JP2011004060A - Automatic noise control device in catv line and catv system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic noise control device in a CATV line, which achieves introduction to a CATV system without fixing a frequency use plan of an up line into the future, and to provide the CATV system.SOLUTION: An arbitrary frequency at which a noise level should be measured is selected by an automatic noise control indication received from a control center. In accordance with an all band measurement indication received from the control center, a frequency setting means (MCU 6) sets a center frequency of a noise level measurement means 2 while automatically successively changing the center frequency at fixed intervals within a range of a frequency band of the up line, and digital data resulting from measurement by the noise level measurement means during the successive change of the center frequency of the noise level measurement means is stored in a storage means (MCU 6), and a transmission means (MCU 6) transmits the digital data resulting from the measurement, which is stored in the storage means, to the control center.

Description

  The present invention relates to an automatic noise control apparatus and a CATV system in a CATV line, and more particularly, in a CATV line that automatically reduces noise that joins an upstream line of a CATV line that performs bidirectional communication between a control center and a home terminal. The present invention relates to an automatic noise control device and a CATV system.

    In general, since the network of the CATV system is a tree type, when the noise from each home terminal gets on the network, the noise from each home terminal gathers on the uplink to the control center and interferes with the normal signal. May not be able to communicate. This noise is usually called upstream inflow noise. Therefore, in order to ensure normal communication, it is necessary to suppress this upstream inflow noise. Noise sources that cause upstream inflow noise include radio waves of shortwave broadcasting, which is a frequency source in the upstream band, and spurious components generated from household appliances such as refrigerators and vacuum cleaners.

  Therefore, in a conventional CATV system that performs bidirectional data communication with a plurality of transmission / reception devices connected in a tree shape to a control center having a broadcasting function via a CATV network, upstream inflow on the CATV line of the network In order to prevent noise from being detected at an early stage and disconnect necessary parts, and to prevent communication problems due to an increase in upstream inflow noise on the upstream side, each of the transmission / reception apparatuses is directed toward the control center. It has been proposed to detect the level of infusion noise and disconnect the uplink on the upstream side of the detection point of infusion noise when the detected level of infusion noise exceeds a threshold value. (For example, refer to Patent Document 1.)

  In this proposed one, the uplink is disconnected because the upstream inflow noise level exceeds the threshold value, so the upstream upstream inflow noise level is equal to the noise level detected in the disconnected uplink. It can be simply reduced, and the adverse effect on bidirectional communication at other home terminals can be eliminated. However, the home terminal whose uplink has been disconnected cannot perform two-way communication. In particular, when there are a large number of home terminals downstream of this disconnection point, such as an apartment house such as a condominium, the influence of the disconnection of the uplink is very large.

  Therefore, even if the noise level exceeds the threshold, depending on the noise level exceeding, it is possible to continue bi-directional communication, and the influence of disconnection of the uplink can be minimized. An automatic noise control device and CATV system in a line is provided. (For example, see Patent Document 2.)

  The proposed automatic noise control apparatus for a CATV line automatically reduces upstream inflow noise on a CATV line that performs bidirectional communication between a control center having a head end and a home terminal. A variable attenuating means inserted in series in the upstream line, a noise level measuring means for measuring the level of upstream inflow noise downstream of the variable attenuating means, and a noise level measured by the noise level measuring means. Attenuation control means for controlling the attenuation rate of the variable attenuation means.

  In this automatic noise control device, the noise level measuring means measures the level of upstream inflow noise on the downstream side of the variable attenuation means inserted in series in the upstream line of the CATV line, and according to the measured level of upstream inflow noise. Since the attenuation control unit controls the attenuation rate of the variable attenuation unit, the attenuation rate of the variable attenuator is increased according to the magnitude of the level of the upstream inflow noise so that the uplink attenuation rate is increased to the extent that the uplink is not disconnected. As a result, the level of uplink inflow noise can be reduced, and an increase in inbound noise in the uplink can be dealt with without immediately disconnecting the uplink. Therefore, even if the noise level exceeds the threshold, depending on the noise level exceeding, the two-way communication can be continued, and the influence of the uplink disconnection can be minimized. It has become.

Japanese Patent Laid-Open No. 11-25258 JP2007-336105A

    However, in the above-described automatic noise control apparatus, the noise level measuring means measures the level of the infusion noise based on the level of the component of the specific frequency in the uplink band that is not used in the uplink, and the specific frequency is detected by the SAW filter. It was set using. For this reason, it is practically impossible to change the frequency once set, and there is a problem that a specific frequency cannot be set unless the uplink frequency use plan is determined in the future. A CATV system incorporating a noise control device is effective, but it is necessary to fix a future frequency utilization plan before the introduction thereof, and the introduction may be delayed or may not be introduced.

  Therefore, in view of the above-described conventional situation, the present invention provides an automatic noise control device and a CATV system in a CATV line that can be introduced into a CATV system without fixing an uplink frequency usage plan in the future. It is an issue.

  An automatic noise control apparatus for a CATV line according to the first aspect of the present invention, which has been made to solve the above-mentioned problems, is serially connected to an uplink line of a CATV line for performing bidirectional communication between a control center having a head end and a home terminal. From a band not used for bidirectional communication in the frequency band of the uplink by the variable attenuating means inserted in the network and the automatic noise control instruction received from the control center via the downlink of the CATV line A noise level measuring means for measuring the level of upstream inflow noise existing within a fixed narrow bandwidth with a selected arbitrary frequency as a center frequency, on the downstream side of the variable attenuation means, and the noise level measuring means Attenuation control means for controlling the attenuation rate of the variable attenuation means in accordance with the noise level, An automatic noise control device in a CATV line, which is connected in series to the CATV line to which a null is connected and automatically reduces upstream inflow noise on the CATV line, via a downlink of the CATV line Frequency setting means for automatically and sequentially changing the center frequency of the noise level measuring means within a range of the frequency band of the uplink in accordance with a whole band measurement instruction received from the control center. Storage means for storing digital data of measurement results by the noise level measurement means when the frequency setting means sequentially changes the center frequency of the noise level measurement means, and the measurement stored in the storage means Sending the resulting digital data to the control center via the CATV line downlink Characterized in that it comprises a stage.

