KR101336133B1 - An apparatus for controlling reverse noise in hfc network and the method thereof - Google Patents

Abstract

The present invention relates to a reverse noise breaker in an HFC network and a method thereof. A reverse noise breaker in an HFC network and a method thereof operate an upstream path only when an upstream signal is input so as to ensure the stability of a network by preventing reverse noise from flowing into an HFC network in a state where the upstream signal is not detected, reduce maintenance costs by removing the necessity for installing a noise filter according to positions of various devices, prevent the interruption of services by turning off a switch even when a corresponding device is broken or down, prevent a signal detection error caused by noise components of a low frequency such as power noise components, adjust the sensibility of a detection signal level according to an upstream signal level of the HFC network through a multi-step comparator capable of setting one or more voltage level values, and save time and costs required for the maintenance and repair of the device. [Reference numerals] (155) Switching noise breaking circuit;(AA,FF) HFC network(Coaxial);(BB) 5~42 MHz band;(CC) 54~870 MHz band;(DD) Switch control circuit;(EE) Subscriber point;(GG) Detection band less than or equal to 42 MHz;(HH) Frequency band;(II) For an upstream signal;(JJ) For an analog broadcast;(KK) Digital broadcast/supplementary services;(LL) Upstream signal;(MM) Detection band less than or equal to 16~42 MHz

Description

Reverse noise control device of HFC network and its method {AN APPARATUS FOR CONTROLLING REVERSE NOISE IN HFC NETWORK AND THE METHOD THEREOF}

The present invention relates to an apparatus and a method for controlling reverse noise of an HFC network, and more particularly, to effectively block reverse (upward) noise generated from a premises in a HFC network and introduced into a cable terminator. The present invention relates to an upstream reverse noise control device and a method for improving service quality, sufficiently securing network stabilization and service bandwidth, and reducing facility maintenance costs.

Hybrid Fiber Coaxal (HFC) networks are communication networks in which fiber and coaxial cables are used interchangeably to transport broadband multimedia content including video, data, voice, or a combination thereof. In general, local cable TV companies use fiber optic cables to deliver multimedia content from cable TV headends to nodes that are close to users in the enterprise or home. The service is provided using existing coaxial cable facilities. In other words, the HFC network uses an optical coaxial mixed network using a coaxial cable from a system operator (SO) to an optical networking unit (ONU), which is a main trunk, and a coaxial cable from an ONU to a subscriber terminal device. Advantages of the HFC network include the following. First, it is possible to realize wideband transmission by constructing a backbone network with fiber optic cable. Second, it is possible to reduce delay of bidirectional data transmitted and received by users due to high bandwidth. Third, reliability of network is very important in two-way data transmission environment. Fourth, to provide individual services in the end subscriber's home is to efficiently provide services by using the existing coaxial cable network. In other words, the network using fiber optic cable is suitable for the part that needs to build a broadband reliable network from SO to each local cable TV company, and the network from ONU to individual premises or premises is the existing cable network. It is efficient to use. Due to the above advantages, cable TV and telephone companies are often applied to configure the HFC network to provide cable broadcasting services.

Of course, for the FTTH (Fiber-To-The-Home), it is also possible to configure all the networks with optical cables for general subscriber equipment, and for certain large subscribers, it is possible to connect optically to buildings, apartments, or offices. Most subscriber equipment, however, accesses a network consisting of optical, coaxial, Internet, or a combination of these via coaxial or LAN cables.

In most network services using two-way communication, a downstream (down) stream from the service provider to the subscriber and an upstream (up) stream from the subscriber to the service provider are transmitted simultaneously. In this case, the downlink signal and the uplink signal use different frequency bands to realize bidirectional communication. Also, for the downlink signal, if the reception environment of a particular subscriber is bad, the effect is limited to that subscriber. However, in case of an uplink signal, signals transmitted from a plurality of subscribers are bundled and transmitted to the service provider. The difference between the upstream signal and the downlink signal is that interference at one point can interrupt the upstream signal of the entire system.

Therefore, in the HFC network, upstreams have a problem in that noise generated from each subscriber is continuously added and amplified to the service provider. In the present invention, the noise included in such an upstream stream is called reverse noise. Such reverse noise may occur in terminal devices such as devices and converters connected to the HFC network, and may cause deterioration of the performance of the HFC network.

