JP2016136123A - Frequency characteristic measurement system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a frequency characteristic measurement system capable of easily measuring frequency characteristics even when the input part and output part of a transmission path are spatially separated from each other.SOLUTION: A frequency characteristic measurement system 1 includes a signal generator 10 and a signal level measurement instrument 20, and the signal generator 10 includes a noise generation part 11 for generating a wide band of noise signals in the frequency band of a broadcast wave, and for outputting the noise signals to a transmission path, and the signal level measurement instrument 20 includes: a level detection part 22 for detecting components of a plurality of frequencies from the electric signal of the transmission path, and for measuring signal strength of each frequency; and a control part 23 for outputting frequency characteristic information on the basis of the signal strength of each frequency.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a system for measuring frequency characteristics in a transmission path of a high-frequency signal.

2. Description of the Related Art Conventionally, as one of measuring devices for frequency characteristics in a high-frequency signal transmission line, there is a device incorporating a high-frequency signal generation unit and a high-frequency signal level measurement unit. The measuring system assumed by this measuring instrument has an electric signal input section and an output section in the vicinity of the measuring instrument, and a signal cable for connecting the measuring instrument and the electric signal input section to the measured system, and The signal cable connecting the output part of the electrical signal from the system under measurement and the level measurement part of the measuring instrument is sufficiently short, and these frequency characteristics do not affect the measured values of the system under measurement.
As an apparatus for measuring a signal level at an output portion of an electric signal, for example, Patent Document 1 discloses a signal level measuring apparatus that measures and analyzes a received signal from an antenna.

Japanese Patent Laid-Open No. 2005-90996

However, for example, when measuring frequency characteristics of a transmission system having a signal input unit on the roof of a high-rise building and a signal output unit on the first floor, if the measuring instrument is installed on the roof, the signal output unit and measuring instrument on the first floor A signal cable for connecting the level measuring unit must be installed separately. Conversely, when the measuring instrument is installed on the first floor, a signal cable for connecting the signal input unit on the roof and the signal generating unit of the measuring instrument must be separately laid.
In general, when the laying cable is long as described above, the frequency characteristic cannot be ignored, and it is necessary to remove the frequency characteristic of the laying cable from the data measured by the level measuring unit of the measuring instrument. Some measuring instruments have a function that eliminates the frequency characteristics of the laying cable, but they are expensive due to their high functionality. Furthermore, it takes time to install a long cable for measurement. In some cases, the cable cannot be laid practically due to circumstances such as safety measures.

Therefore, as one of the conventional level measurement methods, a high-frequency signal generator and a high-frequency signal level measurement device may be used. In this case, a high-frequency signal generator is installed at the input portion of the electrical signal to the system to be measured, and the high-frequency signal is input. Then, a high-frequency signal level measuring device is installed at the output part of the electrical signal from the system under measurement, and the level of the high-frequency signal output from the output part of the system under measurement is measured.
In the case of this measurement method, even if the input part and the output part of the electric signal of the system under measurement are spatially separated, there is no need to lay a signal cable for measurement, so there are few restrictions during measurement. However, the high-frequency signal generator and the high-frequency signal level measuring device are synchronized, that is, the frequency output from the high-frequency signal generator is the same as the frequency that the high-frequency signal level measuring device is measuring. Must match. In reality, it is difficult to synchronize two devices that are separated from each other. Therefore, the generator of the high-frequency signal continuously generates a high-frequency signal having a certain bandwidth and inputs it to the system under test. To do. The high-frequency signal level measuring device has difficulty in efficiency because it measures the level of the high-frequency signal in the band output from the system to be measured asynchronously, and the period of stoppage of the broadcast wave for measurement is also long.

  An object of the present invention is to provide a frequency characteristic measurement system that can easily measure frequency characteristics even when an input unit and an output unit of a transmission line are spatially separated.

  A frequency characteristic measuring system according to the present invention includes a signal generator and a signal level measuring device, and the signal generator generates a noise signal having a wide band in a frequency band of a broadcast wave and outputs the noise signal to a transmission line. The signal level measuring device detects a plurality of frequency components from the electrical signal of the transmission line, and measures a signal strength for each frequency, and a frequency characteristic based on the signal strength for each frequency An output unit for outputting information.

