JPS6347175B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a space diversity reception method for a master station in a time-division digital multidirectional communication system.

When applying a time-division multidirectional communication system to long-distance maritime propagation routes, a space diversity reception method is required to prevent line disconnections due to fading that occur frequently and to obtain the necessary line reliability. . However, the conventional space diversity reception method only deals with signals on the same propagation path that are opposed on a one-to-one basis as input signals. It has been desired to provide a space diversity reception system for signals transmitted in various directions.

The present invention was made in view of these points,
A space diversity reception system can be provided in one central station, in other words, in one master station, for received signals from a plurality of stations arranged in multiple directions, in other words, from slave stations. The present invention will be described below using an example in which three slave stations are installed for one master station.

FIG. 1 is a block diagram showing an embodiment of a space diversity reception method in a master station according to the time division multidirectional communication system of the present invention.
Reference numeral 11 denotes antennas installed at a certain distance from each other, which is a characteristic configuration of the space diversity reception system, and are connected to the main receiver 2 and the SD (space diversity) receiver 12, respectively. .
Reference numerals 3 and 13 each indicate a level detection circuit that detects the level of a signal from the receiver using a signal from a determination processing circuit, which will be described later. 100 generates and sends a level detection instruction signal to the level detection circuit 3,
This is a determination processing circuit that compares and determines the level of the detection signal from 13. SW is a switch that is selected and switched based on the determination result from the determination processing circuit 100, and 110 is a demodulation circuit. In addition, S ₁ and S ₂ in the figure represent the antennas 1 and 1, respectively.
S3 is a received signal from a slave station (not shown) that is applied to the input terminals of the main receiver 2 and SD receiver 12 through S11, and _S3 is a level detection instruction signal sent from the determination processing circuit 100 to the level detection circuits 3 and 13. , S ₄ is a selection signal from the determination processing circuit 100, and S ₅ is an output signal.

FIG. 2 is a time chart for explaining the operation of the space diversity receiver configured as above, and the number of slave stations is 3 as mentioned above, and here the slave stations A, B, Let it be C. S ₁ ~ in the diagram
Each signal of _S5 is as described above, and slave stations A, B, C
A brief explanation will be given of S ₁ and S ₂ , which are the received signals from. First, if we look at the received signal S ₁ that is input through antenna 1 of antennas 1 and 11 installed at a certain distance from each other, this received signal S ₁ occupies time t ₁ to t ₂ . A received signal from slave station A denoted A ₁₂ occupying A ₁₁ and time t ₄ to t ₅ , B ₁₁ occupying time t ₂ to t ₃ and from time t ₅
The received signal from slave station B denoted by B ₁₂ occupying time t ₆ , and C ₁₁ occupying time t ₃ to t ₄ and time t ₆
It has a signal configuration consisting of a received signal from the slave station C, indicated by _C12 , which occupies _t7 .
Therefore, the signal A ₁₁ included from time t ₁ to t ₄ ,
B ₁₁ , C ₁₁ and the signal A ₁₂ included from time t ₄ to t ₇ ,
Each of B ₁₂ and C ₁₂ is a frame with a constant period.
It consists of F ₁ and F ₂ , and in each frame there are N,
In this case, three burst signals, so-called signals from slave stations, are arranged so that they do not overlap in time, and similarly the signals A _1o , B _1o , C _1o , A _1o+1 , B _1o+1 , C _{1o +1} ,…
The frames F _o , F _{o+1 .} . . of the configuration are repeated in order. Also, regarding the received signal S ₂ input through the antenna 11 installed at a certain distance from the antenna 1, this received signal S ₂ is received at time t ₁
A occupies t ₂ from ₂₁ and occupies t ₅ from time t ₄
A received signal from slave station A (hereinafter referred to as a burst signal) denoted by A ₂₂ , B ₂₁ which occupies time t ₂ to t ₃ , and slave station B denoted by B ₂₂ which occupies time t ₅ to t ₆ .
(hereinafter referred to as burst signal) from C ₂₁ which further occupies the time t ₃ to t ₄ and the time t ₆ to t ₇
It has a signal configuration consisting of a received signal from the slave station C (hereinafter referred to as a burst signal) indicated by _C22 occupying the same area, and has the same configuration as the above-mentioned received signal _S1 including the frame configuration. The received signals S ₁ and S ₂ from these time-divided slave stations A, B, and C are as follows:
This is achieved by forming dependent synchronization in which each slave station responds to a signal from the master station, taking into account propagation delays.

Next, the above-mentioned received signals S ₁ and S ₂ are received by the antennas 1 and 11 shown in FIG.
12 will be described below. The received signal _S1 input via the antenna 1 is amplified by the main receiver 2, and then sent to the input terminal 5 of the switch SW via the communication path 4.
A portion of the signal is also supplied to the level detection circuit 3. Further, the received signal S ₂ input via the antenna 11 is amplified by the space diversity receiver 12, and then the amplified received signal S ₂ is supplied to the input terminal 15 of the switch SW via the communication path 14. At the same time, a part of it is supplied to the level detection circuit 13.

Here, the above two level detection circuits 3 and 13
are each provided with level detection instruction terminals 6 and 16.

