JPS59178829A - Failure detecting system of receiver - Google Patents

Abstract

PURPOSE:To prevent mis-detection of a failure of receiver by ORing exclusively the result of comparison of a noise squelch output and a carrier squelch output respectively with a lower limit value so as to block the discriminating operation of a failed receiver with the output of operation. CONSTITUTION:In a figure (a), 10 is a squelch circuit of the 1st receiver and 12 shows a squelch circuit of the 2nd receiver. A squelch gate signal from the squelch circuits 10, 12 is applied to an exclusive OR gate 18 via lines 14 and 16 and ORed exclusively. A figure (b) shows the constitution of the squelch circuits 10 and 12. In the figure (b), the exclusive OR between the output of the 1st detecting circuit 38 detecting whether or not the non-sound band noise component of the demodulated output of each receiver is a prescribed lower limit value or over and of the 2nd detecting circuit 40 detecting whether or not the carrier component of each receiver is a prescribed lower limit or over is operated by an exclusive NOR gate 42 to block the discrimination of a failed receiver depending on the output.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method for detecting the occurrence of a failure in an FM receiver or an A or M receiver equipped with an AGC (automatic gain control mechanism).

Background of the Technology Receiver failure detection is generally performed by operating two or more equivalent receivers in parallel and digitally or analogously processing the squelch mechanism force of each receiver. In this case, each receiver is configured to be able to serve as a reference receiver.

The squelch function of the receiver is a function that prevents receiver noise from being output when a weak electric field is input, and is performed by opening and closing the demodulator output or the audio frequency amplifier using a squelch gate signal.

There are three types of methods for generating squelch gate signals based on differences in squelch output:

(1) A noise squelch method that detects the noise component outside the audio frequency band included in the demodulator output as a squelch output and generates a squelch gate signal depending on the detection level; (2) Squelches the carrier wave (intermediate frequency) component. A carrier squelch method detects it as an output and generates a squelch gate signal depending on the magnitude of the detection level, and (3) a combined method uses both the noise component in the non-audio frequency band of the demodulator output and the carrier wave component as the squelch output.

Prior Art and Problems The following two methods are known as conventional failure detection methods.

(a) As shown in FIG. 1, the first receiver and the second receiver each have a threshold value S for squelch gate signal detection.
Q+ and SQ2, generates a squelch dart signal depending on whether the squelch output exceeds these thresholds, and performs a logical operation on the squelch gate signals from the first and second receivers using an exclusive OR circuit. (b) As shown in FIG. 2, the squelch output of the first receiver and the squelch output of the second receiver are applied to the analogue freezing differential amplifier; A method for determining a faulty receiver by comparing the output of a differential amplifier with a threshold value and determining polarity.

However, in the method (a), when there is a difference between the threshold values SQl and SQ2 of each receiver, there is a risk that an erroneous failure determination may be made in the intermediate region. Even if each receiver has a superior configuration, there will always be differences in characteristics, and the threshold value SQs.

There will always be some differences between SQ2. In addition, in the method (b) above, when the squelch output of each receiver is the sum of both the noise squelch output and the carrier squelch output, the correlation between the noise squelch output and the carrier squelch output is constant. If this is not maintained, there is a risk of incorrect failure determination. For example, abnormal radio interference in terms of level and frequency due to spark discharge caused by sliding between a train's antenna graph and the power supply line, abnormal propagation of radio waves, etc. In other words, the frequency and level are unstable and greatly deviate. Radio waves, or radio waves in the frequency band near the attenuation region of the receiver's intermediate frequency filter, undergo severe phase rotation within the receiver, so even though there is a carrier wave, there is a lot of demodulation noise, and the noise region and carrier in the squelch output curve Linearity with the area is not maintained. This may lead to incorrect failure determination.

OBJECTS OF THE INVENTION Accordingly, the present invention solves the above-mentioned disadvantages of the prior art, and it is an object of the present invention to avoid false detection of receiver failures,
The object of the present invention is to provide a fault detection method that can perform stable detection quickly.

Structure of the Invention A feature of the present invention that achieves the above-mentioned object is that in a receiver fault detection method that determines a faulty receiver according to outputs from squelch mechanisms of a plurality of receivers, the demodulated output of each receiver is a first detection circuit that detects whether the non-voice band noise component is greater than or equal to a predetermined lower limit; and a second detection circuit that detects whether or not the carrier wave component of each receiver is greater than or equal to the predetermined lower limit. , a circuit for calculating an exclusive OR of the outputs of the first and second detection circuits, and a circuit for blocking the faulty receiver determination operation in accordance with the output of the calculation circuit.

Embodiment of the Invention FIG. 3 schematically shows the overall configuration of an embodiment of the invention. In the figure, 10 indicates the squelch circuit of the first receiver, and 12 indicates the squelch circuit of the second receiver.The squelch gate signals from each squelch circuit 10, 1.2 are externally connected via lines 14.16. Shibuorgate 1
8 and is subjected to an exclusive OR operation. Excl-7
The output of the poor gate 18 is applied to the alarm 22 via an AND gate 20. In addition, each squelch circuit 10.1
2 is applied to an OR gate 28 via lines 24 and 26, and the output of this OR gate 28 is applied to the negative input of an AND gate 20 to control ON/OFF of this AND gate 20.

