JPH08163063A - Method for synchronized broadcast - Google Patents

Abstract

PURPOSE: To realize a method for synchronized broadcast in an inexpensive system without use of complicated equipment. CONSTITUTION: In order to emit a broadcast radio wave with identical transmission frequency, modulation and delay time from plural transmission stations (3-5) adjacent to each other or very close to each other, a high frequency signal with a transmission signal modulated in a broadcast studio 1 is sent simultaneously to the plural transmission stations by using optical fiber cables at a low level and the path difference from the studio to the plural transmission stations is eliminated by adjusting the length of the optical fiber cables in a center 2 provided separately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for synchronously broadcasting a television signal or an audio signal, and more particularly to the use of an optical fiber cable at a plurality of transmitting stations whose transmission frequencies modulated by these signals are adjacent to or very close to each other. The present invention relates to a synchronous broadcasting method in which broadcast radio waves having the same transmission frequency, modulation degree and delay time are radiated from the plurality of transmitting stations while being transmitted simultaneously.

[0002]

2. Description of the Related Art Conventionally, various studies have been made on synchronous broadcasting, but a unified technical view and method have not yet been proved. Further, although a technique of transmitting a modulated high frequency signal through an optical fiber cable is well known, for example, only an intermediate frequency (19.5 ± 3 MHz) between a receiving station and a transmitting station in a very specific television relay station. Have been used for the transmission method. This was developed as a measure to prevent lightning strikes on the coaxial line laid between the receiving station and the transmitting station.The frequency used for transmission is low, and it was developed for the purpose of directly using the high frequency signal to be transmitted as the transmission frequency. Not a thing. Further, in this case, since the optical fiber cable transmission line is owned by itself, it is difficult to spread economically.

[0003] As publications on high-frequency signal transmission technology using optical fibers, Shinichi Fujiwara and Tetsuya Okano: "TV relay broadcasting station IF optical multiplex transmission system", IEICE Technical Report OCS 90-66 (March 1991) There is a month.

[0004]

Conventionally, as the most general method for synchronous broadcasting, a broadcast radio wave transmitted from a master station transmitting station is received, and the transmission frequency and modulation of the master station are selected from the received signals. It has been considered to detect a signal component and re-add the detected component to the transmission frequency of the slave station and the modulated signal component to achieve synchronization. There is also an example in which the synchronization control signal is transmitted on another line. However, considering that synchronous broadcasting is carried out by these methods, a very complicated device and a control signal transmission line are separately required, and technically, all the conditions necessary for carrying out synchronous broadcasting cannot be set up.
The utility value of synchronous broadcasting was not emphasized.

In recent years, the technical conditions for using an optical fiber cable have been established. However, although there are concerns over the distance condition due to the use of optical fiber cables, the condition that synchronous broadcasting must be carried out is limited to when broadcasting at the same transmission frequency from multiple adjacent transmission locations. As a result, the condition of the cost increase due to the use of the optical fiber cable can be ignored.

The information transmission system in recent years is
In many cases, general telecommunications carriers and CATV carriers own information and communication networks, and it is possible to search for the terminal in the vicinity of a plurality of nearby transmitting stations, and it is possible for them to own their own optical fiber cables. There is no reason, and borrowing the line makes the cost very cheap. On the basis of these matters, the construction of a system for synchronous broadcasting in a narrow area has been established with high performance, high stability, high reliability, and low cost.

The present invention was made on the basis of the advancement of transmission technology using optical fiber cables and the consideration of the above-mentioned economic effect. The purpose of the invention is not to use a complicated device and to be inexpensive. It is intended to provide a synchronous broadcasting method capable of constructing a system.

[0008]

The synchronous broadcasting method of the present invention which achieves this object radiates broadcast radio waves having the same transmission frequency, modulation factor and delay time from a plurality of adjacent or very close transmitting stations. A high-frequency signal of a transmission frequency modulated in a broadcasting station is simultaneously transmitted at a low level to the plurality of transmitting stations by using an optical fiber cable, and a path difference from the playing station to the plurality of transmitting stations is transmitted. Is
It is characterized in that the lengths of the optical fiber cables are adjusted to be the same in a separately provided central center.