  With the above configuration, an arbitrary frequency selected from a band that is not used for bidirectional communication in the uplink frequency band is used as a center frequency in series with the uplink of the CATV line existing within a certain narrow bandwidth. Since the noise level measurement means measures the level of upstream inflow noise on the downstream side of the inserted variable attenuation means, and the attenuation control means controls the attenuation rate of the variable attenuation means in accordance with the measured level of upstream inflow noise. By increasing the attenuation rate of the variable attenuator according to the magnitude of the level of the upstream inflow noise to the extent that the uplink is not disconnected, the level of the upstream inflow noise can be reduced. Thus, it is possible to cope with an increase in inbound noise in the uplink without immediately disconnecting the uplink. In addition, since an arbitrary frequency is selected by an automatic noise control instruction received from the control center via the CATV line downlink, instead of determining the noise measurement frequency in advance and introducing the equipment, the noise measurement frequency is Can be arbitrarily changed from the top. Further, the frequency setting means automatically sets the center frequency of the noise level measurement means at regular intervals within the range of the uplink frequency band in response to a full band measurement instruction received from the control center via the downlink of the CATV line. The storage means stores the digital data of the measurement results obtained by the noise level measurement means when the center frequency of the noise level measurement means is changed sequentially, and the storage means stores the digital data of the measurement results stored in the storage means. Are transmitted to the control center via the CATV line downlink, the noise level distribution in the uplink frequency band can be automatically measured and aggregated in the control center.

  According to a second aspect of the present invention, there is provided a CATV system comprising a control center having a broadcasting function, and a home terminal connected to the control center via a CATV line in a tree shape, wherein the control center and the home terminal are connected to each other. A CATV system that performs two-way communication between them, further comprising the automatic noise control device according to claim 1, wherein the control sensor transmits the automatic noise control instruction and the full-band measurement instruction, Noise level collecting means for receiving and collecting the digital data of the measurement result transmitted from the automatic noise control device in response to transmission of an automatic noise control instruction.

  With the above configuration, the control center instruction transmitting means transmits an automatic noise control instruction and a full-band measurement instruction, and the noise level collecting means is transmitted from the automatic noise control apparatus in response to the transmission of the automatic noise control instruction. Since the resulting digital data is received and collected, the noise level distribution in the uplink frequency band can be automatically measured and aggregated in the control center.

  According to the first and second aspects of the present invention, since the noise measurement frequency can be arbitrarily changed from the upper level, instead of determining the noise measurement frequency in advance and introducing the equipment, the determined frequency is used permanently elsewhere. It can be changed to any frequency from the center at any time without being lost, the frequency plan can be modified, and the use plan of the uplink frequency can be changed at any time, so that restriction is eliminated and it is drastically The usage will increase. In addition, since the noise level distribution in the uplink frequency band can be automatically measured and aggregated in the control center, the noise source can be determined from the spectrum waveform analysis obtained by analyzing the noise level distribution in the entire uplink frequency band. By identifying the noise source, it is possible to consider the work of eliminating the noise generation, and to eliminate the cause of the noise generation by the work. Therefore, the present invention can provide an automatic noise control apparatus and CATV system in a CATV line that can be introduced into the CATV system without fixing the uplink frequency usage plan in the future.

It is a block diagram which shows the whole structure of the CATV system incorporating the automatic noise control apparatus which concerns on this invention. 1 is a block diagram showing an output of an embodiment of an automatic noise control device according to the present invention. FIG. It is a block diagram which shows one Embodiment of the central controller in FIG. It is a block diagram which shows the specific structure of the noise level measurement part in FIG. It is a block diagram which shows the specific structure of the continuous variable attenuator in FIG. It is a block diagram which shows the specific structure of the level measurement part in FIG. It is a flowchart which shows a part of process which MCU in FIG. 2 performs according to a predetermined program. It is a flowchart which shows the other part of the process which MCU in FIG. 2 performs according to a predetermined program. It is a flowchart which shows another part of the process which MCU in FIG. 2 performs according to a predetermined program. It is a flowchart which shows the process which MCU in FIG. 3 performs according to a predetermined program. It is a flowchart which shows the one part detail in the flowchart of FIG. FIG. 11 is a spectrogram in which the vertical axis represents dB μV and the horizontal axis represents frequency for explaining the processing performed in the flowchart of FIG. 11, (a) shows before processing, and (b) shows after processing.

  Hereinafter, an embodiment of an automatic noise control apparatus in a CATV line according to the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a CATV system configured using an automatic noise control device in a CATV line according to the present invention, and FIG. 2 is a block diagram of a noise control terminal incorporating the automatic noise control device in the CATV line. FIG. 3 is a block diagram of the central controller provided in the control center of the CATV system.

  As shown in FIG. 1, in the head end HE in the control center CC, trunk coaxial cables LA, LB and LC (hereinafter referred to as CATV lines) as CATV lines for the regions A, B and C (hereinafter referred to as CATV lines) are classified by region. They are connected via central controllers CB-A, CB-B and CB-C. For example, the trunk coaxial cable LA is branched into branch coaxial cables La, Lb and Lc (hereinafter referred to as CATV lines) as CATV lines. For example, the CATV line La is inserted into the noise control terminal NB1. The CATV line Lb is connected to the home terminal HT in one individual house H1 via the noise control terminal NB2 inserted and installed on the home terminal HT in a collective housing such as an apartment. Lc is connected to the home terminals HT in the two individual houses H2 and H3 via a noise control terminal NB3 inserted and installed on the line. In the case of collective housing, the noise control terminal may be installed on each floor. With this configuration, the regional central controller CB-A and the noise control terminal on the CATV lines LA and La, Lb and Lc between the headend HE and one or more home terminals HT in the region A NB1, NB2, and NB3 are inserted and arranged in series.

