KR100559782B1 - An apparatus for filtering noises and amplifying signals in telecommunication system using CATV network - Google Patents

Abstract

The present invention relates to a noise filtering and signal amplification apparatus in a communication system using a CATV network. The present invention relates to a downlink signal transmitted from a CATV service center to a subscriber and an uplink signal transmitted from a subscriber to a CATV service center. A first diplex filter separating the; An IF filter unit which removes noise by mixing and modulating a frequency of an uplink signal separated from the first diplex filter with a locally oscillated signal, filtering the bandpass filter (BPF), and then converting the frequency into an original frequency; An LPF for removing a high frequency signal from an upstream signal passing through the IF filter unit; An uplink signal amplifier for amplifying an uplink signal passing through the LPF; At the CATV service center, a second diplex filter for separating an uplink signal and a downlink signal; And a downlink signal amplifier for amplifying the downlink signal passing through the second diplex filter. According to the apparatus of the present invention, in a communication system using a CATV network, interference of signals caused by a complex communication method using a single medium, noise generated in home appliances, interference with signals generated in amateur radio (HAM) communication, and the like, There is an effect that can provide a device that can perform the amplification function while minimizing the effects of interference due to a connector or a cable failure.

CATV, Internet, Intermediate Frequency, BPF, Uplink, Downlink, Diplex Filter

Description

An apparatus for filtering noises and amplifying signals in telecommunication system using CATV network}

1 is a block diagram of an Internet system using a conventional CATV network

2 is a block diagram of an embodiment of an apparatus according to the present invention;

3 is a detailed block diagram of an IF filter part of an embodiment of the apparatus according to the present invention;

4 is a modification of a BPF part of an embodiment of the apparatus according to the present invention;

Figure 5a is a graph of the upward characteristics of a third-party product that is a target product measured by the network analyzer (Nestwork Analyzer)

Figure 5b is a graph of the upward characteristic of the device according to the present invention measured through a network analyzer

<Description of Major Reference Drawings>

40 control unit, 41 first diplex filter, 42 IF filter unit, 43 LPF, 44 uplink signal amplifier, 45 up equalizer, 46 up attenuator, 47 second diplex filter, 48 down attenuator, 49 down equalizer, 50 down signal Amplifier, 51 First Attenuator, 52 First Mixer, 53 First IF Channel Filter, 54 First IF Amplifier, 55 BPF Section, 56 Second IF Amplifier, 57 Second Attenuator, 58 Second IF Channel Filter, 59 Second Mixer, 60 PLL Circuit, 61 LO AMP, 62 Dividers, 64, 65 RF Switches

The present invention relates to a noise filtering and signal amplification apparatus in a communication system using a CATV network. More specifically, it is possible to simultaneously perform noise filtering and signal amplification in a communication system providing a service to a subscriber by using a subscriber access technology such as a cable modem based on a CATV cable network (HFC, mixed optical coaxial cable network). A noise filtering and signal amplification apparatus in a communication system using a CATV network.

1 is a block diagram of a communication system for providing an Internet service using a conventional CATV network. The CATV signal transmitted from the Internet 11 to the router 13 is converted by the CMTS (15, Cable Modem Termination System) and transmitted from the combiner 19 to the transmitting station 17 of the CATV service center 10. And is transmitted through the HFC network 21 to the MATV network 25 or to each home through the branch 23, the CATV signal is transmitted to the TV through the converter 33 and the Internet packet signal to the cable modem 35 Is transmitted to the PC (31).

The CMTS 15 is a system that enables high-speed Internet using an existing cable network or an HFC network. The CMTS 15 provides a function of associating a cable modem and RF at a subscriber end with a data communication network, and assigns a cable modem MAC address to a DHCP server IP range. It is a device that controls and manages modems such as connecting functions.

The HFC network 21 is an abbreviation of Hybrid Fiber Coaxial Cable, and is a network in which fiber and coaxial cables are mixed, and has excellent bidirectional characteristics, and the HFC network is far from a broadcasting station. Data is transmitted by using optical cable, and coaxial cable is used from optical station to subscriber.

The MATV network (25, Master Antenna Television Network) is a public hearing network used in complex buildings such as apartments, shopping malls, large buildings, hotels, etc., and means a single receiving system that connects various TV receivers in the same building or building dense area. In other words, it refers to a network for setting up one main antenna and distributing a TV signal to a plurality of TV receivers therein for viewing.