Major sources of reverse noise include subscriber security, premises amplifiers, indoor cables, converters, TV receivers, and VTRs. Among these, subscriber security is one of the most noisy devices, which has a significant impact on the up / down (upstream / downstream) signal quality of HFC networks. Sources of noise generated in premises amplifiers include leakage currents in switching circuits used in power supplies. Aging transmission cables are also a major source of noise. Of course, the source of the noise may be any device that interferes with the transmission of the signal in the HFC network in addition to the above-described device or cable.

In addition, the noise flowing into the HFC network cannot predict its path and time, and because of the characteristics of the HFC network, the network is opened as the number of high-speed Internet subscribers and cable broadcasting subscribers increases. There is a problem that also increases the noise flowing into.

In order to solve the reverse noise problem on the HFC network, each SO is trying to block the reverse noise by using various filters, but in this case, a filter must be installed in the line between most devices, which is expensive. And due to the complexity of the management, there are many difficulties.

In addition, in order to solve the above problem, there is a method of blocking the reverse noise by installing a power supply connector together with an amplifier so that an upstream path is opened only when an upstream signal exists. When the power is down, the upstream signal cannot be transmitted, and if the signal transmitted from the cable modem is large (input level), saturation occurs in the amplifier, causing spurious frequency components other than the specified frequency band. ) Components were generated.

The present invention was created to solve the above problems, by operating the upstream pass only when the uplink signal is input in the HFC network, by preventing the reverse noise from flowing into the HFC network in the state that the uplink signal is not input It is an object of the present invention to ensure the stability of the device, and to eliminate the need for installing a noise filter depending on the location of many devices, thereby reducing the maintenance cost.

In addition, the present invention is designed so that the upstream pass is operated only when the uplink signal is input in the HFC network, so that the switch is automatically closed when the power is not supplied, so that the service is not interrupted even if the corresponding device fails or goes down. The purpose.

In addition, the present invention uses a low pass filter and a high pass filter in combination with a low pass noise component such as a power supply noise component to detect an input upstream signal. The goal is to avoid detection errors.

It is also an object of the present invention to adjust the sensitivity of the detected signal level in accordance with the upstream signal level of the HFC network through the multistep comparator, which makes it possible to set one or more voltage level values.

In addition, the present invention reduces the device failure rate compared to the conventional F-type power supply connector by using a DC Jack Adapter, saving time and money spent on the maintenance and repair of the device An apparatus and a method for controlling reverse noise of an HFC network that can be used.

An apparatus for controlling reverse noise in an HFC network according to an embodiment of the present invention includes a low pass filter for passing only a band below a specific frequency; A passive element switch installed in the path of the upstream signal; And a switch control circuit for controlling opening and closing of the switch, and after determining whether there is an upstream signal in the specific frequency band passed, switch-off when there is no upstream signal, and switch-on when there is an upstream signal. The reverse noise may be controlled to be introduced into a path of an upstream signal of the HFC network. The apparatus for controlling reverse noise of the HFC network may further include a high pass filter that passes only a band of a specific frequency or more to the signal passing through the low pass filter, and includes a specific frequency band through the low pass filter and the high pass filter. Extraction, thereby preventing detection errors due to low frequency noise in detecting upstream signals, wherein the passive element switch is configured such that the switch state is unconditionally switched on when no input power is supplied, and the switch control The circuit includes a multistep comparator capable of setting one of at least one voltage value as a reference value according to the degree of noise occurring in the installation area of the noise control device, wherein the switch control circuit includes the specific frequency band. Will determine whether it is upstream And a signal detection device for converting the pressure component into a comparator and transmitting the signal to the comparator, wherein the switch control circuit includes: a noise component affecting a switch control signal of the comparator and switching noise that may occur when the passive element switch is controlled. Switching noise cancellation circuit for removing the; further comprising; at least one diplex filter for separating the signal of the HFC network into a low band upstream signal and a high band downstream signal; further comprises, the HFC network The reverse noise control device may be installed alone on an HFC network or included in a network device including an amplifier or attenuator on the HFC network.