As described above, the noise control terminals NB1, NB2, and NB3 are arranged immediately before the home terminal HT. One is installed at the entrance (or on each floor) in the case of collective housing, and individual in the case of individual housing. It is installed at the entrance or the place where the neighborhood is gathered, and the number becomes many. On the other hand, the central controllers CB-A, CB-B, and CB-C are installed in a rack in the control center CC, and are generally installed in each area, and the number thereof is small. Each central controller CB-A, CB-B, and CB-C is connected via an RS232C serial communication line in order to manage a maximum of 16 ⁴ = 65536 noise control terminals. One dedicated computer PC-A, PC-B, and PC-C is provided.

  Although not shown in FIG. 1, the control center CC includes a broadcast device (not shown) for sending a CATV broadcast wave signal to the home terminal HT, an Internet connection device (not shown) for connecting to the Internet, and the like. In addition, a transmission / reception device (not shown) that performs bidirectional communication with each home terminal HT via a CATV line is connected to a host computer HOST for managing the operation of the headend HE.

  The CATV line line has a downlink and an uplink for two-way communication, and between the central controller CB and each noise control terminal in the area (a code NB is used except when indicating a specific one). , Bi-directional communication is performed by the FSK method using the CATV line downlink and uplink. The central controller CB-A shown in the figure performs polling with respect to a maximum of 65,536 noise control terminals in the area A at regular time intervals using the dedicated computer PC-A as a specific operation means. The actual data of the measured noise level temporarily stored in a time series for a certain time in the device NB is transmitted from each noise control terminal NB and collected for 24 hours, and the collected data is stored in a hard disk or the like in the computer PC-A. Store in storage means.

  Next, a specific configuration of the noise control terminal NB will be described with reference to FIG. As illustrated, the noise control terminal NB includes a transmission circuit unit 1, a noise level measurement unit 2, a panel unit 3, a transmitter 4, a receiver 5, and a microcomputer (MCU) 6 that operates according to a program. With.

  The transmission circuit unit 1 includes an upper connection terminal TU and a lower connection terminal TL, and a downlink LD and an uplink LU formed between the upper connection terminal TU and the lower connection terminal TL. The upper connection terminal TU has a cut end of the CATV line which is the upper side as viewed from the noise control terminal among the cut ends of the CATV line cut in the middle, that is, the control center CC side. The cut ends of the CATV lines on the lower side as viewed from the noise control terminal, that is, the home terminal HT side are connected to each other, whereby the noise control terminal is installed in series with the CATV line line. Specifically, each connection terminal is configured as a connector to which a coaxial cable connector provided at each cut end of the coaxial cable constituting the CATV line line is detachably connected.

  The transmission circuit unit 1 also has a downlink LU that connects the upper connection terminal TU and the lower connection terminal TL via a high pass filter (HPF) 11 that passes a frequency band of 70 MHz or higher, and a frequency band of 70 MHz or lower. And an uplink LU that connects the upper connection terminal TU and the lower connection terminal TL via a low-pass filter (LPF) 12 that passes through and a continuous variable attenuator 13. The continuous variable attenuator 13 is a voltage control type variable attenuator composed of pin diodes, and the attenuation amount is continuously changed by a control signal from the MCU 6. The variable attenuator 13 is a disconnector that disconnects the uplink LU when the attenuation factor is 45 dB or more, and is a connector that connects the uplink LU when it is 3 dB or less. The attenuation factor is switched so that each acts as an attenuator that can be set to an arbitrary value.

  The noise level measuring unit 2 has its analog input connected to the uplink LU on the input side of the continuous variable attenuator 13, its digital input connected to the MCU6 digital output, and its output connected to the digital input of the MCU6. Yes. Then, the noise level measurement unit 2 is set to a constant of ± 1 MHz, for example, centered on an arbitrary frequency in the frequency band (for example, 10 MHz to 60 MHz) used for communication of the uplink LU set by the digital output of the MCU 6. A narrow bandwidth input level is detected, and the detected level is output as an absolute value dBμV.

  During normal operation, that is, automatic noise control, the arbitrary frequency set by the digital output of the MCU 6 is a frequency band that is not used for bidirectional communication in the CATV system from the frequency band of the uplink LU. A center frequency, for example 30.5 MHz, is used. This arbitrary frequency setting is performed by an instruction received by the MCU 6 from the central controller of the control center CC. Since there is no signal in the frequency band having the set frequency as a center frequency and a bandwidth of ± 1 MHz, the noise level measurement unit 2 uses a component of 33 dBμV to a specific frequency band (30.5 MHz ± 1 MHz). A noise level of 75 dBμV is measured, and the measurement result is digitized by A-D conversion and output. The digitized noise level data is taken into the MCU 6.

  In addition, when receiving an instruction for noise measurement from the central controller of the control center CC, the MCU 6 automatically sets the input frequency in the above-described manner by sequentially changing the frequency within the range of the uplink frequency band. Scan. By this scanning, the noise level measuring unit 2 measures the noise level including the signal over the entire frequency band used for the uplink LU communication, and digitizes the measurement result by A / D conversion and outputs it. To do. The digitized noise level data is taken into the MCU 6 and stored in the RAM built in the MCU 6 as a storage means, so that the distribution of the noise level in the frequency band used for communication of the uplink LU is automatically performed. Aggregated. Then, the MCU 6 transmits the summation result to the central controller of the control center CC that issued the noise measurement instruction through the uplink LU.

  Since the panel unit 3 sets ID numbers for identifying itself from other noise control terminals, 0000-FFFF can be set for each, and four ID numbers can be set up to a maximum of 65536 ID numbers. It has ID setting switch 31 which consists of a hexadecimal digital rotary switch. The panel unit 3 is also connected to an automatic / manual switch 33 composed of a slide switch for switching the operation to automatic / manual, and a continuous variable attenuator 13 when it is manually switched by the automatic / manual switch 33. And a mode switch 32 for setting the mode so as to function as an attenuator. When the automatic / manual changeover switch 33 is switched to automatic, the attenuation rate is automatically controlled by the measured noise level value so that the continuously variable attenuator functions as a disconnector, a connector, and an attenuator. When the automatic / manual switching switch 33 is switched to manual, a value corresponding to the measurement noise level is used as the attenuation factor when the attenuator is set by the mode switch 32. The panel unit 3 is also provided with, for example, nine LEDs 34 for displaying various states of the noise control terminal by a combination of lighting and non-lighting. The panel unit 3 is connected to the MCU 6, and the ID number set by the ID setting switch 31, the automatic / manual switched by the automatic / manual switch 33 and the setting mode by the mode switch 32 are read by the MCU 6, and the MCU 6 Under the control, the LED 34 is controlled to be turned on / off.

