JP2987077B2 - Synchronous relay method and apparatus for FM broadcast - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for relaying FM broadcast radio waves, and more particularly to a method and apparatus for synchronously relaying FM broadcasts which relay at the same frequency as the frequency of a radio wave of a master station. .

[0002]

2. Description of the Related Art Conventionally, in this type of FM broadcasting, a service area is secured or expanded in an area where a broadcast wave 10 of a master station 7 does not reach, or a radio wave such as a shielded underground mall or a tunnel does not reach. A so-called relay broadcast has been performed in which a radio wave of the master station 7 is received in order to provide a broadcasting service to an area, amplified and then transmitted again.

Here, when the relay station 1a performs a relay broadcast at the same frequency as that of the master station 7, the broadcast wave 10 and the relay wave 11 are shielded in a shielded underground mall or a tunnel. No inconvenience occurs. Further, even in an open space, the broadcast wave 10 and the relay wave 1 are transmitted to the receiver.
When 1 is received, if there is a remarkable difference in the electric field strength between the two even at the same frequency due to the characteristics of FM radio waves, radio waves with low electric field strength are suppressed and only strong radio waves are received, so that no problem occurs. However, if the electric field strengths of both are almost the same, abnormal reception due to interference with the radio wave of the master station, for example, a decrease in electric field strength or generation of noise may occur in places other than unshielded tunnels and underground shopping malls. .

That is, there is no problem when the signal is received at a point where the difference between the electric field strengths of the master station 7 and the relay station 1a is large. However, if the signal is received at the same level of interference,
When the time difference between the two radio waves is small, the signal is received as a simple level fluctuation, but when the time difference happens to be about 20 to 25 μs, an abnormal sound called multipath distortion occurs. For this reason, in order to avoid such abnormal reception, the transmission frequency of the relay station is changed to the frequency of the master station for transmission.

[0005] However, if the number of broadcasting stations and relay stations in a certain area increases, radio waves of many frequencies are required, and the usable frequencies in the same area are limited, and new broadcasting stations and the same frequency are used. It has been difficult to increase the number of relay stations that do not have a sufficient number of relay stations, and it has been impossible to use limited radio waves effectively.

In order to solve such a problem, for example, FIG.
A method and apparatus as shown in FIG. 6 have been proposed. That is, FIG. 5 shows that the broadcast wave 10 of the master station 7 is received by the receiving antenna 1 and amplified by the relay station 1a, and then the relay wave 11 is transmitted from the transmitting antenna 3 by changing the polarization plane without changing the frequency. Is what you do.

FIG. 6 shows the transmission output amplified by the amplifier 2 in order to prevent the repeater wave 11 transmitted in FIG. 5 from being received again by the reception antenna 1 as a jump wave 11 'and causing feedback due to positive feedback. Is taken out through the coupler 15 and the attenuator 14 and the phase changer 13a are adjusted in advance, and the diving wave 11 ′ is adjusted.
The signal is converted to a signal having substantially the same phase as that of the signal and having substantially the same level, and is applied to the input side of the amplifier 2 via the mixer 12 to cancel the diving wave 11 'and prevent howling.

[0008]

However, the above-mentioned means is limited to the case where there is no change in the reception condition. For example, the electric field strength is changed due to a change in the external environment near the reception antenna 1 or a change in the radio wave condition such as reflection. When the secular change occurs, the electric field strength of the diving wave 11 'is measured each time, and howling occurs again unless it is adjusted again.

SUMMARY OF THE INVENTION The present invention has been made in view of the foregoing, and an object of the present invention is to provide a feedback signal which is a part of an output signal to be applied to an input side even when a reception situation such as an electric field intensity changes. An object of the present invention is to provide an FM broadcast synchronous relay method and apparatus that can stably prevent howling even when the reception condition changes by automatically adjusting the level and phase.

[0010]

In order to achieve the above object, the present invention provides an FM broadcast system for receiving a broadcast wave 10 of a master station 7, amplifying the received signal, and transmitting a relay wave 11 at the same frequency. In the relaying method, AM modulation by the identification signal 19 is added to a relay signal for relaying the broadcast wave 10 of the master station 7, and this is amplified to form a transmission signal. The identification signal 19 is extracted from the received signal thus obtained, the feedback signal is adjusted to an optimum level according to the signal level of the obtained identification signal 19, and the feedback signal is added to the reception signal to form a relay signal. The phase of the feedback signal is adjusted so that the signal level of the identification signal 19 included in the signal is substantially minimized, and the transmission signal is transmitted as the relay wave 11.