In addition, the reverse noise control method of the HFC network according to another embodiment of the present invention, the low-pass filter passes a region of a specific frequency size or less in the signal transmitted from the cable modem; Passing a high pass filter only an area of a specific frequency size or more from the signal passing through the low pass filter; Determining, by the signal detection apparatus, whether there is an upstream signal in the signal filtered to the specific region and transmitting the result to the comparator; If the upstream signal is present, the comparator keeping the passive element switch closed to operate the upstream path normally; And blocking the reverse noise by opening the passive element switch to block the upstream path if there is no upstream signal. The method may further include removing noise components that affect the switch control signal of the comparator and switching noise components that may occur when controlling the passive element switch in the switching noise elimination circuit. The switch state can be configured to be in the switch-on state unconditionally when off, and the comparator is a multistep comparator capable of setting one or more voltage values, and the signal detection device is a small signal By reducing the sensitivity and increasing the larger signal, the detection sensitivity can be adjusted to accurately detect the upstream signal even if the reverse noise and the upstream signal are similar in magnitude.

The present invention relates to an apparatus and method for controlling a reverse noise of an HFC network. The upstream path is operated only when an upstream signal is input, thereby preventing reverse noise from entering the HFC network in a state where an upstream signal is not detected. Stability can be secured, and noise filters need not be installed depending on the location of many devices, thus reducing maintenance costs, and the switch is closed even if the device fails or goes down, preventing service interruption. In addition, the detection signal level according to the upstream signal level of the HFC network through a multi-step comparator that can prevent signal detection errors caused by low-frequency noise components such as power supply noise components, and enable setting of one or more voltage level values. To control the sensitivity of And so, there is an advantage that can save time and money spent on maintenance and repair of equipment.

1 is an exemplary diagram for explaining a concept of a reverse noise control apparatus of an HFC transmission network according to an embodiment of the present invention.
2 is an exemplary diagram for explaining a conventional reverse noise control device.
3 is an exemplary diagram for explaining an RNB which is a reverse noise control device of the present invention.
4 is an exemplary diagram for comparing the amount of noise blocked in the reverse noise control device of the present invention and the conventional reverse noise control device.
5 is a flowchart illustrating a process of blocking reverse noise in a reverse noise control apparatus of an HFC network according to the present invention.

First, the noise (noise) generated in the HFC transmission network will be briefly examined.

In the HFC transmission network, various noises, which are combined with uplink transmission signals and affect uplink signal quality, are mixed into the uplink through connector connection parts such as trunk leads, fastening parts of various devices, and insufficient shielding of indoor facilities.

Various noise sources from the headend to the subscriber's premises are mixed into the indoor line, indoor unit, or security device, in which the induced current on the coaxial cable surface such as trunk, lead, and indoor wires is insufficient in connection part of the connector or insufficient shielding characteristics. In some cases, a current induced in a commercial power supply line or indoor wiring may be mixed through a power line of a converter or a TV receiver. This is because proper construction is not done in indoor facilities because current induced by voltage induced between power line and ground line flows to ground through HFC transmission network indoor line and lead line. The upside from the downside is that interference at one point can interrupt the upstream signal of the entire system.

Upstream noise of an HFC transmission network includes ingress noise, impulse noise, random noise, and the like. Influx noise is an RF signal in the shortwave band in the 2 to 30 MHz band, and the tightness of the transmission network connector or passive element is introduced through loose or damaged defective parts. When this noise is introduced, the available channels are reduced.

Impulse noise has fast rise times and short durations, and puts significant broadband energy in the up band. Impulse noise can be caused by loose tightening of connectors or passive components, or by the combination of strong electromagnetic waves from a particular subscriber end connected to a lead or distribution line, or due to passive factors such as electric motors, engine ignition devices, power switches, neon signs, etc. Can be.

As can be expected from the above description, the impulse noise component is about 60 Hz to 20 MHz, but due to natural factors such as a lightning strike, it occurs in a wide range of 2 KHz to 100 MHz, and thus occurs in a wide range from low to high frequency components. .

On the other hand, there are random noises such as thermal noise generated in resistors and semiconductor devices, and the noise power increases by 3dB every time the multi-stage amplifier doubles. On the other hand, one of the important parameters for data transmission in the HFC transmission network is the group delay distortion that the arrival time is different for each frequency. That is, if the propagation speed for each medium is known, it is possible to calculate the propagation time between the headend and the subscriber in the far distance.

RF inrush noise and impulse noise can cause clipping in up-band active devices, which can also cause signal clipping if too high a signal is generated in an indoor device such as a converter. The signal clipping occurs in the up-amp and square ratio.

