JPS6229936B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention is a wireless communication device that has a plurality of antennas and achieves a wide communication range by selectively switching the antennas, in which the reception level from the same partner station is compared between each antenna. The present invention relates to a received level comparison device that makes a determination to select an antenna that receives the maximum level.

A typical application of such a wireless communication device is a system having a master station with multiple antennas that requires a wide communication area in order to communicate with a large number of mobile stations.

In this case, when the slave station communicates with the master station via multiple antennas connected to the main device of the master station, the radio waves emitted from the slave station are received by the multiple antennas with differences in level and delay time. As a result, they interfere with each other.

Also, when communicating from a master station to a slave station, if radio waves are emitted simultaneously from multiple antennas, they may cause significant interference depending on the location of the slave station, making communication impossible. Therefore, in a wireless communication system having a plurality of antennas, it is necessary to limit the number of antennas that communicate with a slave station to one to prevent interference. The method to achieve this is to send the received signal level information from the slave station at each antenna to the main device, and the main device compares the reception level of each antenna.
A conceivable method is to radiate the transmission signal only to the antenna showing the highest level and send an instruction signal to send the received signal from the slave station to the main device.
However, with this method, it is necessary to draw a signal line to send reception level information to each antenna individually, or to multiplex the information onto a single signal line, which requires a large number of signal lines. Alternatively, multiplexing equipment is required. The purpose of this invention is to eliminate the above-mentioned drawbacks, and to easily select the antenna receiving the maximum level from the slave station by transmitting antenna reception level information between one signal line without multiplexing. An object of the present invention is to provide a reception level comparison device that enables the following.

According to the present invention, in a wireless communication device that has a plurality of antennas and uses these antennas by switching, there are a plurality of level detectors that detect reception levels from each antenna, and an output of each of the level detectors. a plurality of couplers that couple the outputs of the couplers to a common line via diodes, a common line that couples the outputs of the couplers to each other, a plurality of current measuring devices that detect the current flowing through each of the couplers, and each of the couplers. A reception level comparison device comprising a judgment circuit that generates an antenna selection signal when the output of a current measuring device exceeds a certain amount, and a reception level comparison device having a plurality of antennas. A wireless communication device used by switching includes a plurality of level detectors for detecting reception levels from each antenna, a coupler for coupling outputs of the respective level detectors to a common line via a diode, and a coupler for coupling the outputs of the respective level detectors to a common line via a diode. A common line that couples outputs to each other, a plurality of current measuring devices that detect the current flowing through each of the couplers, and generating an antenna selection signal when the output of each of the current measuring devices exceeds a certain amount. To provide a reception level comparison device comprising a plurality of determination circuits and a plurality of correction circuits that increase the output of each of the couplers when an antenna selection signal is output from each of the determination circuits. Can be done.

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

FIG. 1 is a diagram showing an example of a wireless button telephone system as an example of a wireless system to which the present invention is applied. In the main device 1, the station lines from the terminal stations are time-division multiplexed and added to the signal line 4. The multiplexed signal is modulated by the modem device (2 and 2') on the main unit side, and the slave station (3 and 3') decodes the signal of its own channel wirelessly via the antenna (6 and 6'). , convert it to voice, and send it to the receiver.

The reception level comparison devices 7, 7' of the present invention are installed together with the modulation/demodulation devices 2, 2', corresponding to each antenna 6, 6', and are connected to each other via a signal line 5. Since such a wireless button telephone system allows slave stations to be moved freely, it is very convenient for use in offices and the like where telephones are often moved due to layout changes. One of the major problems with this wireless button telephone system is to prevent interference between radio waves emitted from and received from the plurality of antennas 6, 6'. The influence of this interference will be explained by taking as an example the case where the slave station 3 is communicating. When transmitting information from the main device 1 to the slave station 3, if radio waves are emitted from multiple antennas 6, 6' on the same channel (same time zone), these radio waves may vary depending on the location of the slave station 3. Causes significant interference.
Furthermore, the radio waves emitted from the slave station 3 are also received by a plurality of antennas 6, 6' at the same time, and it is necessary to determine which antenna should send the received signal to the main device. Therefore, the main device 1
Which antenna should be used to communicate with slave station 3?
It is necessary to determine which antenna is most suitable for communicating with the slave station 3, and to disable other antennas when communicating with the slave station 3. By the way, the location of slave station 3 is
Since the mobile station 3 may move, the selection of the antenna described above must be determined based on the signal from the slave station 3. The antenna switching device of the present invention receives radio waves from the slave station 3 using each antenna 6, 6', and uses only the antenna receiving the maximum level for communication with the slave station 3.

FIG. 2 shows an embodiment of the present invention.

