JPH0318128A - Alarm circuit of receiver - Google Patents

Abstract

PURPOSE:To securely output a reception break signal by detecting the maximum AGC voltage of each AGC circuit in the receiver and outputting an alarm signal for the breaking of a received signal, and comparing an intermediate frequency output with a threshold value and outputting the alarm signal. CONSTITUTION:When the received signal is broken, the control voltage of each AGC in the receiver becomes maximum, each maximum AGC circuit 1 detects that, and an AND circuit 2 outputs the reception break signal. The detected intermediate frequency output is compared with the threshold value and a reception decision circuit 3 outputs the reception break signal; and the output of the circuit 2 or 3 is outputted from an OR circuit 4 and becomes the alarm signal. This constitution securely outputs the alarm signal for the break of reception even when the circuit 3 does not output the reception break signal owing to a noise, etc.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a circuit that detects an alarm state of a received signal or a receiver itself, and is capable of accurately detecting an alarm state of a cutoff of a received signal or a failure of the receiver itself, even if the gain of the entire receiver is large. The purpose of the present invention is to provide a maximum AGC detection circuit 1 that detects the maximum value of the AGC fBIJ control voltage of the amplifier and equalizer in the receiver, and a maximum AGC detection circuit 1 in each detection circuit 1. an AND circuit 2 which generates an alarm signal indicating a disconnection of the received signal when detected; a reception determination circuit 3 which compares the intermediate frequency output of the receiver with a dark value and generates an alarm signal indicating the disconnection of the received signal or equipment failure; It is combined with an AND circuit 2 or an OR circuit 4 which outputs the alarm signal from the reception judgment circuit 3. [Industrial Application Field] The present invention relates to an alarm circuit for a receiver, and particularly to a circuit for detecting a received signal or an alarm state of the receiver itself. With the development of multilevel digital multiplex radio equipment, it is necessary to eliminate distortion during receiver amplifier fading, that is, to improve back-off, and to improve transmission characteristics during fading. [Prior Art] Fig. 3 shows the configuration of a conventionally used receiver up to outputting an intermediate frequency signal, where 11 is a high frequency amplifier, 12 is a local oscillator, and l3 is a high frequency amplifier of the high frequency amplifier 11. A mixer mixes the signal and the local oscillation signal from the local oscillator l2 and converts it into an intermediate frequency signal, 14 is a preamplifier for this intermediate frequency output, 15 is a bandpass filter for the output of the preamplifier 814, and I6 is a An intermediate frequency amplifier for the output of the filter 5, and {7 is an equalizer (equalizing amplifier) for the intermediate frequency signal. In this way, in the receiver, from the above point of view, AGC circuits are used in multiple stages to improve back-off in the high frequency amplifier l1 and the intermediate frequency amplifier I6, at least up to the intermediate frequency output section, and further to improve the transmission characteristics. An equalizer 17 including an AGC circuit is used. And in order to detect the alarm of such a receiver,
The intermediate frequency output of the equalizer 17 is detected by the detector 18 and the DC voltage is applied to the comparator circuit (Schmitt circuit) l9, and compared with the alarm threshold Th, the detected output of the equalizer I7 is lower than the threshold Th. In this case, an alarm signal is generated to indicate a loss of reception signal or a failure of the receiver itself.

[Problem to be solved by the invention]

As described above, due to various improvement requests, the gain of the entire receiver is increasing. For example, in the case of Fig. 3, the gain of the entire amplifier is 60 to 70 dB, and the equalizer is 40 to 50 dB, which is a total of 1.
Since the gain is between 00 and 120 dB, even if the received signal is cut off, the output of the detector 18 will increase due to external noise such as heat (KTBF) 9fi sound or clock signals from other devices. In the end, the comparator circuit 19 exceeds the threshold value Th, and its output becomes normal, resulting in a case in which it is not possible to generate an alarm output for the disconnection of the received signal.

In this case, a method of directly detecting the signal level of each part and comparing it with the dark value to generate an alarm can be considered, but in this case, it is necessary to handle high frequency signals and there are difficulties in setting the dark value. Another problem was that it was expensive. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a circuit that can accurately notify an alarm state of a received signal failure or a failure of the receiver itself even if the gain of the entire receiver is large. [Means for Solving the Problems] As shown in FIG. 1, an alarm circuit of a receiver according to the present invention for achieving the above object is an AGC! II? A maximum AGC detection circuit that detects the maximum value of the I voltage, and a maximum AGC detection circuit that detects the maximum value of the I voltage.
an AND circuit 2 that generates an alarm signal indicating a loss of reception signal when GC is detected; and a reception judgment circuit 3 that generates an alarm signal indicating loss of reception signal or equipment failure by comparing the intermediate frequency output of the receiver with a dark value. , and an OR circuit 4 that outputs the alarm signal from the AND circuit 2 or the reception determination circuit 3.

