JPS6216587B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION When broadcasting programs such as radio, FM, and television audio, the present invention enables the transmission of signals related to programs sent via carrier lines connecting studios. This invention relates to a signal detection method for detecting multiple pilot signals for monitoring and controlling signals.

In the above pilot signals, the signal for monitoring the quality of the program is called the I signal, and the control signal for online real-time switching of the program is called the Q signal. These I and Q signals are transmitted by erasing the 9.5 to 10.4 kHz portion of the carrier band on the carrier line using a band elimination filter, and superimposing the erased portion. In order to increase the reliability of detection, these program quality monitoring signals and program switching control signals are each assigned as a predetermined combination of two frequencies.
Each is transmitted as a frequency-divided signal. 9.5
In the ~10.4kHz carrier band, the frequencies normally used for I and Q signals are 9.72~10.02kHz.
There are 11 frequencies at 30Hz intervals in the range.

Due to their characteristics, the I and Q signals are transmitted continuously, and the Q signal is transmitted at a higher level than the I signal for only 1 to 3 seconds. Therefore, Q
While the signal is being sent, the I signal and Q signal are simultaneously transmitted for that time, resulting in a waveform in which four frequencies (two I signal frequencies and two Q signal frequencies) are combined. On the other hand, on the receiving side, these I,
The Q signal is detected and used for program monitoring and switching control, but the detection method is to extract the I and Q frequency signals from the received signals using a narrow band filter and rectify them. ing.

When determining the presence or absence of the above detection signal, we take measures to prevent false detections due to programs being mixed into the I and Q bands due to incorrect connection of lines (noise margin), and the overall system timing for program switching and supervisory control. (on-delay time), the charging time constant of the rectifier circuit is set to a certain specified value. However, in recent years, due to a system review when updating the program transmission control system,
I had to shorten my on-day time. However, there is a reciprocal relationship between the on-delay time and the noise margin, and with the conventional signal detection method, there is a problem that the noise margin standard cannot be satisfied when the on-delay time is shortened. It has arisen.

SUMMARY OF THE INVENTION An object of the present invention is to provide a signal detection method that can satisfy the noise margin standard even if the on-delay time is shortened, in order to compensate for the drawbacks of the conventional method described above.

According to the present invention, it is applied to a signal transmission method in which an information transmission signal and a plurality of pilot signals for monitoring and controlling the information transmission signal are transmitted in a superimposed manner in the same transmission band, and the plurality of pilot signals are transmitted in a common manner. In a signal detection method comprising a means for amplifying the pilot signal, and a plurality of signal detection means for individually detecting each pilot signal from the output of the common amplification means, the output of the common amplification means is branched. A level comparing means for detecting a noise level from the output is provided, and the amplification gain of the signal in each pilot band received by the plurality of signal detecting means is variably controlled by the output of the level comparing means. A signal detection method is obtained.

Here, in order to facilitate comparison with the present invention,
A conventional signal detection method will be explained with reference to the block diagram of FIG. In this figure, 1 is a signal common amplification section, 2-1 to 2-n are signal detection sections, and 3
indicates the logic part. Further, in the signal common amplification section 1, 1a is a bandpass filter for extracting I and Q signals, 1b is a signal common amplifier, and signal detection sections 2-1 to 2-
In the representatively illustrated signal detecting section 2-1, 2-1a is a narrow band waver for individually extracting one frequency of the I or Q signal;
b is an amplifier for amplifying the level of the extracted I or Q signal, 2-1c is a rectifier for converting the AC signal into DC, and 2-1d is for comparing the level of the rectified DC output with a reference value. It is a level comparator. The signal detection units 2-1 to 2-n all have the same internal configuration, and are all connected in parallel on the input side.

In the conventional example configured in this way, the reception input a is a signal in which I and Q signals are superimposed on the program level, and from this signal, the bandpass waveform generator 1a
Only I and Q signals of 9.72 to 10.02 kHz are extracted, and unnecessary waves beyond that, such as noise and program components, are suppressed. Next, the selected I and Q signals are amplified to a required level by the amplifier 1b and supplied to the signal detection sections 2-1 to 2-n. In addition to this, for example, in the signal detection section 2-1,
Assume that only one wave of the I and Q signals of 9.27 to 10.02 kHz is extracted by the narrowband wave filter 2-1a (actually, a mechanical filter or the like is used). The extracted I or Q frequency is amplified to a required level by a fixed gain amplifier 2-1b,
The rectifier 2-1c converts the AC signal into a DC voltage. The charging time constant in this rectifier 2-1c is set so that this circuit has a delay time of a certain value in order to determine the timing of program switching, but this delay time is used for other purposes such as If abnormal noise (here, it means a random noise component that is caused by a systematic misconnection of a program component whose I and Q superimposed frequency bands are not suppressed) is mixed into the reception input a, It also has the role of smoothing this component to a level that is not detected by the level comparator 2-1d at the next stage (does not reach the threshold level). Therefore, as mentioned above, if the on-delay time is shortened to, for example, half of the conventional time for the purpose of correcting the program switching timing, the charging time constant of the rectifier will become shorter and smoothing will not be possible. The noise component is erroneously detected by the level comparator 2-1d (the rectified output of the noise component approaches the threshold level)
I come to do it. Next, in the level comparator 2-1d, a threshold level is set so that a level-off detection signal is output when the signal level drops beyond a certain level. Finally, each of the detection output signals is applied to the logic section 3, and the logic is calculated for each two frequencies that have been combined in advance, and the outputs C ₁ to _{C r}
It is possible to know which I signal or which Q signal has been received. For example, n=11
If we use 11 frequencies as
The maximum number of frequency combinations is 55, with outputs C ₁ to C _r
= 55, it is possible to discriminate 55 pairs.

