JP7528369B2 - Transmitting Device - Google Patents

Description

The present invention relates to an FM transmitting device having redundancy against modulator abnormalities.

In broadcast transmission equipment, redundancy is implemented to prevent broadcasts from being stopped due to sudden events such as equipment failure. For example, a known configuration uses two transmission units that emit different RF signals, one of which is the transmission unit that is normally used (active system) and the other is the transmission unit that is used as a backup when the active system fails (standby system), and a switch is used to switch between the output of the active system transmission unit and the output of the standby system transmission unit depending on the situation. However, since it takes a certain amount of time for the switch to perform the switching operation, there is a period of time when the output is interrupted during this switching operation. In addition, stricter requirements have been placed on the reliability and characteristics of the switch used for this purpose, making the switch expensive.

Patent Document 1 describes a transmission device in which the two transmission units are not divided into an active system and a standby system as described above, but rather the RF signals output from each are distributed to two, and the combination of the distributed RF signals is changed according to the situation before being combined and output. This configuration prevents signal interruption during switching. However, even in this case, the combination is still switched, so the use of a switch is essential. In addition, the two RF signals need to be combined with their frequencies and phases consistent.

In response to this, Patent Document 2 describes a technology in which a phase controller is provided to match the frequency and phase of the RF signal output by the transmitter of the standby system with the frequency and phase of the RF signal output by the transmitter of the active system, and the matched RF signal is constantly combined and output. In this case, the RF signals of the active system, standby system, and combined signal are identical except for their strength, and even if the active system breaks down and its RF signal is lost, the combined signal will be equal to the RF signal of the standby system, and the desired RF signal can be obtained without the need for a switching operation. As a result, there is no interruption of the signal during switching operation.

JP 2001-326579 A JP 2021-34970 A

In a transmitter for FM broadcasting, the output of the FM modulator is input to a power amplifier in the subsequent stage and is emitted from the transmitter as an RF signal as described above. Since it is necessary to prevent broadcast interruptions due to failure of this FM modulator, it was desirable to achieve similar redundancy in the event of failure of the FM modulator as well.

In this case, it has become necessary to provide two more FM modulators (one in use, one in standby) for each transmitting unit as described in Patent Documents 1 and 2, and to switch between these FM modulators (using a switch), or to extract the output from the two FM modulators without switching the RF signal as in the technology described in Patent Document 2.

However, in this case, if switches are used, the number of switches increases, making the transmission device expensive, or more problems occur with switching. Alternatively, if switches are not used, as in the technology described in Patent Document 2, no problems occur with switching, but the configuration becomes complicated and the transmission device becomes expensive.

For this reason, there was a demand for a transmitting device with a simple structure that had redundancy against FM modulator failure and did not require switching operations.

The present invention has been developed in consideration of the above situation and aims to solve the above problems.

The present invention is a transmitting device that uses an output signal in which a carrier wave has been FM-modulated with an audio signal, and includes a synchronous first modulation section and a synchronous second modulation section, each of which corresponds to one of an active system and a standby system, and which FM-modulates the common carrier wave with the common audio signal in a state in which synchronization is performed by inputting a common reference signal , and a synthesis section that synthesizes a first modulated signal that is an output of the synchronous first modulation section and a second modulated signal that is an output of the synchronous second modulation section, and outputs the result as the output signal. The audio signal, which is a stereo system and has a pilot signal synthesized therein, is input to the synchronous first modulation section and the synchronous second modulation section, and a first modulated signal monitoring section and a second modulated signal monitoring section that respectively recognize the presence or absence of the pilot signal in the first modulated signal and the pilot signal in the second modulated signal, and when the pilot signal is not recognized in either the first modulated signal or the second modulated signal, the output of the one of the first modulated signal and the second modulated signal is stopped .
In this case, when the pilot signal is not recognized in either one of the first modulated signal or the second modulated signal, an output signal adjustment unit may be provided which controls one of the synchronous first modulation unit and the synchronous second modulation unit corresponding to the other of the first modulated signal and the second modulated signal to adjust the intensity of the other of the first modulated signal and the second modulated signal.
In addition, the output signal adjustment unit may control the synchronous first modulation unit and the synchronous second modulation unit based on the detected output level of the output signal or by external control so that the output level is within a predetermined range .

According to the present invention, a transmitting device having a simple structure and redundancy against failure of the FM modulator and not requiring switching operations can be obtained.