According to this configuration, since the frequency characteristic measurement system separates the signal generator and the signal level measurement device, transmission is possible even when the signal input unit and the signal output unit of the transmission line to be measured are spatially separated. The frequency characteristics of the transmission line can be easily measured without considering the characteristics of the connection cable to the path.
At this time, the frequency characteristic measurement system inputs a broadband noise signal to the transmission line, thereby easily and efficiently without synchronizing the signal generator and the signal level measurement device when detecting the signal level. The signal level of the target frequency can be measured.

  The noise generation unit may generate white noise as the broadband noise signal.

  According to this configuration, the frequency characteristic measurement system inputs white noise to the transmission line as a broadband noise signal. Accordingly, since the signal level at the signal input unit is known, the frequency characteristic measurement system can easily determine the frequency characteristic of the transmission line by measuring the signal level at the signal output unit. In addition, since the synchronization mechanism is reduced and the signal generation mechanism is simplified, the manufacturing costs of the signal generator and the signal level measuring device are reduced.

  The signal generator may include an output switching unit that switches between an input signal of the broadcast wave and noise generated by the noise generation unit and outputs the switched signal to the transmission path.

  According to this configuration, when the signal generator is inserted in the middle of the transmission path, it is generated by the noise generator as a signal output from the signal generator and a broadcast wave signal being transmitted to the transmission path. The noise signal for measurement can be output only when measurement is performed by switching the noise signal. Therefore, the frequency characteristic measurement system can easily switch between the actual operation of the transmission path by the broadcast wave and the signal transmission for the measurement of the frequency characteristic, thereby reducing the stop time of the broadcast wave for measurement. Operational restrictions can be reduced.

  The measurement unit may measure signal strength at specified frequency intervals in the frequency band.

  According to this configuration, the signal level measuring device can limit the measurement frequency in the frequency band to be measured by measuring the signal strength at a specified frequency interval, so that the frequency characteristic indicating the relationship between the transmission frequency and the transmission loss. Therefore, the processing load and the manufacturing cost can be reduced.

  The signal level measuring device includes a storage unit that directly inputs an output signal from the signal generator and stores the signal strength of each of the plurality of frequencies of the input signal as calibration data, and the output unit includes: The frequency characteristic information may be output based on a difference between the calibration data and a signal strength of an electrical signal that has passed through the transmission path, measured by the measurement unit.

  According to this configuration, the frequency characteristic measurement system stores the noise signal information output from the signal generator as calibration data, and obtains the frequency characteristic of the transmission path as a difference from the measurement data. Therefore, the frequency characteristic measurement system can be used as a reference signal even if the amplitude frequency characteristic in the measurement band is not flat and has a low stability, and can improve the measurement accuracy of the frequency characteristic.

  The signal generator includes a first transmission unit that transmits a measurement start trigger signal to the signal level measurement device, and the measurement unit starts measurement in response to receiving the start trigger signal. May be.

  According to this configuration, the frequency characteristic measurement system can perform the measurement of the frequency characteristic without delay by transmitting the measurement start trigger signal from the signal generator to the signal level measurement device. As a result, the stop time of the broadcast wave for measurement is shortened, and operation restrictions are reduced.

  The signal level measuring device includes a second transmitting unit that transmits a measurement stop trigger signal to the signal generator, and the noise generating unit receives the stop trigger signal in response to receiving the stop trigger signal. May be stopped.

  According to this configuration, the frequency characteristic measurement system can stop the output of the noise signal to the transmission line without delay by transmitting the measurement stop trigger signal from the signal level measuring device to the signal generator. As a result, the stop time of the broadcast wave for measurement is shortened, and operation restrictions are reduced.

  According to the present invention, the frequency characteristic can be easily measured even when the input unit and the output unit of the transmission line are spatially separated.

It is a figure which shows the structural example of the frequency characteristic measuring system which concerns on embodiment. It is a figure which shows the function structure of the signal generator which concerns on embodiment. It is a figure which shows the function structure of the signal level measuring device which concerns on embodiment. It is a sequence diagram which shows the process of the frequency characteristic measurement system which concerns on embodiment.

Hereinafter, an example of an embodiment of the present invention will be described.
FIG. 1 is a diagram illustrating a configuration example of a frequency characteristic measurement system 1 according to the present embodiment.

  The frequency characteristic measuring system 1 includes a signal generator 10 that generates a high-frequency noise signal and a signal level measuring instrument 20 that measures the amplitude frequency characteristic of a transmission line in the frequency band of broadcast waves.

