JP4079196B2 - Wireless alarm device and program thereof - Google Patents

Description

  The present invention obtains a reception level using a plurality of antennas, confirms the presence of each other by performing radio transmission / reception periodically or irregularly between radio transceivers, and the distance between the radio transceivers is predetermined. The present invention relates to a communication system, a radio alarm device, and a program thereof used for limiting the function of a radio transceiver or generating an alarm when a communication range is exceeded.

  In recent years, security systems have been put into practical use in which an operation lock of an electronic device such as a mobile phone or a personal computer is wirelessly controlled in consideration of security.

  As one form of such a security system, in order to prevent the mobile phone from being stolen, a user of the mobile phone possesses an identification signal transmitter in the form of a card, and the mobile phone and the identification signal transmitter are previously connected. There is a mobile phone that can be used when a predetermined identification code is communicated with each other and the identification code is confirmed by both parties (see, for example, Patent Document 1).

  In Patent Document 1 of such a bidirectional communication system by wireless, in an apparatus mounted on the main body side such as an electronic apparatus, an operation of periodically detecting a signal emitted from a portable device (hereinafter referred to as a wireless key) is continued. It was the composition to be done.

  Further, there are three modes: a search mode, an application mode, and an authentication mode that is an intermediate stage for shifting from the search mode to the application mode, and a configuration that enables operation of the electronic device in the application mode. In the search mode, the electronic device A configuration for restricting the operation is shown. The search mode and the application mode are identified by the radio field intensity.

  For example, when the signal strength is strong (the distance to the user with the wireless key is short), the electronic device can be used as the app mode, and when the signal strength is weak (the distance is long), the electronic device can be used as the search mode. To do.

  As for the measurement of the electric field strength and the reception level, as seen in Patent Document 2, there is an example related to switching control of the reception diversity antenna. Patent Document 2 describes that a reception level of a signal received from a plurality of reception antennas is measured, and an antenna having the highest reception level is used for reception. Furthermore, it is described that it is determined that fading is small when the same antenna is used for reception in a plurality of measurements.

Further, as can be seen in Patent Document 3, there is an example relating to transmission diversity antenna switching control. In Patent Document 3, in a system that repeatedly transmits wirelessly detection information and transmission antenna information such as crime prevention and disaster prevention as a one-word code signal, transmission is performed by switching between two antennas for each one-word transmission data. On the side, the transmission antenna information is read from the received data, the reception level is measured, and control is performed so that the signal from the transmission antenna with the higher reception level is used.
JP 2004-143806 A JP 2002-246969 A JP-A-64-60118

  However, Patent Document 1 does not describe any specific method for measuring radio field intensity. Further, Patent Document 2 has a description about determination of whether fading is large or not based on the measurement result of the reception level, but there is no description about the calculation method of the reception level or the relationship between the distance to the communication partner and the reception level. .

  In addition, as in Patent Document 3, when the same data is transmitted a plurality of times in spite of short data communication and the reception level of each data is compared to select a transmission antenna, short data is transmitted. However, it takes a long communication time and power consumption increases. Furthermore, if the data is very short, demodulation by radio reception cannot be performed, and it is very difficult to read out the information even if the received data includes antenna information.

  In general, the bit synchronization signal required for the bit synchronization of the input signal and the analog circuit rise time of the wireless transmission / reception unit is combined with the frame synchronization signal that represents the data signal, and the minimum However, data demodulation cannot be performed unless data is transmitted prior to data to be transmitted as a few bytes.

  The present invention solves the above-described conventional problems, and can achieve a low power consumption communication system, a wireless alarm device, and a radio power warning device capable of accurately determining a reception level value corresponding to a distance to a communication partner even when fading or multipath occurs. The purpose is to provide a program.

1st invention consists of a 1st transmitter / receiver and a 2nd transmitter / receiver, and the said 1st transmitter / receiver has a plurality of antennas, and is transmitting the said some antenna in the middle of transmitting one packet data The second transmitter / receiver measures at least once each the reception level during the transmission time at each of the plurality of antennas switched during transmission of packet data by the first transmitter / receiver, and A reception level value is obtained from at least one of a maximum value, an average value, or a median value from a plurality of reception levels, and the second transceiver transmits the first transmission / reception based on the reception level value. A distance estimating means for estimating a distance between the first transceiver and the second transceiver, and when the distance estimated by the distance estimating means is greater than or equal to a predetermined distance, the first transceiver or the second transceiver of Those functions of the main unit which is connected to a receiver as configured for generating or or alarm limits.