In the above method, the means for adjusting the phase of the feedback signal includes a signal Φ1 having a slightly advanced phase and a signal Φ having an intermediate phase with respect to the feedback signal.
2 and a signal Φ3 slightly delayed in phase, and a signal Φ2 of the intermediate phase, a signal Φ1 slightly advanced in phase and a signal Φ3 slightly delayed in phase are synchronized by the same ratio. The signal Φ1 slightly advanced in phase and the signal Φ3 slightly delayed in phase are respectively added to the received signal, and the signal level of the identification signal 19 included in each synthesized signal becomes substantially the same level. The phase of the feedback signal is adjusted so that the signal level of the identification signal 19 included in the relay signal is substantially minimized.

Alternatively, the present invention is a method of receiving a broadcast wave 10 of a master station 7, amplifying the received signal, changing the polarization plane of the broadcast wave 10 and transmitting a relay wave 11 while maintaining the same frequency. In the apparatus, an input signal branching means 12a for branching and extracting a received input signal, and a signal extracting means 16a for extracting an identification signal 19 from the extracted input signal
Signal level adjusting means 14 for adjusting a feedback signal to an optimum level according to the level of the extracted identification signal 19; synthesizing means 12b for adding a feedback signal to the input signal; Signal level extracting means 12c and 16b for extracting the signal level of the identification signal 19 included in the signal, and phase adjusting means 13 for adjusting the phase of the feedback signal so that the signal level of the extracted identification signal 19 becomes substantially minimum. And identification signal adding means 17 and 18 for adding an identification signal 19 to the synthesized input signal by AM modulation, and amplifying the signal AM-modulated by the identification signal adding means 17 and 18 and sending it out as a relay wave 11. Amplifying means 2c as an output signal for performing the operation, and extracting a part of the output signal amplified by the amplifying means 2c. And an output signal branching means 15, serial feedback signal and apparatus having a.

Further, in the above apparatus, the phase adjusting means 1
Reference numeral 3 denotes a second branching unit 26 for branching the feedback signal, and a variable from a slightly advanced phase, an intermediate phase, and a slightly delayed phase with respect to the feedback signal branched by the second branching unit 26. First to third phase varying means 131, 132, and 133, a first branching means 25 for branching an input signal, and an input signal branched by the first branching means 25 and the first to third phase varying means 131, 132, and 133. First to third combining means 121, 122, 123 for combining the output signals of the third phase changers 131, 132, 133.
And the first combining means 121 and the third combining means 123
Level detecting means 21 and 23 for detecting the signal level of each of the identification signal components included in the output signal of the first, second and third phase variable devices 131 in response to the outputs of the level detecting means 21 and 23. , 132 and 133 are provided.

[0014]

In the radio wave transmitted as the relay wave 11, the diving wave 1 received again by the own station together with the broadcast wave 10 of the master station 7 is described.
If the ratio of 1 'can be detected, that is, if the reception level of the diving wave 11' can be detected, it is possible to optimally adjust the level of the feedback signal according to the detected level.

Therefore, the FM radio wave transmitted as the relay wave 11 is subjected to AM modulation by a signal of a specific frequency as an identification signal by several percent. Then, the identification signal is extracted from the received signal of the received broadcast wave 10, and if the signal level is detected, the reception level of the diving wave 11 'can be known, and the level of the feedback signal is determined according to the level of the identification signal. Can be adjusted optimally.

Further, when the phase of the feedback signal is substantially opposite to the phase of the input signal and when it is not, the level of the identification signal included in the relay signal combined with the feedback signal is detected. You can know by doing.

That is, the phase of the feedback signal at which the level of the identification signal included in the synthesized relay signal is minimized is a point at which the effect of cancellation is maximized, and this phase is substantially opposite to the input signal. In this case.

As means for adjusting the phase of the feedback signal, a signal whose phase is slightly advanced with respect to the feedback signal, a signal having an intermediate phase and a signal whose phase is slightly delayed with respect to the feedback signal are generated. The phase is varied in synchronization with the same ratio. Then, the signal whose phase is slightly advanced and the signal whose phase is slightly delayed are respectively mixed with the input signal, and the phase of each signal is adjusted so that the signal level of the identification signal included therein is substantially equal. . In other words, this 2
The fact that the signal levels of the identification signals included in the two signals are equal means that the signal levels of the identification signals included in the feedback signal are substantially minimum.

[0019]

Next, an embodiment of the present invention will be described. FIG. 1 is a block diagram showing a configuration of an apparatus according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a receiving antenna for receiving a broadcast wave 10. In this embodiment, a Yagi antenna having a plurality of elements is used. However, the present invention is not limited to this. For example, a dipole type, a vertical type Etc. can also be used. 2a is an amplifier as a buffer, 2b is an amplifier having a built-in buffer and limiter, and 2c is an amplifying means, that is, an amplifier as a power amplifying stage of an output signal.

