Source: http://www.google.com/patents/US20050170784?dq=5958006
Timestamp: 2015-05-04 03:23:47
Document Index: 99073230

Matched Legal Cases: ['art 21', 'art 21', 'art 10', 'art 15', 'art 10', 'art 10', 'art 10', 'art 10', 'art 15', 'art 21', 'art 21', 'art 10', 'art 10', 'art 10', 'art 10', 'art 15', 'art 15', 'art 15', 'art 15', 'art 10', 'art 15', 'art 15']

Patent US20050170784 - Read-write processing apparatus and method for RFID tag - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA read-write processing apparatus communicates with an RFID tag provided with a semiconductor memory to exchange commands and responses through antenna coils. A condition under which only a carrier wave is transmitted is set prior to a communication with the RFID tag and a level from a reception signal...http://www.google.com/patents/US20050170784?utm_source=gb-gplus-sharePatent US20050170784 - Read-write processing apparatus and method for RFID tagAdvanced Patent SearchPublication numberUS20050170784 A1Publication typeApplicationApplication numberUS 11/040,619Publication dateAug 4, 2005Filing dateJan 21, 2005Priority dateJan 27, 2004Also published asDE102005003228A1, DE102005003228B4, US7421249Publication number040619, 11040619, US 2005/0170784 A1, US 2005/170784 A1, US 20050170784 A1, US 20050170784A1, US 2005170784 A1, US 2005170784A1, US-A1-20050170784, US-A1-2005170784, US2005/0170784A1, US2005/170784A1, US20050170784 A1, US20050170784A1, US2005170784 A1, US2005170784A1InventorsTomonori Ariyoshi, Koyo Ozaki, Koji SakachoOriginal AssigneeOmron CorporationExport CitationBiBTeX, EndNote, RefManReferenced by (11), Classifications (26), Legal Events (2) External Links: USPTO, USPTO Assignment, EspacenetRead-write processing apparatus and method for RFID tag
US 20050170784 A1Abstract
A read-write processing apparatus communicates with an RFID tag provided with a semiconductor memory to exchange commands and responses through antenna coils. A condition under which only a carrier wave is transmitted is set prior to a communication with the RFID tag and a level from a reception signal obtained under this condition is extracted as noise level. The extracted noise level is displayed or outputted to an output host apparatus. Images(7) Claims(9)
DETAILED DESCRIPTION OF THE INVENTION FIG. 1 is a block diagram showing the structure of a reader-writer 1 embodying this invention and an RFID tag (hereinafter referred to simply as a tag) 2 as its object of communication. The tag 2 in this example does not contain a power source, being of the type that operates by an induced electromotive force generated by transmitted waves from the reader-writer 1, and is provided with a control part 21 and a semiconductor memory 22. The tag 2 also comprises an antenna coil 23, a capacitor 24 and a load switch 25 (a resistor with a contact point, according to this example) for communication. The control part 21 of this tag 2 includes not only a computer but also peripheral circuits such as a demodulation circuit for demodulating transmitted signals from the reader-writer 1. The reader-writer 1 is formed with a control part 10, an antenna coil 11, a transmitter circuit 12, a receiver circuit 13, an oscillator circuit 14 and a Z conversion circuit 101 for a matching process on the antenna coil 11 placed inside a housing structure (not shown). This housing structure is further provided with a display part 15, an interface (I/F) circuit 16, an input-output (I/O) circuit 17 and a level extracting circuit 18. The control part 10 on the side of the reader-writer 1 is a computer and carries out communication processing with the tag 2 according to a program stored in an internal memory. This control part 10 is also adapted to output high-frequency pulses based on pulse signals from the oscillator circuit 14. The high-frequency pulses become the basis of a carrier wave. When communicating with the tag 2, the control part 10 also serves to output, as a pulse signal, data that represent the content of a command. This output pulse signal is also referred to as a command signal. The transmitter circuit 12, referred to above, includes a driver circuit 102, a modulator circuit 103, a tuning-amplifying circuit 105 and a pair of Z conversion circuits 104 and 106 sandwiching this tuning-amplifying circuit 105. The receiver circuit 13 includes a bandpass filter (BPF) circuit 107, a detection circuit 108, a low pass filter (LPF) circuit 109, an amplifier circuit 110 and a comparator circuit 111. The aforementioned command signal is transmitted from the control part 10 to the modulator circuit 103. The aforementioned display part 15 comprises a numerical displayer and a plurality of display lights (not shown) and may be at an appropriate position on the housing structure. The interface circuit 16 is used for communication with host apparatus (not shown) such as personal computers and PLCs. The input-output circuit 17 is used for taking in external signals and outputting results of processing. The level extracting circuit 18 is for taking out the level of the reception signal as digital