JPS58172029A - Receiver for emergency warning broadcast - Google Patents

Abstract

PURPOSE:To prevent unnecessary, unemergent driving and to stabilize the warning function of the whole system by adding a false signal different from an emergency warning signal to a detection output signal and then decoding the signal. CONSTITUTION:For normal radio broadcast reception, an intermediate frequency signal from an input terminal IF is led to an envelope detector 2. Once an emergency warning broadcast starts, a circuit part for emergency broadcast reception is put in operation by an emergency warning signal right before the starting to supply the output of the envelope detector 2 to an adder 8, and a detection signal which still contains a DC component is supplied through a DC amplifier 5 to an amplifier 7, whose gain is controlled. The false signal corresponding to the input level is led out of the amplifier 7 and supplied to the adder 8, which adds it to the detection signal from the detector 2 to supply the sum signal to a decoder 9. Therefore, an unnecessary, undesired emergency warning signal is cut off according to a set threshold value.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an emergency warning broadcast receiver that receives emergency warning broadcasts using, for example, radio broadcast waves in the medium wave band. This is designed to prevent unnecessary operations caused by interference from the same channel from distant stations.

This type of emergency warning broadcasting receiver has the necessary circuits built into or added to a general medium-wave radio broadcasting receiver, and is equipped with a receiving detection circuit and an emergency warning signal to be added and broadcast at the start of emergency warning broadcasting. Only the necessary circuits for detection are kept in constant operation using a low-power power source such as a battery, and in response to the detection of an emergency warning signal, all the circuits necessary for receiving radio broadcasts, such as the audio amplification circuit, are turned on to respond to an emergency. Devices that are capable of receiving emergency information that is broadcast following an alarm signal are generally used.

However, as is well known, in the medium wave band, the field strength of broadcast waves from distant stations far away from the daytime service area increases significantly due to spatial wave propagation, which increases rapidly at night. Significant same-channel interference interference with distant stations that would never occur occurs, and the reception of emergency warning broadcasts to remote areas that are normally unrelated to the listener using the emergency warning broadcast receiver is difficult. There were many cases where the aircraft responded unnecessarily and caused confusion, such as needlessly waking listeners who were sleeping late at night. In other words, even though the local station for the receiver in question, and therefore the desired station for the receiver, did not send out an emergency alert signal, the same type of emergency alert signal was sent from a distant station, and therefore the interfering station for the receiver in question. Since the emergency warning broadcasting receiver responds in response to the signal, there is a serious drawback that this type of emergency warning broadcasting system becomes a major hindrance causing confusion in the functioning of the entire system.

Moreover, in the past, in response to such large obstacles, for example,
The sensitivity of the code decoder, etc. that decodes the emergency alert signal is intentionally lowered so that it does not respond to the emergency alert signal from the interfering station, which is generally at a low level compared to the detection level of the emergency alert signal from the desired station. Only palliative preventive measures, such as doing so, could be taken; no preventive measures were known that functioned satisfactorily.

The purpose of the present invention is to eliminate the above-mentioned conventional drawbacks, and to avoid responding to unnecessary emergency warning signals from interfering stations based on co-channel interference, such as in the medium wave broadcasting band, which increases rapidly at night. Moreover, it is an object of the present invention to provide an emergency warning broadcasting receiver that can reliably respond to a required emergency warning signal from a desired station.

That is, the emergency warning broadcasting receiver of the present invention adds a false signal different from the emergency warning signal to the detected output signal and then decodes the signal, and then uses the signal level of the false signal as a threshold to normally issue the required emergency warning. This system is designed to substantially reduce the sensitivity of the decoder by eliminating unnecessary and undesired emergency warning signals based on co-channel interference, which have a low level compared to the signal, and is a receiving detection circuit that operates constantly. Equipped with
In an emergency warning broadcasting receiver in which all units are activated in response to the detection of an emergency warning signal, all units are activated in response to the emergency alert signal to which a false signal whose signal level is adjustable after detection is added. It is characterized by:

The present invention will be described in detail below with reference to the drawings.

First, an example of the basic configuration of the emergency warning broadcasting receiver of the present invention is shown in FIG.

In the illustrated configuration, an intermediate frequency signal obtained from a high frequency stage of a heterodyne receiver for medium wave radio broadcasting 6 is input from an input terminal through an intermediate frequency amplification stage l to an envelope detector! When receiving normal radio broadcasting, the detected output audio signal is supplied to the speaker via the audio amplifier 8 for normal radio listening.