  The transmitter 4 and the receiver 5 included in the noise control terminal are connected to the input of the HPF 11 of the downlink LD and the input of the LPF 12 of the uplink LU after their outputs and inputs are interconnected, Its input and output are connected to the MCU 6. Based on the transmission data from the MCU 6, the transmitter 4 transmits an FSK modulated signal of level 60 dB to 100 dB to the receiver of the control center CC using the 70.5 MHz frequency band of the CATV line. Further, the receiver 5 receives the digital FSK modulation signal transmitted up to a single frequency of 50.5 MHz and a minimum of 45 dB transmitted from the transmitter of the control center CC and inputs the demodulated data to the MCU 6. Thereby, the MCU 6 performs bidirectional communication with the control center CC by the transmitter 4 and the receiver 5. The output level of the transmitter 4 is set to a recommended value when each terminal is installed by the gain adjuster 41. At the time of test transmission, a maximum of 100 dB can be output by a command from the central controller CB of the control center CC. ing. Since the transmission / reception frequency is changed by the operator of the CATV system, the value in the above description uses the frequency in the standard specification.

  The MCU 6 includes a read-only memory (ROM) storing a program, a data storage area for storing data in various places, a read / writeable memory (RAM) having a work area used for performing various processes, and a ROM The CPU includes a central processing unit (CPU) that performs various processes in accordance with a program stored in the CPU. The CPU, as will be described in detail later, measures and sets the noise level at a set arbitrary frequency according to the program. Output processing of PWM (pulse width modulation) control signal that controls the attenuation rate of continuous combustible attenuator based on the noise level measured at any given frequency, noise level measurement processing at the scanned frequency, measurement at the scanned frequency Data storage processing related to the noise level, the central controller CB in the control center CC and noise The two-way communication process between the control terminal NB performed. In the noise measurement process, the noise level is measured by an original calibration method. In the two-way communication process, data on the noise level measured at the scanned frequency stored in the storage process is used as a central controller of the control center CC. Send to CB.

  Reference numeral 7 denotes an uplink monitor terminal provided by branching from the branching device 14 provided on the uplink between the upper connection terminal TU and the LFPF 12 of the transmission circuit unit 1.

  Although the mounting arrangement of the noise control terminal NB is not shown, the transmission circuit unit 1, the transmitter 4, and the transmitter 4 are arranged in a small seal case in which components are arranged on a sub board on a mother board of about 170 mm × 82 mm. The receiver 5 and the noise level measuring unit 2 housed in a small seal case in which the constituent electronic components are arranged on the slave board are fixed. On the mother board, an ID setting switch 31, an automatic / manual changeover switch 33, a mode switch 32, and an LED 34 constituting the panel unit 3 are arranged, and an MCU 6 and a DC power source with AC 100V as an input are arranged. ing. All of them are housed in a metal case of 178 mm × 82 mm × 40 mm. In the metal case, a panel unit 3, an AC outlet, an uplink monitor terminal 7, and female connectors for the upper connection terminal TU and the lower connection terminal TL are arranged.

  Next, a specific configuration of the central controller CB-A in the control center CC will be described below with reference to FIG. The central controller CB-A mainly communicates with the noise control terminal located in the area A, collects data from the noise control terminal, and transfers the collected data to the dedicated computer PC-A. . As shown in the figure, the central controller CB-A is arranged with the CATV line from the head end HE as the upper level and each noise control terminal as the lower level. The transmitter 21, the receiver 22, the noise level measuring unit 23, A serial / parallel converter 24, an RS232C driver 25, and an MCU 26.

  The output of the transmitter 21, the input of the receiver 22, and the input of the level measuring unit 23 are interconnected and connected to the CATV line, and the input of the transmitter 21 and the output of the receiver 22 are connected to the serial / parallel converter 24. The output of the noise level measurement unit 33 is connected to the input / output port of the MCU 26 via the input port of the MCU 26.

  The transmitter 21 transmits the data to the receiver of each noise control terminal input from the input / output port of the MCU 26 via the serial / parallel converter 24 on the CATV line as a 70.5 MHz digital FSK modulation signal. The unit 22 receives data transmitted as a 50.5 MHz digital FSK modulation signal from the transmitter of each noise control terminal, and inputs the data to the input / output port of the MCU 26 via the serial / parallel converter 24. The MCU 26 transfers data from each noise control terminal received and input by the receiver 22 to the dedicated computer PC-A via the RS232C driver 25 and stores the data in the computer PC-A in the storage means. At the same time, data is input from the dedicated computer PC-A via the RS232C driver 25.

  The level measuring unit 23 measures the signal strength of the output of the transmitter 21 and the input of the receiver 22 with dB μV to measure the strength of the communication signal, and inputs the measured signal level to the MCU 26 to communicate with the MCU 26. Check to see if it is done properly.

  The central controller CB is not shown in its mounting arrangement, but a transmitter 21 and a receiver 22 in which components are arranged on a child board on a mother board of about 250 mm × 120 mm and housed in a small seal case, The component electronic components are arranged on the substrate, and the noise level measuring unit 23 housed in a small seal case is fixed. In addition to the MCU 26, a DC power source that receives AC 100V is disposed on the mother board. All of these are housed in a metal case. The metal case is provided with an AC outlet, an RS232C connector, and a female connector for connecting the upper and lower CATV lines.