As a result, it is possible to measure each of the reception levels during the transmission time with a plurality of antennas, so that the diversity effect is obtained, and the influence of fluctuations in the reception level due to fading and multipath is eliminated, and the first transceiver and the second transmitter are accurately obtained. The reception level according to the distance of the transmitter / receiver is calculated, and the function of the main unit connected to the first transmitter / receiver or the second transmitter / receiver is limited or an alarm is generated using the determined distance as a threshold value. be able to.

The second invention is a program for causing a computer to realize at least a part of the wireless alarm device described in the first invention . Since it is a program, at least a part of the present invention can be realized with simple hardware by cooperating hardware resources such as an electric / information device and a computer. In addition, the program can be distributed / updated and installed easily by recording on a recording medium or distributing the program using a communication line.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a block diagram of a wireless alarm device using a communication system according to a first embodiment of the present invention.

  In FIG. 1, a communication system 101 includes first transceiver antennas 1a and 1b, a first transceiver 2, an electronic switch 3 for switching the first transceiver antenna 1a or 1b, and a second transceiver antenna 4. , A second transceiver 5, a reception level determination means 6, and a distance estimation means 7.

  Then, the reception level of the signal received by the second transceiver 5 is determined by the reception level determination means 6, and the first transceiver 2, the second transceiver 5, and the like are determined according to the reception level determined by the reception level determination means 5. Is estimated by the distance estimation means 7 and the function restriction means 8 is activated by the output of the distance estimation means 7.

  The first transceiver antennas 1a and 1b are composed of antennas having different directivity characteristics. As an example, the antennas have the same directivity characteristics, but the antennas 1a and 1b can be orthogonalized to make the directivity characteristics orthogonal. Of course, two antennas having different directivity characteristics may be prepared as a single antenna.

  Further, the first transceiver antennas 1a and 1b may be configured with antennas having different polarization characteristics. As an example, the antenna itself is an antenna having the same directivity and polarization characteristics, but the antennas 1a and 1b can be configured to change the antenna arrangement so that the planes of polarization are orthogonal. Of course, two antennas having different shapes and different polarization characteristics may be prepared as a single antenna.

The first transmitter / receiver 2 is a key for authenticating the second transmitter / receiver 5 and is small in size so that a person using the device on which the first transmitter / receiver 2 is mounted is always carried. In order to form lightweight cards, key chains, necklaces, wristwatches, bracelets, rings, etc., they are driven by a small power source such as a battery.

  The operation of the wireless alarm device using the communication system 101 of FIG. 1 will be described with reference to the flowcharts of FIGS.

  Each of the first transmitter / receiver 2 and the second transmitter / receiver 5 includes a wireless transmission unit and a wireless reception unit (not shown).

  Since the first transmitter / receiver 2 is driven by a small power source such as a battery, it is necessary to reduce the communication time as much as possible to reduce the power consumption of the device. Therefore, it is desirable that the transmission signal 21 be intermittent and only for a short time. .

  For example, when transmitting a transmission signal 21 of 2 bytes as shown in FIG. 2 (about 1.67 milliseconds when transmitting at a binary 9600 bps), the first transmitter / receiver is periodically transmitted every 10 seconds (S301). 2 sets the transmitting antenna to the first transceiver antenna 1a with the electronic switch 3 (S302), starts transmission (S303), and after 8-bit transmission (Yes in S304), switches to the first transceiver antenna 1b. (S305) If 8-bit transmission is performed (S306), it is not necessary to switch the antenna to end transmission of one packet data and transmit the same packet data again. In the case of transmission at binary 9600 bps, the transmission signal may be switched to the first transceiver antenna 1b when the transmission signal is transmitted for about 833 microseconds.

  In the above example, the transmission signal 21 from the first transmitter / receiver 2 is periodically transmitted every 10 seconds. The transmission interval of the transmission signal 21 depends on the moving speed and usage of each device. Accordingly, the distance may be set within an interval that requires confirmation of the distance.

  In order for the second transmitter / receiver 5 to detect the start of transmission from the first transmitter / receiver 2, there is a method of performing carrier sense, but in order to perform carrier sense, reception must be started in advance. Therefore, the power consumption for the receiving operation while not actually transmitting / receiving signals is wasted.

  For this reason, the second transmitter / receiver 5 performs synchronization processing in advance in order to perform a reception operation in synchronization with the transmission timing of the first transmitter / receiver 2.

