider route 26 (step S12).

  The mixer 12 mixes the signal under measurement output from the DUT 1 and the local oscillation signal generated by the local oscillator 11 and converts the frequency into an IF signal having a predetermined first frequency (step S13). Is output to the changeover switch 13.

  The frequency divider 17 divides the IF signal input from the changeover switch 13 into a predetermined frequency division ratio (1/32 in this embodiment) (step S14), and the frequency-divided IF signal passes through the changeover switch 18 to the ADC 19. Output to.

  On the other hand, in step S11, when it is determined that amplitude information is necessary (Yes), the control unit 23 controls the changeover switches 13 and 18 to select the mixer route 25 (step S15).

  The mixer 12 mixes the signal under measurement output from the DUT 1 and the local oscillation signal generated by the local oscillator 11 and converts the frequency into an IF signal (step S16). 15 is output.

  The mixer 15 mixes the IF signal from the mixer 12 and the local oscillation signal generated by the local oscillator 14 and converts the frequency into an IF signal having a predetermined second frequency (step S17). Output to BPF16. The BPF 16 performs filtering of the output signal of the mixer 15, extracts a signal in a predetermined frequency region, and outputs the signal to the ADC 19 via the changeover switch 18.

  The ADC 19 converts the IF signal from the mixer route 25 or the frequency divider route 26 from an analog value to a digital value (step S18).

  The measurement unit 20 measures a digital value signal from the ADC 19 for the measurement item set by the operation unit 22 (step S19).

  The display unit 21 displays the measurement result of the measurement unit 20 (step S20).

  As described above, the spectrum analyzer 10 according to the present embodiment can select either the mixer route 25 that passes through the mixer 15 or the divider route 26 that passes through the frequency divider 17. When the instrument route 26 is selected, the apparent frequency bandwidth can be expanded without losing the phase information, so that a wideband signal can be measured with a simple configuration.

  As described above, the measuring apparatus and the measuring method according to the present invention have an effect of being able to measure a broadband signal with a simple configuration, and are useful as a measuring apparatus and a measuring method capable of measuring a broadband signal. is there.

1 DUT (device under test)
10 Spectrum analyzer (measuring device)
12 mixer (first frequency conversion means)
13, 18 changeover switch (route selection means)
15 mixer (second frequency conversion means)
17 Divider (Divisor means)
19 ADC (signal conversion means)
25 Mixer route (first route)
26 Divider route (second route)

Claims (4)

First frequency conversion means (12) for converting the frequency of the signal under measurement;
Signal converting means (19) for converting an analog signal into a digital signal;
First and second paths (25, 26) provided between the first frequency converting means and the signal converting means;
Route selection means (13, 18) for selecting one of the first and second routes;
Second frequency converting means (15) for frequency converting the output signal of the first frequency converting means in the first path;
Frequency dividing means (17) for dividing the output signal of the first frequency converting means to a predetermined frequency dividing ratio in the second path;
A measuring device (10) comprising:   2. The measuring apparatus according to claim 1, wherein the path selecting unit selects the second path in measurement that does not require amplitude information of the signal under measurement.   The measuring apparatus according to claim 1 or 2, wherein the first frequency converting means converts a signal whose frequency continuously changes with time as the signal under measurement. A measuring method using the measuring device (10) according to claim 1,
A first frequency conversion step (S13, S16) for frequency-converting the signal under measurement by the first frequency conversion means;
A signal converting step (S18) for converting an analog signal into a digital signal by the signal converting means;
A route selection step (S12, S15) for selecting one of the first and second routes by the route selection means;
A second frequency converting step (S17) for converting the frequency of the output signal of the first frequency converting step in the first path by the second frequency converting means;
A frequency dividing step (S14) for dividing the output signal of the first frequency conversion step into a predetermined frequency dividing ratio in the second path by the frequency dividing means;
A measurement method comprising:

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