  Specifically, as shown in FIG. 4, the noise level measuring unit 2 of the noise control terminal includes a PLL synthesizer 2-1 that generates a frequency signal set by data from the MCU 6, and a duplexer 2-2. By mixing in the mixer 2-3, the component of the uplink LU demultiplexed from the uplink LU is mixed with the frequency signal generated by the PLL synthesizer 2-1 and converted into an intermediate frequency signal. The intermediate frequency filter 2-4 that passes the obtained intermediate frequency signal, the amplifier 2-5 that amplifies the intermediate frequency signal that has passed the intermediate frequency filter to a certain level, the intermediate frequency filter 2-4, and the amplifier 2-5 An integrator 2-6 for DC-converting the intermediate frequency signal having a narrow band, and a DC amplifier 2-amplifying the DC signal converted by the integrator 2-6 to a certain level And a 10-bit AD converter 2-8 for AD-converting a DC signal obtained by the DC amplifier 2-7 and outputting digital data, and the digital data output from the AD converter 2-8 is taken into the MCU 6 It is. The amplification factors of the amplifier 2-5 and the DC amplifier 2-7 are set so that the input of the 10-bit A / D converter 2-8 is adjusted to the optimum DC level. Further, since calibrated data calibrated at various frequencies is prepared in the ROM in the MCU 6, it is immediately read into the MCU 6 as a true value dB μV calibrated from the measured value data.

  Incidentally, the PLL synthesizer 2-1 includes a crystal reference oscillator that oscillates at a reference frequency fr, a frequency divider with a fixed frequency division ratio 1 / M, a phase detector, an LPF (low-pass filter), a VCO (voltage controlled oscillator), It consists of a programmable frequency divider with a frequency ratio of 1 / N, where F is the frequency of the VCO, fr is the frequency of the reference oscillator, and Fr is the comparison frequency, Fr = fr / M, F = Fr × N By establishing N and changing N, the F of the VCO can be changed with the frequency pitch of Fr. By changing N with the digital output of the MCU 6, a frequency signal that changes with the frequency pitch of Fr is output from the VCO. Can do.

  The calibrated data prepared in advance in the ROM in the MCU 6 includes a PLL synthesizer 2-1, a mixer 2-3, an intermediate frequency filter 2-4, and an amplifier 2-5 that constitute the noise level measurement unit 2. In order to cancel individual characteristics (level characteristic, frequency characteristic, attenuator characteristic, variation of each used part, etc.) such as integrator 2-6, DC amplifier 2-7, AD converter 2-8, etc. It is created as follows. For example, the MCU 6 records data of measurement output values when a signal having an intensity of, for example, 30 dBμV, 45 dBμV, 55 dBμV, and 70 dBμV of the center frequency of the frequency band to be measured is input from the analog signal generator to the noise level measurement unit 2. In general, since the gain characteristic changes with the natural logarithm LogX, the true value Y is Y = aLogex + b from the measurement data X for four different intensities recorded at one frequency, so the a and b values are calculated. Since the a and b values for each measurement frequency are calculated and stored in the MCU 6 as calibrated data, the digital value for each measurement frequency is calculated based on this data. In accordance with the input value X, the true value YdBμV can be calculated by Y = aLogueX + b. By having the calibrated data as described above, a high-performance level measuring device is configured with an inexpensive component configuration, and all individual components and individual system errors are canceled. The noise level measuring unit 2 configured by this level measuring device can be incorporated in an automatic noise control terminal as a part manufactured at low cost.

  With the above configuration, the noise level measurement unit 2 measures the signal strength of a single frequency (for example, 30.5 MHz) in the range of 33-75 dBμV. The MCU 6 performs the following control according to the measured noise level. First, when the measured value is 40 dBμV or less, assuming that the noise level is low, the attenuation rate of the continuous variable attenuator 13 is minimized, the uplink is substantially connected, and when the measured value is 70 dBμV or more, Assuming that the noise level is high, the attenuation rate is set to 45 dB or more, and a disconnection state that substantially blocks the uplink is set. When the measured value is in the range of 40-70 dBμV, a value up to an attenuation factor of 4 dB-25 dB proportional to the measured noise level is set in the continuous variable attenuator 13. This control is performed fully automatically by the MCU 6.

  Specifically, as shown in FIG. 5, the continuous variable attenuator 13 in the transmission circuit unit 1 generates a PWM signal whose pulse width output from the MCU 6 is variable in accordance with the noise level measured by digitization. A pulse width demodulating circuit 13-1 for demodulating and converting to a DC voltage, and a diode voltage control unit 13-2 for outputting a voltage having a magnitude corresponding to the noise level generated by the demodulation by the pulse width demodulating circuit 13-1. And a pin diode attenuator 13-3 that is controlled so that the attenuation rate changes continuously and continuously to a minimum value of −45 dB by the control voltage output from the diode voltage controller 13-2, and the noise level measuring unit 2 The attenuation rate of the continuously variable attenuator 13 is controlled in accordance with the noise level measured by, and the details will be described later.

  Further, as shown in detail in FIG. 6, the level measuring unit 23 in the central controller CB receives a signal to be measured and is automatically switched according to the strength of the input signal. 30- having a three-stage attenuator and one-stage amplifier 23-1 that can measure from a weak signal of 30 dBμV to a huge signal of 110 dBμV, and a PLL synthesizer in which the frequency to be measured is set by the MCU 26. A 950 MHz double-conversion tuner 23-2 and a signal having a frequency selected by the tuner 23-2 are input, passed through a narrowband SAW filter and an amplifier at an intermediate frequency, and converted into a DC analog level signal by peak value rectification or average value rectification. Peak value / average value rectification detection unit 23-3 to be converted and peak value / average value rectification detection unit 2 A two-stage switching amplifier 23-4 and a two-stage switching amplifier 23-4 that amplify the output signal 3-3 at two different amplification factors and adjust the signal to a magnitude suitable for later A / D conversion. The A / D converter 23-5 converts the amplified signal level into 16-bit digital data. The digital data representing the signal level converted by the A / D converter 23-5 is taken into the MCU 26. The MCU 26 is an individual of a three-stage attenuator and one-stage amplifier 23-1, a 30-950 MHz double-conversion tuner 23-2, a peak value / average value rectification detection unit 23-3, and a two-stage switching amplifier 23-4. A calibrated table according to the characteristics is prepared, and the input 16-bit digital value is calculated by a built-in natural logarithmic equation that matches the size and frequency characteristics, and the intensity of the input signal is an absolute value. Measured in dBμV. The measurement result is displayed on the three-digit digital display 23-7 or transferred as data to the host computer HOST.