data and is formed with a detector circuit 112 and an A/D converter circuit 113. FIG. 2 is a timing chart for the signals related to the transmission and reception by the reader-writer 1 described above. FIG. 2(1) shows the signals related to the command transmission to the tag 2 and FIG. 2(2) shows the signals related to the reception of a response. In FIG. 2(1), (a) shows the aforementioned carrier wave. In the illustrated example, its frequency is set as 13.56 MHz. In FIG. 2(1), (b) shows a command signal. According to the illustrated example, it is a pulse width modulated signal of data of each bit comprising a command with �1� showing the low level and �0� showing the high level. The modulator circuit 103 uses the command signal to modulate (ASK modulation) the carrier wave to generate a transmission signal (c). According to the illustrated example, ASK modulation with degree of modulation 10% is carried out. The generated transmission signal is provided to the antenna coil 11 after undergoing an amplification process by the tuning-amplifying circuit 105 and an impedance matching process by the Z conversion circuits 104, 106 and 101 and transmitted to the tag 2 as electromagnetic waves. As the control part 21 of the tag 2 demodulates the transmission signal from the reader-writer 1 and recognizes the contents of the command, it carries out a process corresponding to this command and generates a response that shows the results of this process. In order to return this response, the control part 21 switches the load switch 25 on and off on the basis of the data arrangement as shown in (d) and (e) of FIG. 2(2). In this example, the length of time for transmitting a bit of signal is set equal to the time necessary to repeat the switching on and off of the load switch 25 sixteen times. If the data item to be transmitted is �0�, the load switch 25 is switched on and off eight times during the first half of the aforementioned length of time and the load switch 25 remains switched off during the second half. If the data item to be transmitted is �1�, on the other hand, the load switch 25 is kept switched off during the first half and the load switch 25 is switched on and off eight timed during the second half of the period. When the reader-writer 1 and the tag 2 are in a relationship where communication is possible, their antenna coils 11 and 23 are in an electromagnetically coupled condition. Thus, as the impedance of the tag 2 is periodically changed by the switching of the load switch 25 on and off, the impedance of the reader-writer 1 also changes accordingly, causing also the current that flows through its antenna coil 11 to change. The receiver circuit 13 serves to detect from this change a signal that represents the aforementioned response, eliminating noise by means of the bandpass filter circuit 107 and thereafter extracting by means of the detection circuit 108 the carrier wave that has been affected by the aforementioned changes in impedance. After the frequency components of the carrier wave are further eliminated by means of the low pass filter circuit 109, an amplification process is carried out by means of the amplifier circuit 110 such that a reception signal (f) as shown in FIG. 2 is detected. The frequency of the reception signal (f) after the frequency component of the carrier wave is removed is 424 KHz. The reception signal corresponding to the period during which the load switch 25 is switched on and off (data signal) includes waves which have an amplitude greater than a specified value and change in synchronism with this switching. Waves with an amplitude greater than the specified value also appear due to noise in the environment in the reception signal while the load switch 25 is maintained in the off-condition (base signal). The comparator circuit 111 compares the amplitude of this reception signal with a specified reference level and generates a binary signal (g) in FIG. 2. By this binarization process, a signal change corresponding to the switching of the load switch 25 is extracted. The control part 10 partitions this binary signal (g) in units of bits and thereby obtains a demodulated signal (h), demodulating the data of the individual bits. The detection circuit 112 of the level extracting circuit 18 takes in the reception signal (f) of FIG. 2 and extracts an envelope that includes each peak of the reception signal as shown in FIG. 3. This envelope signal is converted into a digital signal by means of the A/D converter circuit 113 and inputted to the control part 10. The control part 10 makes use of this input from the level extracting circuit 18 to obtain information indicative of the noise level immediately before and during a communication and carried out a process of reporting this to the user. The reader-writer 1 starts a communication with the tag 2 as it receives a command (such as a read command or a write command) from a host apparatus and provides the tag 2 with a similar command. As the tag 2 carries out a process according to this command and returns a response, the reader-writer 1 transmits this response back to the host apparatus. In general, a plurality of tags 2 are sent into the communication region of the reader-writer 1 sequentially at specified intervals. Each tag stops at a position opposite the reader-writer 1 for a specified length of time during which a communication process is carried out according to a flow as shown in FIG. 4. The arrival of a tag 2 at the opposite position of the reader-writer 1 is detected by means of a sensor (not shown). The host apparatus inputs its detection signal and outputs a command to the reader-writer 1. The size of the communication region is determined based on the range in which power necessary for communication with the tag 2 can be induced. When the tag 2 enters this communication region, it comes to be in the condition capable of responding to a command from the reader-writer 1. FIG. 4 shows this flow of communications among the reader-writer 1, the tag 2 and a host apparatus. Line (1) shows the signals exchanged between the host apparatus and the reader-writer 1, Line (2) shows the signals transmitted from the reader-writer 1 to the tag 2, and Line (3) shows the signals transmitted from the tag 2 to the reader-writer 1. The portions shown by dotted lines indicate periods during which data are being processed (command analysis or response analysis) by the reader-writer 1 or the tag 2. Whether it is a command analysis or a response analysis that is being carried out is also indicated. In what follows, the flow of basic data processing for the tag 2 will be explained with reference to reference symbols A, B, etc. of FIG. 4. Firstly, the host apparatus generates a command showing processes to be carried out by the tag 2 and transmits it to the reader-writer 1 (A). After analyzing the content of this command, the reader-writer 1 transmits to the tag 2 a first data readout command (B). In the above, the first data readout is for the purpose of acknowledging the fixed data such as the identification data of the tag 2 and is commonly referred to as the �system read�. While this system read is being carried out, the tag 2 receives signals of the system read through the antenna coil 23 which is electromagnetically coupled to the antenna coil 11. After acknowledging and analyzing the system read command, the tag 2 generates a response including specified data and returns it to the reader-writer 1 (C). The beginning portion (shown with a hatching) of this response (C) contains a fixed data arrangement of several bits. This portion is for indicating that the data which follow are the response from the tag 2 to this system read and is referred to as the �start code�. While this response (C) is being transmitted, the reader-writer 1 receives signals of this response through the antenna coil 11 electromagnetically coupled to the antenna coil 22. The reader-writer 1 analyzes the content of the received response and if it is judged to be a normal response, a second command is transmitted to the tag 2 (D). The purpose of this second command is to provide the tag 2 with the content of the command (A) from the host apparatus and to thereby cause this command to be executed. Thus, this command is hereinafter referred to as the execution command. After, analyzing this execution command and executing the process corresponding to its content, the tag 2 generates a response that indicates the details of the process and returns it to the reader-writer 1 (E). Upon recognizing that the response from the tag 2 is normal, the reader-writer 1 transmits it to the host apparatus (F). In the reception signal detected by the receiver circuit 13, as shown in FIG. 2, there is a big difference between the data signal corresponding to a period when a data communication from the tag 2 is being carried out (when the load switch 25 is being repeatedly being switched on and off) and the base signal while no data communication is taking place (while the load switch 25 is maintained in the switched-off condition) and hence the transmission data from the tag 2 can be correctly demodulated by a binarization process. If large noise appears suddenly during a communication process with the tag 2, however, a level change exceeding the binarization threshold value may appear in the base signal and there is a possibility that the transmission data cannot be demodulated correctly. In view of this problem, the reader-writer 1 is provided with the function of reporting on the level of noise that may be present at the time of communication processing. In what follows, two examples of this reporting function will be described sequentially. According to the first example, the level of the signal extracted by the level extracting circuit 18 is checked before the communication with the tag 2 is commenced and under the condition where the tag 2 is not inside the communication region of the reader-writer 1. Since the aforementioned carrier wave is constantly being transmitted independently of the communication with the tag 2, the changes in the level of the reception signal when the tag 2 is not inside the communication region and is not engaged in any communication should be reflecting the condition of the noise. Since the level extracting circuit 18 is adapted to extract the level when the reception signal shifts in the higher direction, it can extract the level reflecting the size of noise when no communication is being carried out. In what follows, the level which is extracted by the level extracting circuit 18 under the condition where no communication is being carried out will be referred to as the noise level. The control part 10 carries out the process of sampling the noise level a plural number of times before a communication is carried out, calculates an average value of the sampled values and causes it to be displayed on the display part 15. FIG. 5 is a flowchart showing a detailed control routine by the reader-writer 1. In FIG. 5, N(i) indicates an arrangement for storing the sampled values of noise level. This routine is started as a command (A) is received from a host apparatus and the counter i is initially set to zero (Step ST1). Thereafter, in the loop of Steps ST2-ST5, input data from the level extracting circuit 18 are taken in (Step ST2) for a specified number of times (100 times in the illustrated example) and each of these inputted values is stored in a memory as noise level N(i) (Step ST3). After all these noise level values are inputted (YES in Step ST5), the average value Nav of these 100 noise level values N(i) is calculated (Step ST6) and displayed by the display part 15 (Step ST7). The display part 15 may be adapted to display the numerical value of this average Nav itself or to use a bar graph to make a display in comparison with a specified threshold value. After the series of processes described above has been completed and the tag 2 has entered the communication region of the reader-writer 1, the series of communications with the tag 2 as shown in FIG. 4 is started (Step ST8). The aforementioned display of the average value Nav is continued until the communication process is completed or even until the next command is received from the host apparatus after the communication process is completed such that the user will have sufficient time to notice the display. In the case of the occurrence of a communication error, not only it is reported by means of an alarm but also the display of the average value Nav is continued for a specified length of time. By a control as described above, the user can be informed of the level of noise that is being generated immediately before each of the communication processes. Especially when a communication error has occurred, the user can easily determined whether this error was a result of noise or not. The second of the examples to be described next is for processing a reception signal being exchanged between the tag 2 after the tag 2 has entered the communication region of the reader-writer 1 and has started a communication process. Explained in detail, this is done by taking note that the aforementioned start code is included at the beginning of the response from the tag 2, extracting the rate of level change in the reception signal corresponding to this start code a signal-to-noise (SN) ratio and causing it to be displayed by the display part 15. FIG. 6 shows an example of this signal processing on the start code. The timing chart in FIG. 6 shows the correspondence between a portion of data contained in the response from the tag 2 and the on/off operations of the load switch 25. The portion of the reception signal on the side of the reader-writer 1 corresponding to data item �0� of this response is shown enlarged. This also shows a level change reflecting the on-off operations of the load switch 25. In other words, this level change is extracted by using the envelope signal extracted by the level extracting circuit 18. Since the data arrangement of the start code is known, the control part 10 can separate this reception signal into a portion that corresponds to the aforementioned data signal and another portion that corresponds to the base signal by comparing between the data arrangement of the reception signal binarized by the comparator circuit 111 of the receiver circuit 13 and the aforementioned known data arrangement. According to this example, while a signal corresponding to the start code is being received, the envelope signal extracted by the level extracting circuit 18 is separated into signal PS corresponding to the data signal and signal PN corresponding to the base signal, the average value of signal PS is treated as the signal level S, the average value of signal PN is treated as the noise level N and their ratio is calculated. FIG. 7 shows the routine according to the second example. This routine is also started as a command is received from a host apparatus, and a command for the aforementioned system read is transmitted to the tag 2 (Step ST11). After a response to this command is received from the tag 2 (or when the starting bit of the start code of this response is recognized) (YES in Step ST12), the process of detecting the start code as a whole is continued (Step ST13). In this step, the data arrangement corresponding to the start code is recognized on the basis of the binary signal from the comparator circuit 111. At the same time, the output from the level extracting circuit 18 corresponding to the start code is taken in while it is separated into aforementioned signals PS and PN and storing them in a memory (not shown). After the start code is thus detected, the processing of Steps ST14-ST16 and that of Steps ST17 and ST18 are carried out in parallel. In Step ST14, average values of signal levels that have been accumulated separately for signals PS and PN extracted in Step ST13 are obtained to determine signal level S and noise level N as defined above. The SN ratio is calculated by dividing the noise level N by the signal level S (Step ST15) and is displayed by the display part 15 (Step ST16). In Step S17, on the other hand, the substantial content of the response is obtained from the portion of the reception signal after the start code detected in Step ST13 and this content is analyzed. Thereafter, the remainder of the communication process such as the transmission of the execution command, the reception of a response from the tag 2 to this command and the transfer of this response to a host apparatus is carried out (Step ST18). In this example, too, the display of the SN ratio is continued until the process of Step ST18 is completed or until a next command is received from the host apparatus. In the case of the occurrence of an error, an alarm is outputted to report it and the display of the SN ratio is maintained for a specified length of time. By this second example, since the SN ratio can be displayed during a communication process, the user can ascertain the level of noise that is being generated while carrying on the communication process. In the case of a communication error, in particular, it can be ascertained easily whether this error was caused by noise or not from the displayed SN ratio. As a variation of the second example, the difference between the signal level S and the noise level N may be obtained instead of their ratio. Although it was explained above that Steps ST14-ST16 and Steps ST17 and ST18 are carried out in parallel, the step of analyzing the response (Step ST17) and the step thereafter may be carried out after the SN ratio has been obtained. In such a case, the routine may be so arranged that the step of analyzing the response (Step ST17) and the steps thereafter are stopped if the calculated SN ratio happens to exceed a specified threshold value. Since communications under a condition of large noise can thus be avoided in this manner, communications can be carried out successfully with a higher level of reliability. After the communication process is thus stopped, it is preferable to restart the same routine from the beginning after a specified length of time has elapsed. By both of the examples described above, communication processes can be carried out by sending tags 2 sequentially into the communication region of the reader-writer 1 and noise level and SN ratios can be calculated and displayed on the display part 15 between or during these processes. The selection between the two examples may be made, depending upon the time difference between when a tag which has completed its communication leaves the communication region of the reader-writer 1 and when the next tag arrives in the communication region and the processing time assigned to each tag. If this time difference is sufficiently long, the first example may be used. If this time difference is small, the second example may be used. The control according to either of the examples may be carried out not only during a real operation but also during a preliminary test period. In such a case, the user can estimate the level of noise that is likely to be generated from the display of either the noise level or the SN ratio such that the environment can be rearranged if this level is found to be too high. Since the signal level is expected to become lower as the tag 2 is separated from the reader-writer 1 farther away especially in the case of the second example, the distance between the reader-writer 1 and the tag 2 can be adjusted on the basis of the displayed SN ratio. Each of the examples described above was designed such that the communication process is carried out after the tag 2 entering the communication region of the reader-writer 1 is stopped but there are cases where the communication process is carried out while the tag 2 is in motion. In such a case, the reader-writer 1 carries out the aforementioned system read repeatedly until a response is obtained from the tag 2 and transmits the execution command if a response is obtained from the tag 2, concluding that it has become possible to communicate with the tag 2. When the first of the examples described above is applied to such a case, the process of detecting the noise level is carried out immediately before every system read such that, at the point in time when a response from the tag 2 is obtained to a system read, the noise