12a is an input signal branching means, ie, a splitter for branching an input signal by the received broadcast wave 10,
16a is an identification signal extracting means, that is, an AM detector for AM detection of the branched input signal, and 14 is the AM detector 16a.
The variable attenuator 12c which operates in accordance with the output of the amplifier 2b constitutes a part of the signal level extracting means, and a distributor for branching the input signal to the amplifier 2b. Amplifier 2b
Detector for detecting an input signal to the AM, 13a
Is a phase variable device that varies the phase according to the output of the AM detector 16b.

Reference numeral 18 denotes a part of the identification signal adding means, an oscillator for oscillating the identification signal 19, 17 denotes identification signal adding means, that is, a modulator for modulating the output signal of the amplifier 2b with the identification signal. 2c is an amplifying means, that is, an amplifier for power-amplifying the output signal of the modulator 17 and outputting the transmission wave 11, and 15 is an output signal branching means, that is, an amplifier 2
c for splitting and extracting a part of the output signal of c and giving it to the variable attenuator 14 and the phase variable device 13;
b is a synthesizing means, that is, the output of the phase variable
A mixer 3 for mixing with the output of a is a transmitting antenna for transmitting a relay wave.

The broadcast wave received by the receiving antenna 1 is carried by the cable 5 as an input signal.
A part of this input signal is branched by the divider 12a,
The signal is input to the AM detector 16a, AM detected, and the identification signal is extracted. The input signal is also input to the amplifier 2a, and after being amplified, is input to the distributor 12c via the mixer 12b.
Detection is performed, and an identification signal component is extracted.

The input signal that has not been split by the distributor 12c is input to an amplifier 2b, and the limiter in the amplifier 2b removes the identification signal component, that is, the AM component, and amplifies the signal to a predetermined level. The output of the amplifier 2b is input to the AM modulator 17 and AM-modulated by the identification signal 19 oscillated by the oscillator 18.

The AM-modulated signal is input to the amplifier 2c, power-amplified, and becomes a transmission signal for transmitting the relay wave 11. Then, a part of the transmission signal is branched by the distributor 15 and is combined with the output signal of the amplifier 2a by the mixer 12b via the variable attenuator 14 and the phase variable unit 13.

The output signal not split by the distributor 15 is emitted by the transmitting antenna 3 into the air as a relay wave 11. In this embodiment, the transmitting antenna 3 uses a dipole antenna as a vertical parastack. This is because it is suitable for forming a null point in the electric field intensity distribution on the ground, that is, a point with zero electric field intensity. The present invention is not limited to such an antenna, and does not prevent the use of, for example, a multi-element Yagi antenna or a vertical antenna.

Next, the operation of the present invention will be described with reference to FIGS. FIG. 2 is a diagram illustrating the principle of a configuration example of the variable attenuator 14, FIG. 3 is a diagram illustrating the operation principle of the phase variable device, and FIG. 4 is a flowchart illustrating the operation of the present invention.

First, the broadcast wave 10 of the master station 7 as a broadcast station is received by the receiving antenna 1 of the relay station 1a (S1). If this broadcast wave 10 is, for example, horizontally polarized, the receiving antenna 1
Also has a configuration suitable for receiving horizontally polarized waves.

A part of the received signal obtained by receiving the broadcast wave 10 is taken out by the distributor 12a, and A is detected by the AM detector.
The identification signal 19 is extracted by performing M detection (S
2). Then, the attenuation of the variable attenuator 14 is adjusted according to the level of the identification signal 19 (S3).

The variable attenuator 14 is provided in a feedback path for extracting a part of the output signal, adding the input signal with a substantially inverted phase, and adjusting the level of the feedback signal. Therefore, for example, a variable resistor can be changed in accordance with the signal level of the identification signal 19 by mechanical means, an electronic regulator using a semiconductor can be used, or the output can be output in proportion to the bias voltage as shown in FIG. By using an amplifier in which the voltage changes as shown by a straight line L having a slope θ, the configuration can be easily made.

A part of the transmission signal, which is an output signal, is taken out and the feedback signal whose phase is almost reversed is added to the input signal (S4). As a means for changing the phase of the feedback signal, a phase variable device 13 is used. The phase changer 13 has an inductance component and a capacitance component, and changes the phase by changing one or both of them.

Therefore, a part of the relay signal, which is the input signal synthesized with the feedback signal by the mixer 12b, is extracted by the distributor 12c, and detected by the AM detector 16b to extract the signal level of the identification signal component. The phase of the feedback signal is adjusted by the phase variable device 13 according to the level (S5).

