JPH02202729A - Switching system for directional diversity antenna - Google Patents

Abstract

PURPOSE:To prevent possibility of data discontinuity at the time of instantaneous switching of a receiving system and to improve the communication quality by providing a receiving system detecting means for detecting a receiving system which can obtain the maximum receiving level, a switching request means and a switching means, etc. CONSTITUTION:A receiving signal is supplied to a level detecting system switch 5 through an antenna group 1 and branching devices 2a-2d, and a receiving output is supplied to a control part 6 through channels 5a-5d selected in order by a timing pulse from a timing pulse generating part 51. The control part 6 calculates a receiving level through an amplifier 61, etc., and a CPU 64 with regard to a receiving output, detects a receiving system of the maximum receiving level, and also, in the case of it is detected that its receiving system is different from the receiving system connected up to the present, the number of times of its detection is counted. Also, in the case of it exceeds a prescribed number of times, a switching instructing signal of the receiving system is outputted to a switching driving part 7. As a result, the receiving system is switched through the driving part 7 and a receiving system switch 3, data discontinuity at the time of instantaneous switching of the receiving system is eliminated, and the communication quality can be improved.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a directional diversity antenna switching system, and more specifically, to a mobile device in which the outputs of two or more receiving systems are switched to reduce fading. This invention relates to a directional diversity antenna switching system for

<Prior Art> Radio waves on the ground propagate through multipath propagation paths under the influence of buildings and the like. When the phases of radio waves arriving from different propagation paths are in the same phase, the electric field becomes strong (and when the phases are reversed, the electric field becomes weak. The period of weakening of the electric field, that is, fading) The period at which this occurs is a pitch of approximately one wavelength.Since the moving body moves at high speed in an electric field that varies at the above-mentioned period, a fast and deep phasing occurs.

In order to alleviate the above-mentioned fast and deep fading, a diversity antenna switching method has been devised.

This diversity antenna switching method uses the receiving frequency,
When the polarization, radio wave arrival angle, antenna position, etc. are different,
As shown in Figure 5, this method focuses on the fact that the received field strengths of the two antennas are different, and as shown by the thick solid line in the figure, the antenna output is switched to output the stronger reception level to receive the signal. By doing this, deep fading is prevented.

In particular, in mobile radio communications, radio waves arrive from different directions within a horizontal plane, so for example, directional diversity antenna switching is used as a diversity antenna switching method for mobile communications on roads where visibility is obstructed by buildings. A position diversity antenna switching method is adopted in which multiple antenna elements are separated from each other.

Among these, the directional diversity antenna switching method is installed in ground mobile stations such as vehicles because the device can be configured compactly.

Directional diversity antenna switching methods include (1) a method in which the direction of one antenna element is variable, and (2) a method in which two to four antenna elements with different directivities are switched depending on the reception level.

A receiving device using the method (2) above changes the direction of one antenna to follow the maximum reception level, thereby preventing deep fading. However, in order to follow this maximum reception level, a servo mechanism to detect the direction in which the maximum reception level can be obtained and a complicated coupler to connect the rotating antenna and reception cable are required.
It is difficult to provide a high-speed tracking function for fading that occurs in mobile radio communications.

For this reason, the method described in (1) above in which about 2 to 4 antenna elements are switched according to the reception level is often used. For example, the present inventors devised a diversity receiving antenna control device in Utility Application No. 82-167587. The diversity reception antenna control device according to the prior application includes a splitter that splits the received signal from each antenna element, an amplifier that amplifies the received signal from the splitter, a detector that detects the amplified signal, and a detector that detects the detected signal. a level calculation means for calculating a reception level; a signal processing means for comparing the calculated reception levels with each other and detecting a reception system that provides a maximum reception level;
The apparatus includes a switch that switches from a previously connected receiving system to a receiving system that provides the maximum reception level in response to a receiving system detection signal from the signal processing means.

The operation of the diversity reception antenna control device of the prior application is as follows.

