JPS60223337A - Angular diversity receiver - Google Patents

Abstract

PURPOSE:To prevent interruption or deterioration in talking due to fading by using a reception circuit having a smaller timewise mean reception level between two sets of reception circuits when the frequency of inversion of quantitative relation of instantaneous reception levels is a prescribed value or below to retrieve an antenna having higher reception input. CONSTITUTION:Six directivity antennas 10a-10f are installed in a base station while the horizontal azimuth is shifted sequentially by 60 deg. each. A reception input of each directivity antenna is connected to a connection switch circuit 30 via preamplifier circuits 20a, 20b-20f in common use for filter circuits. Any of the 6 systems of reception inputs of the connection switch circuit 30 is connected to two reception circuits 40A, 40B under the control of a control circuit 50. In case of the figure D, although the reception levels LA, LB are both fluctuated considerably because of fading, since the fluctuation of the both is casued nearly in phase, the inversion of the quantitative relation is hardly caused. Moreover, it is meaningless to hold the connection of the reception circuit 40B having a low input level because the both are fluctuated in phase. In such a case, the reception circuit 40B is used to retrieve the antenna reception sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an angular diversity receiving device used in a base station of a mobile radio system.

Conventional configuration and its problems In a mobile radio system, in order to receive radio waves from mobile stations scattered in various places, a plurality of directional antennas are set up in different directions such that ii < i L. An angular diversity receiving apparatus has been proposed in which the antenna whose reception input is greater than or equal to a predetermined value necessary to ensure speech quality is selected each time, and the receiving circuit is connected to the antenna. In other words, when the radiated power from a mobile station is weak, it is difficult for the base station to receive it with a single omnidirectional antenna. When the direction seen from the base station gradually changes and the antenna with the maximum input changes accordingly, the above-mentioned connection switching attempts to always connect the receiving circuit to the antenna with the maximum input.

Switching the connection between the antenna and the receiving circuit as described above is usually performed by software and therefore takes some time, but it is possible to sufficiently follow slow changes in the base station receiving input due to the movement of the mobile station. However, when a base station receives radio waves from a mobile station traveling at high speed through high-rise buildings that block radio waves, the reception input changes rapidly and gradually.

Such sudden changes in reception input, which are unique to mobile communications, are somewhat different from fading, which is unique to wireless communications between stationary bodies, in that the rate of change is fast, but below we will discuss such rules. All fluctuations in reception sensitivity that do not have any characteristics are collectively referred to as fading.

It is generally difficult to increase the speed of connection switching between the plurality of antennas and the receiving circuit so as to follow the rapid fading phenomenon peculiar to mobile communications.

To solve this problem, it is necessary to add one receiving circuit and switch connections between a total of two receiving circuits and three or more antennas based on the time-averaged reception level. The operation of changing the connection with the antenna until the receiving circuit has reception sensitivity equal to or higher than a predetermined value necessary to ensure call quality, and the instantaneous reception level (v) of the receiving circuit having reception sensitivity equal to or higher than the predetermined value. A device has been proposed that performs two-stage connection switching in which the output with the higher value is instantly selected using hardware and the output is supplied to the subsequent stage in parallel.

However, the conventional device described above is configured so that the connection with the antenna is not changed any more as long as the reception level is above a predetermined value, so there is an antenna with a higher reception input than the two connected antennas. However, it is absurd that this cannot be detected. For this reason, there is a risk that the quality of the call will deteriorate due to the influence of fading.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems.The purpose of the present invention is to reduce the possibility of interruption or deterioration of calls due to fading by connecting the antenna to the antenna with the maximum reception input. An object of the present invention is to provide an angular diversity receiving device.

Structure of the Invention In order to achieve the above object, the present invention provides a control means for controlling connection switching between two reception circuits and an antenna, such that the frequency of inversion of the magnitude relationship of the instantaneous values of each reception level is less than or equal to a predetermined value. Sometimes, the receiver circuit is further configured to include means for searching for an antenna with a higher reception input by using the one of these two receiving circuits with a smaller time-average reception level.

In other words, the fact that the frequency of reversal of the magnitude relationship of the instantaneous values of each reception level is low means that the influence of fading is small because the mobile station is stationary and is located in a place with few layers or shields, or the influence of fading is small. If one of the antennas has a sufficiently large receiving input compared to the other, in such a case, even if a receiving circuit with a low receiving level is used to search for an antenna with a larger receiving input, this This method focuses on the fact that there is little risk of call interruption or deterioration due to fading during the search.

DESCRIPTION OF EMBODIMENTS FIG. 1 shows an angle 4)<- to which an embodiment of the present invention is applied.
FIG. 2 is a block diagram illustrating the configuration of communication channels of the city receiving device. Although this receiving circuit is provided for each of a plurality of communication channels, only the configuration of a specific communication channel on the illustrated tube is shown.