FIG. 4 shows the configuration of each squelch circuit 10, 12 in FIG. 3. In the figure, 30 is a noise squelch detection circuit that detects the high-frequency noise component of the receiver demodulated output and generates a positive rectified output, and 32 is a carrier squelch detection circuit that detects the carrier component and generates a negative rectified output. It is. The outputs from the noise squelch detection circuit 30 and the carrier squelch detection circuit 32 each have incoming call input characteristics as shown in FIG. These outputs are added together in an adder 34, and the characteristics of both are set so as to be linearly joined. In this case, -15 ~ in terms of receiver input
It is set so that meetings can be held arbitrarily within the range of +15 dBμV. The output of adder 34 is compared with a predetermined threshold in comparison circuit 36, resulting in the formation of a squelch gate signal. This squelch gate signal
As shown, the signals are output from squelch circuits 10.12 of each receiver and applied to exclusive OR gates 18 via lines 14.16, respectively. The relationship between the squelch dart signal from each receiver, the output of the exclusion channel 18, the power, and the fault determination contents is as shown in the following table.

In the present invention, only true faults are detected by adding the judgment blocking condition to such judgment results.

The judgment is inhibited by turning off the AND gate 20, and the AND gate 20 is turned on and off by the output of the OR gate 28. As described above, the fault determination prevention signal is applied to the OR gate 28 from each squelch circuit 10.12. In each squelch circuit, a fault determination prevention signal is formed by comparison circuits (first and second detection circuits) 38 and 40 and an exclusive no-agut 42. That is, the comparison circuit 38 determines whether the noise squelch output from the noise squelch detection circuit 30 is equal to or greater than a predetermined lower limit value of 1 or not. If above, tt 1
n, an 'O' signal is output from the comparator circuit 38. On the other hand, the carrier squelch output from the carrier squelch detection circuit 32 is outputted by the comparator circuit 40 when its absolute value is a predetermined lower limit value and is 2 or more. It is determined whether or not there is a signal. If it is above, a signal of 0 is output from the comparison circuit 40. If it is less than 0, a signal of 0 is output from the comparison circuit 40. The fault determination prevention signals applied to the gate 42 and their meanings are as shown in the following table.

If the failure determination prevention signal from one or both of the receivers becomes 1'', the output of the OR gate 28 becomes 1'', the AND gate 20 closes, and the failure determination operation is inhibited.

The fault determination operation is blocked by the comparison circuits 38 and 40.
This is a case where the outputs of both are '0' or both are '1#'.

The outputs of the comparison circuits 38 and 40 are both "0" when the squelch output is smaller than Ll and the absolute value of the carrier squelch output is smaller than L2 (a in FIG. 6).
part). In this range, the linearity between the noise squelch output and the carrier squelch output cannot be maintained, and the level is unstable, so failure determination is not performed. On the other hand, the outputs of the comparison circuits 38 and 40 are both 1'' when the noise squelch output is 51 or more and the carrier squelch output is L2 or more.

Normally, in such a situation, the failure judgment operation is carried out because it cannot be resolved. That is, the squelch output is - in Fig. 6.
The fault determination operation is performed only when the range is within one of the diagonal lines.

Effects of the Invention As explained in detail above, according to the present invention, the results of comparing the noise squelch output and the carrier squelch output with the lower limit values are subjected to an exclusive OR operation, and the output of the operation is used to prevent the faulty receiver determination operation. Because I try to do it,
Erroneous detection of receiver failure can be completely prevented. Since correct detection can be performed stably, there is no need to intentionally cause a time delay when detecting @rose, and receiver failure detection can be performed at a relatively high speed.

[Brief explanation of the drawing]

Figures 1 and 2 are explanatory diagrams of conventional failure detection methods;
FIG. 4 is a block diagram of the squelch circuit shown in FIG. 3, FIG. 5 is a squelch output characteristic diagram, and FIG. 6 is a block diagram showing the entire embodiment of the present invention. It is a figure explaining a range. 10.12...Squelch circuit, 18...Exclusion or gate, 20...And gate, 22.
... Alarm, 28... OR gate, 30... Noise squelch detection circuit, 32... Carrier squelch detection circuit, 34... Addition circuit, 36, 38.40... Comparison circuit, 42...・Exclusivino boot. 1st receiver 2nd receiver Fig. 4 0 U Fig. 5

Claims (1)

[Claims] 1. A receiver fault detection method that determines a faulty receiver according to outputs from squelch mechanisms of a plurality of receivers,
a first detection circuit that detects whether the non-voice band noise component of the demodulated output of each receiver is greater than or equal to a predetermined lower limit; and a first detection circuit that detects whether the carrier wave component of each receiver is greater than or equal to the predetermined lower limit. A second detection circuit for detecting the faulty receiver, a circuit for computing an exclusive OR of the outputs of the first and second detection circuits, and a circuit for blocking the faulty receiver determination operation according to the output of the arithmetic circuit. A fault detection method for a receiver is characterized by: 2. The fault detection method according to claim 1, wherein the squelch mechanism of each receiver uses both a non-voice band noise component and a carrier wave component of the demodulated output. 3. Claim 2, wherein the squelch mechanism includes an adder circuit that adds a non-voice band noise component and a carrier wave component of the demodulated output, and a circuit that compares the output of the adder circuit with a predetermined threshold value. Fault detection method described in section.