If there is an AM component of the identification signal of the jumping wave 11 'that cannot be completely removed even by the feedback signal, it has an adverse effect, and this is removed by the limiter in the amplifier 2b (S6). Then, when the signal transmitted as the relay wave 11 is received as the jump wave 11 ', the identification signal 19 for identifying this is AM-modulated and added (S7).

This signal is power-amplified by the amplifier 2c to obtain a transmission signal (S8), and a part of the transmission signal is extracted by the distributor 15 and used as a feedback signal (S9). Then, the remaining transmission signal is transmitted from the transmission antenna 3 as a relay wave 11 (S10). At this time, if the received broadcast wave 10 is a horizontally polarized wave, the relay wave 11
It is emitted as a different polarization plane, for example, vertically polarized.

As described above, even if the receiving condition of the external electric field, the reflected wave, or the like changes, the identification signal 19 is added and the relay wave 11 is transmitted, so that the diving wave 11 'can be easily identified. The feedback signal is adjusted according to the reception level of the identification signal, and the phase of the feedback signal is varied according to the level of the input signal combined with the feedback signal, thereby automatically stabilizing howling due to the diving wave 11 '. Can be prevented.

Next, a more specific configuration example of a method and a device for varying the phase of the feedback signal will be described. FIG. 4 is a diagram illustrating a configuration of a device that varies the phase of a feedback signal.

In the figure, reference numeral 25 denotes a distributor which is a first branching means, 26 denotes a distributor which is a second branching means, and 131 and
132 and 133 are phase variable devices as first to third phase variable means, and 121, 122 and 123 are first to third phase variable devices.
Mixers 21 and 23 are level detecting means for extracting the signal level of the identification signal from the outputs of the first synthesizing means and the third synthesizing means, and 24 is an output from the respective level detecting means. The phase changers 131 and 13
2, 133 which is a control means.

Thus, the feedback signal (N3) is input to the variable attenuator 14, and the output of the variable attenuator 14 is branched by the distributor 26 to 3
Are input to the three phase changers 131, 132 and 133.
This phase variable device includes a phase variable device 131 whose phase is slightly advanced with respect to an input signal in advance, a phase variable device 132 of the same phase which is an intermediate phase, and a phase variable device 1 whose phase is slightly delayed.
33, and according to an instruction from the control means,
The phase is changed synchronously by the same ratio.

The outputs of the phase changers 131, 132, 133 are input to mixers 121, 122, 123, respectively. The input signals are branched and input to the mixers 121, 122, and 123 by the distributor 25, respectively, and the phases thereof are slightly advanced with respect to the feedback signals output from the phase changers 131, 132, and 133. The signal is a signal whose phase is slightly delayed from that of the signal, and is combined with a signal whose phase is changed in conjunction therewith.

The output of the mixer 122, which is combined with the signal of the intermediate phase φ2 with respect to the feedback signal of the combined signal, is output as a relay signal (N2). The mixer 121 is combined with a signal whose phase is slightly advanced and a signal whose phase is slightly delayed with respect to the feedback signal.
The output of 123 is input to level detecting means 21 and 23, respectively. The level detecting means 21 and 23 detect the signal level of the identification signal from the synthesized signal.
It is composed of a detector and the like.

The output of each level detecting means is input to the control means 24. The control means 24 compares the output signals from both of the level detection means, determines whether to advance or delay the phase angle of the feedback signal according to the level of the signal level, and adjusts the phase variable devices 131, 132, 133. .

Next, the operation will be described. That is, with respect to an intermediate phase centered in the initial state, a variable phase device that produces three phase states of the same phase, a phase slightly delayed and a phase advanced respectively is prepared, and the intermediate phase output and the input signal Is controlled so that the signal level of the identification signal component included in the relay signal obtained by combining the above is minimized.

That is, as shown in FIG. 3, when the phase of the input signal and that of the feedback signal are substantially at point A, which are opposite to each other, a signal for relay obtained by combining the signal output of the phase changer 132 and the input signal is used. The signal output, which is the signal level of the included identification signal component, becomes the minimum s1, and the identification signal component of the signal obtained by combining the output of the phase changers 131 and 133 of the phases C and B slightly shifted before and after the input signal with the input signal. Are the same. However, when the phase of the input signal and the phase of the feedback signal are different, the signal output s4 at the point A 'where the phase of the feedback signal is delayed is larger than s1, and the phases C', slightly shifted before and after it.
The signal output of B ′ becomes an output s3 smaller than the signal output s4 of the center phase A ′ and a larger output s5. Therefore, it is determined whether the phase of the feedback signal is advanced or delayed based on the magnitude of the signal output. The point where the signal output of the phase slightly shifted forward and backward from the center phase becomes the same level is that the feedback signal is almost in opposite phase. Can be determined.