On the other hand, when an emergency warning broadcasting system that uses the same medium-wave broadcast waves functions and starts emergency warning broadcasting, immediately before the start of the emergency warning broadcasting, the transmission of audio signals by normal broadcast programs is interrupted and the emergency warning broadcasting system is activated. ° and automatically activates the emergency broadcast reception circuit section of the receiver. As the emergency warning signal, it is common to use, for example, a so-called frequency shift keying signal, which is a medium-wave broadcast wave that is amplitude-modulated with an appropriate deep modulation depth using sine waves of two unrelated frequencies in the audio frequency band. Conventionally, such an emergency alarm signal is extracted from the envelope detector 2 and guided to a decoder, either directly or via a suitable buffer amplifier, and other signals that may be included in the detection output, For example, only the required emergency warning signal is extracted by clearly distinguishing it from normal audio signals, and a power-driven relay or switch is activated to put all devices into an operating state capable of receiving emergency broadcast audio signals. The above is the operation when receiving emergency warning broadcasts late at night after regular radio broadcasts have ended, and in such a case, only the receiving circuit up to envelope detector B and the above-mentioned decoder circuit are operated. This is an emergency warning broadcast reception operation in which, for example, a small power storage battery or the like is used to operate the emergency warning broadcast at all times, and a high power consumption audio amplifier or the like is stopped. is interrupted and a sine wave sound due to the emergency alarm signal is heard, then
You will listen to audio information for emergency warning broadcasts in the same way as regular breaking news.

However, if the emergency warning signal obtained from the envelope detector 2 is directly supplied to the decoder, which normally operates with extremely high sensitivity, as described above, the strong co-channel interference will occur. If the input level ratio between the desired signal and the interfering wave, that is, the so-called D/U ratio, is small, the electric field strength of the interfering wave is strong, or the desired signal is unmodulated, the signal from the interfering station will be detected. The same type of unnecessary emergency warning signal is effectively decoded and detected, causing the serious trouble mentioned above.According to actual confirmation, the above-mentioned D/U ratio is Such damage occurred even to a certain degree.

In the receiver of the present invention having the configuration shown in the figure, in order to prevent the occurrence of such disturbances, the detection output signal of the envelope line detector type is directly supplied to the adder 8, and the detection output signal containing the DC component is is applied to an amplifier (with adjustable gain) via a DC amplifier 6, and the amplification gain of the amplifier 7 is controlled according to the DC level of the detected output signal.

The above-mentioned amplifier T is supplied with the above-mentioned false signal for reducing decoding sensitivity from the false signal generator 6 as a target for variable gain amplification. However, such false signals include, for example, noise caused by a noise diode, a sine wave signal with a frequency different from the frequency component of emergency warning signal 1, a square wave signal, etc., which are clearly distinguishable from necessary and unnecessary emergency warning signals. By using distinguishable types of signals, supplying such false signals to a variable gain amplifier and controlling the amplification gain according to the DC component of the envelope detection output signal, the signal level can be adjusted according to the receiver input level. The false signal is extracted and supplied to the adder 8 and added to the envelope detection output signal directly supplied from the detector 2 as described above.1 The added output signal is sent to the decoder 9.
The emergency warning signal in a predetermined format is decoded and detected using the W4 value as an appropriate false signal level corresponding to the receiver input level, and the power supply drive circuit IO is controlled by the decoded output signal, so that it can be used, for example, late at night. Then, the power supply voltage is supplied to the audio amplifier 8 which is inactive, so that the audio of the emergency information that comes in following the emergency warning signal can be heard through the speaker 4. Therefore, unnecessary and undesired emergency alarm signals mixed in by co-channel interference from jamming stations (which are usually at a lower level than the emergency alarm signal from the desired station) should be set appropriately according to the receiver's human power level. Therefore, the emergency warning broadcasting receiver of the present invention having the configuration shown in the figure is capable of detecting the occurrence of conventional disturbances based on co-channel interference due to wide variations in the receiver input level of the desired signal. It can be almost completely prevented.

In other words, in general, the DC component of the envelope detection output signal increases or decreases approximately in proportion to the receiver input level, as shown in Figure 8. , the adder 8 increases the signal level of the false signal added to the envelope detection output signal, and the decoder 9 increases the threshold level for eliminating unnecessary emergency warning signals (on the contrary, the desired In areas where the received electric field strength of waves is low, the signal level of the false signal added to the envelope detection output signal is reduced, and the desired emergency warning signal itself is eliminated by the threshold level (signal selection in the decoder 9). This allows the receiver to respond appropriately only to the emergency warning signal from the desired station over a wide range of receiver input levels of the desired wave.