Subscriber noise generated in terminal devices such as devices and converters connected to the HFC transmission network is the most difficult in HFC networks, and most of them are blocked by installing HPF at tap off.

In order to improve the quality of service of HFC transport network, the following maintenance issues should be considered. 1) Minimize artificial interruptions of service, 2) preventive inspection activities should be carried out more thoroughly, and 3) shorten troubleshooting time.

In conclusion, bidirectional HFC networks include system thermal noise, amplifier nonlinear distortion, coaxial cable attenuation, and echo mismatch due to impedance mismatching. Due to the) -type structure, multiple subscribers share the transmission network, causing funneling, in which incoming noise from the subscriber end, such as impulse noise and burst noise, is concentrated to the transmitter, making it worse than the downlink channel. . Therefore, in order to provide high quality bidirectional communication through HFC network, it is necessary to accurately analyze the uplink system performance deterioration factors and to improve system performance.

Hereinafter, an embodiment of a reverse noise control apparatus and method thereof of an HFC transmission network according to the present invention will be described with reference to the accompanying drawings.

1 is an exemplary view for explaining the concept of the reverse noise control apparatus of the HFC transmission network according to an embodiment of the present invention.

As shown in FIG. 1, the reverse noise control device (hereinafter referred to as RNB) 100 of the HFC network includes a cable modem 200 and a cable termination device (hereinafter referred to as a cable modem termination system (CMTS)). Installed between the 300 to control the reverse noise. Noise sources generated from premises cable damage, connector damage, and out-of-compliance products (cables, connectors, splitters, other devices (including cable modems) and terminators) move toward the head end of the HFC network and gradually merge into the HFC network. In this case, the RNB 100 may be installed in the street to block the noise source in the home from entering the HFC network. In more detail, the noise generated in each home is first merged in the home distribution box, and then again in the divider 500 that distributes to several homes. Is gathered in one place to flow into the CMTS (300) to reduce the quality of service of the HFC network, at this time, by installing the RNB 100 of the present invention on the roadway between the distributor and the CMTS (300), the aggregated up in one place Noise can be prevented from entering the HFC network.

For reference, the RNB is installed in an HFC network area using a coaxial cable, and the coaxial cable area of the HFC network includes a device from an ONU located in the headend direction to a device at a subscriber point. The ONU may be included in the CMTS. In the description of the present invention, the CMTS to the device of the subscriber point is regarded as a coaxial cable area of the HFC network.

Each group (Group A, Group B, Group C, Group D) shown in FIG. 1 is a cable modem 200 or a group of subscribers, each of which is handled by one RNB 100. For example, an HFC network is installed. For apartments, Group A is located on the first and second floors of apartments, Group B on the third and fourth floors of apartments, Group C on the fifth and sixth floors of apartments, and Group D on the seventh and eighth floors of apartments. Can be. As such, one RNB 100 blocks the noise of several cable modems 200 or subscribers, thereby significantly reducing maintenance costs compared to the conventional method in which a noise filter has to be installed in each distribution box 500. It is also possible to increase the noise blocking efficiency.

More specifically, as shown in (a) of FIG. 1, the HFC network is a funnel structure (funnelling structure), and the reverse noise generated from all devices in the home and output from the cable modem 200 to the network is Combined along the funnel structure of the HFC network to reach the CMTS 300, the reverse noise is increased enough to degrade the quality of the HFC network. That is, in FIG. 4A, all noises from the A group, the B group, the C group, and the D group are combined in the distributor 500 and introduced into the HFC network through the CMTS 300. In addition, the transmission signal (TX signal) of the cable modem uses a time division multiple access (TDMA) method, so that even though multiple modems cannot transmit upstream signals at the same time, there is a reverse noise in all time zones. All will be introduced into the CMTS (300).

As shown in FIG. 1B, the RNB 100 of the present invention can effectively block and distribute noise. As described above, since the cable modem 200 uses the TDMA scheme, each cable modem group transmits an upstream signal for each time zone. At this time, if the RNB 100 of the present invention is installed between the splitter and each cable modem group, each RNB 100 passes the reverse noise only when there is an upstream signal. When a particular cable modem group transmits an upstream signal, according to the characteristics of the TDMA scheme, another cable modem group does not transmit an upstream signal, and thus a specific cable transmitting the upstream signal is blocked because the upstream path of each RNB is blocked. Reverse noise from other cable modem groups other than the modem group will be blocked. In this case, the installation location of the RNB 100 is important, because if the installation location of the RNB is between the distributor 500 and the CMTS, even if the upstream signal is transmitted in a specific group, the reverse noise of all cable modem groups must pass through the same time. Because it is not. Although the cable modem group is much more complicated and diverse than that shown in Fig. 4, by using the cable modem's TDMA scheme and the RNB of the present invention as described above, the total amount of reverse noise flowing into the HFC network through the CMTS is greatly increased. Can be reduced.

On the other hand, the noise control device including the conventional amplifier 400 has to readjust the premises amplifier balance every time a new device is installed or the installed position is changed, but the RNB 100 does not include the amplifier 400. As a result, there are fewer limits on the installation position and the positional variation than the noise control device including the conventional amplifier. That is, in the case of a large number of apartments, there may be a more detailed group of cable modems than in FIG. 1, and accordingly, multiple RNBs 100 may be installed on each floor. It will be possible. In addition, the method of blocking the noise of the RNB 100 of the present invention is to activate or turn off the upstream path according to the signal input from the cable modem 200, and according to the distribution of households using the two-way broadcasting service. The RNB installation location may vary, and even after the RNB 100 is installed, the uplink noise may be efficiently blocked by adjusting the RNB 100 installation location even if the distribution of the bidirectional broadcast service subscribers is changed. In addition, only upstream passes are open to households with two-way services, so reverse noise from households that do not use two-way services is always blocked.

In addition, the RNB 100 of the present invention does not need to establish a new premises network in order to install the device. By reusing existing public antenna (MA) or cable antenna (CA) facilities that are already installed in apartments such as apartments, installation costs, resources, and time can be saved.

2 is an exemplary view for explaining a conventional reverse noise control device.

As shown in FIG. 2, the downstream (downward) signal uses frequencies in the 54-870 MHZ band and the upstream (upward) signals use the frequencies in the 5-42 MHz band. For this purpose, a diplex L / C filter is installed at the downstream input part and the upstream output part to separate the frequency of the input / output signal.

The separated downstream band signal is amplified and output through an amplifier (AMP) installed in the middle of the downstream pass.

The upstream signal also uses frequencies in the 5-42 MHZ region. When the upstream signal is transmitted from the cable modem, only the upstream signal in the 5-42 MHZ region is filtered out of the diplex L / C filter installed in the upstream input unit of the conventional reverse noise blocking device and passed through the upstream pass. By controlling the power supply of the amplifier AMP, reverse noise is blocked. The method of controlling reverse power by controlling the power of the amplifier AMP is performed by using a 5-42 MHZ LPF (Low Pass Filter) installed in the upstream signal input unit. The RF Detect determines whether there is an upstream signal input from the cable modem among the signals filtered by the 5-42 MHZ LPF, and transmits the result to a transistor. At this time, the transistor controls the power of the amplifier AMP installed in the upstream path according to the presence of the input upstream signal. If there is no upstream signal input from the cable modem, the amplifier AMP is turned off to cut off all signals passing through the upstream path. If there is an upstream signal input, the amplifier is powered up to the upstream signal. Allow to pass.

However, in the conventional reverse noise control device, when an entire device or a power supply of a transistor goes down due to a failure, the upstream signal sent from the cable modem passes because the power of the amplifier AMP installed in the upstream pass is not applied. In addition, the transistor is a small amount of output of the power to the amplifier (AMP) installed in the upstream pass in response to a low frequency reverse noise signal, such as power supply noise component (approximately 60 HZ) in the region of 42 MHZ or less. You can even raise it. In addition, even if power is not applied to the amplifier AMP, some signals must pass because the upstream pass line is not actually disconnected. That is, the conventional reverse noise control apparatus does not completely block reverse noise even if there is no upstream signal input from the cable modem. In addition, since the conventional reverse control device uses an amplifier (AMP), when the signal level transmitted from the cable modem is applied to a large level, saturation occurs in the amplifier (AMP), so that the frequency of the non-regulated frequency band is reduced. There is a problem that spurious components, which are unnecessary frequency components, are generated, and there is a problem in that the device defective rate is high because the F type power supply connector is used.

3 is an exemplary diagram for explaining an RNB which is a reverse noise control device of the present invention.