In FIG. 2, 6 indicates a receiving antenna, and 7
01 is a received signal amplifier, 702 is a square circuit, 70
3 indicates a low-pass filter, which together constitutes a level detector 70. 71 and 71' indicate couplers, which are connected to the signal line 5, which is a common line, through diodes 72 and 72', respectively. The signal line 5 is commonly connected to a diode corresponding to each antenna, and is grounded via a resistor 73. In Figure 2, reference numbers with a ``''' indicate components connected to different antennas corresponding to the respective numbers, and items with the same number with and without a ``'' have the same characteristics. Use elements that have Here, the operation of the present invention will be described when radio waves from the same slave station are received by antennas 6 and 6', and the radio waves received by antenna 6 are stronger. The radio waves received by antenna 6 are sent to amplifier 7
01, squared by a squaring circuit 702, waved by a low-pass filter 703, and then passed through a coupler 7.
1. The coupler 71 is composed of a resistor 711 and a diode 72. Radio waves received by antenna 6' are input to diode 72' through a similar process. In this way, a voltage corresponding to the strength of the radio waves received by the antennas 6, 6' is applied to the diodes 72, 72', respectively. If the signal received by the antenna 6 is stronger than the signal received by the antenna 6', the input voltage of the diode 72 will be higher than the input voltage of the diode 72', and the potential of the signal line 5 will be higher than the input voltage of the diode 72. The value is a value that is lower than the voltage by the junction voltage of the diode 72. At this time, the potential difference between the input and output of the diode 72' is smaller than the junction voltage, and no current flows into the diode 72'. This situation is the same even when there are many antennas instead of two, and current flows only through the coupling circuit (corresponding to diode 72) corresponding to the antenna receiving the strongest radio waves. Therefore, by detecting the current flowing through the diode 72, it is possible to determine whether or not the own antenna 6 is receiving the maximum level signal. Next, the operation of the current measuring device 712 will be explained. The current flowing through the diode 72 changes the voltage across the resistor 711 to the differential amplifier 7.
12. Therefore, by using a comparator 714 that compares the output of the differential amplifier 712 with the output of the constant voltage generator 713 and sets the output terminal 74 to a high level only when the output of the differential amplifier 712 is larger, the maximum voltage can be increased. Only the terminal 74 corresponding to the antenna 6 receiving the level becomes high level, and the value of the terminal 74 can be used as an antenna selection signal. This comparator 714 serves as a determination circuit. Therefore, by providing a gate circuit that opens the transmission/reception gate only in the time slot where the terminal 74 indicates a high level, it is possible to easily select the optimum antenna for each slave station.

FIG. 3 shows a second embodiment of the present invention. Also in the second invention, the portions coupled to the signal line 5 via the level detector 70 and the diode 72 are the same as in FIG. 2, so they are omitted. Further, the portion corresponding to the input from 6' in FIG. 2 is also omitted. In FIG. 3, the same reference numerals as in FIG. 2 indicate the same components as in FIG. 2, respectively. In FIG. 3, the input from the level detector applied to input terminal 718 is added to the voltage from switch 716 by voltage adder 717, and is transmitted to output terminal 719 via resistor 711. Output terminal 719 is connected to diode 72. The output of the switch 716 is grounded when the terminal 74 is at low level, and in this case, the output of the switch 716 is grounded.
The current detector in the figure functions identically to that in FIG. When a signal is received from the antenna and the received signal reaches its maximum value, the terminal 74 changes to high level. At this time, the switch 716 is connected to the constant voltage generator 715.
The output of is added to adder 717. Therefore, once the received signal reaches the maximum value in the antenna, the output of the output terminal 718 of the level detector appears to increase, and even if the input decreases somewhat, the diode input ( terminal 719) indicates a high potential. In this way, the constant voltage generator 71
5, switch 716, and adder 717 realize a correction circuit required in the second invention. By adding such operations, even if the slave station is approximately equidistant from multiple antennas and the received signals of approximately the same level can be obtained from multiple antennas, the antennas may be damaged due to slight electric field fluctuations during data transmission. Unstable operations such as switching can be prevented.

As explained above, by using the present invention, it is possible to compare which antenna is most suitable for communication with a slave station in a wireless communication system having a plurality of antennas, and to determine the most suitable antenna. can.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of a wireless button telephone system to which the present invention is applied, Fig. 2 is a block diagram showing an embodiment of the present invention, and Fig. 3 is a diagram showing an embodiment of the second embodiment of the present invention. FIG. In addition, in Figure 1,
1 is the main unit, 2 and 2' are modulators, 3 and 3' are slave stations, 4 is a signal line for transmitting and receiving signals between the main unit 1 and modem 2, and 5 is for transmitting and receiving the level between the main unit side antennas. Signal line, 6, 6' is main device side antenna, 7,
7' is a received level comparison device of the present invention, and in FIGS. 2 and 3, 70, 70' are level detectors 71, 71' are combiners, 712, 71
2' is a current detector, 714 and 714' are judgment circuits,
715...constant voltage generator, 716...switch,
717...Adder.

Claims (1)

[Claims] 1. A wireless communication device having a plurality of antennas and using these antennas by switching, comprising a plurality of level detectors for detecting the reception level from each antenna, and a plurality of level detectors for each of the level detectors. a plurality of couplers that couple outputs to a common line via diodes, a common line that couples the outputs of the couplers to each other, a plurality of current measuring devices that detect the current flowing through each of the couplers, and each of the couplers. A receiving level comparison device comprising: a determination circuit that generates an antenna selection signal when the output of the current measuring device exceeds a certain amount. 2. In a wireless communication device that has a plurality of antennas and uses these antennas by switching, there are a plurality of level detectors that detect the reception level from each antenna, and the output of each of the level detectors is connected through a diode. a coupler that couples to a common line; a common line that couples the outputs of the couplers to each other; a plurality of current measuring devices that detect current flowing through each of the couplers; and an output of each of the current measuring devices is constant. and a plurality of correction circuits that increase the respective coupler outputs when the antenna selection signals are output from the respective determination circuits. A reception level comparison device featuring: