JP4164433B2 - Bidirectional CATV amplifier - Google Patents

Description

  The present invention relates to a bidirectional CATV amplifying apparatus having a monitor terminal provided on a transmission line of a CATV system.

  A bidirectional CATV amplifier provided on a transmission line of a CATV system generally includes a monitor terminal for monitoring the level of an input / output signal. This monitor terminal is coupled to an input / output signal path via a directional coupler, and can be measured at a value that is −20 dB lower than the actual input / output signal level.

  FIG. 2 is a block diagram showing a configuration of a conventional bidirectional CATV amplifier. In FIG. 2, 10 is a downstream input / upstream output terminal provided on the head-end device side of the CATV system, and a downstream signal (70 to 770 MHz) from the head-end device input to the downstream input / upstream output terminal 10 is It is sent to the downstream amplification unit 31 and amplified.

  The downlink amplification unit 31 includes a high-pass filter (HPF) 12 that selects a downlink signal using a frequency band of 70 to 770 MHz, a directional coupler 13 with a coupling amount of −20 dB, a downlink amplification circuit 15, and a coupling amount of −20 dB. The directional coupler 16 and a high-pass filter (HPF) 17 that allows the downstream signal (70 to 770 MHz) to pass therethrough, and an output signal of the high-pass filter (HPF) 17 is sent to the downstream output / upstream input terminal 18.

  The downlink input signal taken out from the coupling terminal of the directional coupler 13 is sent to the downlink input monitor terminal 14, and the downlink output signal taken out from the coupling terminal of the directional coupler 16 is sent to the downlink output monitor terminal 19. Sent.

A downlink signal is output from the downlink output / uplink input terminal 18 and sent to a television receiver or the like at the home of the CATV subscriber.
Further, the downstream output / upstream input terminal 18 receives an upstream signal transmitted from a terminal device of a CATV subscriber's home such as the personal computer. This upstream signal uses a frequency band of 10 to 55 MHz. The uplink signal input from the terminal device to the downlink output / uplink input terminal 18 is sent to the uplink amplification unit 20 and amplified.

  The upstream amplifying unit 20 includes a low-pass filter (LPF) 21 that passes an upstream signal of 10 to 55 MHz, a directional coupler 22 having a coupling amount of −20 dB, an upstream amplifier circuit 24, and a directional coupler having a coupling amount of −20 dB. It consists of a low-pass filter (LPF) 26 that passes an upstream signal of 25, 10 to 55 MHz, and an output signal (upstream signal) of this low-pass filter (LPF) 26 is output to the transmission line via the downstream input / upstream output terminal 10. To the headend device.

The upstream input signal taken out from the coupling terminal of the directional coupler 22 is sent to the upstream input monitor terminal 23, and the upstream output signal taken out from the coupling terminal of the directional coupler 25 is sent to the upstream output monitor terminal 27. Sent.
JP 2000-175173 A

  In the conventional bidirectional CATV amplifying device, the monitor device is connected to the downlink input monitor terminal 14, the downlink output monitor terminal 19, the uplink input monitor terminal 23, and the uplink output monitor terminal 27, so that the actual input / output level can be controlled. Each signal level can be measured with a value reduced by -20 dB.

  In measuring the signal level, in the measurement of the uplink output at the uplink output monitor terminal 27, it is necessary to simultaneously measure the noise level existing in the band in addition to the actual uplink signal. This noise level is an important measurement item because it affects upstream signals used on the Internet.

  However, since the noise level is as low as 20 to 30 dBμ, the value is reduced by the coupling amount (−20 dB) by the directional coupler 25, and the value at the upstream output monitor terminal 27 is 0 to 10 dBμ. This level of 0 to 10 dBμ is a value that cannot be easily measured using a spectrum analyzer. Therefore, in order to measure the noise level of the upstream signal, a measuring instrument is directly connected to the downstream input / upstream output terminal 10 or an auxiliary amplifier of about 20 dB is connected to the upstream output monitor terminal 27 to amplify the monitor output. , Measuring. For this reason, the work becomes complicated, and the auxiliary amplifier is also generally unreliable, resulting in an error in measurement. Further, during operation of the CATV system, a measuring instrument cannot be directly connected to the output terminal, so that accurate measurement is difficult.

  The present invention has been made to solve the above-described problems, and provides a bidirectional CATV amplifier capable of easily and accurately measuring the level and noise level of an upstream output signal even during operation. Objective.