  In the level measuring unit 23, a signal to be measured is input to a three-stage attenuator and a one-stage amplifier 23-1. The three-stage attenuator and the one-stage amplifier 23-1 are controlled by the MCU 26 so that the attenuation factor and the amplification factor are automatically switched depending on the signal strength, and can measure from a weak signal of 30 dBμV to a huge signal of 110 dBμV. . In the 30-950 MHz double conversion type tuner 23-2, the frequency to be measured is set in the PLL synthesizer by the MCU 26. The signal of the selected frequency is sent to the peak value / average value rectification detector 23-3, and is converted into a DC analog level signal by peak value rectification or average value rectification through an intermediate frequency narrowband SAW filter and amplifier. The The output signal of the peak value / average value clear current detection unit 23-3 is adjusted to a signal size suitable for A / D conversion through the two-stage amplifier 23-4, and the A / D converter 23-5 sets 16 Converted to a bit digital signal. The digital signal is read into the MCU 26. The MCU 26 has a pre-calibrated table. The input 16-bit digital value is calculated by a built-in natural logarithmic equation that matches the size and frequency characteristics, and the strength of the input signal is calculated. Measured in absolute value dBμV. The measurement result is displayed on the three-digit digital display 23-7 or transferred as data to the host computer HOST.

  Since the frequency to be measured is in the range of 50 to 950 MHz, the level measurement unit 23 has in advance in a calibrated table created by inputting signals of four different intensities for every 50 MHz. The calibrated table is created by inputting signals of four different strengths for each frequency from the digital and analog signal generators, for example, signals of 30 dBμV, 45 dBμV, 55 dBμV, and 70 dBμV to the level measuring unit 23, and A / D The measurement output value is AD converted in the converter 23-5, and the data is recorded in the MCU 26. The true value Y is calculated from the four recorded measurement data X with different intensities, and the a and b values are calculated for each measurement frequency by using the fact that Y = aLogueX + b. This is stored in the MCU 26 as a calibrated table. Based on this table, in accordance with the digital input value X, the true value YdBμV can be calculated by Y = aLogueX + b. By using this calibrated table, a high-performance level measuring unit is configured with an inexpensive component configuration, and all individual parts and individual system errors are canceled.

  The operation of the noise control terminal 2 described above will be described with reference to the flowcharts of FIGS. 7 to 9 showing the processing performed by the MCU 6 according to the program.

  The MCU 6 of the noise control terminal NB starts operation by turning on the power and performs initialization processing (step S1), and then sets parameters necessary for control set by the computer PC-A dedicated to the control center CC. A parameter necessary for the control transmitted by the transmitter 21 is received (step S2). Subsequently, a process for receiving text from the dedicated computer PC-A is performed (step S2-1). When there is text reception from the dedicated computer PC-A (when step S2-2 is YES), if the received information relates to noise control of the noise control terminal NB (step S2-3 is YES). ), The measurement frequency of the noise level measurement unit 2 is set based on the frequency specified for the measurement included in the received information (step S2-4), and all the bands by the noise control terminal NB are set. If it is a request for noise level measurement information (when step S2-5 is YES), the lowest measurement frequency is set in the noise level measurement unit 2 (step S2-6), and the noise level at the set frequency is measured. Then, the measured value is stored in a predetermined area of the RAM in the digital output 6 of the MCU 6 (step S2-7). When the set frequency is not the maximum measurement frequency (when step S2-8 is NO), the set measurement frequency is incremented by a predetermined frequency pitch, and the set frequency is the maximum measurement frequency. Until the frequency is reached (until step S2-8 becomes YES), the measurement of the noise level at the set frequency and the storage of the measured value are repeated. When the set frequency reaches the maximum measurement frequency (when step S2-8 is YES), the stored measurement value is transmitted as measurement data to the computer PC-A dedicated to the control center CC ( From step S2-10), the measurement frequency of the noise level measurement unit 2 is set based on the frequency designated for the measurement included in the information already received from the dedicated computer PC-A of the control center CC. (Step S2-4).

  When the automatic / manual changeover switch 33 of the panel unit 3 is automatic (when step S3 is YES), a noise level of 33 dBμV to 75 dBμV is measured (step S4). When the measured noise level is every 10 minutes (when step S5 is YES), it is recorded as time series noise data by storing noise level data for 2 hours in the data area of the RAM in the MCU 6. (Step S6).

  When the measured noise level is 40 dB or less (when Step S7 is YES), the attenuation rate of the variable attenuator 13 is set to the lowest value to establish a connection state that substantially allows the signal to pass (Step S8). When the measured noise level is not 40 dB or less (when step S7 is NO), it is determined whether it is 70 dB or more (step S9), and when it is 70 dB or more (step S9 is YES), variable attenuation is performed. The attenuation rate of the device 13 is set to the maximum value so that the signal is substantially cut off (step S10), and the fact that the CATV line is cut off is sent to the central controller CB-A of the control center CC by interruption processing. Report (step S12). When the measured noise level is not 70 dB or more (when step S9 is NO), the attenuation rate of the variable attenuator 13 is set to a value obtained by referring to an attenuation table prepared in advance for each 1 dB. (Step S12). When the cut-off state of the CATV line is released by setting the attenuation factor (when step S13 is YES), the central controller CB-A of the control center CC uses the interrupt process to release the cut-off state of the CATV line. (Step S12). When there is a state or error to be displayed on the display LED 34, a signal for turning on / off the LED is output (step S14). When there is a processing request from the host computer HOST of the control center CC (when step S15 is YES), the requested processing is performed (step S16), and when there is a processing request from the central controller CB-A When step S17 is YES, the requested process is performed (step S18). Among these processing requests, there is a processing request by polling from the central controller CB-A, and when there is this request, the data for up to 2 hours stored in the memory in the MCU 6 is transferred to the central controller CB. Is done.