The process of transmitting the data packet from the user's PC 31 to the Internet 11 is the reverse of the above-described data packet receiving process, which is converted into data suitable for the HFC network 21 in the cable modem 35 and the HFC network 21. The data is converted again while passing through the CMTS (15) and transmitted to the Internet (11) via the router (13).

The frequency range used in the CATV network as described above is the 5 MHz to 750 MHz band, the download channel used for data transmission from the CATV service center 10 to the user is 550 MHz to 750 MHz, and the cable TV broadcasting channel is 54 MHz to 450 MHz, and the upload channel used for data transmission from the user side to the CATV service center 10 is 5 MHz to 42 MHz.

The internet service system using CATV network has a significant meaning in that it can provide fast and stable internet service to subscribers using the existing HFC network, but it also has a problem to be solved to provide better service. . That is, the quality of communication is caused by the interference of signal caused by the complex communication method by the single medium, the noise generated by home appliances, the interference caused by amateur radio (HAM) communication, and the like caused by the connector or cable defect. It is necessary to prevent it from falling. In particular, this problem is opposite to the signal transmitted from the CATV service center to the subscriber (hereinafter referred to as a 'downward signal'), that is, the signal transmitted from the subscriber side to the CATV service center to the CATV service center (hereinafter referred to as an 'upward signal'). ') Stands out.

The present invention has been made to solve the problems in the communication system using a conventional CATV network as described above, the object of the present invention is to eliminate unnecessary noise in the communication, and to amplify the up and down signals. It is to provide a noise filtering and signal amplification device in a communication system using a CATV network that has an amplification function that can be used in the field without a separate amplifier.

Summary of the Invention

The present invention is a device for noise filtering and signal amplification in a communication system using a CATV network,

A first diplex filter for separating a downlink signal transmitted from the CATV service center toward the subscriber and an uplink signal transmitted from the subscriber side toward the CATV service center;

IF filter unit for removing noise by converting the frequency of the uplink signal separated from the first diplex filter into the intermediate frequency mixed with the local oscillated frequency, filtered by a band pass filter (BPF), and then converted back to the original frequency Wow;

An LPF for removing a high frequency signal from an upstream signal passing through the IF filter unit;

An uplink signal amplifier for amplifying an uplink signal passing through the LPF;

At the CATV service center, a second diplex filter for separating an uplink signal and a downlink signal;

And a downlink signal amplifier for amplifying the downlink signal passing through the second diplex filter.

The technical feature of the present invention is that when the uplink signal is transmitted, the original frequency is mixed with the locally oscillated frequency to create an intermediate frequency (IF), and the IF signal is filtered using a band pass filter. The method reduces the effects of the input and output stages by reducing the frequency to the original frequency, the channel frequency can be varied by changing the local oscillator (LO) in the IF stage, and the multiple filters in the IF stage. It is possible to vary the bandwidth used by connecting and switching in parallel. In addition, the variable channel and the variable bandwidth may be performed remotely through the communication unit.

On the other hand, when the downlink signal is transmitted, a downlink amplifier is added to compensate for the loss of the downlink signal and at the same time, the gain and the slope can be varied, so that it can be widely used in the actual field. Has characteristics.

Technical features of the present invention may be further highlighted by the configuration, operation, and effects of the preferred embodiments of the present invention described with reference to the accompanying drawings.

Example

2 is a block diagram of an embodiment of a noise filtering and signal amplifying apparatus 200 in a communication system using a CATV network according to the present invention.

As shown in Fig. 2, in the present embodiment, a first diplex filter 41 which separates a down signal and an up signal from the user side 20, and the first diplex filter 41 are separated from the first diplex filter 41. An IF filter unit 42 for modulating the frequency of the uplink signal to an intermediate frequency, filtering with a band pass filter, and then reducing the frequency to an original frequency to remove noise, and a high frequency signal from the uplink signal passing through the IF filter unit 42 A high frequency elimination filter 43 for removing a signal, an uplink signal amplifier 44 for amplifying an uplink signal passing through the high frequency elimination filter 43, and an uplink equalizer for compensating signal attenuation in a specific frequency band ( 45, an equalizer, an up attenuator 48, a second diplex filter 47 that separates an upstream signal and a downlink signal from the HFC network 21 side, a down attenuator 486, and a down equalizer 49 And outputted from the downward equalizer 49. It comprises a downlink signal amplification unit 50 for amplifying the downlink signal.