[For production]

In the alarm circuit of the receiver of the present invention shown in FIG. 1, when the received signal is cut off, the AGC gain of each amplifier becomes maximum, so Acc*I? Since all n voltages are maximum, each maximum AGC detection circuit l detects this and AND
Circuit 2 reports an alarm condition in which the received signal is cut off. At this time, no matter how the reception judgment circuit 3 judges the intermediate frequency output of the receiver, an alarm signal will be generated from the OR circuit 4. Even if it is judged as normal reception, OR times N! 4, an alarm signal is reliably output.

On the other hand, if there is a device failure in the receiver itself, the AGC control voltage of all amplifiers will not reach the maximum value, so any one of the maximum
The C detection circuit 1 cannot detect the maximum AGctl, +L'4B voltage, and therefore the AND circuit 2 does not output an alarm signal, but the intermediate frequency output of the receiver is cut off, so the reception judgment circuit 3 detects this. After determining this, the OR circuit 3 outputs an alarm signal indicating a receiver failure. Therefore, in any case, regardless of the magnitude of the gain of the receiver, it is possible to generate a received signal disconnection alarm or a fault alarm for the receiver itself. [Embodiment] FIG. 2 shows an embodiment of the alarm circuit of the receiver according to the present invention shown in FIG.
Similar to the conventional example shown in the figure, AGC type amplifiers 1l and 1 have a two-stage configuration.
6 and one equalizer 17, and the maximum AG
As the C detection circuit 1, the state in which the AGC voltage of each amplifier and equalizer is near the maximum value is defined as a threshold value S H + ~S H
Using Schmitt circuits 11 to 13 that detect y, the reception judgment circuit 3 is composed of a detector l8 and a Schmitt circuit 19 that compares the output of this detector with a threshold Th, as in FIG. Note that the Schott circuits 11-13 have respective threshold values SH, ~SH. The manual polarity of the Schmidt circuit 19 is selected so that when the threshold value Th is exceeded, the output is at the "H" level, and conversely, when the threshold value Th is exceeded, the output is at the "L" level. In this embodiment, first, if a reception signal cutoff occurs while the receiver itself is normal, the AGC of each amplifier l1, l6 and equalizer 17 has the maximum gain, so each of the amplifiers l1, l6 and equalizer 17 has a maximum gain. The dark value SH of the comparison object, ~
Since the voltage exceeds SH, the outputs of Schmitt circuits l, .about.1 become "H" level, AND circuit 2 becomes enabled, and its output becomes "H" level. Therefore, the output of the OR circuit 4 will generate an alarm signal regardless of the output of the equalizer 17. That is,
At this time, since the gain of each amplifier is maximized, the output of the equalizer 17 is large, and therefore the Schmitt circuit 19
Even if the output of
When the AGC control voltage of the amplifier 16 fails, the Schmitt circuit! 2 does not exceed the dark value S Hz, the output of the Schmint circuit 12 becomes "L" level, and the output of the AND circuit 2 becomes "L" regardless of other human power, but the final stage etc. Since the output of the converter l7 decreases, the output of the Schmitt circuit l9 becomes 'H' level, and an equipment failure alarm signal is output from the OR circuit 4. Note that the present invention has a multi-stage AGC amplification function. It goes without saying that the invention can be applied to any receiver. [Effects of the Invention] As described above, in the alarm circuit of the receiver according to the present invention, the AGCi!I+ control of the amplifier and equalizer in the receiver is effective. When all the voltages reach their maximum values, an alarm signal is generated regardless of the intermediate frequency output of the receiver, so it is possible to reliably detect a received signal disconnection state in a receiver with a large overall gain. , the reliability of alarm information is improved.Also, in this case, it is superior in terms of detection accuracy and cost.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the basic configuration of an alarm circuit of a receiver according to the present invention, FIG. 2 is a circuit diagram showing an embodiment of an alarm circuit of a receiver according to the present invention, and FIG. 3 is a conventional circuit diagram. This is a circuit diagram showing an example configuration. In Fig. l, ■...Maximum AGC detection circuit, 2...AND circuit, 3...Reception judgment circuit, 4...OR circuit, 11, 16...AGC type amplifier, l7... Equalizer. In the figures, the same reference numerals indicate the same or corresponding parts. Alarm signal principle diagram of the present invention

Claims (1)

[Claims] A maximum AGC detection circuit (1) that detects the maximum value of the AGC control voltage of the amplifier and equalizer in the receiver, and each detection circuit (
an AND circuit (2) that generates an alarm signal of a loss of reception signal when the maximum AGC is detected in 1); and an AND circuit (2) that generates an alarm signal of loss of reception signal or equipment failure by comparing the intermediate frequency output of the receiver with a threshold value. reception judgment circuit (3
); and an OR circuit (4) that outputs the alarm signal from the AND circuit (2) or the reception determination circuit (3).