JP3707160B2 - Mobile object identification device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mobile object identification device, and more specifically to a technique used when a plurality of interrogators are arranged adjacent to each other.
[0002]
[Prior art]
In recent years, the field and technology of radio waves are rapidly expanding in fields such as satellite communications and mobile communications, and mobile identification devices are also known as such relatively new technologies for radio wave applications.
The mobile object identification device is subject to the Radio Law as one of the wireless communication facilities, and the Radio Industry Association has applied the Radio Law applicable to each radio wave utilization technology in this relatively new field of radio wave use. Standards are established based on the standards to promote understanding of the correct radio law in the industrial field and promotion of radio wave use.
[0003]
Regarding the mobile object identification device, technical requirements are defined in two standards, “RCR-STD1 mobile object identification device” or “RCR-STD29 specific low power radio station mobile object identification device”. Everything used in conforms to one of these standards.
The technical features of the mobile unit identification devices defined in these standards are that only interrogators can transmit radio waves for communication by themselves, and responders use radio waves transmitted by interrogators. It is in the point of adopting a method of receiving and retransmitting part of it to the interrogator. As a result, communication between the interrogator and the responder is performed only during the period in which the interrogator is transmitting radio waves, and the response radio waves transmitted from the responder have the same frequency as the interrogator. Become. That is, a major feature of communication in the mobile unit identification apparatus is that the response radio wave transmitted from the responder depends on the radio wave transmitted from the interrogator that has been received.
[0004]
By the way, when the mobile unit identification apparatus is actually used, a plurality of interrogators and a larger number of responders are often used in one system. For example, as shown in FIG. 10, in a system for identifying vehicles entering and exiting a parking lot and managing the state, one interrogator is installed on each of the entrance and exit sides of the entrance and exit. A responder (not shown) is attached to each of a large number of vehicles using the.
[0005]
When a plurality of interrogators are used in this way, the frequency bands of the radio waves transmitted by the interrogator are all the same, so the radio waves transmitted from one interrogator are transmitted to other questions that are communicating with the responder. If it is received by the response unit, the other interrogators generate noise radio waves from other than the responding unit in communication, so that communication with the response unit is hindered. The phenomenon in which one interrogator becomes a noise wave for other interrogators and disturbs communication with the responder is hereinafter referred to as mutual interference.
[0006]
Here, as means for preventing mutual interference when the plurality of interrogators are used, a method of installing a radio wave shielding object 50 as shown in FIG. 10 between the interrogators or adjacent as shown in FIG. A method is known in which an interrogator alternately transmits radio waves to communicate with a responder.
[0007]
[Problems to be solved by the invention]
However, in the case of FIG. 10 described above, radio waves arrive from directions other than expected due to the wraparound of the radio waves (diffraction phenomenon) and the reflection of radio waves from the surrounding buildings and other structures, which is very important for the production and installation of shields. There is a problem that requires cost and effort.
Moreover, in the thing of the said FIG. 11, there exists time which has stopped radio wave transmission, and the responder which entered the communication area of the interrogator at the time of a pause will not be identified until the next time the responder transmits radio waves, There appears to be a problem that the response speed of the responder seems to be slow.
[0008]
In view of the above problems, the present invention has an object of providing a mobile object identification device that can be arranged so that radio wave interference does not occur as much as possible when a plurality of interrogators are arranged adjacent to each other.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the first to third aspects of the present invention, a plurality of classifications are made based on the magnitude of the frequency of the interrogation radio wave, and the plurality of classifications are determined in order according to the magnitude of the frequency. It is characterized in that a display portion on which the displayed symbol is displayed is provided on the surface of the casing.
[0010]
Here, the oscillation circuit constituting the interrogator includes various elements as components, and these components have slight variations in their characteristic values. Therefore, an interrogator that transmits an interrogation radio wave using the frequency signal from the oscillation circuit as a carrier wave is produced for each interrogator with a slight difference in the frequency of the interrogation radio wave.
As shown in FIG. 4, when the interrogator is classified into, for example, A to E based on the magnitude of the frequency of the interrogation radio wave, the interrogator of the class A and the class B adjacent to each other has the radio wave frequency. Although there is a high possibility of causing mutual interference, the influence of the mutual interference of radio waves is reduced between the interrogators of classification A and classification C to E that are separated from each other in frequency.