  When the automatic / manual change-over switch 33 of the panel unit 3 is not automatic (when step S3 is NO), if the mode switch 32 has selected the connection mode (when step S19 is YESES), the variable attenuator A line connection process is performed to set the attenuation rate of 13 to the lowest value so that the signal is substantially allowed to pass (step S20). If the mode switch 32 selects the disconnect mode (YES in step S21). ), A line cutting process is performed to set the attenuation rate of the variable attenuator 13 to the maximum value and to cut the signal so as to substantially cut off the signal (step S22). When the mode switch 32 does not select either the connection mode or the disconnection mode (when both of steps S19 and S21 are NO), the line level is measured (step S23), and according to the measured value (step S24). And S25), connection processing (step S26), disconnection processing (step S27), and attenuation rate setting processing according to the measured noise level (step S28).

  As is clear from the above description, the microcomputer (MCU) 6 serves as an attenuation control means for controlling the attenuation rate of the variable attenuator 13 in accordance with the measured noise level from the control center via the downlink of the CATV line. In response to the received all-band measurement instruction, the frequency setting means uses noise as frequency setting means for automatically changing and setting the center frequency of the noise level measurement unit 2 at regular intervals within the range of the uplink frequency band. As storage means for storing the digital data of the measurement result by the noise level measurement section 2 when the center frequency of the level measurement section 2 is sequentially changed, the digital data of the measurement result stored in the storage means is used as the downlink of the CATV line. Each functioning as a transmission means for transmitting to the control center. The microcomputer (MCU) 6 also serves as storage means for storing in advance an approximate expression Y = allogX + b in which coefficients a and b are determined based on the output level X when signals of at least three different levels Y of a specific frequency are input. When the converted DC level is substituted into the approximate expression stored as X, and the calculation means 6-3 for obtaining Y as the upstream inflow noise level is controlled to an attenuation factor that substantially brings the uplink LU into a disconnected state. As the transmission control means for transmitting the noise level to the control center CC by the transmitter 4, it also functions as a noise level storage means for storing the measured noise level in a time series for a predetermined time.

  Next, the operation of the central controller CB will be described with reference to the flowchart of FIG. 10 showing the processing performed by the MCU 26 according to the program.

  The MCU 26 of the central controller CB starts operation by turning on the power and performs initialization processing (step S31), and then performs reception processing of parameters necessary for control set by the dedicated computer PC-A (step S31). Step S32). Subsequently, reception processing from the host computer HOST is performed (step S33). When there is text reception from HOST (when step S34 is YES), if the received information is for the central controller CB (when step S35 is YES), internal processing of the central controller CB is performed ( Step S36), if it is a request for the level measurement information of the noise control terminal NB (when Step S37 is YES), depending on the content, the signal of the output of the transmitter 21 and the input of the receiver 22 is sent to the level measurement unit 23. The strength of the communication signal is measured with dB μV, and the measured signal level is input to the MCU 26 to check whether the communication is properly performed by the MCU 26, and the result is transmitted to the HOST or NB reception for dictating Result of internal processing (step S46) of noise level data of all frequency bands received from the noise control terminal NB in the processing (step S41) And it transmits the HOST (step S38). If the received information is a transfer text to the noise control terminal NB (when step S39 is YES), the text is transmitted to the noise control terminal NB (step S40).

  Thereafter, a reception process from the noise control terminal NB is performed (step S41). When there is text reception from the noise control terminal NB (when step S42 is YES), if the received information is a transfer text to the HOST (step S43 is YES), the text is transmitted to the HOST (step S42). S44). If the received information is for the central controller CB (when step S45 is YES), internal processing of the central controller CB is performed (step S46). In this internal processing, as shown in the flowchart of FIG. 11, when the text reception from the noise control terminal NB is noise level data in the entire frequency band as shown in FIG. As shown in the figure, in each of the portions where the signal height is high (YES in step S46-1), the lower limit dBμV value and the upper limit dBμV value are detected in the frequency bands of Modem 1 and 2, respectively (step S46). -2) By calculating a corrected (pseudo) waveform as shown in FIG. 12B based on both detected values (step S46-3), noise level data excluding signal components is obtained.

  According to the above-described embodiment, all the automatic noise control terminals NB transmit the noise level time-series data to which the ID number is added, the noise level data of all frequency bands, the automatic disconnection status, etc. to the central controller CB by FSK communication. The data can be stored and analyzed by the computer of the central controller CB. Although not particularly mentioned in the above description, a database of information corresponding to the ID number that can specify the installation location of the automatic noise control terminal NB to which the ID number is set is stored in the computer on the control center CC side. Stored.

  In addition, since a frequency band that is not used at all in the vicinity of the uplink of the CATV line used for bidirectional communication such as the Internet is selected and set, the level existing in the single frequency band is detected. The level existing here can be determined as harmful noise for the Internet uplink line, and an extremely inexpensive calibration-type noise level measuring device can be used as a component in the automatic noise control terminal NB.

  In the CATV system of the embodiment, automatic disconnection, automatic attenuator insertion, and automatic recovery are possible in the Internet uplink of a specific frequency used in a certain CATV company. Therefore, measurement is performed in the automatic noise controller NB. It is possible to automatically perform stepless attenuation insertion control in conjunction with the noise level. Also, in the CATV system of the embodiment, since the noise measurement frequency can be arbitrarily changed from the upper level in the Internet uplink used by a certain CATV company, the usage design of the uplink can be easily changed. In addition, since the noise level distribution of the entire uplink frequency band can be easily obtained by using the frequency variable function of the noise level measuring unit 2, the noise source can be inferred from the frequency components and waveform conditions. In addition, by periodically acquiring the noise spectrum generated in the property where the noise control terminal NB is installed, it is possible to infer a frequency band in which a failure may occur due to noise generation. By identifying the noise source, it is possible to consider the work of eliminating the noise generation, and the cause of the noise generation can be removed by the work.