[0044]

As described above, according to the present invention, the identification signal is added to the relay wave, thereby detecting the level of the diving wave, adjusting the level of the feedback signal, and combining the input signal with the feedback signal. Since the phase of the feedback signal is adjusted by the level of the identification signal component included in the relay signal, the level of a part of the output signal applied to the input side even when the reception situation such as electric field strength changes. By automatically adjusting the phase and the phase, it is possible to provide an FM broadcast synchronous relay method and apparatus capable of stably preventing howling even when the reception condition changes.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of an FM broadcast synchronous relay device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an operation principle of a linear amplifier as a signal level adjusting unit.

FIG. 3 is a diagram showing an operation principle of a phase variable device as a phase adjusting unit.

FIG. 4 is a diagram illustrating a configuration example of a device that varies a phase of a feedback signal.

FIG. 5 is a flowchart showing the operation of the present invention.

FIG. 6 is a diagram showing an example of a conventional FM broadcast relay method.

FIG. 7 is a diagram illustrating an example of a conventional FM broadcast relay device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Receiving antenna 2 Amplifier 2a, 2b, 2c Amplifier 3 Transmitting antenna 4 Tower 5, 5a Cable 6 Broadcast wave transmitting antenna 7 Master station 10 Broadcast wave 11 Relay wave 12a Distributor 12b Mixer 12c Distributor 13, 13a Phase variable device Reference Signs List 14 attenuator, variable attenuator 15 coupler, distributor 16a, 16b AM detector 17 AM modulator 18 oscillator 19 identification signal 21, 23 level detecting means 24 control means 25, 26 distributor 131, 132, 133 phase variable device 121, 122 , 123 mixer

Claims (4)

(57) [Claims] 1. An FM broadcast relay method for receiving a broadcast wave of a master station, amplifying the received signal and transmitting a relay wave at the same frequency, wherein a relay signal for relaying the broadcast wave of the master station is provided. The AM signal is amplified by the identification signal, and the amplified signal is amplified to obtain a transmission signal. A part of the transmission signal is used as a feedback signal, and the identification signal is extracted from the received reception signal, and according to the signal level of the obtained identification signal. Adjusting the feedback signal to an optimal level, adding the feedback signal to the received signal to form a relay signal, and changing the phase of the feedback signal so that the signal level of the identification signal included in the relay signal is substantially minimized. Adjusting and transmitting the transmission signal as a relay wave. 2. The means for adjusting the phase of the feedback signal produces a signal advanced in phase, a signal having an intermediate phase, and a signal delayed in phase with respect to the feedback signal, and the three signals have the same phase. The phase-advanced signal and the phase-delayed signal are synchronized with each other by the ratio, and the phase-delayed signal is added to the received signal. 2. The method according to claim 1, wherein the phase of the feedback signal is adjusted as a phase at which the signal level of the identification signal included in the use signal is substantially minimized. 3. An FM broadcast relay apparatus for receiving a broadcast wave of a master station, amplifying the received signal and transmitting a relay wave at the same frequency, wherein the input signal branching means for branching out and extracting the received input signal. Signal extracting means for extracting an identification signal from the extracted input signal, signal level adjusting means for adjusting a feedback signal to an optimum level according to the level of the extracted identification signal, and a feedback signal for the input signal. Combining means for adding, signal level extracting means for extracting the signal level of the identification signal included in the relay signal combined by the combining means, and a feedback signal so that the signal level of the extracted identification signal is substantially minimized. Phase adjustment means for adjusting the phase of the input signal; identification signal adding means for adding an identification signal to the synthesized input signal by AM modulation; Amplifying means for amplifying the signal modulated by the signal adding means and outputting the amplified signal as a relay wave, and an output signal which extracts a part of the output signal amplified by the amplifying means and serves as the feedback signal An FM broadcast synchronous relay device comprising a branching unit. 4. The phase adjusting means includes a second branching means for branching a feedback signal, and a feedback signal branched by the second branching means from a leading phase, an intermediate phase and a delayed phase. First to third variable
, A first splitter for splitting an input signal, and an input signal split by the first splitter and an output signal of the first to third phase changers. First to third combining means; each level detecting means for detecting a signal level of an identification signal included in an output signal of the first combining means and the third combining means; 4. The FM broadcast synchronous relay apparatus according to claim 3, further comprising control means for receiving the respective outputs and adjusting the first to third phase variable devices.