[0009]

[Embodiment] The conditions for occurrence of interference in reception in a place where a plurality of incoming radio waves coexist in broadcast radio waves are as follows. The transmission frequencies are not the same. The degree of modulation is not the same. The delay time of the transmission frequency and the modulation frequency is a certain value or more. The D / U value of the selected radio wave is below a certain value. Regarding the conditions, when installing a broadcasting station, consider in detail and
Although the / U value is designed to be a certain value or more, it is difficult to satisfy the condition because of recent radio wave conditions. When the condition value of is secured to some extent (for example,
Speaking of FM broadcasting, the D / U ratio is 14 dB or more) ,,, By satisfying the conditions, it is possible to reduce interference in the receiving place.

Regarding the conditions of and, in general,
Since the transmission frequency and the modulation factor at each transmitting station are independent, it is technically and costly difficult to synchronize them with each other. Therefore, according to the present invention, for example, the following FM transmission system is constructed. (a) Low power (11) FM-modulated in stereo at the performance room
A high frequency radio wave (transmission frequency) of about 0 dBμv) is output. (b) The transmission system uses an optical fiber cable to branch and transmit the modulated high frequency waves to multiple transmitting stations. (c) At each transmitting station, the transmitted high frequency signal is amplified to the specified output and transmitted. With the above system construction, it is possible to emit broadcast radio waves having the same transmission frequency and modulation degree from each transmitting station.

The delay time difference due to
In the case of M broadcasting, the delay time difference is required to be 20 μsec or less), but if the length of the optical fiber cable that is the transmission medium is adjusted during transmission to keep it above a certain value, it will be received as synchronous broadcasting. A problem-free evaluation can be obtained.

Hereinafter, the method of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a basic system diagram of an embodiment according to the broadcasting method of the present invention. In this example, FM synchronous broadcasting will be described as an example, but the broadcast wave to be transmitted may be a television broadcast wave or a radio broadcast wave.

At the FM broadcasting performance station 1 installed in the city, the broadcasting program signal 11 is transmitted via the modulation signal power supply line 12 to the F
The signal is input to the M modulation unit 13, and the FM modulation unit 13 outputs the stereo F
Perform M modulation. Next, the output high frequency signal is input to the E / O adapter (electrical / optical converter) 15 via the high frequency signal feeder line 14. At this time, the FM broadcast wave band (76 MHz) is input to the E / O adapter input. The voltage of 110 dBμV is supplied at the designated transmission frequency of one wave within 90 MHz). The high frequency signal (transmission frequency) of the FM broadcast supplied to the E / O adapter 15 is sent to the central center 2 of the CATV operator by the optical fiber cable 16 owned by the existing CATV operator that is pulled into the performance room 1. First transmitted.

Next, by utilizing the existing local networks 24, 25 and 26 of the CATV business operators, branch distribution is performed to the vicinity of a plurality of FM broadcasting radio wave transmitting stations 3, 4 and 5. At this time, it is necessary to newly install an optical fiber cable from the terminal location near the transmission station to the planned transmission location 27,2
Although there are 8 and 29, most of them are carried out by the CATV business operator in order to use the local networks 24, 25 and 26 of the CATV business, and the expense is good with the borrowing fee + α.

From the system diagram shown in FIG. 1, the path difference of the high frequency signal (transmission frequency) to each of the transmitting stations 3, 4 and 5 causes a problem with respect to the delay time difference which is a condition for synchronous broadcasting, but the optical fiber cable is extremely thin. Therefore, it is possible to adjust the length of the difference in the path lengths in the CATV central center 2 to make them the same length. That is, in the CATV central center 2, the time difference adjusting units 22 and 23 are inserted into the output of the optical signal distributor 21. For example, when the longest transmission station 3 among the transmission lines in each transmission station system is taken as a reference, the transmission stations 4 and 5 are used.
This is to adjust the time difference related to the transmission path length difference with respect to. The time difference adjusting units 22 and 23 are drums around which optical fiber cables are wound, and adjust the time difference of, for example, about 1 to 20 μsec.