FIG. 2 is a diagram showing a partial configuration of a transmitting device according to an embodiment. FIG. 1 is a diagram showing a partial configuration of a conventional transmitting device.

Next, a specific embodiment of the present invention will be described with reference to the drawings. A transmitting device according to an embodiment of the present invention is used for stereo FM broadcasting. This transmitting device has two FM modulators, so it has redundancy against abnormalities (failures) in the FM modulators, but no switching operation that would cause an interruption in the output signal is performed. Figure 1 is a diagram showing the configuration of this transmitting device 1.

In Fig. 1, only a portion of the configuration up to the point where an FM signal modulated by a stereo audio signal is output in this transmitting device 1 is shown. Therefore, the configuration in Fig. 1 corresponds to the portion that outputs the FM modulated signal in the transmitting devices described in, for example, Patent Documents 1 and 2, and can be applied to both active and standby transmitting devices.

Here, a synchronous first modulator (synchronous first modulation section) 11 and a synchronous second modulator (synchronous second modulation section) 12 are used to FM-modulate a carrier wave with a common audio signal, with FM1 (first modulation signal) being generated by the synchronous first modulator 11 and FM2 (second modulation signal) being generated by the synchronous second modulator 12. Although the synchronous first modulator 11 and the synchronous second modulator 12 each operate independently, their operations are synchronized by inputting a common reference signal.

In addition, in this transmitting device 1, FM1 and FM2 are combined by the combiner (combiner) 13 to produce an output signal, which is then output. Therefore, no switching operation is performed in this transmitting device 1, and therefore no interruption of the output signal occurs when switching.

The above operation and other components in FIG. 1 are described in detail below. First, the synchronous first modulator 11 and the synchronous second modulator 12 operate synchronously as described above. For this purpose, the reference signal generator 20 in FIG. 1 is used. Specifically, for example, an Rb (rubidium) oscillator can be used as the reference signal generator 20. As is well known, the Rb oscillator emits a 10 MHz signal and a 1 PPS (Pulse Per Second) signal, and is used when using these signals as a common reference signal to synchronize relay stations in different locations, for example, in synchronous broadcasting.

Therefore, by inputting this reference signal to the synchronous first modulator 11 and the synchronous second modulator 12, FM1 and FM2 can be synchronized (the phases can be made the same). Such a synchronous modulator is described, for example, at https://nitsuuki.com/products/fm_radio/fm_sync_broadcasting.html. Since FM1 and FM2 are modulated with a common audio signal, FM1 and FM2 essentially become the same signal. In addition, since the input audio signal is a stereo audio signal, both FM1 and FM2 contain pilot signals that are added in the case of the stereo system.

Therefore, the output signal obtained by combining FM1 and FM2 by the combiner 13 is the same signal as FM1 and FM2, but differs only in output level (amplitude). In this case, if the synchronous first modulator 11 fails, FM1 is lost, and if the synchronous second modulator 12 fails, FM2 is lost. In this case, only the output level of the output signal fluctuates, and the output signal is equal to FM2 in the former case and FM1 in the latter case. In the end, the same output signal is obtained before and after the failure of the synchronous first modulator 11 and the synchronous second modulator 12. Therefore, even if a failure occurs in the synchronous first modulator 11 or the synchronous second modulator 12, the output signal is not interrupted.

1, the reference signal generator 20 is a component of the transmitting device 1, but the reference signal generator may be provided externally as long as a similar reference signal can be input to the synchronous first modulator 11 and the synchronous second modulator 12. Also, a reference signal generator other than the Rb oscillator may be used as long as a reference signal for synchronizing the operation of the synchronous first modulator 11 and the synchronous second modulator 12 can be obtained.

In the operation described above, if a failure occurs in the synchronous first modulator 11 or the synchronous second modulator 12, the output signal is not lost, but the output level (amplitude) fluctuates. However, in this case, the fluctuation in the output level can also be suppressed. In FIG. 1, the output signal monitor 14 and the output signal adjustment unit 15 are used for this purpose.

The output signal monitor 14 extracts a portion of the output signal output from the combiner 13 via the directional coupler 31 and detects the output level (amplitude) of the output signal. Meanwhile, the output levels of FM1 and FM2 in the synchronous first modulator 11 and the synchronous second modulator 12 can be adjusted by an output control signal issued from the output signal adjustment unit 15 to each of the synchronous first modulator 11 and the synchronous second modulator 12. The output signal adjustment unit 15 can adjust the output levels of FM1 and FM2 based on the output level of the output signal detected by the output signal monitor 14 so that the output level of the output signal is within a certain range.

