JPS6194421A - Synchronous satellite international broadcasting system - Google Patents

Abstract

PURPOSE:To attain stable international broadcast by transmitting a broadcast program to respective areas on the earth for a specific period at fixed time daily through a synchronous satellite which moves on a circular track in an equator plane. CONSTITUTION:An up link signal received by a receiving antenna 8 is preamplified 9 and branched, and converted to IF by a down converter 10 for every carrier. This IF signal is branched to a switch 12 and the branched signal is demodulated by a demodulator 18 and recorded by a tape recorder 19. The switch 12 disconnects an IF amplifier 11 and connects a modulator 20 to an IF amplifier 13 after the time of transmission from a transmitting station, thereby sending the playback signal of the recorder 19 to a down link. The frequency of each down link is sent from the down link to receiving stations on the basis of the frequency of a pilot oscillator 21.

Description

[Detailed Description of the Invention] [Technical Field] The present invention utilizes a synchronous satellite international broadcasting system, in particular a synchronous orbiting satellite launched into a circular orbit above the equator, to perform scheduled broadcasting to various points on the earth. Concerning synchronous satellite international broadcasting system.

[Prior art]

Conventionally, international broadcasting has been carried out using shortwave bands that utilize ionospheric propagation, but good reception is not possible due to fading and interference, and there are many areas where it is difficult to hear. On the other hand, with the internationalization of the economy and society, the number of people living overseas who have left their home countries and are active in various parts of the world is increasing, and the areas where they live now extend to all parts of the world. The importance of Kazutomo is growing. For this reason, countermeasures such as increasing transmission power and increasing the number of overseas relay stations are being considered, but despite requiring large construction and operating costs, the Due to the shortage, instability of propagation conditions due to ionospheric propagation, and basic problems with z5, alignment cannot be an essential solution.

[Purpose of the invention]

The purpose of the present invention is to solve the above-mentioned problems of current international broadcasting, and to provide a synchronous satellite international broadcasting system that allows stable reception of broadcasts from one's home country at a certain time every day for a certain period of time at any point on the earth. The goal is to provide the following.

[Structure of the invention]

The synchronous satellite international broadcasting system of the present invention transmits a communication satellite equipped with a transbonder having an information storage device at an altitude of approximately 36,000 km above the equator, e 20,000 km;
It is launched into a circular orbit of 4,000 km; 10,000 km, and is controlled so that it passes through two fixed positions on the circular orbit at a fixed time every day, from one point on the earth to each point on the earth. Each is configured to transmit information at a fixed time every day.

〔Example〕

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a conceptual diagram of the synchronous satellite international broadcast system of the present invention, where 1 is a synchronous satellite, 2 is a transmitting station, 3 is a receiving station, and 4 is a control station. A transmitting station 2 transmits a broadcast program to a synchronous satellite 1 that slowly moves in the direction of the arrow above the equator during a certain period of time when the satellite is in a position where it can communicate. The synchronous satellite 1 records this program on a tape recorder, reproduces it, and repeatedly transmits it while moving. A large number of receiving stations 3a and 3b scattered all over the earth receive this broadcast program when the satellite comes to the communicable positions 1a and lb, respectively. The synchronous satellite 1 is controlled by a control station 4 to appear at a fixed position at a fixed time every day, and the receiving station 3 can easily receive it with a simple receiving antenna that rotates clockwise around a single rotation axis. I can do it. The satellite orbit, available communication time, satellite repeater, and configuration of the transmitting and receiving earth stations will be sequentially explained below.