[0011]
Therefore, when the symbols that are determined in order according to the magnitude of the frequency are displayed on the surface visible from the outside of the interrogator, that is, on the surface of the casing, when the interrogators are arranged adjacent to each other, The person who places the interrogator can easily understand whether the frequency is between adjacent interrogators or between different frequency interrogators by just looking at the symbol on the display, and as far as radio interference is possible. It can be arranged so that it does not occur.
[0012]
According to a fourth aspect of the present invention, the interrogator oscillation circuit has a function of adjusting the frequency magnitude of the frequency signal.
This makes it possible to freely set the frequency of the interrogation radio wave, rather than relying on variations in the characteristic values of the components that make up the oscillation circuit. Can be produced only, and the production efficiency is improved.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, a preferred embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 shows the electrical configuration of the interrogator 1 and the responder 20 of the mobile object identification device of the present invention. In FIG. 1, an interrogator 1 generates an oscillation output at a frequency f ₁ in the frequency band in order to output, for example, a 2450 MHz band quasi-microwave assigned as a predetermined frequency region as a carrier wave. A modulation circuit 3 that modulates an oscillation output of the frequency f ₁ provided from the oscillation circuit 2 as a carrier wave with an interrogation signal provided thereto from the control circuit 7 and outputs the modulated signal to the transmission / reception antenna 6 via the circulator 5, and a circulator A receiving circuit 4 that demodulates a radio wave signal applied from the transmitting / receiving antenna 6 via 5 to obtain a response signal and outputs the response signal to the control circuit 7, and outputs a query signal to the modulation circuit 3 at a predetermined timing. The control circuit 7 that receives the response signal via the control circuit 7 and controls the operation of the oscillation circuit 2 and an interface for connecting to an external device (not shown) -Face circuit 8 and power supply circuit 9 for supplying a predetermined DC voltage to interrogator 1 itself.
[0014]
On the other hand, according to the program stored in the memory 24 in advance, for example, when the interrogator 1 receives the interrogation radio wave from the interrogator 1, the transponder 20 retransmits a part of the radio wave, so that the frequency of the interrogation radio wave is approximately the same. The response radio wave is output as a response signal of various data such as an identification code, and includes a transmission circuit 21, a reception circuit 22, a control circuit 23, a memory 24, a transmission / reception antenna 25, a battery 26, and the like. .
[0015]
FIG. 2 shows the appearance of the interrogator 1 of the mobile object identification device of the present invention. In FIG. 2, the external surface of the interrogator 1 is formed by a casing 11, and a label 12 indicating the degree of variation in the transmission frequency of the interrogator 1 is affixed to the casing 11. As shown in FIG. 1, the label 12 displays a symbol “A” indicating the degree of variation in transmission frequency.
[0016]
Hereinafter, the degree of variation in the transmission frequency displayed on the label 12 will be described. FIG. 3 shows an electrical configuration of the oscillation circuit 2 that determines the transmission frequency of the interrogator 1. The oscillation circuit 2 provided in the interrogator 1 mainly includes a dielectric vibrator 34 having a stable natural frequency, a microstrip circuit element 33a coupled to the dielectric vibrator 34, a transistor 35 that amplifies vibration, and the like. As a component, a transmission frequency equal to the natural frequency of the dielectric vibrator 34 is output from the output terminal 36. In addition, 31a-31e is a resistor, 32 is a capacitor | condenser, 33b is a microstrip circuit element.
[0017]
As described above, the oscillation circuit 2 includes elements such as the dielectric vibrator 34, the resistor 31, the capacitor 32, and the microstrip circuit element 33b for determining the transmission frequency as constituent parts. There is a slight variation in the characteristic value of each solid. Therefore, the transmission frequency of the interrogator is produced with a slight difference for each interrogator.
[0018]
FIG. 4 shows an example of the distribution of the number of interrogators produced with respect to variations in transmission frequency.
A to E are obtained by classifying the transmission frequency variation range into five categories so that the number of units in each category is substantially equal. When classified in this way, for example, the interrogators of class A and class B adjacent to each other in transmission frequency are highly likely to cause mutual interference of radio waves. Interrogation between the interrogators is very low.
[0019]
Here, the reason will be described with reference to FIG.
FIG. 5 is a characteristic diagram of reception frequency bands in two interrogators having different transmission frequencies. The interrogator x is the transmission frequency fx, the interrogator y is the transmission frequency fy, and the respective reception frequency bands are Wx and Wy. As described in the prior art, since the frequency that the interrogator receives from the responder is almost the same as the frequency that the interrogator is transmitting, the reception frequency bands of the interrogator x and the interrogator y are the respective transmission frequencies fx. And fy.
