JPS589441A - Multioffice transmission method and signal transmitter - Google Patents

Abstract

PURPOSE:To realize a multioffice transmission communication system having the reduced interference between the signal transmitters and a large diversity effect, by turning the direction of a directional antenna connected to plural scattered transmitters synchronously with the symbol period of the time series information. CONSTITUTION:The signal is applied to a time series signal input terminal 1 and a symbol timing signal input terminal 2 and then to a signal transmitter 3 including a modulator and an electric power amplifier. A control circuit 8 supplies a control signal to a phase shifting circuit 7 to turn the direction of a directional antenna by 360 deg. within a horizontal plane is a symbol period and in response to the symbol timing signal. Such signal transmitters 9, 10 and 11 are distributed scatteringly. Then the same time series information is supplied to those transmitters from a time series information source 12 along with the symbol timing signal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-station transmission method and apparatus for wirelessly transmitting time-series information mainly to mobile bodies.

In wireless communication targeting a mobile object, it is difficult to maintain a stable communication line at all times because the radio wave propagation conditions change as the mobile object moves. Furthermore, when considering not only temporal fluctuations but also spatial service areas, there are areas where it is difficult to construct communication lines, such as behind obstacles to radio wave propagation.

Conventionally, multi-station transmission systems have been used to overcome such obstacles. The multi-station transmission system is intended to reduce shadows on radio wave propagation and construct a stable communication line by transmitting the same information from a plurality of regionally distributed transmitting stations.

However, in this system, if the carrier frequencies of each transmitting station are selected to be the same, the radio waves transmitted from each transmitting station will interfere with each other, resulting in areas where the electric field strength is strong and areas where it is weak. In particular, at points where the distance to the two transmitting stations is equal, there are points where the electric field strength is almost zero. As a method to solve such problems, a method has been proposed in which the carrier frequencies of each station are shifted. When this method is used, the electric field strength does not steadily decrease at a certain point,
The electric field strength changes at a period corresponding to the frequency difference, and a sufficient electric field strength can be obtained on average.

However, in order to fully utilize the effects of this method, it is necessary to select a difference in carrier wave frequency large enough to generate one or more beats within the symbol period of time-series information.

Therefore, as the number of transmitting stations increases, it is necessary to separate the frequencies between these stations by more than the symbol frequency (the reciprocal of the symbol period), resulting in an increase in the overall required band. In addition to being undesirable from the point of view of effective frequency utilization, widening the required band also requires widening the reception band on the receiver side, which has the undesirable effect of increasing noise power.

SUMMARY OF THE INVENTION An object of the present invention is to provide a multi-station transmission method and a transmission device thereof that eliminates such drawbacks.

In the multi-station transmission method of the present invention, a transmitter that modulates a carrier wave based on input time-series information and a transmitter output are connected, and a directional antenna whose pointing direction is rotatable is synchronized with the symbol period of the time-series information. This is realized using a transmitting device consisting of a control circuit that controls the directivity of the antenna.

This will be explained in detail below using the drawings. FIG. 1 is a block diagram showing an embodiment of a transmitting device used in the method of the present invention, l is a time series signal input terminal, 2 is a symbol timing signal input terminal, and 3 is a transmitter including a modulator and a power amplifier. , 4.5.6 are transmitting antenna elements, and 7 is a phase shift circuit that changes the phase of the transmitting high-frequency signal supplied to the transmitting antenna element 45.6. Configure an aided array antenna system. Reference numeral 8 denotes a control circuit that supplies a control signal to the phase shift circuit 7 in response to the symbol timing signal to rotate the pointing direction of the antenna by 360' in a horizontal plane in one symbol period.

FIG. 2 shows an embodiment of a multi-station transmission communication system realized using the transmitting device shown in FIG.

9.10.11 are the same transmitters as shown in Figure 1, which are distributed regionally, and these transmitters receive the same time series information from 12 time series information sources as symbol timing signals. Supplied with.

is not negligibly small compared to the symbol period, the time-series information source 12 shifts the timing of sending information to each transmitting device in advance so that the information reaches each transmitting device at the same time. do.

