JPS627285A - relay amplifier - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a repeater amplifier used in a transmission system including a television signal, such as a CATV transmission system.

Conventional CATV has a tendency to become multichannel in order to provide not only simple retransmission but also a variety of services such as independent broadcasting and paid program service (Pay TV).

Accordingly, transmission lines, especially relay amplifiers, are required to have particularly high performance. Many of the major factors that reduce the reliability of such transmission systems are related to repeater amplifiers that include active elements.

One of the problems associated with repeater amplifiers is increased distortion due to excessive signal levels or amplifier failure. Early detection of such distortion-increasing failures can shorten the time required for recovery, which is very useful.

Conventionally, the method for detecting distortion-increasing faults is to simultaneously transmit a viroft signal of a specific frequency and find the distortion-increasing fault indirectly by knowing the level of this pilot signal at the input or output of a relay amplifier. A method was taken. An example of such a conventional repeater amplifier will be described below with reference to the drawings. ' Fig. 5 shows a block diagram of a conventional repeater amplifier.

In FIG. 5, 1 is an input terminal, 2 is an upper and lower signal separation filter, 3 is a down line amplifier, 4 is an up line amplifier, 6 is an upper and lower signal separation filter, 7 is an output terminal, 18 is a first filter, and 402 is a DC Detector, 17 is a modulation signal generator,
16 is a modulator, 15 is a carrier wave oscillator, 14 is a multiplexer,
The relay amplifier 5 is configured as described above.

The operation of the relay amplifier configured as above will be described below. A downlink signal consisting of a downlink video signal and a pilot signal of a specific frequency added to check the operating state of the downlink amplifier 3 enters from the input terminal 1, is separated by the upper and lower signal separation filter 2, and is sent to the downlink amplifier 3. It is amplified by 3. The pilot signal amplified together with the downlink video signal is extracted by the first filter 18, detected by the DC detector 402, and the output level of the downlink amplifier 3 is measured. Therefore, if the level of this test signal appears to be abnormally high, it can be predicted that distortion has occurred. In this example, the return carrier wave obtained from the carrier wave oscillator 15 is transmitted to the modulator 1 using a signal obtained from the modulation signal generator 17 whose frequency etc. can be changed according to this level value.
6 and returns it to the head end as an upstream signal, it is possible to monitor the generation of distortion due to an excessive input level of the relay amplifier at the head end.

(Japanese Unexamined Patent Application Publication No. 50-33723, etc.) Problems to be Solved by the Invention However, in the above configuration, problems occur due to disturbances in the characteristics within the band and the line amplifier's power becomes excessive in some parts of the band. distortion may not be detected. This is because only the frequency of the pilot signal is monitored. Furthermore, if the line amplifier has a push-pull configuration, it may not be possible to detect an increase in distortion due to a failure of the line amplifier itself, such as loss of balance.

In view of the above problems, the present invention provides a relay amplifier that can directly and accurately detect an increase in distortion during actual video transmission service, rather than using an indirect method such as level monitoring. It is something.

Means for Solving the Problems In order to solve the above problems, the relay amplifier of the present invention includes means for supplying an unmodulated pilot signal to the input of one or more line amplifiers in the relay amplifier, and each of the above-mentioned problems. A first pilot signal connected to the output of the line amplifier for extracting a pilot signal cross-modulated by the nonlinearity of the line amplifier.
a filter, a detector capable of extracting the envelope of the pilot signal, and a second wave detector capable of passing one or more frequency components of the horizontal scanning frequency of the transmitted television signal and frequencies that are integral multiples thereof. This device includes a filter and a level detector that detects the level of the detection signal that has passed through the second filter.

Effect: With the above-described configuration, the present invention makes it possible to accurately detect a distortion increase failure in a repeater amplifier by extracting the cross-modulation component from the transmitted television signal to the pilot signal and monitoring its level. .

Embodiment Hereinafter, a relay amplifier according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a circuit diagram of a relay amplifier according to a first embodiment of the present invention. In FIG. 1, 18 is a first filter, 19 is a signal amplifier, and 20 is a detector, and these constitute a signal amplification and detection section 21. Further, 25 is a <Ilot signal generator, 9 is a second filter, 10 is a detection signal amplifier, 1
) is a level detector, 12 is a determiner, and 13 is a determination output terminal, and these and the pilot signal amplification/detection section 21 constitute a total increase detection section 22. Furthermore, ■ is an input terminal,
7 is an output terminal, 8 is a line amplifier, 24 is a multiplexer, and the unidirectional repeater amplifier 5 is constructed by the above.

Regarding the relay amplifier configured as above, the following is the first section.
The operation will be explained using the diagram and FIG.

When a signal passes through a line amplifier that is generally not linear, the output contains more than the input signal components.

Now, when the input signal X is expressed by the following formula, x = Ac
os at + B cos bt −
...-■ The component corresponding to the so-called third-order distortion of x3 is expressed by the following equation using the 0 equation.

x3-(Acos at+Bcos bt)'=1
/ 4 (A3cos 3at+B3cos 3bt)
+ 3/4 (A” B cos (2a±b)
t +AB2cos (2b+a) t 1+ 3
/ 4 (A' cos at+ B' cos bt
)+ 3/2 (AB” cos at+BA” c
os bt)・・・・・・■ ■In the equation, the first term is the third harmonic component, the second term is the intermodulation component, the third term is the fundamental wave nonlinear component, and the fourth term is the cross modulation component. It is an ingredient. Furthermore, in the equation (2), if the first term is an unmodulated pilot signal and the second term is a television signal, then the video signal is s (t), and 3 = l + S
(t) ・・・・・・■ A, a, and b are constants. Therefore, focusing on AB''cosat, which is a cross-modulation component, it is expressed as follows. This indicates that the video signal component and its second-order distortion component appear in the pilot signal envelope of the line amplifier output. On the other hand, the video signal s(t) has very strong components at the horizontal scanning frequency and its integral multiples.Therefore, by detecting the pilot signal of the line amplifier output, we detect the horizontal scanning frequency and frequency components at its integral multiples. By detecting an increase in the level of , it is possible to detect an increase in distortion of the amplifier. Note that this also applies when there are multiple television signals input to the line amplifier.

In FIG. 1, a television signal or the like is input to the input terminal 1, and a pilot signal generator 25 is further input to the multiplexer 24.
The unmodulated pilot signal obtained is injected and amplified by the line amplifier 8. The pilot signal that has undergone cross modulation in the output signal is extracted by the first filter 18,
A pilot signal amplifier 19 amplifies the signal, and a wave detector 20 performs envelope detection.

The detector 20 is a half-wave rectification type, a full-wave rectification type, a square law detector,
Any device that can extract the envelope may be used, such as a synchronous detector using PLL or the like.

As mentioned above, the output of the detector 20 includes the horizontal scanning frequency and frequency components that are integral multiples thereof, and the second filter 9 passes one or more of these components. . If the output signal of the second filter 9 is called a detection signal, the second filter 9 serves to improve the S/N ratio of the detection signal and stabilize the total increase detection operation.

FIGS. 2A to 2C show examples of frequency characteristics of such a second filter 9. However, in 7 and FIG. 2, fH indicates the horizontal scanning frequency.

The detection signal obtained in this way is sent to the detection signal amplifier 1.
After being amplified by 0, the level is detected by a level detector 1), and the level is determined by a determiner 12 after passing through an appropriate time constant circuit. If the determiner 12 determines that the small signal level has become abnormally high, the determiner 12 outputs a total increase failure occurrence signal to the determination output terminal 13.

As described above, according to this embodiment, an unmodulated pilot signal is supplied to the input of the line amplifier 8 by the pilot signal generator 25 and the multiplexer 24, and the pyro signal is cross-modulated by the distortion of the line amplifier 8. a first filter 18 that extracts the pilot signal; a detector 20 that extracts the envelope of this pilot signal; and a second filter 9 that passes one or more components of the horizontal scanning frequency and its integral multiples. By providing the level detector 1), it is possible to directly and accurately detect a total increase fault in the relay amplifier by detecting an increase in the level of the intermodulation component from the television signal to the pilot signal.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a circuit diagram of a relay amplifier showing a second embodiment of the present invention. In the same figure, 21 is a pyro/7) signal amplification/detection section, 9 is a second filter, 10 is a detection signal amplifier, 1) is a level detector, and 12 is a determiner, which is the same as the configuration shown in FIG. It constitutes the detection section 22. Also, 13
1 is a judgment output terminal, 1 is an input terminal, and 7 is an output terminal, which is the same as the configuration shown in FIG. The difference from the configuration in FIG. 1 is that the detector 20 in the pilot signal amplification/detection section 21 is composed of a synchronous detector 27 that uses the output of the pilot signal generator 25 as a reference signal. Note that the unidirectional relay amplifier 5 is configured as described above.

The operation of the relay amplifier configured as described above will be described below. The method of detecting an increase in distortion is exactly the same as in the first embodiment, and when the distortion of the line amplifier 8 increases, the determination device 12
outputs a distortion increase failure occurrence signal to the determination output terminal 13.

The difference from the first embodiment is that the method for extracting the envelope of the pilot signal is a synchronous detection method using a synchronous detector 27, and the regeneration of the reference signal is not by a method such as PLL, but by a pilot signal generator 25. Since the signal is directly supplied from the detector, the configuration is simple, the S/N ratio of the signal after detection can be improved, and stable operation can be expected. However, the synchronous detector 27 includes a function to change the phase of the reference signal if necessary.

As described above, by providing the synchronous detector 27 and supplying its reference signal directly from the pilot signal generator, the configuration is simple and the distortion increase detection operation can be performed stably.

A third embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a circuit diagram of a relay amplifier showing a third embodiment of the present invention. In the figure, 1 is an input terminal, 7 is an output terminal, 22 is a total increase detection section, and 24 is a multiplexer, which is the same as the configuration shown in FIG. 1.

The difference from the configuration shown in FIG. 1 is that there are two line amplifiers, such as a down line amplifier 3 and an up line amplifier 4, and that a modulation signal generator 17, a carrier wave oscillator 15, a modulator 16, and a multiplexer 14 are provided. The upper and lower signal separation filters 2 and the upper and lower signal separation filters 6 provide a bidirectional relay amplifier 5 as a whole.
is configured.