The received output of each antenna element is branched to an amplifier and a switch by a splitter. The received output branched to the amplifier side is envelope-detected by a wave detector, and then
The level calculation means calculates the reception level based on the detected signal. Next, the signal processing means detects the receiving system that provides the maximum level from among the receiving levels of the respective receiving systems calculated by the level calculating means, and outputs a switching signal to the switch.

Next, the switch connects the receiver to the receiving system that provides the maximum reception level.

According to the prior application, the signal processing means constantly compares the reception levels of each reception system, so if fading occurs, it is possible to quickly switch to the reception system that provides the maximum reception level. .

<Problems to be Solved by the Invention> However, in the directional diversity antenna switching method as exemplified above, if the receiving antenna is switched to the receiving antenna that can obtain the maximum receiving level based on the comparison of receiving levels as described above, Even when a moving object approaches a protrusion or corner of a structure on the road and the reception level reverses, the reception system switches instantly. For this reason, there is a problem that switching occurs frequently and phase discontinuity states due to switching occur frequently.

To explain in more detail, mobile communications include control data,
This is done using a PSK modulated wave signal, an FSK modulated wave signal, etc., which modulates a carrier wave with a constant amplitude using a series of block data consisting of call data, etc., so when a series of block data is being transmitted, the receiving antenna cannot be switched. If this is done frequently, phase change points and frequency change points may not be detected, data continuity may be impaired, and data may be lost.

Furthermore, since wireless communication is performed asynchronously, if an error occurs at the -degree switching timing, it will take time to recover the synchronization, which may hinder subsequent data acquisition.

This invention was made in view of the above problems,
It is an object of the present invention to provide a directional diversity antenna switching method that prevents the risk of continuous data transmission during instantaneous switching of reception systems and makes it possible to improve communication quality.

Means for Solving the Problems> In order to achieve the above object, the directional diversity antenna switching system of the present invention includes a splitter that splits the received signal of each receiving system, and a switch between the receiving levels from the splitter. a receiving system detecting means for comparing the receiving system and detecting the receiving system that can obtain the maximum receiving level; A switching request means outputs a switching request signal, and when the switching request signal from the switching request means is counted a preset number of times, the previously connected receiving system is changed to the receiving system that can obtain the maximum reception level. It has a switching means for driving a switching device for switching.

1 Effect> With the above directional diversity antenna switching method, signals from the outside are received by each receiving system, and the received output is supplied to the receiving system detection means and the switching device through the branching device. do. Then, when the receiving system detecting means compares the receiving levels from each receiving system and detects the receiving system from which the maximum receiving level can be obtained, that is, which receiving system has the largest output, the switching requesting means , outputs a switching request signal for switching the previously connected receiving system to the receiving system that provides the maximum reception level. The switching means will issue a drive signal for switching the reception system to the switch only when the number of times the switching request signal has been issued is counted by a set number of times.

<Example> Hereinafter, embodiments will be described in detail with reference to the accompanying drawings showing examples.

FIG. 1 shows a block diagram showing an embodiment of the present invention,
The directional diversity antenna switching system of the embodiment includes an antenna group (1) consisting of four independent antenna elements (1a) to (ld), and a branching system that branches received signals from each antenna element (la) to (1d). Containers (2a) to (2d),
a reception system switch (3) to which the reception signal is supplied through the branchers (2a) to (2d); a receiver (4) to which the reception signal is supplied through the reception system switch (3); A level detection system switching device (5) that switches the received signals from the devices (2a) to (2d) at predetermined timings, and a branching device (2
a) to (2d), and a control unit (6) that detects the level of each received signal from (2d) and supplies a switching instruction signal for the receiving system to the switching drive unit (7); It has a switching drive section (7) that outputs a switching signal to the reception system switching device (3).

To explain in more detail, the antenna group (1) consists of four antenna elements (la) to (ld) each having independent directivity, as shown in the horizontal directivity characteristic diagram of FIG.
are arranged so as to be shifted by 90 degrees from each other so that the maximum reception level can be obtained for radio waves from the direction in which each of the antenna elements (la) to (ld) directly faces.

I have to.