As shown in Fig. 3, the reverse noise control device (RNB) of the HFC network of the present invention uses a downstream path using a frequency in the 54-870 MHZ region and a frequency in the 5-42 MHZ region. The upstream path is separated, and the switch control circuit including the RF Detect 140, the comparator 150, and the switching noise canceling circuit 155 is provided with a switch 160 in the upstream path. The upstream path is opened or blocked by turning the switch on or off depending on the presence or absence of an input signal. In this case, when the switch 160 is closed and the upstream path is blocked, all upstream signals including reverse noise are blocked from passing through the RNB. That is, since the RNB 100 of the present invention does not fundamentally block noise, reverse noise, which was blocked while the upstream path is open, is also transmitted along with the uplink signal.

More specifically, in the RNB 100 of the present invention, a diplex L / C filter 110 is installed at the downstream input part to filter downstream signals of the 54-870 MHZ frequency band. RNB 100 uses a bufferless diplex L / C 110. In this case, filtering the frequency domain of the downstream signal may be filtered through a method using at least one of a high pass filter and a low pass filter. The downstream signal passed through the downstream pass is output to the cable modem 200. On the other hand, when the cable modem 200 sends the upstream signal to the RNB 100, only the upstream signal of the 5-42 MHZ region is filtered by the diplex L / C filter installed in the upstream input of the RNB 100. In this case, an on / off signal is sent to a single-pole double-throw (SPDT) RF switch 160 installed in an upstream path to open and close the upstream path, thereby preventing reverse noise from passing through. Unlike the conventional reverse noise control device described above, 5-42 MHZ LPF (120) is installed in the upstream signal input unit to control reverse power by controlling the power of the SPDT RF switch 160. Only signals of less than 42 MHZ are filtered out of the signal transmitted from the modem, and the second 16 MHZ High Pass Filter (HPF) 130 passes only signals of 16 MHZ or more out of the signals filtered below 42 MHZ. In other words, HPF with cutoff of 16 MHZ and MHZ LPF with cutoff of 42 are linked to each other to gradually extract only signals in the region of 16 MHZ or more and less than 42 MHZ and send them to RF Detect 140. Will be. The RF Detect 140 determines whether there is an upstream signal in the filtered 16 to 42 MHZ region band, and converts the result into a DC component and transmits the result to the comparator 150. On the other hand, the reason why the LPF is in the range of 5-42 MHZ is because the frequency range of 5 MHZ or less does not carry any upstream signals, so it can be ignored.

Meanwhile, the RF Detect 140 may transmit a result of whether an upstream signal is present to the comparator 150 using a digital signal. The reason why the digital signal is used at this time is that the digital signal is robust to interference of noise. If the upstream signal presence result is transmitted as an analog signal, noise may occur in the switch on / off operation due to noise. For example, even if the RF Detect 140 sends a signal that there is no upstream signal, the comparator 150 may incorrectly determine that there is an upstream signal because of noise included in the signal. The gate controller then closes the switch 160 installed in the upstream pass even though the cable modem did not send an upstream signal, and reverse noise may enter the HFC network through the RNB 100.

On the other hand, the comparator 150 controls the switch by sending an ON / OFF signal to the switch 160 installed in the upstream path based on the digital signal sent by the RF Detect 140, the cable modem 200 upstream signal When no signal is transmitted, reverse noise cannot pass through the upstream pass.

In addition, a switching noise cancellation circuit 155 is present between the comparator 150 and the SPDT RF switch 160. The switching noise removing circuit 155 may minimize the noise component affecting the switching control signal while maintaining the RF characteristics by using two stages of the Schottky diode, and switching noise that may be generated when the SPDT RF switch is controlled. Can be removed.

The SPDT RF switch 160 is a passive element switch composed of one pole and two throws. The SPDT RF switch 160 may be configured to allow the RF signal to pass even when the input power is turned off. The SPDT RF switch performs the following three operations in connection with the switch control circuit (RF Detect, comparator, switching noise cancellation circuit). First, if the switch control circuit detects an upstream signal when the RNB is in normal operation, the SPDT RF switch is turned on to open the upstream path and pass the upstream signal. Second, if the switch control circuit does not detect the upstream signal when the RNB is in normal operation, the SPDT RF switch is turned off to block the upstream pass so that reverse noise is not passed. Third, in case of an emergency (when the input power is off), the SPDT RF switch is always turned on regardless of the presence or absence of the upstream signal so that the upstream path is always open.