[0020]
As a result, under the condition where the reception frequency bands Wx and Wy do not overlap, even if the radio wave of the frequency fx transmitted by the interrogator x is received by the interrogator y having the reception frequency band centered on the frequency fy, Since it is out of the reception frequency band of the device y, it is not greatly affected. That is, the influence of the mutual interference of radio waves is small between the interrogator x and the interrogator y that are separated from each other in frequency.
[0021]
Therefore, if five classifications A to E are used as shown in FIG. 4, there is a high possibility that radio frequency interference occurs between the interrogators of classification A and classification B whose frequency bands are adjacent to each other. The interfering effects of radio waves are reduced between the interrogators of the classification A and the classifications C to E separated from each other.
Therefore, the transmission frequency of each interrogator is measured during the production of the interrogator, and the value of the transmission frequency or a symbol indicating the position of the transmission frequency with respect to the whole is indicated for each interrogator. It is displayed at a position visible from the outside. At this time, in this embodiment, any one of the symbols “A to E” is displayed on the label 12 indicating the degree of variation in the transmission frequency of the interrogator 1.
[0022]
Thereby, the user who installs the plurality of interrogators 1 can easily understand whether or not the transmission frequency is between adjacent interrogators only by confirming the symbols A to E displayed on the interrogator 1. As shown in FIG. 6, the class A interrogator 1a and the class E interrogator 1e, which are separated from each other in transmission frequency, are arranged adjacent to each other so as not to cause mutual interference of radio waves. Will be able to.
[0023]
As described above, the present embodiment pays attention to the fact that the transmission frequency of the interrogator is produced with a slight difference for each interrogator, and measures the transmission frequency of the interrogator in advance. By displaying the symbols “A to E” corresponding to the frequencies on the interrogator, the installed user can easily understand whether or not the transmission frequency is between adjacent interrogators, and radio wave interference does not occur. It is something to arrange.
[0024]
In this embodiment, the symbol “A” indicating the degree of variation in the transmission frequency is displayed on the label 12, but basic information such as the producer and product type is not given to the user but, for example, the user. You may display on the displayed nameplate 13 as a part 14 of a serial number. Since the nameplate 13 is always attached to the interrogator and does not require a new display label, it is advantageous in terms of cost. (See Figure 7)
FIG. 8 shows another embodiment of the oscillation circuit of the interrogator 1.
[0025]
In another embodiment, a function capable of adjusting the transmission frequency is provided in advance in the interrogator.
The oscillation circuit 40 shown in FIG. 8 is a so-called PLL oscillation circuit. The crystal oscillator 41 has a stable intrinsic frequency f ₀ (12.88 MHz), and the frequency of the crystal oscillator 41 is divided to obtain a reference frequency. reference frequency divider 42 to produce a (having about 100kHz), set value input terminal 42a for setting the reference frequency, the frequency output f ₁ which is fed back to the feedback control of the frequency output f ₁ of the oscillation circuit A frequency divider 43 that divides and outputs to the comparator 44, a comparator 44 that compares the phases of the output frequency of the reference frequency oscillation circuit 42 and the output frequency of the frequency divider 43, and outputs a voltage corresponding to the difference. The voltage control oscillator 45 outputs a frequency (2450 MHz) corresponding to the output voltage of the comparator 44. The voltage controlled oscillator 45 is generally called a VCO.
[0026]
The frequency output f ₁ of the oscillation circuit 40 is as follows: the natural frequency f ₀ of the crystal unit 41, the frequency division ratio of the reference frequency frequency dividing circuit 42, and the frequency division ratio of the frequency divider 43 n.
[0027]
[Expression 1]
f ₁ = (f ₀ / m) × n
Therefore, the frequency output can be easily changed by changing the setting value of the frequency division ratio m by the setting position input terminal 42a.
FIG. 9 shows the distribution of the number of interrogators produced with respect to the transmission frequency of the interrogators thus produced. The transmission frequency of the interrogator is five types of frequencies fa (= 2449.8 MHz), fb (= 2449.9 MHz), fc (= 2450.0 MHz), fd (= 2450.1 MHz), fe (= 2450.2 MHz) Is adjusted by changing the set value of the frequency division ratio m. When the symbols “A to E” indicating the classification of the transmission frequency are displayed on the interrogator with the transmission frequency adjusted in this way, as in the above-described embodiment, when a plurality of interrogators are arranged adjacent to each other, It can be installed so that radio waves do not interfere with each other. A curve f shown in FIG. 9 is a characteristic curve of the reception gain of the responder 20, and the transmission of the interrogator is performed so that the transmission frequency of the produced interrogator is included in the reception frequency band W ₀ of the responder. The frequencies fa, fb, fc, fd, fe, etc. are set.