In Figure 2, Earth 5 may be at an altitude of 35°786 above the equator.
It is well known that the circular orbit satellite 6 launched eastward at Km appears stationary from the earth because the earth's rotational angular velocity v1 and the satellite's orbital angular velocity V match, making it a geostationary satellite. It is used not only as a communication satellite but also as a weather satellite and a broadcasting satellite. In contrast, altitude 3 above the equator
The westward circular orbit satellite 7 launched at 5,941 km has an orbital angular velocity of V.

is almost the same as the earth's rotational angular velocity V1 and in the opposite direction, so it is a synchronous satellite with a period of exactly 12 hours when viewed from the earth. This satellite appears at a fixed location at a fixed time twice a day at any point on the earth and moves slowly, so it is easy to track from the ground and the radio waves from the satellite can be easily received using relatively simple receiving equipment. Is it possible to receive it? Ayu 3
The diagram shows various latitudes on the earth (0', 20°, 40°, 60°)
The elevation angle when looking at the circular orbit satellite 7 from the point is calculated, and the horizontal axis represents the time in minutes from the time when the satellite arrived in the middle of the rain. From this figure, for example, from Japan at about 35 degrees north latitude, this satellite can be seen twice a day at an elevation angle of 10 degrees or more for over 4 hours, and even at a point at 60 degrees latitude, it can be seen at an elevation angle of 5 degrees or more for 4 hours each day. If you can see this satellite, you will know.

Therefore, during this period, a broadcast program was transmitted from the ground for about 3 hours, and the satellite sent it back to the ground and recorded it on a tape recorder.After the program transmission from the ground was completed, it was played repeatedly and then sent again. If a satellite orbits the earth from a location and then receives and records the next broadcast program when it returns to its original position, this broadcast program can be received at almost every point on the earth within 12 hours. Unlike direct broadcasting using geostationary satellites or satellite communication, this method does not provide instantaneous communication, but it uses a single satellite to send the same communication content stably and on time to numerous receiving points scattered around the world. This makes it suitable for applications such as international broadcasting.
There is.

Figure 4 is a trajectory diagram showing the position of a satellite passing through a point at longitude 1101 at 6:00 GMT, and at 18:00 in the evening.
The satellite, which passed through longitude 110 + 1, followed the sun and moved from east to west in the direction of the arrow until it reached longitude 110 at 6 the next morning.
Return to g, next time we will go around the earth at night and at 6 pm longitude 1lO1lK will appear again. In Japan (Akashi) at 135 degrees east longitude, the satellite will be heading south at time A (30:30 GMTi, JET
...Japan Standard Time...10:30) and B (13:30 GMT, 22:30 J8T) between C and D and E and F for about 4 hours each. You can see satellites. Therefore, from Japan to GMT O~
As shown in the figure, broadcast programs are broadcast in hourly units to the satellite at 3 o'clock and 6 o'clock and from 12 to 15 o'clock.1. it, I and 11
Send ゜n/, i/. This broadcast program is stored in a tape recorder within the satellite and simultaneously transmitted from the satellite to the ground via a transbonder. When the transmission from the ground is completed, the broadcast program stored in the tape recorder is repeatedly played back in the order of 1, n, and H as shown in the figure, and the satellite moves westward while transmitting this toward the ground. At a point at 60 degrees west longitude on the other side of the earth (southern South America), the satellite indicated by a can be seen for 4 hours from 6:00 to 10:00 GMT, so satellites I, II, and I can be seen during the 3-hour period from 7:00 to 10:00 GMT. You can receive this broadcast program in order. At a point of 120 degrees west longitude (Pacific coast of North America) (
Since the 4-hour satellite indicated by r-1b is visible, II, I, I
Or 'I! , I, If, the order is changed, but all the transmitted broadcast programs can be received. The content of each broadcast program is determined by what the recipient wants, but it is possible to transmit not only audio broadcasts but also text information, and pay broadcasts targeted only to specific recipients are also possible. For example, ■ is an audio broadcast of news, music, etc., ■ is a text broadcast such as Shingetsu Digest 5 Stock Information, etc., and ■ is a paid broadcast targeted at specific users. The terrestrial receiving equipment can consist of a receiver and a motor-driven directional antenna that slowly and automatically rotates in clockwork around a rotational axis approximately parallel to the Earth's axis. Since the radius of the earth cannot be ignored relative to the altitude of the satellite, in order to track the satellite by rotating the antenna at a constant speed around one axis of rotation, the axis of rotation must be not parallel to the earth's axis but slightly tilted, and Although it is necessary to make the rotation speed slightly faster than one rotation per 12 hours, if these values are selected for whitening, the maximum tracking direction error for 4 hours can be kept within ±1°. Therefore, if the position control on the satellite's orbit is about ±0.5°, which is the same as that of a geostationary satellite, the receiving antenna's 3
The width of the a-beam may be selected to be approximately 5° (upper 2°5°) or more.