level which was obtained immediately before or the average value of noise levels obtained by a plurality of detection processes in the recent past may be displayed. In the case of the second example, the noise level may be detected after a response is obtained from the tag 2 and a routine which is similar to the one according to FIG. 7 but in which the system read is repeated may be carried out. The noise level and the SN ratio obtained as explained above may be outputted to a host apparatus instead of being displayed. In such a case, the host apparatus will be able to carry our controls such as displaying the transmitted data from the reader-writer 1, determining the size of noise and outputting an alarm in the case of a large noise. The reader-writer 1 may be adapted to create history data by correlating the calculated results of noise level and SN ratio each time with the results of the communication process and to store them in a memory. FIG. 8 shows an example of such history data, correlating the results of each communication process with the noise level measured immediately before that communication result. These noise levels are values measured before the communication process is started and under the condition where the tag 2 is not inside the communication region of the reader-writer 1, similar to the first example described above. For the measurement of these noise levels, a routine similar to Steps ST1-ST6 of FIG. 5 may be repeated for a plural number of cycles but it is preferable to adopt as the history data the noise levels measured immediately before a communication process. In this example, data related to each of communication processes are collected as a page and each page is assigned a number (page number) indicative of the cycle (how many cycles before) in which the data were obtained in the communication process. The page number is 1 for the communication process carried out immediate before and is increased as the time goes farther back. In other words, every time a communication process is carried out, the number of the page related to the communication process immediately before is set to 1 and the numbers of older pages are incremented by 1. Each page contains not only data read out of the tag 2 as data showing the results of a communication but also data item �normal� or �abnormal� to indicate whether the communication process was successful or not. In this example, it is so arranged that in the case of a failure in the communication a retry (the process of repeating the same communication again) can be carried out up to a predetermined number of times and if the communication succeeds by a retry, the data item showing the result will say �normal�. If the communication does not succeed after the retry is repeated for the predetermined number of times, the result is shown as �abnormal�. Explained more in detail, the data items �normal� and �abnormal� are expressed by a flag. Although not shown in FIG. 8, the number of times a retry was repeated may also be included in the result of communication. Although the data read out from the tag 1 are 8-bit data, data with the upper 4 bits and the lower 4 bits separated are also stored in order to show them as hexadecimal data (�base 16�). In the example of FIG. 8, the original 8-bit data are shown as �raw data� and the upper and lower 8-bit data are shown in hexadecimal notation. For noise level, too, not only raw data in 8 bits but also data in hexadecimal notation (�base 16�) are stored in order to show the upper and lower 4-bit portions separately. The noise level is also shown in terms of being �large� or �small� and this determination is shown in the table. This determination may be made by comparing the calculated noise level with a specified threshold value. In addition to �large� and �small�, another classification �medium� may also be introduced to indicate that the noise level is somewhere between �large� and �small�. These results of determination are also indicated by means of a flag. The reader-writer 1 is adapted to transmit the history data to a host apparatus in response to a call command therefrom. The host apparatus may display the transmitted history data on a display device or carry out a process of printing them out such that the user can analyze the cause of a communication error in detail from such outputted history data. From the data shown in FIG. 8, for example, it may be concluded that a communication error occurred because of noise in the communication process corresponding to page number 11 and that the communication error in the communication process corresponding to page number 50 was not because of noise but was due to some other cause such as an inadequate position of the tag 2 or a fault in a circuit on the side of the tag 2. If history data of operations of apparatus set near the reader-writer 1 are stored (say, by a host apparatus), the cause of occurrence of noise may be analyzed on the basis of the conditions of operations of such other apparatus when there is a communication error due to noise. If it is found that