[0028]
As described above, in the other embodiments, since the interrogator is provided with a function capable of adjusting the transmission frequency, compared to the above-described embodiment, the transmission frequency can be set instead of depending on variations in component characteristics. The production number of interrogators can be appropriately managed and produced for each transmission frequency, and the production efficiency is improved.
In the above embodiment, the symbols “A to E” are used to classify the transmission frequencies of the interrogators. However, the present invention is not limited to this, and may be displayed using numbers, characters, or colors. . When the symbols “A to E” are displayed as in the present embodiment, the symbols “A to E” are continuous symbols with a predetermined order, and are easy to understand because they are easy to understand.
[Brief description of the drawings]
FIG. 1 is a diagram showing an electrical configuration of a mobile object identification device according to an embodiment of the present invention.
FIG. 2 is an external view of the interrogator shown in FIG. 1, and shows one embodiment of the present invention.
FIG. 3 is a diagram showing an electrical configuration of the oscillation circuit shown in FIG. 1;
FIG. 4 is a diagram showing a distribution of the number of interrogators produced with respect to transmission frequency variation.
FIG. 5 is a characteristic diagram of a reception frequency band in two interrogators having different transmission frequencies.
FIG. 6 is an overall configuration diagram of a mobile object identification device according to an embodiment of the present invention.
FIG. 7 is an external view of an interrogator according to another embodiment.
FIG. 8 is a diagram showing an electrical configuration of a PLL oscillation circuit.
FIG. 9 is a diagram illustrating the relationship between the distribution of the number of production units with respect to the transmission frequency of the interrogator and the reception frequency band of the transponder.
FIG. 10 is a diagram showing a conventional mobile unit identification apparatus in which a radio wave shielding object is installed between interrogators.
FIG. 11 is a diagram showing a conventional mobile unit identification apparatus in which adjacent interrogators alternately transmit radio waves.
[Explanation of symbols]
1 Interrogator 2 Oscillator 3 Modulator 4 Receiver 7 Control Circuit 11 Casing 12 Label 20 Responder

Claims (4)

A mobile object identification device comprising an interrogator (1) and a responder (20) that communicate wirelessly,
The responder (20)
The interrogation radio wave attached to the mobile body is transmitted from the interrogator (1), and a response radio wave having a frequency substantially the same as the frequency of the interrogation radio wave is obtained based on the information stored in the memory (24). Consists of what is sent to the device (1)
The interrogator (1)
A casing (11) forming an external surface;
An oscillation circuit (2) for oscillating a predetermined frequency signal;
A modulation circuit (3) for inputting the frequency signal from the oscillation circuit (2), modulating the frequency signal based on an interrogation signal given from the control circuit (7) as a carrier wave, and transmitting the interrogation radio wave;
A receiving circuit (4) that receives the response radio wave from the responder (20), demodulates the response radio wave, and outputs a response signal to the control circuit (7);
The interrogation signal is output to the modulation circuit (3) at a predetermined timing, the response signal is input from the reception circuit (4), the oscillation circuit (2), the modulation circuit (3), and the reception circuit A control circuit (7) for controlling the operation of (4);
Provided on the surface of the casing (11), which is classified into a plurality of classes based on the frequency of the interrogation radio wave, and a symbol determined in order according to the frequency of the plurality of classifications is displayed. A mobile object identification device comprising a display unit (12). The mobile object identification device according to claim 1,
When arranging a plurality of the interrogators (1) adjacent to each other, a symbol displayed on the display unit of the first interrogator (1a) and a symbol displayed on the display unit of the second interrogator (1e) However, the mobile object identification device is arranged so that the order of the symbols determined in the order is not continuous. The mobile object identification device according to claim 1,
The classification of the display unit (12) is a mobile object identification device characterized in that the frequency is measured at the time of production of the interrogator (1), and the display unit (12) is classified into a plurality of categories according to the magnitude of the measured frequency. The mobile object identification device according to claim 1,
An oscillator (2) of the interrogator (1) has a function (41 to 45) capable of adjusting the frequency magnitude of the frequency signal.

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