  A bidirectional CATV amplifying device according to the present invention includes a downlink amplifying unit that amplifies a CATV downlink signal input via a downlink input / uplink output terminal and outputs the amplified signal to the downlink output / uplink input terminal, and the downlink output / uplink input. An upstream amplification unit that amplifies the CATV upstream signal input via the terminal and an upstream output signal amplified by the upstream amplification unit are divided into two, and one of the distribution signals is output to the downstream input / upstream output terminal. And a distributor for outputting the other distributed signal to the upstream output monitor terminal.

  According to the present invention, the upstream output signal amplified by the upstream amplifying unit of the bidirectional CATV amplification device is divided into two by the distributor, and the distributed signal is output to the upstream output monitor terminal. The output signal level and noise level of the same value as the actual upstream output signal can be measured at the upstream output monitor terminal without blocking the upstream output signal. Further, when no measurement is performed, it is possible to reliably prevent external noise from being mixed by blocking between the distributor and the upstream output monitor terminal and terminating the upstream output monitor terminal with a dummy resistor.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a bidirectional CATV amplifier according to an embodiment of the present invention.
In FIG. 1, reference numeral 30 denotes a downstream input / upstream output terminal provided on the head end device side of the CATV system. A CATV downstream signal (70 to 770 MHz) from the head end device input to the downstream input / upstream output terminal 30 is Then, it is sent to the downstream amplification unit 31 and amplified.

  The downstream amplification unit 31 includes a high-pass filter (HPF) 32 that selects a downstream signal using a frequency band of 70 to 770 MHz, a directional coupler 33 with a coupling amount of −20 dB, and a slope adjustment with a frequency characteristic correction amount of 2 dB. SLOPE 35, a slope adjuster 36 with a frequency characteristic correction amount of 4 dB, an attenuator (ATT) 37 with a signal attenuation of 2 dB, an attenuator 38 with a signal attenuation of 4 dB, an amplifier 39 for amplifying the downstream signal, 0 to 0 Variable slope adjuster 40 for correcting frequency characteristics in a range of −10 dB, variable gain adjuster 41 for adjusting a signal level in a range of 0 to −10 dB, a plurality of stages, for example, three stages of amplifiers 42, and a coupling amount of −20 dB A high-pass filter (HPF) 44 that allows a downstream signal (70 to 770 MHz) to pass through. HPF) output signal 44 is sent to the downstream output / uplink input terminal 45.

  The downlink input signal taken out from the coupling terminal of the directional coupler 33 is sent to the downlink input monitor terminal 34, and the downlink output signal taken out from the coupling terminal of the directional coupler 43 is sent to the downlink output monitor terminal 46. Sent to.

Downlink signals are output from the downlink output / uplink input terminal 45 and sent to a television receiver or the like at the home of a CATV subscriber.
The downstream output / upstream input terminal 45 receives a CATV upstream signal transmitted from a terminal device of a CATV subscriber's home such as the personal computer. This upstream signal uses a frequency band of 10 to 55 MHz. The uplink signal input from the terminal device to the downlink output / uplink input terminal 45 is sent to the uplink amplification unit 50 and amplified.

  The upstream amplifying unit 50 includes a low pass filter (LPF) 51 that passes an upstream signal of 10 to 55 MHz, a directional coupler 52 having a coupling amount of −20 dB, an attenuator 54 that can switch a signal attenuation amount between 5 dB and 10 dB, A band switch 55 for switching the pass frequency band of the signal line to 10 to 55 MHz or 30 to 55 MHz, an amplifier 56 for amplifying the upstream signal, and a variable gain adjuster 57 for adjusting the signal level in the range of 0 to −10 dB, 0 to − Variable slope adjuster 58 that corrects frequency characteristics in the range of 10 dB, amplifier 59 that amplifies the upstream signal, upstream signal line is turned on to amplify the upstream signal, or signal line is turned off to cut the upstream signal Amplification switching device 60 for switching whether to perform, a slope capable of switching the frequency characteristic correction amount between -2 dB and -4 dB An attenuator 62 whose signal attenuation is switched between 2 dB and 4 dB, an attenuator 63 whose signal attenuation is switched between 6 dB and 12 dB, a distributor 64 which distributes the upstream signal into two, and one of the distributors distributed by this distributor 64 A low-pass filter (LPF) 65 that passes a signal (10 to 55 MHz) is output, and an output signal (upstream signal) of the low-pass filter (LPF) 65 is output to the transmission line via the downstream input / upstream output terminal 30, and the head end Sent to the device.