Also, a calling/response channel provided in common to each communication channel is also omitted from illustration.

In this device, six directional antennas 10a, 10
b, 10c... 10f is placed. Each directional antenna sequentially has 6 antennas from 10a to 1Of.
They are installed at base stations with their horizontal orientations shifted by 0 degrees. The receiving power of each directional antenna is coupled to the connection switching circuit 30 via preamplifier circuits 20&, 20b, . . . 2Of, which also serve as filtering circuits.

The connection switching circuit 30 connects any one of the above-mentioned 6-system reception inputs to the two reception circuits 40A and 40B under the control of a control circuit 5o described later.

Since it is theoretically possible to omit the preamplifier circuits 2C)a to 2Of or to arrange them at the subsequent stage of the connection switching circuit 3o, the essential function of the connection switching circuit 30 is as follows. , six directional antennas 10a to 10f
is selectively connected to the two receiving circuits 40A and 40B.

Outputs representing the reception input levels of the two receiving circuits 40A and 40B are supplied to the control circuit 60 and the comparison circuit To via output lines 42A and 42B, respectively.

When the control circuit 50 receives a call designation at the terminal 61 indicating that this call channel has been designated for calls from the set amplifier channel in charge of calling and responding, the control circuit 50 outputs the output line 42.
A and 42B start the connection switching operation of the connection switching circuit 30 based on the time-averaged reception level of each receiving circuit.

This time-average reception level may be created by hardware by passing the reception level of each reception circuit through an integrating circuit, or may be created by sampling the reception level of each reception circuit a predetermined number of times in the control circuit 5o. It may be created by a software method of calculating the average value of .

The control circuit 50 compares each of the temporal average values of the reception levels monitored by the two receiving circuits with a predetermined value necessary to ensure call quality, and for receiving circuits that exceed the predetermined value, A control command is issued to the connection switching circuit 30 to maintain the connection with the antenna and to switch the connection to another available antenna for the receiving circuit that does not reach a predetermined value. The control circuit 60 is a typical data processing device that includes an input/output interface circuit, a CPU, a memory, etc. in addition to the comparison circuit described above.

The comparison circuit 7Q connects the receiving circuit 40A to the receiving circuit 40A via the signal lines 42A and 42B when the receiving device is in communication with a mobile station.
The switches 61 and 62 in the gate circuit 6o are switched by comparing the instantaneous values of the reception levels of and 40B and outputting a high or low signal according to the comparison result. The gate circuit 6o connects the output of the receiving circuit with the larger l instantaneous value to the output line 63 connected to the subsequent stage.

The connection switching control by the comparison circuit 70 and the gate circuit 6o is performed at high speed as well as the connection switching control by the control circuit 5o and the connection switching circuit 30. That is, this receiving device selects two antennas whose time average value is equal to or higher than a predetermined value by the control circuit 6Q and the connection switching circuit 30, and prevents the order of these reception levels from instantaneously changing due to fading or the like. In this case, the comparator circuit 70 and the gate circuit 60 select the output of the receiving circuit having the higher instantaneous value at high speed.

FIG. 2 is a block diagram showing an example of the configuration of the control circuit 50, in which 51 is a terminal for receiving a call designation for this call channel from the 7-1-up channel that is in charge of calling and responding, and 52 is a block diagram showing an example of the configuration of the control circuit 50. microprocessor (
C; PU), 53 is a memory, 54 is an interface circuit, 56.56 is an A-D conversion circuit, 67 is a counter, 58
is a timer.

The reception level monitored by the reception circuits 40A and 40B is
The data is read into the CPU 52 via the signal lines 42A, 42B, the A/D conversion circuit 65.56, and the bus 68.

The CPU 52 compares the read time average value of the reception level with a predetermined value necessary for ensuring call quality, and establishes a new connection based on the comparison result and the IB connection control history stored in the memory 53. Create a control command and send this command to bus 68. It is sent to the connection switching circuit 30 via the interface circuit 54 and the signal line C0NT.

The output of the comparator circuit 7o in FIG. 1 is also supplied to a counter 57 in the control circuit 50. This counter 57 is counted up every time the output of the comparison circuit To is inverted, and is forcibly cleared at a predetermined period. Receiving circuit 40A
The magnitude relationship between the instantaneous values of and 40B is frequently reversed, and as a result, when the count value of the counter 57 reaches a predetermined value prior to the above-mentioned clearing, the counter 57 resets the timer 58. On the other hand, when the frequency of the reversal of the magnitude relationship decreases, the counter 57 (and thus the timer 58, which is no longer reset) overflows L and interrupts the CPU 52.