The signal generator 10 is provided, for example, in the vicinity of an end (input unit) of a transmission line A (coaxial cable or the like) in a building connected from a roof antenna of a building. Near the end (output unit) of the transmission line.
As described above, in the frequency characteristic measurement system 1, in the existing signal transmission system in which the input part and the output part of the electrical signal are separated in space and the signal transmission distance is long, the input of the signal input from the input part is performed. The relationship between the signal level and the output signal level of the signal appearing at the output unit is measured for each frequency.

FIG. 2 is a diagram illustrating a functional configuration of the signal generator 10 according to the present embodiment.
The signal generator 10 is inserted in the middle of the transmission line A to be measured or connected to the entrance of the transmission line A to be measured. The signal generator 10 includes a noise generation unit 11, an output switching unit 12, and a first transmission unit 13.

The noise generation unit 11 generates broadband high-frequency noise in the frequency band of the broadcast wave and provides it to the output switching unit 12. This high-frequency noise is white noise or similar noise that can be regarded as white noise, and has an equivalent output level over a wide frequency range.
Note that the noise generation unit 11 may change the output level of noise in accordance with a predetermined operation input.

  The output switching unit 12 switches between an electric signal of a broadcast wave that is input and transmitted to the transmission line to be measured and a high-frequency noise provided from the noise generation unit 11 and outputs the switched signal to the transmission line A to be measured.

  The first transmission unit 13 starts measurement with respect to the signal level measuring device 20 in response to a user operation or when the output switching unit 12 switches the output to the transmission line A to be measured to a noise signal. Send trigger signal.

FIG. 3 is a diagram illustrating a functional configuration of the signal level measuring device 20 according to the present embodiment.
The signal level measuring device 20 includes a high-frequency signal processing unit 21, a level detection unit 22 (measurement unit), a control unit 23 (output unit), a storage unit 24, a display unit 25, and an external interface (I / F). 26. The signal level measuring device 20 inputs a high frequency signal from the transmission line A to be measured, measures a signal level for each frequency, displays a frequency characteristic, or outputs data to an external device (for example, PC) connected by USB or the like. To do.

  The high-frequency signal processing unit 21 includes a low-noise amplifier and a mixer, amplifies a high-frequency signal (white noise) input from the transmission line A to be measured, mixes it with a LO (Local Oscillator) signal, and then IF (Intermediate Frequency). ) Generate a signal.

The level detection unit 22 includes, for example, a low noise amplifier, a PLL (Phase Locked Loop) as a high frequency transmitter, a VCO (Voltage Controlled Oscillator), a detection circuit that converts a signal of a predetermined frequency into a voltage value, and FSK (Frequency Shift Keying) demodulation. A circuit, an RSSI (Received Signal Strength Indicator) detection circuit, and the like.
The level detection unit 22 detects a plurality of frequency components in the frequency band to be measured when the control unit 23 controls the VCO, and outputs signal level data (RSSI) of the IF signal from the RSSI detection circuit.
The level detection unit 22 provides the LO signal to the high frequency signal processing unit 21.

In response to receiving the start trigger signal from the signal generator 10, the control unit 23 controls the VCO of the level detection unit 22, thereby acquiring signal intensities at a plurality of frequencies at designated frequency intervals. And the control part 23 is based on the difference of the signal strength for every frequency in the noise output from the signal generator 10, and the signal strength of the signal which passed through the acquired transmission path, and the amplitude frequency characteristic of a to-be-measured transmission line Output information (eg, level data).
At this time, the control unit 23 may read and use calibration data, which will be described later, from the storage unit 24 as the signal strength of the noise input to the transmission path. When white noise with a constant signal intensity at each frequency is input, the calculation with the calibration data may be omitted.

  The storage unit 24 obtains the signal strength (RSSI) for each frequency of the signal when the noise signal inputted without going through the transmission path is taken from the signal generator 10 directly connected to the signal level measuring device 20. Record as calibration data. Thereby, even if the output of the signal generator 10 is an unstable signal that cannot be regarded as white noise, the control unit 23 can exclude this signal characteristic from the measured frequency characteristic of the transmission path.

  The display unit 25 displays the amplitude frequency characteristic information output from the control unit 23 as numerical data or graph data such as a spectrum waveform and presents it to the user.