  First, the search signal is intermittently and repeatedly transmitted from the first transmitter / receiver 2 or the second transmitter / receiver 5, and the partner transmitter / receiver periodically performs a reception operation, and when the search signal is received, the received time The communication is synchronized by generating the communication timing from the base point.

  The second transmitter / receiver 5 starts a reception operation every 10 seconds (Yes in S401) in accordance with the start of transmission from the first transmitter / receiver 2 (S402). For example, when communicating at a binary value of 9600 bps, Every microsecond (S405), the reception level value is measured 8 times (S404). As a method for measuring the reception level value, the reception signal level received by the second transceiver 5 is A / D converted, and an analog value corresponding to the reception signal level is converted into data to obtain a reception level value.

  When the reception level is determined by transmitting very short packet data in order to shorten the communication time and suppress the power consumption of the device as in this embodiment, the reception level measurement is transmitted. If the expected time is performed at time intervals divided at equal intervals by at least the number of antenna switching times, at least the reception level of the transmission signal from each antenna should be able to be measured.

  However, if the timing at which the second transceiver 5 starts reception does not exactly coincide with the timing at which the first transceiver 2 starts transmission of the transmission signal 21 (for example, if reception starts a little earlier). Even if the reception level is measured, there is a possibility that the reception level of noise is measured instead of the signal level of the transmission signal.

  For this reason, if the measurement of the reception level is performed a plurality of times at short intervals during the time when it should be transmitted (1.67 milliseconds in the above example), the maximum value is determined as the reception level value. Even if the transmission and reception timings do not start in complete synchronization, the reception level of the signal transmitted from each antenna can be measured and determined as the reception level value. At the same time, since the effect of time diversity can be obtained by measuring a plurality of times, the reception level value can be obtained more accurately.

  The reception level measurement interval may be determined by the synchronization timing tolerance. For example, if the reception level measurement is performed eight times with two antennas during 1.67 milliseconds as described above, the measurement interval is about 600 μm. If the transmission / reception timing error is on the order of seconds, it is possible to measure the reception level of the transmission signal of either of the two antennas at least once.

  If there is fading or multipath, the reception level varies with time. For example, FIG. 10 shows a probability distribution diagram of reception levels due to reception diversity shown on page 194 of “Modulation and Demodulation of Digital Wireless Communication (by Yoichi Saito)”.

  The value indicated by M in FIG. 10 is the number of antennas, and the horizontal axis indicates the difference from the median value (a numerical value located at the center when a large number of measured values are arranged in descending order). When the reception level is observed to be larger than the median level (the rate at which the probability is approximately 99% in the probability distribution), it is at most about 6 dB. However, when the reception level is observed to be low (approximately 1% probability in the probability distribution). In many cases, the ratio is greatly attenuated to 20 dB.

  For this reason, the reception level determination means 6 takes the largest value from among the plurality of reception level values measured by the second transceiver 5 (S406), so that the position and time that are the characteristics of the fading described above are obtained. The reception level value corresponding to a more accurate distance can be determined by suppressing the phenomenon of abrupt reception level attenuation due to the above.

  An example of another reception level value determination method will be described below.

  When the eight reception level values measured with the reception signal 22 in FIG. 2 are used, the average value of the eight reception levels is set to the correct reception level value, or the fourth or fifth corresponding to the median value is arranged in descending order. It is also possible to determine the reception level value of the eye as the correct reception level value.

Then, the distance estimation means 7 uses a value determined as the reception level value, a predetermined threshold value, a table of the relationship between the reception level value and distance stored in a table or the like, or “reception level = A × distance”. ^The distance can be estimated from the relational expression " ^B ". Here, A and B are certain constants.

  For example, if it is determined by the distance estimation means 7 that the distance between the first transceiver 2 and the second transceiver 5 corresponds to 2 m or less in distance, no function restriction request is made to the function restriction means 8.

  If the distance estimating means 7 determines that the distance between the first transmitter / receiver 2 and the second transmitter / receiver 5 is greater than 2 m, a function restriction request is made to the function restriction means 8.

  For example, when the system is installed in a mobile phone, the function restriction is one of the functions of the mobile phone by prohibiting key operations, prohibiting electronic money functions, and prohibiting outgoing calls. It is to make part or all unusable.

  The second transmitter / receiver 5 performs continuous reception when the power is turned on, and when the received signal 22 from the first transmitter / receiver 2 determines that the distance is equal to or less than 2 m, the second transmitter / receiver 5 is based on the timing of receiving the received signal 22. The reception process is started every 10 seconds when the first transceiver 2 performs transmission, and when reception is completed, the reception process is stopped to reduce power consumption.