The CPU that has accepted this interrupt uses the A-D conversion circuit 55.
．． 56 and disconnects the receiving circuit with the lower value from the currently connected antenna and connects another antenna with the disconnection margin until an antenna with a time-average reception level greater than a predetermined value is found. The connection switching circuit 3o is instructed to repeat up to As a result of this connection switching, if a corresponding antenna is found, the connection with that antenna will continue as long as the state remains above a predetermined value. The newly connected antenna may be different from the antenna that was connected immediately before the start of the reception level search operation, or may be the same antenna. In either case, after the antenna connection state is newly maintained, if the magnitude relationship of the reception levels is not reversed at a predetermined frequency, the above search operation is repeated again. As a result of such a search, if reversal is performed at a predetermined frequency, this means that an antenna with higher reception sensitivity than the antenna connected immediately before the start of the search has been connected.

FIG. 3 is a conceptual diagram showing an example of fluctuations in the reception level, where the horizontal axis shows the passage of time, and the vertical axis shows the reception levels LA and LB of the receiving circuits 40 and 4 OB, and the changes necessary to ensure speech quality. The predetermined value LO is shown. In the case of (A) in the same figure, the influence of fading on the reception level LA is large, and the magnitude relationship between the two reception levels is reversed relatively frequently, and in such a case, the dependence on the reception circuit 40B is Search operation is not performed because the value is high.

On the other hand, in the case of ), the influence of fading is small and there is almost no reversal of the magnitude relationship between the reception levels, for example because the mobile station is stationary in the suburbs with few obstacles. In such a case, the receiving circuit 40B with a lower input is used to search for the receiving input of the antenna. Also,(
In case C), the reception level /l/LA fluctuates significantly due to facing, but its time average value is quite large compared to the other reception level /l/LB, so the magnitude relationship is reversed. Since the frequency is low, a search is performed by the receiving circuit 40B.

Furthermore, in the case of (D), the reception level /L/LA A and LB
Both fluctuate significantly due to fading, but
Since both fluctuations occur in almost the same phase, there is almost no reversal of the magnitude relationship. This is a dangerous situation in which there is a strong possibility that both reception levels will fall below the predetermined value at the same time. There is no point in maintaining the connection. In such a case, the antenna reception sensitivity is searched using the reception circuit 40B.

In the above example, the connection switching circuit 30 is controlled by software, but the control may be performed by hardware as long as it is based on the time-averaged reception level.

In addition, although an example has been shown in which the frequency of reversal of the size relationship of received novels is detected from the number of reversals, the above-mentioned reversal frequency can be calculated by detecting the time rate during which the output of each receiving circuit is supplied to the subsequent stage. You can also do that.

Furthermore, although an example in which six antennas are used has been described, any appropriate number may be used as long as it is three or more. Especially 6
If the antennas are divided into groups of three and these two groups are installed apart from each other, there is an advantage that the effect of angular diversity and the effect of space diversity can be combined. This also applies to the case where two antenna systems each consisting of six antenna systems are installed.

Detailed Description of the Invention As described in detail, the present invention is capable of reversing these two values when the frequency of reversal of the magnitude relationship between the instantaneous values of each reception level is less than or equal to a predetermined value.
The antenna is further configured to search for an antenna with a higher reception input by using the one with the lowest time-average reception level among the reception circuits of the receiver, so the reception circuit always uses the antenna with the highest human power. This has the effect of providing an angular diversity receiving device that can be connected and is less likely to be interrupted or deteriorated due to fading.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a block diagram showing an example of 114 components of the control circuit 60 shown in FIG. FIG. 3 is a conceptual diagram illustrating fluctuations in reception level to explain the operation of the invention. 10a to 10f... directional antenna, 20a to 2O
f...Preamplifier circuit, 30... Connection switching circuit, 40A, 40B... Receiving circuit, 5o...
...Control circuit, 60...Gate circuit, 7o...
comparison circuit, 52...CPU, 53...memory, 54...interface circuit, 55,5
6.A-D conversion circuit, 57... Counter, 68
...Timer. Name of agent: Patent attorney Toshio Nakao and 1 other person

Claims (1)

[Claims] Three or more directional antennas installed at a base station facing different directions to receive radio waves from mobile stations, and two receiving antennas connected to any of these antennas via a connection switching means. control the connection switching means to change the connection with the antenna at the circuit and the trench where the time-averaged reception level of each of the reception circuits is equal to or higher than a predetermined value when the base station is in communication with the mobile station; determining the magnitude relationship between the instantaneous values of the reception levels of the control means and each of the reception circuits;
The control means includes a gate means for transmitting only the output of the receiving circuit having a larger instantaneous value of the receiving level to a subsequent stage, and the controlling means controls the frequency of reversal of the magnitude relationship of the instantaneous value of the receiving level of each receiving circuit to be less than or equal to a predetermined value. When , the connection switching between the receiving circuit whose time-averaged reception level is smaller among the two receiving circuits and the antenna which is in the idle state of connection is performed.
4. An angular diversity receiving device characterized by comprising means for controlling the time-average reception level to be changed again until it becomes equal to or higher than the predetermined value (iK).