The branchers (2a) to (2d) are conventionally known ones, and supply the reception output from each of the antenna elements (la) to (ld) to the reception system switcher (3), and also This is supplied to the level detection system switch (5). however,
It is also possible to use a divider that equally divides and outputs the above signal.

The reception system switch (3) connects any one of the branchers (2a) to (2d) to the receiver (4) in response to a switching signal from the reception system detection section (6). Therefore 1q1 at least 4 channels (3a) to (3d)
have.

The level detection system switcher (5) includes a timing pulse generator (51) that sequentially outputs pulse signals from four output terminals.
), and depending on this timing pulse, the turnout (2a) ~
It has four channels (5a) to (5d) which sequentially connect the receiving system detecting section (2d) and the receiving system detecting section (6). , whereby the reception outputs from the splitters (2a) to (2d) are selectively supplied to the reception system detection section (6).

The control unit (6) includes an amplifier (61) that amplifies the received output from the level detection system switch (5), a detector (62) that detects the amplified signal, and an A that digitizes the detected analog signal. /D converter (63) and a logic operation unit (B) that calculates the reception level based on the converted digital signal.
4) and a memory (65) that temporarily stores the calculated level.
). The logic operation unit (64) is composed of a microprocessor, and after storing the reception level of each reception system, compares the stored reception levels with each other to detect the reception system with the maximum reception level, and also detects the reception system with the maximum reception level. When it is detected that the receiving system that provides the maximum level is different from the previously connected receiving system, the number of times this detection is detected is counted, and when the number of times exceeds a predetermined number, the switching drive unit (7) switches the receiving system. Outputs an instruction signal.

The switching drive section (7) generates a switching drive signal for selecting a reception channel based on the signal output from the logic operation section (B4).

When receiving the switching drive signal, the receiving system switching device (3) drives the receiving system switching device (3) to select a predetermined channel (3).
a) to (3d) are selected, and the receiving system and receiver (4) are selected.
It connects the

The operation of the above directional diversity antenna switching method is as follows.

The control unit (6) operates according to the flowchart shown in FIG. First, when it is detected that the receiving system that provides the maximum level is different from the previously connected receiving system, an index n indicating the number of times this detection has been made is set to 0 (step 2). Next, the signal from the outside is transmitted to each antenna element (la) to (1d).
This received output is sent to branchers (2a) to (2d).
) is supplied to the reception system switch (3), and a part of the reception output is supplied to the level detection system switch (5).

The level detection system switcher (5) selects channels (5a) that are sequentially selected by a series of timing pulse signals supplied from the timing pulse generator (51).
The received output is supplied to the control section (6) through (5d) (step (2)).

Next, the received output is amplified by an amplifier (61), detected by a detector (62), and detected by an A/D converter (63).
), and furthermore, the logic operation section (64) calculates the reception level based on the converted digital signal (step (2)). Then, a part of the calculated reception level is stored in the memory (65), and after the reception level of each reception system is stored, the reception system CHx with the maximum reception level is detected by comparing the stored reception levels with each other ( Step ■
).

In step (2), it is determined whether the channel CHx from which the maximum reception level is obtained is the same as the channel that is being received, and if it is the same as the channel that is being received, the process returns to step (2). If there is a difference, proceed to step ■,
It is determined whether the index n set above is O. If it is 0, set the above channel CHx as CHo in step ■,
Hold in memory (65). Then, increment n by 1 and return to step (2). Therefore, n=1 at this point.

Next, in response to the next timing pulse output, the reception level of each antenna is monitored, and the channel CHx where the maximum reception level can be obtained is detected (steps ■ to steps ■
). In step (2), it is determined whether the channel is the same as the channel being transmitted, and if it is different, n is determined in step (2).

n-1, this time we proceed to step ①, and the detected channel CHx becomes the hold channel CHo.
determine whether it is the same as If they are the same, step [
phase], set the channel switching flag, and return to the start. Therefore, the reception output supplied to the reception system switch (3) is passed through the channels (3a) to (3d) selected according to the switching signal supplied from the switching drive section (7) to the receiver (4). ). If they are different, the process proceeds to step (2), where the channel CHo is updated to the channel CHx detected immediately before, and the process returns to step (2) without switching the receiving channel.