  Further, the reception level value determined by the reception level determination means 6 exceeds the effective value (the electric field intensity level that can be regarded as exceeding the noise level, for example, −110 dBm) as the reception signal 22 from the first transceiver 2. If not, the reception interval may be shifted, so continuous reception is performed until it is determined by the reception signal 22 from the first transmitter / receiver 2 that the distance corresponds to 2 m or less, and then the reception process is performed again every 10 seconds. Return.

  Also, as in this embodiment, when transmitting very short packet data in order to shorten the communication time and reduce the power consumption of the device, demodulation of the received signal is technically difficult, but the first If the transmission signal 21 from the transmitter / receiver 2 can be confirmed on the receiving side by entering information and data that can identify the communication partner such as the ID indicating the bit synchronization signal and the first transmitter / receiver 2, the second transmitter / receiver Since the first transmitter / receiver 2 can be identified by demodulating the data received by 5 and confirming the ID, the reception level in the transmission signal of another system is not mistaken.

  In the case of confirming the ID as described above, the first transmitter / receiver antenna 1 is surely switched until the ID is confirmed after detecting the bit synchronization so that the ID can be received without interruption. For example, at the time of switching antennas, reception may be prevented from being interrupted by controlling the electronic switch 3 so that both the transceiver antenna 1a and the transceiver antenna 1b can be received.

  As described above, according to the present embodiment, the first transceiver 2 transmits signals using the first transceiver antennas 1a and 1b in order, and the second transceiver 5 The reception level of the signal transmitted from each of the two first transmitter / receiver antennas 1 is measured a plurality of times, and the reception level determination means 6 determines the reception level value therefrom.

  Thus, even if the signal reception level from one antenna is attenuated due to fading due to the position and time of the antenna, the average value, median value, or maximum value of the measurement value can be selected so that the signal reception level from the other antenna can be selected. By calculating the reception level and the like, a stable reception level value is obtained, and the distance between the first transceiver 2 and the second transceiver 5 corresponding to the reception level value is estimated more accurately. In addition, it is possible to accurately manage the distance for performing function control of a mobile phone or the like.

  In the present invention, since the transmission antenna is switched during wireless transmission, there is a concern about the influence on the received waveform due to the momentary distortion of the wireless signal, but the frequency shift keying (FSK) ; If a signal using frequency modulation such as frequency shift keying) is used, the original transmission amplitude is constant, and therefore amplitude fluctuation at the time of switching the transmission antenna is not easily affected by demodulation of received data. The error rate can be made very low.

The switching speed of the transmission antenna varies depending on the receiving circuit, the demodulation method, and the processing time. For example, if switching can be performed within 1/3 or less of the bit length, data sampling is performed in most cases. Can be demodulated correctly enough.

  For example, in an FSK signal demodulating circuit as shown in FIG. 5A, a voltage corresponding to the frequency shift of the FSK is obtained as a detection signal by frequency detecting the input signal in FIG. A demodulated output can be obtained by sampling with a timing circuit corresponding to the received signal speed.

  If it takes about 1/3 when the bit of the transmission data is switched, the waveform between bits is distorted as in the input signal of FIG. 6, but an accurate demodulated output can be obtained by appropriately taking the timing of the sampling signal. it can.

(Embodiment 2)
FIG. 7 shows a block diagram of a wireless alarm device using a communication system in the second embodiment of the present invention.

  7 is different from FIG. 1 in that the reception level determination means 6 and the distance estimation means 7 are provided on the first transmitter / receiver 2 side, and further the alarm means 9 is notified of the output of the distance estimation means 7. That is.

  Further, the second transceiver 5 directly controls the function restriction means 8 according to the “function restriction instruction” entered in the packet data received from the first transceiver 2.

  The operation of the communication system 102 in FIG. 7 will be described with reference to FIG.

  When the first transmitter / receiver 2 is activated, first, the request signal 41 is transmitted using the electronic switch 3 as the first transmitter / receiver antenna 1a (see the request signal 41 in FIG. 8A).

  The second transceiver 5 receives the signal (see the received signal 42 in FIG. 8B). Thereafter, the communication partner is confirmed by the ID included in the header or the data area to be the request signal 42 from the first transmitter / receiver 2, and the response signal 44 is transmitted (see the response signal 44 in FIG. 8D). . The response signal 44 includes the ID of the second transceiver 5 in the header or data area.