  The external interface 26 is a wired communication interface such as a USB or a wireless communication interface, and outputs amplitude frequency characteristic information as, for example, CSV format data to an external device such as a connected PC.

  The second transmission unit 27 transmits a measurement stop trigger signal to the signal generator 10 after the measurement of the signal level is completed. The signal generator 10 stops outputting the noise signal in response to receiving this stop trigger signal.

FIG. 4 is a sequence diagram showing processing of the frequency characteristic measurement system 1 according to the present embodiment.
In this processing, it is assumed that the calibration processing for the noise signal of the signal generator 10 is completed in the signal level measuring device 20 and the calibration data is stored.

In step S <b> 1, the signal generator 10 starts sending the noise signal generated by the noise generator 11 to the transmission path by the output switching unit 12.
In step S <b> 2, the signal generator 10 transmits a measurement start trigger signal to the signal level measuring device 20 by wired or wireless as means for synchronizing the measurement timing.

  In step S3, when the signal level measuring device 20 receives the start trigger signal, the signal level measuring device 20 executes a level measurement program of a frequency sampling method, thereby performing a signal at a specified frequency interval in a measurement band (for example, 0 to 3.0 GHz). Start amplitude level (RSSI) measurement.

  In step S4, the signal level measuring device 20 calibrates the measurement result. That is, the signal level measuring device 20 executes a signal calibration program as a means for calibrating the noise that is the reference signal, and obtains a difference between the measurement data and the calibration data stored in the storage unit 24 in advance, thereby transmitting the signal. The amplitude frequency characteristic information of the road is generated.

In step S5, the signal level measuring device 20 displays the spectrum waveform of the amplitude frequency characteristic on the display unit 25.
In step S6, the signal level measuring device 20 stores the spectrum waveform of the amplitude frequency characteristic as electronic data in the storage unit 24 or an external recording device so that it can be displayed or output later.

  In step S <b> 7, the signal level measuring device 20 transmits a measurement stop trigger signal to the signal generator 10 by wireless or wired as means for terminating the signal level measurement and synchronizing the measurement timing.

In step S8, when the signal generator 10 detects the stop trigger signal, the signal generator 10 stops outputting the noise signal. Specifically, the output switching unit 12 switches the output signal to the transmission path from the noise signal from the noise generating unit 11 to the broadcast wave. Further, the noise generator 11 may stop generating the noise signal.
Further, the signal generator 10 receives a stop trigger signal from the transmission of the start trigger signal, and when a predetermined time (for example, 10 seconds) elapses, the signal generator 10 receives an error or transmits / receives the stop trigger signal. The output of the noise signal may be stopped by determining that the signal has failed.

According to the present embodiment, since the frequency characteristic measurement system 1 separates the signal generator 10 and the signal level measurement device 20, the signal input unit and the signal output unit of the transmission line to be measured are spatially separated. In addition, the frequency characteristics of the transmission line can be easily measured without considering the characteristics of the connection cable with respect to the transmission line.
At this time, the frequency characteristic measurement system 1 inputs a broadband noise signal to the transmission line, so that the signal generator 10 and the signal level measurement device 20 are not easily synchronized when detecting the signal level. The signal level of the target frequency can be measured efficiently.

  Further, the frequency characteristic measurement system 1 inputs white noise as a broadband noise signal to the transmission line. Therefore, since the signal level at the signal input unit is known, the frequency characteristic measurement system 1 can easily obtain the frequency characteristic of the transmission line by measuring the signal level at the signal output unit. Further, since the synchronization mechanism is reduced and the signal generation mechanism is simplified, the manufacturing cost of the signal generator 10 and the signal level measuring device 20 is reduced.

  When the signal generator 10 is inserted in the middle of the transmission path, the signal generated from the signal generator 10 is a broadcast wave signal being transmitted to the transmission path, and the noise generated by the noise generator 11. A noise signal for measurement can be output only when switching between signals. Accordingly, the frequency characteristic measurement system 1 can easily switch between actual operation of a transmission path using broadcast waves and signal transmission for measurement of frequency characteristics, thereby shortening the stop time of the broadcast waves for measurement. Operational restrictions can be reduced.