In this case, if the output signal adjustment unit 15 changes the output levels of FM1 and FM2 and recognizes the output level of the output signal, even if the output level of one of FM1 and FM2 is abnormally low, it can perform an operation to set the output level of the output signal to a certain range by increasing the output level of the other. In this case, it takes a certain amount of time to complete this operation, and although the output level of the output signal changes during that time, there is no interruption in the output signal during that time. In addition, such adjustment of the output levels of FM1 and FM2 by the output signal adjustment unit 15 may be performed from outside the transmitting device 1. In this case, for example, an output signal monitor may be provided externally.

In this way, when performing the operation to make the output level of the output signal constant, the output signal adjustment unit 15 does not need to directly recognize that a failure has occurred in, for example, one of the synchronous first modulator 11 and the synchronous second modulator 12. In contrast, the first modulation signal monitoring unit 16 and the second modulation signal monitoring unit 17 in Figure 1 directly recognize that a failure has occurred in the synchronous first modulator 11 and the synchronous second modulator 12. This point will be explained below.

As mentioned above, a stereo audio signal is used here. As is well known, this audio signal is actually a composite signal that uses a left signal (L) and a right signal (R), as described in, for example, JP 2007-103986 A, and is a combination of the L+R component, the L-R component, and a 19 kHz pilot signal, and in the synchronous first modulator 11 and the synchronous second modulator 12, the carrier wave is FM modulated with this composite signal. On the receiving side that receives this signal, the pilot signal can be used to properly reproduce L and R. For this reason, under the prerequisite that the audio signal is stereo, FM1 and FM2 always contain this pilot signal.

Here, a part of FM1 is input to the first modulation signal monitoring unit 16 via the directional coupler 32, and a part of FM2 is input to the second modulation signal monitoring unit 17 via the directional coupler 33, and the first modulation signal monitoring unit 16 and the second modulation signal monitoring unit 17 check the presence or absence of a pilot signal in these. If a pilot signal is not recognized in FM1, it can be assumed that the synchronous first modulator 11 is not operating properly, and the same is true for FM2 (synchronous second modulator 12). In this way, if a pilot signal is not recognized in FM1, the first modulation signal monitoring unit 16 issues an alarm to the control unit 18, and if a pilot signal is not recognized in FM2, the second modulation signal monitoring unit 17 issues an alarm to the control unit 18.

The control unit 18 outputs an on/off control signal to each of the synchronous first modulator 11 and the synchronous second modulator 12 to control the power supply (on/off). Therefore, the control unit 18 can turn off the synchronous first modulator 11 when an alarm is received from the first modulated signal monitoring unit 16, and can turn off the synchronous second modulator 12 when an alarm is received from the second modulated signal monitoring unit 17.

In general, it is considered that when the synchronous first modulator 11 fails, FM1 is not generated and the output signal is equal to FM2, and when the synchronous second modulator 12 fails, FM2 is not generated and the output signal is equal to FM1. However, when the synchronous first modulator 11 or the synchronous second modulator 12 fails and generates inappropriate outputs as FM1 and FM2, the inappropriate outputs become noise, and the output signal (FM1+FM2) also becomes inappropriate. For this reason, it is preferable to turn off the synchronous first modulator 11 when FM1 is inappropriate, and the synchronous second modulator 12 when FM2 is inappropriate. The control unit 18 can perform such operations.

In this operation, when the synchronous first modulator 11 and the synchronous second modulator 12 are off, the output level of the output signal fluctuates, but the output signal is not interrupted. After the synchronous first modulator 11 and the synchronous second modulator 12 are turned off, the output level of the output signal can be set to an appropriate range by the operation of the output signal adjustment unit 15 as described above. In other words, by using the output signal adjustment unit 15, the first modulation signal monitoring unit 16, and the second modulation signal monitoring unit 17 as described above, even if a failure occurs in either the synchronous first modulator 11 or the synchronous second modulator 12, the output signal is not interrupted and the output level of the output signal can be maintained within a certain range.

Figure 2 shows a partial configuration of a conventional transmitting device 9 to be compared in correspondence with Figure 1. In this transmitting device 9, two independent normal FM modulators, a first modulator 91 and a second modulator 92, are used for FM modulation, as in the transmitting device 1 described above, and a common audio signal is input to these, and a carrier wave is FM-modulated to generate an FM signal (FM11 by the first modulator 91, FM12 by the second modulator 92). Here, the first modulator 91 is used as the active system, and the second modulator 92 is used as the standby system. Unlike the previous example, the first modulator 91 and the second modulator 92 do not operate in sync.