For reference, in the head-end CMTS, a transmission frequency for performing data communication with a cable modem, analog broadcasting, internet, digital broadcasting, and additional service signals are carried in various frequency bands and transmitted to the HFC network. The -42 MHZ band is used for upstream signals, the 54-500 MHZ band for analog broadcasting, the 500-552 MHZ band for the Internet, and the 552-750 MHZ band for digital broadcast and supplementary service signals.

As described above, the RNB 100 of the present invention uses two filters (LPF, HPF) as compared to the conventional reverse noise control device using only one filter (LPF) to reduce the frequency of the low frequency range such as the power source noise component. Since the detection error is less, the switch 150 is closed even when the comparator 150 or the power supply of the switch is down. Therefore, an upstream signal transmitted from the cable modem 200 may be passed to the output. In addition, in detecting the upstream signal transmitted from the cable modem 200, the RNB 100 of the present invention uses a comparator 150 that can set a multi-step (for example, 0.4V, 3V, 5V, etc.) to set a reference value. Sensitive High / Low Switch that can be set in various ways and can switch on / off the switch by controlling the switch IC (eg open = 5V, close = 0V) if the input is greater than the set voltage value You can also use In addition, RF Detect adjusts the detection sensitivity by reducing smaller signals and increasing larger signals, so that upstream signals can be accurately detected even if the reverse noise and upstream signals are similar in magnitude. In addition, since the RNB 100 of the present invention uses a DC Jack adapter, a device failure rate is significantly reduced compared to a conventional reverse noise control device.

For example, the reference value of the comparator 150 is set high in an area where noise is high, and the reference value is set low in an area where noise is low, and the reference value of the comparator 150 is variable according to the noise generating environment. Various adjustments can be used.

For reference, it has been described that the RNB of the present invention does not include an amplifier, but any amplifier including an AMP, a buffer, a repeater, and the like may be configured to include the RNB 100 of the present invention, and conversely, the RNB 100 of the present invention. It is also possible that is configured to include the amplifier).

4 is an exemplary diagram for comparing the amount of noise blocked by the reverse noise control device of the present invention and the conventional reverse noise control device.

As shown in FIG. 4, the conventional reverse noise control device transmits an upstream signal from a cable modem to operate an upstream path and a noise difference when the cable modem does not input an upstream signal to operate the upstream path. Is 28 dB, and the RNB of the present invention has a noise difference of 46 dB when the upstream path is operated by transmitting an upstream signal from the cable modem and when the upstream path is not operated because the upstream signal is not input from the cable modem. The RNB of the invention can further block about 16 dM of noise than the conventional reverse noise control device.

As described above, the RNB of the present invention exhibits higher reverse noise blocking efficiency than the conventional reverse noise control device. Unlike the conventional reverse control device, the RFC detects an upstream signal transmitted from a cable modem. Since two filters (LPF, HPF) are used, there is less detection error caused by low frequency noise such as power supply noise. Also, even if the upstream pass is blocked using an amplifier, the upstream pass line is not broken. While positive reverse noise can be passed to the output, blocking the upstream pass with a switch ensures that the upstream pass line is blocked, so that reverse noise will not pass to the output unless the cable modem is transmitting an upstream signal. No conventional reverse noise agent In the device, because the saturation (Saturation) phenomenon at the amplifier (AMP) up and could result in a spurious (spurious) component.

5 is a flowchart illustrating a process of blocking reverse noise in the reverse noise control apparatus of the HFC network according to the present invention.

As shown in FIG. 5, the 5-42 MHZ LPF installed in the upstream signal input unit of the RNB passes only the frequency range of 42 MHZ or less in the signal transmitted from the cable modem (S101). The filtered frequency band below 42 MHZ is sent to the 16 MHZ HPF, and the HPF passes only the frequency band above 16 MHZ, so that only signals below 42 MHZ above 16 MHZ are sent to RF Detect (S102). ). The RF Detect determines whether there is an upstream signal transmitted by the cable modem in the 16 MHZ to 42 MHZ signals filtered through the two filters, converts the result into a DC component, and transmits the result to the comparator (S103). The comparator determines whether to close or open the switch according to the presence or absence of an upstream signal converted into the DC component received from the RF Detect (S104). If a result of the upstream signal is received, the switch installed in the upstream path of the RNB is kept closed to allow the upstream path to operate normally (S105). If the upstream signal is received, the switch is opened. Blocking the upstream pass prevents reverse noise from passing through the RNB (S106).