  The upstream input signal taken out from the coupling terminal of the directional coupler 52 is sent to the upstream input monitor terminal 53, and the other signal distributed by the distributor 64 is passed through the changeover switch 66 to the upstream output monitor terminal. 67.

  The changeover switch 66 is a switch for turning on / off between the distributor 64 and the upstream output monitor terminal 67. When switched to the ON side, the distribution output terminal of the distributor 64 is connected to the upstream output monitor terminal 67. When switched to the off side, the distribution output terminal of the distributor 64 and the upstream output monitor terminal 67 are turned off, the distribution output terminal of the distributor 64 is grounded, and the upstream output monitor terminal. Dummy resistors 68 and 69 are connected between 67 and ground, respectively. That is, when the changeover switch 66 is switched to the on side, the distribution output terminal of the distributor 64 is connected to the upstream output monitor terminal 67 to enable measurement of the upstream output signal and noise level. When switched to the OFF side, the distribution output terminal of the distributor 64 and the upstream output monitor terminal 67 are terminated by dummy resistors 68 and 69 to prevent external noise from being mixed.

  In the bidirectional CATV amplifier configured as described above, the downstream input monitor terminal 34, the downstream output monitor terminal 46, and the upstream input monitor terminal 53 are connected to the actual input / output level by connecting the monitor device. Each signal level can be measured with a value reduced by -20 dB.

  When a monitor device is connected to the upstream output monitor terminal 67 and the changeover switch 66 is turned on, the output signal level having the same value as the actual upstream output signal and the noise level mixed in the upstream signal are set. Can be measured. That is, the upstream amplifying unit 50 divides the upstream output signal into two by the distributor 64, outputs one distributed signal to the downstream input / upstream output terminal 30 via the low pass filter (LPF) 65, and outputs the other distributed signal. Since the signal is output to the upstream output monitor terminal 67 via the changeover switch 66, the upstream output monitor terminal 67 can measure the output signal level and the noise level having the same value as the actual upstream output signal.

  Further, by dividing the upstream output signal by the distributor 64, the upstream output monitor terminal 67 can measure at any time without disconnecting the upstream output signal even in actual operation.

  At the time of non-measurement, the selector switch 66 is switched to the OFF side to cut off between the distribution terminal of the distributor 64 and the upstream output monitor terminal 67, and the distribution terminal of the distributor 64 and the upstream output monitor terminal 67. Are terminated by dummy resistors 68 and 69, respectively, so that external noise can be reliably prevented.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying constituent elements without departing from the scope of the invention in the implementation stage.

It is a block diagram which shows the structure of the bidirectional | two-way CATV amplification apparatus which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the conventional bidirectional | two-way CATV amplifier.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 30 ... Downlink input / uplink output terminal, 31 ... Downlink amplification part, 32 ... High pass filter (HPF), 33 ... Directional coupler, 34 ... Downlink input monitor terminal, 36 ... Slope adjuster, 38 ... Attenuator, 39.0 ... Amplifier 40 ... Variable slope adjuster 41 ... Variable gain adjuster 42 ... Amplifier 43 ... Directional coupler 44 ... High pass filter (HPF) 44 ... Directional coupler 45 ... Downstream output / upstream input Terminals 46: Downstream output monitor terminal 50: Upstream amplification unit 51: Low pass filter (LPF) 51, 52 ... Directional coupler 53: Upstream input monitor terminal 54: Attenuator 55: Band switch 56 ... Amplifier 57 ... Variable gain adjuster 58 ... Variable slope adjuster 59 ... Amplifier 60 ... Amplification switching device 61 ... Slope adjuster 62, 63 ... Attenuator, 4 ... distributor, 65 ... low-pass filter (LPF), 66 ... change-over switch, 67 ... ascending output monitor terminal, 68, 69 ... dummy resistor.

Claims (1)

  A downstream amplifying unit that amplifies a CATV downstream signal input via a downstream input / upstream output terminal and outputs the amplified CATV downstream signal to the downstream output / upstream input terminal; and a CATV upstream signal input via the downstream output / upstream input terminal. The upstream amplifying unit to amplify and the upstream output signal amplified by the upstream amplifying unit are divided into two, one distributed signal is output to the downstream input / upstream output terminal, and the other distributed signal is transmitted to the upstream output monitor terminal. A bidirectional CATV amplifying apparatus comprising: a distributor for outputting.

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