  In the first transmitter / receiver 2, first, the electronic switch 3 is set to the first transmitter / receiver antenna 1a to start receiving the response signal 44 (FIG. 8C, the received signal 43). Is switched to the first transceiver antenna 1b to continue reception. When the reception level is measured four times every 200 microseconds from the start of reception and four more bits are received (that is, 16 bits are received and the reception level is measured eight times), the reception level determining means 6 The reception level value at the antenna 1a and the reception level value at the antenna 1b are determined from each of the four reception levels measured in step 4 and the four reception levels received in the latter half, and the two reception levels are compared to obtain a large value. The first transceiver 2 is notified of the antenna from which the reception level value is obtained.

  In the first transceiver 2, if the antenna notified from the reception level determining means 6 (for example, the reception level value at the antenna 1 a is “−90 dBm” and the reception level value at the antenna 1 b is determined to be “−80 dBm”). The remaining signal of the received signal 43 is received by the antenna 1b by switching with the electronic switch 3.

When the reception of the reception signal 43 is completed, the first transceiver 2 determines the distance level by determining the reception level value at the antenna 1a and the reception level value at the antenna 1b, which is larger, as the reception level value of the reception signal 43. Notify the means.

  The distance estimation means 7 estimates the distance between the first transceiver 2 and the second transceiver 5 from the determined reception level value, as in the first embodiment.

  The request signal 41 and the response signal 44 include the IDs of the first transmitter / receiver 2 and the second transmitter / receiver 5, respectively. Authenticate that there is.

  For example, the request signal 41 is sequentially transmitted from the first transmitter / receiver 2 every 20 seconds, and the response signal 44 is returned from the second transmitter / receiver 5. By repeating this, mutual authentication is maintained. The transmission interval of the request signal 41 may be set within an interval where authentication needs to be maintained according to the application.

  The first transmitter / receiver 2 transmits the next request signal 41 by switching the electronic switch 3 to the antenna having the larger reception level value of the previous response signal.

  Thus, in the state where the response signal 44 is returned to the request signal 41 and the two are authenticated, the distance estimating means 7 sets the distance between the first transceiver 2 and the second transceiver 5 to be, for example, If it is determined that it corresponds to 2 m or less, the warning from the warning means 9 is not performed.

  Further, by including a notification of “no function restriction” in the data of the request signal 41 from the first transceiver 2, the second transceiver 5 allows the function restriction unit 8 of the electronic device such as a built-in mobile phone. No function restriction request is made to

  If the distance estimating unit 7 determines that the distance between the first transmitter / receiver 2 and the second transmitter / receiver 5 is greater than 2 m, the distance estimating unit 7 notifies the notifying unit 9 of the distance. Send a signal. When the notification means 7 receives the notification signal, the notification means 7 sounds a buzzer or the like to notify that the first transmitter / receiver 2 and the second transmitter / receiver 5 are separated by a predetermined distance or more, that is, forgetting.

  The first transmitter / receiver 2 includes the notification of “function restriction instruction” in the data of the request signal 41, so that the receiver 7 notifies the function restriction means 8 to the function restriction means 8, so Restrict the function of.

  As described above, according to the present embodiment, the first transceiver 2 receives the response signal from the second transceiver 5 by using the first transceiver antennas 1a and 1b in order. Thus, the reception level of the signal received by each of the two antennas of the first transceiver is measured a plurality of times, and the reception level determination means 6 determines the reception level value therefrom.

  Thus, even if the signal reception level from one antenna is attenuated due to fading due to the position and time of the antenna, the average value, median value, or maximum value of the measurement value can be selected so that the signal reception level from the other antenna can be selected. By calculating the reception level and the like, a stable reception level value is obtained, and the distance between the first transceiver 2 and the second transceiver 5 corresponding to the reception level value is estimated more accurately. In addition, it is possible to accurately manage the distance for performing function control of a mobile phone or the like.

In addition, the method of switching a plurality of receiving antennas during reception as in the present embodiment has one receiving circuit of the receiving antenna as compared with the method of receiving the same signal simultaneously with a plurality of receiving antennas and taking the better one. This is advantageous in terms of circuit scale and cost.

  In the present embodiment, the transmission antenna at the time of transmitting the request signal 41 is fixed. However, as shown in FIG. 9A, the electronic switch 3 is first connected from the first transceiver 2 to the first transceiver. The request signal 41 may be transmitted to the antenna 1a, and transmission may be continued by switching the electronic switch 3 to the first transceiver antenna 1b after transmitting 8 bits.