In the above state, the determination processing circuit 100 supplies the level detection instruction signal _S3 as shown in FIG. supply
In addition, the level detection instruction signal _S3 and the received signal at this time
The time relationship between S ₁ and S ₂ may be within one burst signal as shown in FIG. Next, the level detection circuits 3 and 13 that have received the level detection instruction signal S ₃ perform level detection and output each time, and send it to the determination processing circuit 100 . That is,
The level detection circuits 3 and 13 send the detected signals to the determination processing circuit 100 via communication paths 8 and 18, respectively.
The detection signal is applied to the detection signal input terminals 9 and 19. The determination processing circuit 100 detects the slave station _{A in the frame F1 using the signals from the level detection circuits 3 and 13, in other words, the signal P a1 of} the level detection instruction signal S3 shown in _FIG .
The received signal S ₁ from S 1 , the burst signal A ₁₁ in S ₂ and
When each level detection signal of A ₂₁ is received via the communication paths 8 and 18, its magnitude is determined. The determination processing circuit 100 uses the determination result as a selection signal _S4 and switches between the time _t4 and _t5 occupied by the burst signals _A12 and _A22 , which are the received signals from the slave station A in the next frame _F2 . The signal is sent to the switch SW to control the switch SW. Toggle switch here
The SW is selected and switched according to the selection signal S ₄ to select one of the received signals S ₁ and S _2. When the selection signal S ₄ is at a high level (H), the switch is switched to the input terminal 5 side. When the switching is low level (L), it is configured to switch to the input terminal 15 side.

Therefore, in the example in FIG. 2, the received signals S ₁ ,
Burst signals A ₁₁ and A ₂₁ in frame F ₁ of S ₂
As a result of comparing and determining, since _A11 is large, P _a2 is obtained as the selection signal _S4 , and the changeover switch SW is switched to the input terminal 5 side as shown.
As a result, the received signal _S1 having good characteristics is selected as the signal from slave station A in frame _F1 , and the output signal _S5 in the next frame _F2 is the received signal _S1 as shown in FIG. A burst signal A ₁₂ is obtained, and the output signal S ₅ is sent to the next demodulator 110 to be demodulated;
A demodulated output is obtained. In addition, in a frame not shown, received signals S ₁ and S ₂ from slave station A
When the magnitude of is reversed and S ₂ becomes larger, the selection signal S ₄ becomes low level as determined by the judgment processing circuit, and therefore the selector switch SW is switched to the input terminal 15 side, and the selection signal S 4 becomes low level. In the next frame, input signal _S2 is selected as the signal.

Similarly, for the received signal from slave station B in frame _F1 , the level detection instruction signal _S3 is
At P _b1 , the received signal S ₁ , the burst signal B ₁₁ in S ₂ and
The level of B ₂₁ is detected, and the determination processing circuit 100 determines whether the detected level is large or small. In FIG. 2, the burst signals B ₁₁ and B ₂₁ are compared and determined. Since B ₂₁ is large, a low level P _b2 is obtained in the selection signal S ₄ , and the changeover switch SW is switched to the input terminal 15 side. In the next frame _F2 , the burst signal _B22 having good characteristics is selected, and the output signal _S5 is the burst signal _B22 as shown in FIG. Further, the determination process for the received signal from the slave station C is performed in the same manner as described above, and the burst signal _C12 is selected as the output signal _S5 .

In the above explanation, slave station A in frame _F1 ,
Although this has been done only for the received signals from B and C, the same processing operation as described above is repeated for frames F ₂ , F ₃ . . . F _o even when the number of slave stations is three or more.

Note that the propagation loss attenuation rate when fading occurs is usually about 1 dB/10 milliseconds, so the frame period (time from time t ₁ to t ₄ in Figure 2)
If the time is about several milliseconds, it is considered that the received signals from the same slave station between adjacent frames are at almost the same level. It is possible to realize a space diversity reception method that maintains good performance even when the level is detected and the switching selection is made for the received signal from the corresponding slave station in the next adjacent frame based on the judgment result of its magnitude. It is.
Furthermore, it is clear that the switching selection may be made after a plurality of frames instead of the next frame as long as performance is not impaired.

Furthermore, although the demodulator 110 is arranged after the changeover switch SW in the embodiments described above, two demodulators are prepared and inserted into the communication paths 4 and 14, and the demodulators of the respective outputs are demodulated. Even if the signal is switched, the desired effect will not be impaired.

As described above in detail, according to the present invention,
It is now possible to provide a space diversity reception method for the master station in a time-division multidirectional communication system that can handle received signals from multiple slave stations placed in multiple directions, and also eliminates fading at high frequencies on maritime propagation routes. This can be expected to have an excellent effect in ensuring the necessary line reliability even on lines where noise occurs.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the space diversity receiving system according to the present invention, and FIG. 2 is a time chart for explaining the operation of FIG. 1. 1 and 11 are antennas, 2 is the main receiver, 12 is
SD receiver, 3 and 13 are level detection circuits, 4 and 1
4 is a communication path, 5 and 15 are input terminals, 6 and 16 are level detection instruction terminals, 7, 8, 17, and 18 are communication paths, 9 and 19 are detection signal input terminals, 100 is a determination processing circuit, and 110 is a demodulation SW is a changeover switch, S ₁ and S ₂ are received signals, S ₃ is a level detection instruction signal, S ₄ is a selection signal, and S ₅ is an output signal.

Claims (1)

[Claims] 1. In a digital multi-directional communication system using a master station and two or more slave stations arranged in multiple directions, the communication signal has a frame structure and is synchronized with the frame. It has a time-division configuration in which it periodically receives signals in bursts from slave stations arranged in the same direction, and the master station is connected to antennas installed at a certain distance from each other in order to receive signals from the slave stations. A main receiver and a space diversity receiver are arranged, and the output side of both receivers detects the level of the received signal from each slave station for each frame, and also detects the level of the received signal from each slave station in each frame. means for each burst signal corresponding to the station, further comparing the levels of the detected signals from the two receivers to determine whether the signal is large or small; and a changeover switch for selecting a signal received by one of the receivers, and as a result of determining the magnitude of the level of the burst signal in the detected frame by the above means, a response is taken at least one frame after the detected frame. A space diversity reception method characterized by switching a changeover switch so that a received signal from a slave station that receives the signal can be selected as an output according to the determination result.