FIG. 4 shows an example of the characteristics of the signal-to-interference ratio or signal-to-noise ratio in the detector output with respect to changes in the input level of the desired wave receiver of the receiver of the present invention that performs the above-mentioned emergency warning broadcast receiving operation. As shown in the figure, even in the receiver of the present invention, in the same reception operation state as the conventional one in which a false signal is not added to the detection output signal, the detection output increases as the receiver input level of the desired wave increases, as usual. While the signal-to-interference ratio (S/N) or signal-to-noise ratio (S/N) increases, the configuration shown in Figure 1 allows a false signal with a signal level corresponding to the receiver input level of the desired wave to be converted into the detected output signal. If the S/I or S/N is intentionally lowered by addition, false signals will be added compared to normal reception conditions in a high input level range where co-channel interference is relatively unlikely to occur. Just S
Even in the range of medium and low input levels, where the S/N is significantly reduced and co-channel interference is noticeable,
The S/N to S/N values are maintained as they are, and the DyU ratio of the receiver input, which deteriorates significantly in the mid-low range of the receiver input level of the desired signal, that is, the input level ratio of the desired signal to the interference signal. In contrast, it is possible to eliminate undesired emergency warning signals caused by interference waves by setting an appropriate signal level of the false signals to be added as a threshold. In contrast to the operating characteristics of the receiver of the present invention shown in the dotted line in FIG. 4, the adder 8 If you lower the receiver input level of the desired wave while fixing the signal level of the false signal added to the detection output signal to a level that operates appropriately in the middle range of the receiver input level, for example, Although the S/I ratio of the detection output drops extremely in the input level region, the signal level of the false signal added to the detection output signal can be adjusted to an optimal value according to the received field strength of the desired wave at the reception point. Even in a fixed state, as long as reception is continued at the same point, the present invention can fully achieve the effect of preventing co-channel interference.

For convenience of comparison with the basic configuration shown in FIG. 1, the other configuration example of the receiver of the present invention shown in FIG. Figure 1 and number 1! As is clear from the diagram, the diode D1 resistor R1, R, and the capacitor at, , a
, is the envelope detector g &:@? M, amplifier Dm and capacitor 0. corresponds to the buffer amplifier 6, and the transistor Q1 corresponds to the noise diode, the differential amplifier DA,
, resistance R,,R4,R.

R and the capacitor C1 correspond to the false signal generator 6, the amplifier Dm corresponds to the variable gain amplifier 7, and the differential amplifier D
and resistors R, , R8 correspond to the adder 8.

As is clear from the above description, according to the present invention, the envelope detector and the clipper can be used together, except in the case of poor conditions where the D/'U ratio at the receiver input of the emergency warning broadcast receiver is extremely low. By combining these, it is possible to reliably respond only to the emergency warning signal based on the desired wave, and to prevent unnecessary and undesired responses to the same type of emergency alert signal due to the same channel interference wave. It is possible to eliminate the confusion caused by same-channel interference, which has been common in the past, and to ensure a stable warning function for the entire system. This technology is not limited to so-called emergency warnings in the event of a disaster, which has traditionally been done using broadcast waves, but also involves the selective detection of program identification signals, broadcast station identification signals, etc. in traffic information broadcasting. The present invention can be similarly applied to dissemination of emergency information in minute meters, and the frequency, modulation format, etc. of broadcast waves are not limited to the above-mentioned examples.

Moreover, the receiver of the present invention can obtain the desired effect even in an arbitrarily moving reception state by automatically adjusting the signal level of the false signal added to the detected output signal according to the receiver input level. Instead, by simply adding a fixed level of false signals, as long as the reception area is fixed, the desired effect can be sufficiently obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram 4ii1 showing an example of the basic configuration of the emergency warning broadcasting receiver of the present invention, FIG. FIG. 8 is a characteristic curve diagram showing an example of the detection level characteristic, and FIG. 4 is a characteristic curve diagram showing an example of the signal-to-interference ratio characteristic. l...Intermediate frequency amplifier, 2...Enveloping line detector, 8.
...Audio amplifier, 4...Speaker, 5...Buffer amplifier, 6...False signal generator, 7...Variable gain amplifier,
8... Adder, 9... Decoder, lO... Power supply drive circuit, Dm, ~Dm,... Amplifier, D... Diode, Q... Transistor, R1-R8. ...Resistance, 0
1 to c4... Capacitor 0 Patent applicant Japan Broadcasting Corporation Figure 8 do 60 80 to. Threat 4

Claims (1)

[Scope of Claims] L An emergency warning broadcasting receiver equipped with a receiving detection circuit that operates constantly and which operates fully upon detection of an emergency warning signal, in which a false signal whose signal level can be adjusted after detection is provided. An emergency warning broadcasting receiver characterized in that it operates with full authority in response to the added emergency warning signal. Tortoise The receiver for emergency warning broadcasting according to claim 1, wherein the signal level of the false signal can be automatically adjusted according to the detection level of the emergency warning signal.