  Since the signal level measuring device 20 can limit the measurement frequency in the frequency band to be measured by measuring the signal strength at a specified frequency interval, the signal level measuring device 20 roughly grasps the frequency characteristic indicating the relationship between the transmission frequency and the transmission loss. Therefore, the processing load and manufacturing cost can be reduced.

  Further, the frequency characteristic measurement system 1 stores information on the noise signal output from the signal generator as calibration data, and obtains the frequency characteristic of the transmission path as a difference from the measurement data. Therefore, the frequency characteristic measurement system 1 can be used as a reference signal even if it is a low-stability noise signal whose amplitude frequency characteristic in the measurement band is not flat, and can improve the measurement accuracy of the frequency characteristic.

  Further, the frequency characteristic measurement system 1 can perform the measurement of the frequency characteristic without delay by transmitting a measurement start trigger signal from the signal generator 10 to the signal level measuring instrument 20. As a result, the stop time of the broadcast wave for measurement is shortened, and operation restrictions are reduced.

  Further, the frequency characteristic measuring system 1 can stop the output of the noise signal to the transmission line without delay by transmitting a measurement stop trigger signal from the signal level measuring device 20 to the signal generator 10. As a result, the stop time of the broadcast wave for measurement is shortened, and operation restrictions are reduced.

  As mentioned above, although embodiment of this invention was described, this invention is not restricted to embodiment mentioned above. Further, the effects described in the present embodiment are merely a list of the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the present embodiment.

  In the present embodiment, the configuration and operation of the frequency characteristic measurement system have been mainly described. However, the present invention is not limited to this, and each component may be provided as a method or program for measuring frequency characteristics. Good.

  Further, the present invention may be realized by recording a program for realizing the function of the frequency characteristic measurement system on a computer-readable recording medium, causing the computer system to read and execute the program recorded on the recording medium. Good.

  The “computer system” here includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a portable medium such as a flexible disk, a magneto-optical disk, a ROM, and a CD-ROM, and a hard disk built in the computer system.

  Furthermore, “computer-readable recording medium” means that a program is dynamically held for a short time, like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. It is also possible to include one that holds a program for a certain time, such as a volatile memory inside a computer system that becomes a server or client in that case. Further, the program may be for realizing a part of the above-described functions, and may be capable of realizing the above-described functions in combination with a program already recorded in the computer system. .

DESCRIPTION OF SYMBOLS 1 Frequency characteristic measurement system 10 Signal generator 11 Noise generation part 12 Output switching part 13 1st transmission part 20 Signal level measuring device 21 High frequency signal processing part 22 Level detection part (measurement part)
23 Control unit (output unit)
24 storage unit 25 display unit 26 external interface 27 second transmission unit

Claims (7)

A frequency characteristic measuring system having a signal generator and a signal level measuring instrument,
The signal generator is
A noise generator that generates a broadband noise signal in the frequency band of the broadcast wave and outputs it to the transmission line,
The signal level measuring instrument is
Detecting a plurality of frequency components from the electrical signal of the transmission line, and measuring a signal intensity for each frequency;
An output unit that outputs frequency characteristic information based on the signal intensity for each frequency.   The frequency characteristic measurement system according to claim 1, wherein the noise generation unit generates white noise as the broadband noise signal.   The frequency characteristic measurement system according to claim 1, wherein the signal generator includes an output switching unit that switches an input signal of the broadcast wave and noise generated by the noise generation unit and outputs the switched signal to the transmission path.   The frequency characteristic measurement system according to any one of claims 1 to 3, wherein the measurement unit measures signal strength at a specified frequency interval in the frequency band. The signal level measuring device includes a storage unit that directly inputs an output signal from the signal generator and stores the signal intensity of each of the plurality of frequencies of the input signal as calibration data;
5. The output unit according to claim 1, wherein the output unit outputs the frequency characteristic information based on a difference between the calibration data and a signal strength of an electric signal that has passed through the transmission path, measured by the measurement unit. The frequency characteristic measurement system described in 1. The signal generator includes a first transmission unit that transmits a measurement start trigger signal to the signal level measuring device,
The frequency characteristic measurement system according to claim 1, wherein the measurement unit starts measurement in response to receiving the start trigger signal. The signal level measuring device includes a second transmission unit that transmits a measurement stop trigger signal to the signal generator,
The frequency characteristic measurement system according to any one of claims 1 to 6, wherein the noise generation unit stops the output of the noise signal in response to receiving the stop trigger signal.

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