FIG. 3 is a diagram showing the positional relationship between each transmitting device in FIG. 2 and a moving receiving device. In Figure 3, 13.14.
15 indicates the position of the transmitter.

The transmitting devices located at positions 13, 14, and 15 are hereinafter referred to as A and B.
, distinguished by the name C. The arrows labeled 13, 14, and 15 indicate the pointing direction of the antenna at a certain time (tO). It is assumed that this pointing direction rotates clockwise on the paper at a rate of 3600 per symbol period. 16.17.18 shows the reception position of the mobile receiver.

FIG. 4 is a waveform diagram showing the received signals at reception positions 16, 17, and 18 of FIG. 3. In the diagram, the horizontal axis shows time and the vertical axis shows the envelope amplitude of the signal. Figure 3 shows the received signal waveform at the receiving position 16 in FIG. This point is equidistant from transmitters A, B, and C, and receives signals with equal strength.

In addition, at time to, only the signal from transmitter C is received, and since the received information is sequentially integrated and detected over T as the antenna directivity direction rotates, the signals from each transmitter are effectively detected. used.

The waveform in FIG. 4(b) is the received signal waveform at the receiving position 17 in FIG. At this point, the signal of transmitter 113 is most strongly received. Since the signals from transmitters A and C arrive in close proximity to each other, they are received somewhat in the same pattern and cause interference, but this is the waveform of the received signal from transmitter B. At this point as well, the signal from transmitter B is strongly received by the iron. However, since the arrival directions of the signals from transmitters B and C completely overlap, interference occurs.

However, in this case as well, since the signal from transmitter B is dominant, the influence of interference is slight.

In particular, when a frequency modulation method is used as the modulation method, the effect of suppressing weak signals is excellent, so it is effective for such a multi-station transmission system.

In the above explanation, only the receiving points 16, 17, and 18 were described, but such effects can be obtained from the transmitting devices A, B, and C.
It is clear that there are wide expectations in areas including

Also, since the directivity direction of the transmitting antenna is rotated, the reception time per station becomes 1 power, and the received energy per symbol appears to decrease, but this effect is due to the antenna gain based on the directivity of the transmitting antenna. There is no need to increase the output power of the transmitter used in the transmitter even if this method is adopted. It is clear that this method is effective not only when there are three transmitters, but also when a large number of transmitters are arranged randomly on a plane.

In addition, in the embodiment of the transmitting device shown in FIG. 1, a phased array antenna is used as the directional antenna whose directional direction can be rotated. Rotational directivity can be obtained by switching antennas, or if the symbol period is as long as 1'', a unidirectional antenna can be mechanically rotated.

As explained above, according to the present invention, it is possible to realize a multi-station transmission communication system with less interference between transmitting devices and a large diversity effect, and to enable communication targeting mobile users with wide JI.
It is highly effective when used in applications where it is necessary to cover the IJ area without any dead areas.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a transmitting device used in the method of the present invention, FIG. 2 is an example of a multi-station transmission communication system using the method of the present invention, and FIG. FIG. 2 is a waveform diagram of a received signal. In the figure, l is a time-series information manual terminal, 2 is a symbol timing signal manual terminal, 3 is transmission + iL4, 5.6 is a transmission gamma element, 7 is a phase shift circuit, and 8 is a control circuit for the antenna pointing direction. Shindai Uchihara, Patent Attorney/EiJ Diagram Z

Claims (1)

[Claims] (1) In a system that transmits the same time-series information from multiple transmitters that are geographically distributed, the directional direction of the directional antenna connected to each transmitter is rotated in synchronization with the symbol period of the time-series information. A multi-station transmission method characterized by: (2) A transmitter that modulates a carrier wave based on time-series information; a directional antenna whose output is connected to the transmitter; and a directional antenna that can be rotated in the ζ direction; A transmitting device comprising a control circuit that controls.