Currently, Inmarsa's maritime satellite communication system uses a frequency in the 1-5 GHz band for downlink from the satellite to the ship, configuring the voice telephone line in the 80PC-FM system, and the standard ship station A parabolic antenna with a diameter of 1.2 m is used as the antenna, and its beam width is approximately 11°. Since the beam width of a parabolic antenna is inversely proportional to the antenna diameter, and the antenna gain is proportional to the square of the diameter, 5
Antenna with a beam width has approximately four times the power gain as a ship station antenna, and even if the transmission bandwidth of the broadcast program is 1QkHz, which is approximately three times that of a telephone line, similar to a standard broadcast relay line, the maritime satellite communication system Satellite transmission power equivalent to (several watts)
) can be received. Therefore, it is possible to carry several tens of channels on one satellite, and if one satellite is shared by each country, it is possible not only technically but also economically. If, for example, the 2.5 GHz band allocated to the broadcasting satellite service is used as the downlink frequency band, the diameter of the receiving antenna on the ground can be approximately 1.5 m. The configuration of the receiver is, for example, a low-noise FET amplifier and an SC
The PC-FM receiver body is divided into two parts, and the former can be connected to the receiver body by attaching a parabolic anti-6G primary radiation connection and using a cable. The receiver body is a normal SCPC-FM
If the receiver is configured to generate a local oscillation frequency using the pilot signal from the satellite as a reference, narrowband reception is possible by eliminating fluctuations in the satellite's oscillation frequency as well as frequency changes due to the Doppler effect. be.

Figure 5 is a block diagram of an embodiment of a satellite repeater. The SHF band frequency (for example, 14 GHz band) is used for uplink, and the satellite commonally amplifies multiple carriers and then repeats them for each carrier. , a case is shown in which the power is amplified in common by modulating the man-hour wave again, and furthermore, the outputs of a plurality of power amplifiers are combined and transmitted from a global antenna. In FIG. 5, an uplink signal received by a receiving antenna 8 is amplified by a preamplifier (LNA) 9, then branched, and converted to an intermediate frequency by a down converter (D/C') 10 for each carrier. IF amplifier (IFA) 11, switch (SW) 12. It is converted to the 2.5 GHz band by an up converter (U/C) 14 through an IF amplifier (I FA) 13, and is then connected to a traveling wave tube amplifier (TWT) 15 and a multiplexer (C
OMB) 16 and is transmitted from the transmitting antenna 17.

The switch 12 branches the signal from the F amplifier 11, and the branched signal is demodulated by a demodulator (DEM) 18 and recorded on a tape recorder (T/R) 19. When the transmission time from the transmitting station ends, the switch 12 disconnects the IF amplifier 11 and connects the modulator (MOD) 20 to the JP amplifier 13.
The playback signal of the tape recorder 19 is transmitted to the downlink. The frequency of each downlink is determined by the pilot oscillator (P
Transmitting local oscillator (TL) with reference to the frequency of IL) 21
O) 22 and the frequency of the pilot oscillator 21 is sent from the downlink to the receiving station as a reference frequency.

Note that each frequency of the receiving local oscillator (RLO) 23 is generated based on the frequency of the reference oscillator (08C) 24, and the frequency of the reference oscillator 240 is controlled by the pilot oscillator 21. The switching control of the switching device 12 is performed according to a timetable set in advance by commands from the control station, and the broadcast program sent from the transmitting station at a fixed time is relayed heterodyne by the satellite repeater and sent back to the ground at the same time. is recorded on a tape recorder. When the transmission time from the ground is over, the satellite's receiving circuit is disconnected and the playback program from the tape recorder is sent to the downlink.