In this way, we decided to switch the reception channel for the first time when the same maximum reception level channel different from the channel currently being received is detected twice in a row. Instantaneous channel switching due to disturbances can be avoided.

In addition, in the above flowchart, switching is performed when a channel with a maximum reception level different from the channel currently being received appears twice in a row, but it is not limited to two times, and even if it is three times in a row, switching is performed. It may be times. generally consecutive 0
You may switch it when it appears twice. The optimal number of times will be determined through field tests and the like.

Furthermore, they do not necessarily have to appear consecutively. For example, if the signal appears three times while the reception level is monitored five times, the signal may be switched. In general, out of ko times of monitoring, the maximum level different from the channel currently being received was no times (no≦
ko) You may switch if it appears.

FIG. 4 shows an algorithm for switching when a channel with a maximum level different from the channel currently being received appears no times out of kO times of monitoring. Steps numbered the same as in FIG. 3 have the same meaning. Unlike in Fig. 3, -1 is set at step ■, and CHx+ is set at step ■.
If it is CHo, proceed to step (2) and increment k by 1. In step ■, even if CHX -CHo, switching is not performed immediately, and in step @, n
is incremented by one, and in step @ it is determined whether this n has reached a predetermined number of times no. If no has been reached, the process proceeds to step (2) and k is incremented by 1. Proceed from step [Yes] to step ■, where k is the set value k.

If it has not been reached, return to step ■. k is the set value ko
If reached, the procedure is aborted and the process returns to the start. Also,
When this n reaches the predetermined number of times no in step (2), the process moves to step [phase] and switching is performed for the first time.

Since the above procedure is adopted, channel switching is performed only when a channel with a maximum reception level different from the channel currently being received appears no times, and the number of channel detections is k.

limited to times. In other words, the number of times a maximum level different from that of the channel currently being received appears within a limited number of monitoring times called ko times is counted, and if it appears no times, switching is performed.

Note that the present invention is not limited to the above-described embodiments, and for example, the number of antenna elements is not limited to four, but may be any number as long as it is two or more. Various design changes can be made without changing the gist of the invention.

<Effects of the Invention> As described above, according to the directional diversity antenna switching method of the present invention, the switching means does not switch the receiving system with a single switching request, but instead switches the receiving system with a plurality of set switching requests. Since it was decided to switch only when it counted, even when a moving object instantaneously passes a non-continuous structure such as a protrusion or corner of a structure on the road, the receiving system does not switch, and the fading caused by the structure can be avoided. The receiving system only switches when it is repeatedly affected.

Therefore, it is possible to prevent frequent occurrence of phase discontinuity due to switching when switching the receiving system.

Therefore, even when a series of block data is being transmitted, the frequency of phase changes and frequency changes due to switching of reception antennas can be minimized, and communication quality can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the directional diversity antenna switching system according to the present invention, FIG. 2 is a diagram showing the directivity of the diversity receiving antenna according to the embodiment, and FIG. 3 is the antenna in the above embodiment. FIG. 4 is a flowchart showing a switching procedure. FIG. 4 is a modified example of the flowchart. FIG. 5 is a graph showing changes in reception level when fading occurs. (1)... Antenna element, (2a) to (2d)... Branch, (6)... Receiving system detection means, switching requesting means, control unit functioning as switching means.

Claims (1)

[Claims] Compare the reception levels of 1, 2 or more receiving systems A receiving system that can obtain the maximum reception level by comparing Detects the maximum reception from the receiving system that is currently receiving data. Switch to a receiving system that can obtain the level Directional diversity antenna switching In the method, Compare the levels of the received signals of each receiving system. The receiving system that can obtain the maximum receiving level a receiving system detection means for detecting the Previously connected according to the detection signal from the stage to obtain the maximum reception level of the receiving system. sends a switching request to switch to the receiving system that is switching requesting means and switching requesting means Switching request signals from multiple preset When counting the number of times, the number of previously connected The maximum reception level can be obtained from the receiving system that was In order to switch to the receiving system that characterized by having a switching means for driving Directional diversity antenna switching method.