In addition, both the first modulator 91 and the second modulator 92 have a self-diagnosis function, and if an alarm is issued when an abnormality occurs in the first modulator 91, the control unit 93 controls the switch 94 in response to an external command or this alarm, and can select the output FM11 of the first modulator 91 and the output FM12 from the second modulator 92 and output them to the power amplifier side. At this time, the one that is not selected, FM11 or FM12, is input to the terminator 95 and disappears. Here, FM11 is normally selected and FM12 is led to the terminator 95, and when an alarm is issued from the first modulator 91, the control unit 93 controls the switch 94 to select the second modulator 92 (FM12) and lead FM11 to the terminator 95.

In the configuration of Figure 2, for example, when the control unit 93 recognizes an alarm from the first modulator 91 and switches the switch 94, in order to avoid the effects of noise, etc., it is necessary to start this switching operation after it is recognized that the alarm has continued for a certain period of time or more. Also, in the operation of the switch 94, a certain amount of time is required from when the control unit 93 issues a switching command until the switch 94 issues a post-switching signal. For this reason, the output signal was often interrupted when the switching operation was performed.

In contrast, in the above-mentioned transmitting device 1, a synchronous first modulator 11 and a synchronous second modulator 12 are used instead of two independent normal FM modulators, the first modulator 91 and the second modulator 92, and a combiner 13 is used instead of the switch 94. Therefore, even if a failure occurs in either the synchronous first modulator 11 or the synchronous second modulator 12, there is no interruption in the output signal.

However, if a failure occurs in either the synchronous first modulator 11 or the synchronous second modulator 12, the output level of the output signal may fluctuate. To address this, the output level can be kept within a certain range by using the output signal adjustment unit 15, the first modulated signal monitoring unit 16, the second modulated signal monitoring unit 17, etc., as described above.

The present invention has been described above based on an embodiment. This embodiment is merely an example, and it will be understood by those skilled in the art that various modifications are possible in the combination of the components, and that such modifications are also within the scope of the present invention.

This application claims the benefit of priority based on Japanese Patent Application No. 2021-079438, filed on May 10, 2021, the entire disclosure of which is incorporated herein by reference.

The present invention is suitable for obtaining a transmitting device of a simple structure that has redundancy against failure of the FM modulator and does not require switching operations.

1, 9 Transmitter 11 Synchronous first modulator (Synchronous first modulation section) 12 Synchronous second modulator (Synchronous second modulation section) 13 Combiner (Combiner section) 14 Output signal monitor 15 Output signal adjustment section 16 First modulated signal monitoring section 17 Second modulated signal monitoring section 18, 93 Control section 20 Reference signal generator 31-33 Directional coupler 91 First modulator 92 Second modulator 94 Switch 95 Terminator

Claims (3)

A transmitting device using an output signal in which a carrier wave is FM-modulated with an audio signal,
a synchronous first modulation unit and a synchronous second modulation unit, each of which corresponds to one of a working system and a standby system, and which performs FM modulation of the common carrier wave by the common audio signal in a state where synchronization is performed by inputting a common reference signal;
a combiner that combines a first modulated signal that is an output of the synchronous first modulating unit and a second modulated signal that is an output of the synchronous second modulating unit and outputs the combined signal as the output signal;
Equipped with
The audio signal having a stereo system and a pilot signal mixed therein is input to the synchronous first modulation unit and the synchronous second modulation unit,
a first modulated signal monitoring unit and a second modulated signal monitoring unit that respectively recognize the presence or absence of the pilot signal in the first modulated signal and the presence or absence of the pilot signal in the second modulated signal,
a transmitting device which, when the pilot signal is not recognized in either one of the first modulated signal and the second modulated signal, stops output of the one of the first modulated signal and the second modulated signal. 2. The transmitting device according to claim 1, further comprising an output signal adjusting section that, when the pilot signal is not recognized in either one of the first modulated signal or the second modulated signal, controls one of the synchronous first modulating section and the synchronous second modulating section corresponding to the other of the first modulated signal and the second modulated signal to adjust an intensity of the other of the first modulated signal and the second modulated signal. The transmitter according to claim 2, characterized in that the output signal adjustment unit controls the synchronous first modulation unit and the synchronous second modulation unit based on the detected output level of the output signal or by external control so that the output level is within a predetermined range.

Images