As shown in Figure 5, when transmitting from a transmitting station, the transmitted wave is looped back by the satellite repeater and can be received by the transmitting station. Therefore, the transmitting station can control its own transmitting frequency so that the receiving frequency is a specified value, and the influence of satellite frequency fluctuations and the Doppler effect can be eliminated. Since the transmission from the ground is repeated periodically, it is possible to predict the frequency to be transmitted from the reception frequency (or pilot frequency) from the satellite just before the transmission time, and it is possible to transmit at this frequency when starting the transmission. Strict loop control is possible if the return signal is received. Frequency allocation should be done so that broadcast programs from the ground will not be received at the same time on the same frequency channels that the satellites are in close contact with.Even if the frequencies at the beginning of the mission are slightly different, it may cause interference to adjacent channels. There isn't. Therefore, the satellite's transmitting and receiving local oscillators do not necessarily have to be synchronized as shown in FIG.

An example using a synchronized satellite in a circular westward orbit with a 12-hour cycle has been described above.
If the satellite is launched eastward at a time of becomes possible. In this case, the lower satellite altitude reduces free-space propagation loss, which is advantageous, but the beam width of the satellite's global beam antenna becomes wider, which reduces the gain and compensates for this by reducing the satellite's transmission power. There is no big difference. On the ground side, reception in high visibility areas becomes somewhat difficult, and the tracking error due to the -axis rotating receiving antenna increases, so the beam width of the receiving antenna needs to be made slightly wider. Similarly, it was launched eastward at an altitude of 20,208.
The orbital angular velocity of a circular orbit satellite of m is approximately 2 of the earth's rotational angular velocity.
It will double and become a 24-hour synchronous satellite. In this case, 1 per day
The communication time for each transmission and reception will be approximately 6 and a half hours. In addition to the above, satellites with a period of 8 hours, 6 hours, etc. can be considered, and conversely, a satellite with a period of 48 hours that appears once every two days can also be considered. Table 1 is a list of the results of calculating the direction of movement and altitude of these satellites. Among these satellites, those with a period of more than 48 hours cannot be used for the purpose of broadcasting at a fixed time every day, and the 24-hour synchronized satellites around the west cannot be used because the altitude is too high. Also, the altitude is about 10,000K
Those lacking in m have a narrow communication area and the error in the tracking direction of the uniaxially rotating receiving antenna is large, and those with a cycle of less than 6 o'clock...j have short usage time per use, both of which are problematic for practical users.

Note that similar usage can be considered for satellites in inclined circular orbits other than those in the equatorial plane, but it is not practical because there are areas where reception is not possible in places other than the poles of the earth, and it becomes difficult to control the position of the satellite. It seems that the value is not high.

[Effects of the Invention] As explained in detail above, according to the iv3 satellite international broadcasting system of the present invention, the synchronous satellite orbiting in a circular orbit in the equatorial plane broadcasts the I/C constant time + ij broadcast 6 every day.
Programs can be sent to almost any area on earth, and can be received using a simple clock-type antenna that rotates once every 1%. This has the effect of providing stable international broadcasting that could not be expected otherwise.

4. f+ in the drawing? i14? Fig. 1 is a system conceptual diagram of the present invention, Fig. 2 is an orbit explanatory diagram explaining the satellite orbit of an embodiment of the present invention, and Fig. 3 is a satellite elevation angle and visible time of an embodiment of the present invention. FIG. 4 is an explanatory diagram of the relationship between a satellite position and a broadcast program according to an embodiment of the present invention, and FIG. 5 is a block diagram of an embodiment of a satellite repeater.

1...Synchronized satellite, 2...Transmitting station, 3.
...Receiving station, 4...Control station, 5...
...Earth, 6.7...Circular Orbit Technique 1 Go to Figure \--1/- Figure 2

Claims (1)

[Claims] A communication satellite equipped with a transbonder with an information storage device is placed at an altitude of approximately 36,000 km above the equator; 20,000 K.
It is launched into a circular orbit of either m; 14,000 km; A synchronous satellite international system characterized by being configured to transmit information at a fixed time every day.