The frequency band or numerical value described in the present invention does not necessarily mean a fixed range or numerical value, but corresponds to one embodiment, and thus may vary according to a standard or environment to which the present invention is applied. Even if used in the numerical value, if it includes the technical features of the present invention, of course it should be considered to be included in the protection scope of the present invention.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, I will understand the point. Accordingly, the technical scope of the present invention should be defined by the following claims.

100: RNB 110: diplex L / C filter
120: 5-42 MHZ LPF 130: 16 MHZ HPF
140: signal detection device 150: comparator
155: switching noise cancellation circuit
160: SPDT RF switch 200: cable modem
300: CMTS 400: Amplifier
500: Dispenser

Claims (13)

In the reverse noise control device of the HFC network,
A filter that passes only signals of a specific frequency band by using a low pass filter that passes only a band below a specific frequency and a high pass filter that passes only a band above a specific frequency to the signal passing through the low pass filter;
A passive element switch installed in a path of an upstream signal configured to be in a switch-on state unconditionally when an input power is not supplied; And
And a switch control circuit for controlling opening and closing of the passive element switch.
By extracting a specific frequency band through the low pass filter and the high pass filter, it is possible to prevent detection error caused by low frequency noise in detecting upstream signals.
Even if input power is not supplied to the reverse noise control device, a path of an upstream signal is secured so that communication can be performed even in a power failure situation.
By switching off the passive element switch when there is no upstream signal in the specific frequency band passed and switching on the passive element switch when there is an upstream signal, reverse noise flows into the path of the upstream signal of the HFC network. The reverse noise control device of the HFC network, characterized in that the control. delete delete The method according to claim 1,
Wherein the switch control circuit comprises:
And a comparator capable of setting one of at least one voltage value as a reference value according to a degree of noise occurring in an installation region of the reverse noise control device. The method of claim 4,
Wherein the switch control circuit comprises:
And a signal detector for determining whether there is an upstream in the specific frequency band and converting the result into a voltage component and transmitting the result to the comparator. The method according to claim 5,
Wherein the switch control circuit comprises:
Reverse noise control of the HFC network, characterized in that it further comprises; switching noise removal circuit for removing the noise component affecting the switch control signal of the comparator and switching noise that may occur when the passive element switch is controlled. Device. The method according to claim 1,
And at least one diplex filter for separating signals of the HFC network into upstream and downstream signals according to frequency bands. The method according to claim 1,
The reverse noise control device of the HFC network,
A device for reverse noise control of an HFC network, which may be installed alone on an HFC network or configured to be included in a network device including an amplifier or attenuator on the HFC network. In the reverse noise control method of the HFC network,
A filtering step of passing only signals of a specific frequency band, including a low pass filter for passing only a band below a specific frequency of an upstream signal and a high pass filter for passing only a band above a specific frequency to the signal passing through the low pass filter;
Determining whether there is an upstream signal in the specific frequency band through a switch control circuit; And
As a result of the determination of the presence of the upstream, when there is no upstream signal, the passive element switch installed in the upstream pass is switched off, and when there is an upstream signal, the reverse noise is upstream of the HFC network by switching on the passive element switch. Controlling the flow of signals into a path;
By extracting a specific frequency band through the low pass filter and the high pass filter, it is possible to prevent detection error caused by low frequency noise in detecting upstream signals.
The passive element switch is installed in the path of the upstream signal so that the switch state is switched on when the input power is not supplied, and the path of the upstream signal is secured even when the input power is not supplied, so that communication can be performed even in a power outage. Reverse noise control method of the HFC network, characterized in that. The method of claim 9,
The controlling may include detecting a signal upstream in the specific frequency band, converting the result into a voltage component, and transmitting the result to a comparator. The method of claim 9,
The controlling may include removing noise components affecting a control signal of the passive element switch and switching noise components that may occur when the passive element switch is controlled. Control method. delete The method of claim 10,
And the comparator can set one of at least one voltage value as a reference value according to the degree of occurrence of the reverse noise.

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