  Similarly to the first embodiment, as shown in FIG. 9B, the transmission antennas 1a and 1b are measured such that the second transceiver 5 measures the reception level value eight times every 200 microseconds. If the reception level value is measured including the respective transmission timings, the reception level determining means and the distance estimation means for estimating the distance from the reception level value of the received signal received by the second transceiver 5 are provided. Thus, it is possible to control the function restriction on the function restriction means 8 earlier.

  Furthermore, if the reception level value in the second transmitter / receiver 5 is included in the response signal and sent to the first transmitter / receiver 2, it is selected for determination as the reception level value in the first transmitter / receiver 2. Can be included.

  For example, if the reception level value at the antenna 1a is “−90 dBm”, the reception level value at the antenna 1b is “−85 dBm”, and the reception level included in the response signal is “−80 dBm”, the reception level value is Can be determined to be “−80 dBm” by taking the maximum value, and the distance between the first transceiver 2 and the second transceiver 5 can be estimated more accurately.

  In addition, when the reception level value at each antenna of the response signal from the second transmitter / receiver 5 is determined, the request signal is transmitted by switching in order from the antenna having the smaller reception level value at the next transmission. For example, the reception side can measure the reception level at each of the plurality of antennas and transmits the data portion of the request signal with an antenna having a high reception level without switching the antenna as it is. Less damage.

  In each of the above embodiments, the first transmitter / receiver antenna is composed of two. However, the antenna is composed of three or more and is switched to all the antennas during transmission or reception, or among the configured antennas. By switching one or more times, the maximum reception level can be obtained, so that the influence of fading can be further suppressed.

  Note that the format of the transmission signal, the number of bits, and the communication interval exemplified in this embodiment are merely examples, and the present invention is not limited thereto.

  In addition, the means described in the present embodiment cooperates hardware resources such as a CPU (or microcomputer), RAM, ROM, storage / recording device, electrical / information device including I / O, a computer, a server, and the like. You may implement with the form of a program. In the form of a program, new functions can be easily distributed / updated and installed by recording them on a recording medium such as magnetic media or optical media or distributing them via a communication line such as the Internet.

  As described above, the communication system, the wireless alarm device, and the program according to the present invention are limited in operation of portable electronic devices such as a mobile phone, a camera, a video camera, a notebook computer, a PDA, and a portable audio device, and the owner is nearby. Otherwise, it can be used in vehicles such as automobiles, motorcycles, and the like for which function restriction is to be performed, and a device that can quickly perform an alarm action or a function restriction action when left misplaced or stolen can be provided.

Block diagram of the wireless alarm device in the first embodiment of the present invention The figure explaining the transmission / reception signal of Embodiment 1 of this invention Transmission flowchart of the first transceiver in the first embodiment of the present invention Reception flowchart of the second transceiver in the first embodiment of the present invention The figure which shows the circuit and demodulation waveform which demodulate the FSK signal of Embodiment 1 of this invention The figure which shows the demodulation waveform at the time of transmission antenna switching in the demodulation of the FSK signal of Embodiment 1 of this invention Block diagram of the wireless alarm device in the second embodiment of the present invention The figure explaining the transmission / reception signal of Embodiment 2 of this invention The figure explaining another transmission / reception signal of Embodiment 2 of this invention. Probability distribution map of reception level by diversity

Explanation of symbols

1 First transceiver antenna (1a, 1b)
2 first transmitter / receiver 3 electronic switch 4 second transmitter / receiver antenna 5 second transmitter / receiver 6 reception level determination means 7 distance estimation means 8 function restriction means 9 alarm means 101 and 102 communication system

Claims (2)

It consists of a first transceiver and a second transceiver,
The first transceiver has a plurality of antennas and switches the plurality of antennas while transmitting one packet data,
The second transmitter / receiver measures at least one reception level during transmission time at each of the plurality of antennas switched during transmission of packet data by the first transmitter / receiver at least once. From the level, obtain the reception level value using at least one of the maximum value, average value, or median value ,
The second transceiver has distance estimation means for estimating a distance between the first transceiver and the second transceiver based on the reception level value, and the distance estimated by the distance estimation means A wireless alarm device that restricts the function of the main unit connected to the first transmitter / receiver or the second transmitter / receiver or generates an alarm when the distance is equal to or greater than a predetermined distance. The program for making a computer implement | achieve at least one part of the radio | wireless alarm apparatus of Claim 1.

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