Next, an embodiment of the present invention will be described with reference to the block diagram of FIG. In this diagram,
1' is a signal common amplification and noise detection section, 2'-1
2'-n represents a signal detection section, and 3 represents a logic section. First, in the signal common amplification and noise detection section 1', 1a and 1b have the same functions as the band wave amplifier and the signal common amplifier in FIG. The rectifier 1d is a level comparator for detecting the noise level. In addition, the signal detection section 2'
-1 to 2'-n, 2-1a, 2-1c and 2-1d have the same functions as the narrowband waveform generator, rectifier and level comparator in FIG. 1, respectively, and 2-1b ', whereas the gain of the gain amplifier 2-1b in FIG. 1 is fixed,
This is a variable gain amplifier whose level can be varied by an external control signal.

In this embodiment, the output of the signal common amplifier 1b is applied to the signal detection units 2'-1 to 2'-n, and is further branched and applied to the rectifier 1c, where it is applied to the I and Q signal bands. All of the signals are directly rectified and converted to DC levels. Therefore, even if components other than the I and Q signals are input through this band, they are not distinguished and are rectified as they are. It should be noted that the level of unnecessary waves (program level) other than the I and Q signals mixed into this band is, for example, more than ten dB higher than the normal signal wave level at the peak level. Therefore, the DC output of the rectifier 1c is considerably higher than the DC output obtained by rectifying the signal wave. Therefore, the threshold level of the next stage level comparator 1d is set to the level of the highest level of the signal wave, and when a higher level than this is input, unnecessary wave components other than the signal are mixed in. The output is taken from the level comparator 1d. Here, the precondition is that unnecessary waves mixed in the IQ band are not received at the same time as the I and Q signals. Therefore, anything exceeding the threshold level of the level comparator 1d can be considered as unnecessary waves. The output of the level comparator 1d is supplied to each variable gain amplifier of the signal detection sections 2'-1 to 2'-n. Taking the signal detection section 2'-1 as an example, when the level comparator 1d detects an unnecessary wave, its output is used to detect the variable gain amplifier 2-1.
The gain of 1b' is reduced. As a result, the level of unnecessary waves appearing in the output of the narrowband transducer 2-1a is suppressed, and the output rectified by the rectifier 2-1c is made to be below the threshold level of the level comparator 2-1d. controlled by. Note that all other operations of the signal detection sections 2'-1 to 2'-n are the same as those of the signal detection section in FIG. 1, and the operation of the logic section 3 is also the same as that of the logic section of FIG. be.

As is clear from the above explanation, according to the present invention, when unnecessary waves of a level higher than the signal level are mixed into the band in which the pilot signal is used, the level of the unnecessary waves is lowered to prevent false detection of unnecessary waves. By doing so, the noise margin standard can be met regardless of the on-delay time length, which has a significant effect on improving the reliability of program signal monitoring and control. It will be done.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a conventional signal detection system, and FIG. 2 is a block diagram showing the configuration of an embodiment according to the present invention. In the figure, 1 is a signal common amplification section, 1' is a signal common amplification and noise detection section, 1a is a bandpass filter, 1b is an amplifier, 1c is a rectifier, 1d is a level comparator, 2-1 to 2-n,
2'-1 to 2'-n are signal detection sections, 2-1a is a narrow band waver, 2-1b is a fixed gain amplifier, 2-1
b' is a variable gain amplifier, 2-1c is a rectifier, 2-1
d is a level comparator, and 3 is a logic section.

Claims (1)

[Claims] 1 Applied to a signal transmission method in which an information transmission signal and a plurality of pilot signals for monitoring and controlling the information transmission signal are transmitted in a superimposed manner in the same transmission band, means for commonly amplifying the plurality of pilot signals; , a signal detection method comprising a plurality of signal detection means for individually detecting each pilot signal from the output of the common amplification means, the output of the common amplification means is branched and the noise level is determined from the output. A signal detection method characterized in that a level comparison means for detecting the signal is provided, and the amplification gain of the signal in each pilot band received by the plurality of signal detection means is variably controlled by the output of the level comparison means. .