there is a high probability that a certain apparatus is in operation at the time of occurrence of a communication error, it may be predicted that this apparatus is the cause of noise and a proper measure may be taken to reduce the noise. The first example shown in FIG. 5 was explained above as detecting a noise level before the start of a communication, reporting its result and always restarting the communication after the elapse of a certain specified length of time. Instead, it may be arranged to wait until the noise level becomes low if it is found to be above a specified threshold value. FIG. 9 shows a control routine for such an arrangement. The routine according to FIG. 9 is also started as a command is received from a host apparatus. At the start of this routine, the counter i for counting the sampling number of noise level is set to zero (Step ST21) and the output value from the level extracting circuit 18 is detected and stored as the noise level N(i) (Step ST22). If this value is less than a specified threshold value N0 (YES in Step ST23), the counter i is incremented by 1 (Step ST24). If N(i) is not less than the threshold value N0 (NO in Step ST23), the counter i is reset to zero (Step ST26). The above is repeated until the counter value i reaches 100, or until all of 100 consecutively sampled noise levels are found to be below the specified threshold value N0 (YES in Step ST25) and it is only then that the communication process is started (Step ST27). By this routine, a communication error due to noise can be avoided with a high level of reliability. The example described above with reference to FIG. 9 is somewhat similar to the prior art disclosed in aforementioned Japanese Patent Koho 9-190518 in that communications are started only after it is ascertained that noise level is low. According to the prior art technology of Japanese Patent Koho 9-190518, however, it is necessary to carry out a communication with the tag in order to check the noise level and two correlation calculations must be performed in order to check the noise level. According to the present invention, by contrast, the process is not complicated because only the noise level is checked and there is no particular need to carry out any communication with the tag. Moreover, the technology according to Japanese Patent Koho 9-190518 does not require that the condition of a low noise level should continue for a specified length of time. Although the noise level may happen to be low some time before the start of a communication, noise level may suddenly rise thereafter to cause a communication error. According to the example shown in FIG. 9, by contrast, a communication process is not started unless the condition of low noise level lasts for a specified length of time. Thus, communications are be started under a more reliably stable condition and it is much less likely that the noise level will rise suddenly during a communication. In other words, communication errors caused by noise can be avoided much more reliably. Referenced byCiting PatentFiling datePublication dateApplicantTitleUS7333786 *Sep 21, 2004Feb 19, 2008Sony CorporationRelaying apparatus and communication systemUS7448547 *Mar 12, 2007Nov 11, 2008Impinj, Inc.Decoding with memory in RFID systemUS7510117 *Jun 4, 2004Mar 31, 2009Impinj IncDecoding with memory in RFID systemUS7533614Sep 8, 2005May 19, 2009Reich Ronald EMemory enhanced ammunition cartridge and method of making and using the sameUS7543742 *Jul 26, 2007Jun 9, 2009Denso Wave IncorporatedReader/writer for contactless integrated circuit cards and management system for vending machinesUS7612673May 30, 2007Nov 3, 2009Kimberly-Clark Worldwide, Inc.RFID system for lifting devicesUS7667574Dec 14, 2006Feb 23, 2010Corning Cable Systems, LlcSignal-processing systems and methods for RFID-tag signalsUS8207826 *Oct 3, 2006Jun 26, 2012Ncr CorporationMethods and apparatus for analyzing signal conditions affecting operation of an RFID communication deviceUS20080088416 *Oct 3, 2006Apr 17, 2008John Frederick CrooksMethods and Apparatus for Analyzing Signal Conditions Affecting Operation of an RFID Communication DeviceUS20110210832 *May 9, 2011Sep 1, 2011Toshiba Tec Kabushiki KaishaRadio communication apparatusWO2008146180A1 *Apr 4, 2008Dec 4, 2008Kimberly Clark CoRfid system for lifting devices* Cited by examinerClassifications U.S. Classification455/67.13, 455/67.7, 324/500, 455/67.14, 340/10.1International ClassificationG06K17/00, H01Q11/08, H04B5/00, H01Q7/00, H01Q1/36, H04B5/02, G06K7/00, H04B1/59Cooperative ClassificationH04B5/00, H01Q1/362, H04B5/0056, H04B5/0062, H01Q7/00, H04B5/0081, G06K7/0008, H01Q11/08European ClassificationG06K7/00E, H01Q1/36B, H01Q11/08, H04B5/00, H01Q7/00Legal EventsDateCodeEventDescriptionSep 22, 2011FPAYFee paymentYear of fee payment: 4Jan 21, 2005ASAssignmentOwner name: OMRON CORPORATION, JAPANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:ARIYOSHI, TOMONORI;OZAKI, KOYO;SAKACHO, KOJI;REEL/FRAME:016214/0142;SIGNING DATES FROM 20050114 TO 20050121RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services