  The maximum data transferred from the automatic noise control terminal NB to the central controller CB by polling is 48 bytes. The breakdown is 1 byte for the head code, 4 bytes for the ID number, and 3 bytes for the automatic status (disconnected). , Pass, insertion attenuator value), noise level value every 10 minutes-2 hours is 24 bytes (maximum 2 digits x 12 times), and the end code is 1 byte. Also, instead of data every 10 minutes-2 hours, noise level data measured in a band of ± 1 MHz with a frequency set to all frequency bands of 10 to 60 MHz at 1 MHz intervals as a center frequency can also be transferred. .

  These stored data are analyzed by a dedicated computer PC attached to the central controller CB, and the ID number is displayed on the display according to the area of the automatic noise control terminal disconnected and the automatic noise control terminal disconnected automatically. Flashes and a warning is issued. Therefore, by looking at this cover, it is possible to identify the automatic noise control terminal that caused the trouble, respond immediately to inquiries and complaints from the user, and respond appropriately from information such as the repair time and noise status from past results. can do. At the same time, it is possible to accurately determine whether an emergency response is necessary.

  The analysis of collected cutting data is executed with the data of one day, one week and one month, and the automatic noise control terminal and area with a high frequency of cutting and the automatic noise control terminal and area with a lot of noise are displayed. Therefore, a line improvement work plan can be easily made.

  By analyzing the generation time of the noise data for the noise level and the generation time, noise countermeasures for each automatic noise control terminal and the area can be specifically established. The quality of local lines can be improved through implementation and guidance of noise reduction measures for home appliances.

  Because the noise level and time integration result can be used to plan the countermeasure work, it is possible to limit automatic noise control terminals and areas that are prone to generate noise. Helps resolve complaints.

  Since the actual state of noise in the vicinity of each terminal device remains as management data, the actual state of these data is analyzed, giving a great direction to the noise countermeasure work plan and expansion plan, and normal CATV management. Important guidance can be given.

  In addition to being able to easily control the electrical transmission characteristics of the transmission network near the CATV terminal, which could not be performed in the past, based on on-site detection data, the data communication between the central controller and the automatic noise control terminal The control data and the control mode can be set for the terminal as a whole, for each terminal, and for each group. Automatic cutting, automatic attenuation insertion, and automatic recovery automatically performed by each noise control terminal can be freely performed by remote control from the center. Further, automatic / manual switching is freely performed from the center, and various threshold values can be set. The labor of management of a conventional CATV line is greatly reduced, and line stability can be easily obtained by labor saving, signal quality improvement and automation.

  In particular, the noise level measuring unit 2 can perform level measurement, which has been expensive until now, at low cost and high performance by using a conventional consumer receiver component that is easily available and inexpensive, and using a unique calibration method. In addition, in order to perform noise measurement at a single frequency for use in an automatic noise control terminal, calibration level measurement without a frequency selection function is used.

  Since an automatic noise measuring instrument is installed in the CATV line, it can be manufactured at an economical price that can be adopted, and it is possible to automatically detect noise sources and insert a stepless attenuator that were problems on the CATV line. It became. Since the automatic insertion of the continuously variable attenuator is performed at the noise source, the noise merging is prevented and the merging noise increasing upstream is extremely reduced. Furthermore, since these noise measurement data are stored and analyzed in a computer connected via the central controller by FSK communication between the central controller and individual automatic noise control terminals, noise generation is performed in the field. The situation and location are clarified, facilitating user service, providing data to the improvement work plan, and at the same time significantly improving the signal quality management of the CATV line.

  In the above-described embodiment, transmission of time series data, noise level data of all frequency bands, automatic disconnection status, etc. from the automatic noise control terminal NB to the central controller CB is performed by FSK communication. Communication may be performed in compliance with DOCSIS (Data Over Cable Service Interface Specifications) approved by the Association.

  In the above-described embodiment, the panel unit 3 may be configured to perform an ID setting switch 31, a mode switch 32, mode switching, and automatic / manual switching according to an instruction from the control center CC. By doing so, the outer diameter of the noise control terminal NB can be reduced to 154 × 67 × 36 mm.

CC control center HE Headend CB Central controller (noise level collecting means)
HT Home terminal LA to LC CATV line LU Uplink NB, NB1, NB2, NB3 Automatic noise control terminal (automatic noise control device)
13 Continuously variable attenuator (variable attenuation means)
2 Noise level measurement unit (noise level measurement means)
4 Transmitter (Transmission means)
5 Receiver (Receiving means)
6 MCU (attenuation control means, frequency setting means, storage means, transmission means)

Claims (2)

Variable attenuation means inserted in series on the uplink of the CATV line performing bidirectional communication between the control center having the head end and the home terminal, and the automatic received from the control center via the downlink of the CATV line Level of upstream inflow noise present within a certain narrow bandwidth with an arbitrary frequency selected from a band not used for bidirectional communication in the frequency band of the uplink as a center frequency by a noise control instruction Noise level measuring means for measuring the downstream side of the variable attenuation means, and attenuation control means for controlling the attenuation rate of the variable attenuation means according to the noise level measured by the noise level measuring means. Is connected in series to the CATV line to which the An automatic noise controller in CATV line to reduce the,
In response to a full band measurement instruction received from the control center via the downlink of the CATV line, the center frequency of the noise level measuring means is automatically and sequentially set within a range of the frequency band of the uplink. Frequency setting means for changing and setting;
Storage means for storing digital data of measurement results by the noise level measurement means when the frequency setting means sequentially changes the center frequency of the noise level measurement means;
An automatic noise control apparatus for a CATV line, comprising: transmission means for transmitting digital data of the measurement result stored in the storage means to the control center via a downlink of the CATV line. In a CATV system comprising a control center having a broadcasting function and a home terminal connected to the control center in a tree shape via a CATV line, and performing bidirectional communication between the control center and the home terminal,
The automatic noise control device according to claim 1, further comprising:
The control center transmits an instruction transmission means for transmitting the automatic noise control instruction and the full-band measurement instruction, and the measurement result digital data transmitted from the automatic noise control device in response to the transmission of the automatic noise control instruction A CATV system, comprising: noise level collecting means for receiving and collecting the signal.

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