The high-frequency signals (transmission frequencies) that are branched and distributed reach the transmitting stations 3, 4, and 5 respectively, and the respective O / O
The high frequency signals (transmission frequency) output from the FM broadcasting performance station 1 are input to the E adapters (optical / electrical converters) 31, 41, 51, and output from each of them. Here, a high frequency signal (transmission frequency) of the same condition is input to each of the transmission units 32, 42, 52 of the transmission stations 3, 4, 5.
In each transmitting unit, devices having the same delay time standard, that is, input filters 33, 43, 53, power amplifiers 34, 44,
54 and the output filters 35, 45 and 55, the transmitter output, that is, the respective transmission antennas 36, 46 and 56.
Therefore, FM broadcast radio waves having the same transmission frequency, the same degree of modulation, and the same delay time can be obtained.

Within the service area of each transmitting station, FM broadcast waves from other transmitting stations adjacent to the own station arrive (for example, transmitting stations 4, 5 within the service area of transmitting station 3). In the place where the electric field strength of the adjacent station with respect to the electric field strength of the own station is about 14 dB or less, the reception condition evaluated as the FM broadcast wave can be obtained. In addition, it is clear that the same result can be obtained for television broadcast waves and radio broadcast waves.

The optical fiber cable is conventionally used in broadcasting stations, etc.
Although erected for private transmission, the present invention provides an inexpensive method by renting an optical fiber cable transmission line owned by a general telecommunications carrier, particularly a line owned by a CATV carrier. ing. The optical fiber cable used has low transmission characteristics (transmission loss <0.4d
B / km, connection loss <0.1 dB / location), and low output level long distance transmission is possible.

Although the present invention has been described in detail with reference to the embodiment shown in FIG. 1, the present invention is not limited to the embodiment, and various modifications can be made within the scope of the present invention. It will be apparent to those skilled in the art that modifications can be made.

[0020]

According to the method of the present invention, synchronous broadcasting can be easily operated by radiating broadcast waves having the same transmission frequency, modulation degree, and delay time from a plurality of transmitting stations without using a complicated device. This makes it possible to achieve a great effect in effective use of frequencies. In addition, because you do not own the optical fiber cable, you can build a system at low cost,
Further, at each transmitting station, the transmitting device can be simplified, highly reliable performance can be maintained, and unnecessary maintenance cost can be reduced.

[Brief description of drawings]

FIG. 1 shows a basic system diagram of an embodiment according to the synchronous broadcasting method of the present invention.

[Explanation of symbols]

 1 FM Broadcasting Theater 2 Central Center 3, 4, 5 Transmitting Station 11 Broadcasting Program Signal 12 Modulation Signal Power Supply Line 13 FM Modulation Section 14 High Frequency Signal Power Supply Line 15 E / O Adapter 16, 24, 25, 26 Existing Fiber Optic Cable 21 Optical signal distributor 22, 23 Time difference adjustment unit 27, 28, 29 Newly installed optical fiber cable 31, 41, 51 O / E adapter 32, 42, 52 Transmitter 33, 43, 53 Input filter 34, 44, 54 Electric power Amplifier 35,45,55 Output filter 36,46,56 Transmission antenna

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shin Suzuki 4-14 Kamiyama-cho, Shibuya-ku, Tokyo, N.K.

Claims (1)

[Claims] 1. In order to radiate broadcast radio waves having the same transmission frequency, modulation degree and delay time from a plurality of transmitting stations (3-5) which are adjacent to or very close to each other, they are modulated in the broadcasting station (1). A high-frequency signal having a transmission frequency is simultaneously transmitted at a low level to the plurality of transmitting stations by using an optical fiber cable, and a path difference from the playing place to the plurality of transmitting stations is separately provided in a central center. (2) A synchronized broadcasting method characterized in that the length of the optical fiber cable is adjusted to be the same.