The operation of the relay amplifier configured as described above will be described below. The method of detecting an increase in distortion is exactly the same as in the first embodiment, and when the distortion of the downlink amplifier 3 increases, the total increase detection section 22 outputs a distortion increase fault occurrence signal. In this example, the carrier wave oscillator 1 is a signal obtained by a modulation signal generator 17 whose frequency etc. can be further changed by this signal.
By modulating the return carrier wave obtained in step 5 with the modulator 16 and sending it back to the head end as an upstream signal, it is possible to monitor the occurrence of a failure due to an increase in distortion in the relay amplifier 5 at the head end.

As described above, the modulation signal generator 17, the carrier wave oscillator 1
5. By providing the modulator 16 and the multiplexer 14, it is possible to monitor the occurrence of a failure due to an increase in distortion in the relay amplifier 5 at the head end.

In this embodiment, the distortion increase detection unit 22 is connected to the down line amplifier 3 to detect the occurrence of distortion in the down line amplifier 3, but the total increase detection unit 22 is connected to the up line amplifier 4. However, the occurrence of distortion in the up-line amplifier 4 may be detected. Furthermore, two systems of total increase detection sections 22 may be provided, one connected to the down line amplifier 3 and the other connected to the up line amplifier 4, so that the occurrence of distortion in both amplifiers may be detected. The multiplexer 14 may be provided on the output side of the uplink amplifier 4. Furthermore, in any of the above cases, the total increase detection section 22 may use a synchronous detector 27 that uses the output of the pilot signal generator 25 as a reference signal, similar to the second embodiment.

Furthermore, in any of the first, second, and third embodiments, the pilot signal frequency may be a frequency within the transmission band that does not overlap with the transmission signal, or a frequency outside the transmission band.

Effects of the Invention As described above, the present invention provides means for supplying an unmodulated pyconto signal to the input of one or more line amplifiers in the relay amplifier in a relay amplifier for a transmission system including television signals, and a first filter connected to the output of the line amplifier for extracting a pilot signal cross-modulated by the nonlinearity of the line amplifier; and a detector capable of extracting the envelope of the pilot signal; A second filter that can pass one or more frequency components of the horizontal scanning frequency of the television signal and frequencies that are integral multiples thereof, and a level detector that detects the level of the detection signal that has passed the second filter. By extracting the cross-modulation component from the pilot signal from the transmitted television signal and monitoring its level, it is possible to accurately detect a distortion increase failure in the repeater amplifier.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a circuit configuration of a relay amplifier in a first embodiment of the present invention, FIG. 2 is a diagram showing an example of frequency characteristics of the second filter 9, and FIG. 3 is a diagram showing an example of the frequency characteristics of the second filter 9. FIG. 4 is a diagram showing the circuit configuration of the relay amplifier in the third embodiment of the present invention,
FIG. 5 is a diagram showing the circuit configuration of a conventional repeater amplifier. 1...Input terminal, 2...Upper and lower signal separation filter, 3...Down line amplifier, 4...
...up line amplifier, 5...relay amplifier, 6.
...Upper and lower signal separation filter, 7...Output terminal, 8...Line amplifier, 9...2nd
Filter, 10...Detection signal amplifier, 1)...
... Level detector, 12 ... Judgment device, 13
...Judgment output terminal, 14...Multiplexer,
15... Carrier wave oscillator, 16... Variable A
ll unit, 17...Modulation signal generator, 18...
...First filter, 19...Pilot signal amplifier, 20...Detector, 21...
Pilot signal amplification detection unit, 22... Full increase detection unit, 24... Multiplexer, 25... Pilot signal generator, 27... Synchronous detection vessel. Name of agent Patent attorney Toshio Nakao 1 person Figure 1 50th century amplification ticket Figure 2 JH'2IH3fH edge carving leather collection Figure 3 Mogu-ku Behi Pebe

Claims (4)

[Claims] (1) In a relay amplifier for a transmission system including television signals, means for supplying an unmodulated pilot signal to the input of one or more line amplifiers in the relay amplifier, and means connected to the output of each of the line amplifiers. a first filter that extracts the pilot signal cross-modulated due to the nonlinearity of the line amplifier; and a detector that can extract the envelope of the pilot signal that has passed through the first filter;
a second filter capable of passing one or more frequency components of the horizontal scanning frequency of the television signal being transmitted from the detector output signal and frequencies that are integral multiples thereof;
A relay amplifier comprising a level detector for detecting the level of the detection signal that has passed through the second filter, and detecting an increase in distortion of the line amplifier by an increase in the level of the detection signal. (2) The repeater amplifier according to claim (1), wherein the transmission system is a CATV transmission system. (3) The detector is of a synchronous detection type, and the reference signal of the synchronous detector is directly supplied from the pilot signal generation means,
2) The relay amplifier described in section 2). (4) Claim No. 1, characterized in that the frequency of the pilot signal is outside the input signal band of the line amplifier.
), (2) or (3).