The operation of the noise filtering and signal amplifying apparatus 200 according to the present invention having the configuration as shown in FIG. 2 will be described below.

The upstream signal uploaded from the user side 20 is a signal occupying a frequency band of 5 MHz to 42 MHz, and is separated from the downlink signal of 54 MHz to 750 MHz in the first diplex filter 41 to separate the IF filter 42. Is entered. The upstream signal input from the IF filter unit 42 is mixed with the locally oscillated frequency, converted into an intermediate frequency (IF) band, and filtered. 3 shows a detailed configuration diagram of the IF filter section 42.

The upstream signal inputted to the IF filter unit 42 is adjusted to an appropriate level through the first attenuator 51, and then made through the PLL circuit 60 in the first mixer 52, and LO (Local). Oscillator) is mixed with the localized frequency amplified by the amplifier 61 and modulated into a signal of the intermediate frequency band (hereinafter referred to as "IF signal"). The IF signal is filtered by the first IF channel filter 53 to remove interference from the local oscillation signal and the uplink signal generated by the oscillator, and then amplified by the first IF amplifier 54 and input to the band pass filter unit 55 (BPF unit). do. The BPF unit 55 filters signals of unnecessary bands, and it is preferable to use the SAW filter 66 to produce a sharp signal. The signal output from the BPF unit 55 is amplified once again by the second IF amplifier 56, adjusted to the level of the appropriate signal by the second attenuator 57, and then passed through the second IF channel filter 58. After eliminating the frequency and minimizing the interference between the local oscillation signal and the uplink signal, the second mixer 59 is mixed with the local oscillation signal output from the oscillator 63 and restored to the frequency band of the original uplink signal.

4 shows a modified embodiment of the BPF section 55. As shown in FIG. In this embodiment, a plurality of SAW filters 66 having different pass bands are connected in parallel and switched under the control of the controller 40 to vary the use bandwidth. On the other hand, it is preferable that the frequency generated by the PLL circuit 60 be changed in accordance with the control of the controller 40.

Referring back to FIG. 2, the upstream signal from which noise is removed through the IF filter unit 42 is input to the high frequency elimination filter 43. The high frequency elimination filter 43 is mainly composed of a small downlink signal that is left without being removed by the first diplex filter 41 and amplified while passing through the IF filter unit 42, and that of the down band generated by the IF filter unit 42. It removes the signal. Since the frequency of the downlink signal is higher than the frequency of the uplink signal, a high frequency reject filter 43 is used, and either the LPF or the BPF may be used as the high frequency reject filter 43.

The uplink signal passing through the high pass filter 43 is amplified by the uplink signal amplifier 44 to compensate for the attenuation in the IF filter section 42, and is output through the uplink equalizer 45 and the uplink attenuator 46. The level is adjusted and sent to the HFC network 21.

In the case of the downlink signal transmitted from the HFC network 21 to the user side 20, it is separated from the uplink signal in the second diplex filter 47, adjusted to an appropriate level through the downlink attenuator 48, and then downlinked equalizer 49. ) To compensate for the attenuation of the signal according to the frequency characteristics of the transmission line, and is amplified by the downlink signal amplification unit 50 and transmitted to the user side 20. In the downlink signal transmission system, the gain and the inclination are variable so that the application range is wide in the actual field.

5A and 5B are graphs measured by a network analyzer in order to compare upward characteristics of a device and a third party product according to the present invention, and FIG. 5A is an upward characteristic of a third party product, and FIG. It is an upward characteristic of the device according to the invention. The horizontal line indicated by the circle in the graph is about the gain of the upward frequency characteristic.

When the CATV full frequency (upward: 5 to 42 MHz, downward: 54 to 750 MHz) is applied as the upstream input of a third-party product and the channel setting is 38 MHz, the output side shows the gain of the device according to the present invention. It can be seen that the high reflection coefficient characteristics are good, and particularly important is that the gain on the downstream side is -1.9409 dB for a third party product, for example, for marker 2 (65 MHz), but the device according to the present invention -23.985 dB, which is much better.

It can be seen that similar waveforms appear not only in marker 2 but also in the entire downlink region. In other words, it can be seen that the apparatus according to the present invention is outputted by changing the downlink signal component of the upstream input side to a signal component that is not attenuated by the upstream output side much. In addition, it can be seen indirectly from this graph that the downlink signal component generated on the upside can be removed much by the apparatus according to the present invention as compared to other products.

The embodiments described above are exemplary and should not be used to limit the technical scope of the present invention. The technical scope of the present invention should be determined by reasonable interpretation of the following claims.

 According to the apparatus of the present invention, in a communication system using a CATV network, interference of signals caused by a complex communication method using a single medium, noise generated in home appliances, interference with signals generated in amateur radio (HAM) communication, and the like, There is an effect that can simultaneously perform the amplification function while minimizing the effects of interference due to connector or cable failure.

In addition, it is possible to vary the frequency of the channel used by allowing the frequency generated from the oscillator to be variable, and the structure of connecting a plurality of BPFs having different pass bands in parallel to the filter part of the IF stage to use the bandwidth by switching control. There is an effect that can be varied. On the other hand, the variable channel and the variable bandwidth can be performed remotely.

Claims (8)

As a device for noise filtering and signal amplification in a communication system using a CATV network, A first diplex filter for separating a downlink signal transmitted from the CATV service center toward the subscriber and an uplink signal transmitted from the subscriber side toward the CATV service center at the subscriber side; An IF filter unit for removing noise by mixing an uplink signal separated from the first diplex filter with a locally oscillated signal, filtering the bandpass filter (BPF), and then converting the signal to an original frequency again; A high frequency elimination filter for removing a high frequency signal from an upward signal passing through the IF filter unit; An uplink signal amplifier for amplifying an uplink signal passing through the LPF; A second diplex filter for separating an uplink signal and a downlink signal at the CATV service center; Including a downlink signal amplifier for amplifying the downlink signal passed through the second diplex filter, The IF filter unit, A first attenuator for adjusting the input upstream signal to an appropriate signal level; A first mixer which modulates the uplink signal output from the first attenuator and the local oscillation signal generated by the oscillator and modulates it to an intermediate frequency; A first IF channel filter for removing interference from an uplink signal and a local oscillation signal generated by an oscillator from an IF signal output from the first mixer; A first IF amplifier amplifying the IF signal output from the IF channel filter; A BPF unit for removing noise from the IF signal amplified by the IF amplifier; A second IF amplifier for amplifying the IF signal output from the BPF unit; A second attenuator for adjusting the IF signal output from the second IF amplifier to an appropriate signal level; A second IF channel filter for filtering out unnecessary frequencies such as an uplink signal and a local oscillation signal from the IF signal output from the second attenuator; And a second mixer for mixing the IF signal output from the second IF channel filter and the local oscillation signal output from the oscillator to restore an uplink signal. Noise filtering and signal amplification apparatus in a communication system using a cable TV network. The method of claim 1, Between the second diplex filter and the downlink signal amplifier, A downlink attenuator for adjusting the downlink signal passing through the second diplex filter to an appropriate level; Noise filtering and signal amplification apparatus in a communication system using a cable TV, characterized in that it further comprises a down equalizer for correcting the overall frequency characteristics of the down signal output from the down attenuator. The method of claim 1, The high frequency rejection filter is LPF, the noise filtering and signal amplification device in a communication system using a cable TV network. The method of claim 1, The high frequency rejection filter is a BPF, the noise filtering and signal amplification device in a communication system using a cable TV network. delete The method of claim 1, The BPF unit may be configured by connecting a plurality of BPFs having different pass bands in parallel, and further including a control unit configured to control switching of the BPF unit, thereby controlling the control unit to vary the pass bandwidth. Noise filtering and signal amplification apparatus in a communication system using a cable TV network. The oscillating unit according to any one of claims 1 to 6, wherein An oscillator for generating a local oscillation signal, an LO amplifier for amplifying a local oscillation signal, and a divider for branching a local oscillation signal and inputting the first and second mixers, Noise filtering and signal amplification apparatus in a communication system using a cable TV network, characterized in that the channel frequency can be varied by changing the frequency of the local oscillation signal output from the oscillator. The method of claim 6, The BPF is a noise filtering and signal amplification apparatus in a communication system using a cable TV network, characterized in that the SAW filter.

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