CN113792833A

CN113792833A - Impedance self-adjusting ISO15693 label reading-writing device and adjusting method thereof

Info

Publication number: CN113792833A
Application number: CN202111059266.XA
Authority: CN
Inventors: 孙国; 郑彦斌
Original assignee: Xiamen Yintian Electronic Technology Co ltd
Current assignee: Xiamen Yintian Electronic Technology Co ltd
Priority date: 2021-09-10
Filing date: 2021-09-10
Publication date: 2021-12-14
Anticipated expiration: 2041-09-10

Abstract

The invention discloses an impedance self-adjusting ISO15693 label reading and writing device and an adjusting method thereof, wherein the impedance self-adjusting ISO15693 label reading and writing device comprises: a microcontroller; the transmitting circuit is provided with a microcontroller interface, the microcontroller interface is electrically connected with the microcontroller, and the microcontroller controls the transmitting circuit to be turned on or turned off; the antenna load is used for coupling with the near field of the tag, transferring energy to the tag and exchanging data; the impedance matching network is connected between the transmitting circuit and the antenna load and adjusts the input impedance and the output impedance of the impedance matching network through software on the microcontroller; and the receiving circuit is used for receiving the data of the label, processing the radio frequency signal and outputting a digital signal to the microcontroller. The invention obviously improves the checking accuracy of the ISO15693 label reader-writer and the success rate of reading and writing label data, simplifies the debugging process in the production of the reading-writing device and reduces the labor cost.

Description

Impedance self-adjusting ISO15693 label reading-writing device and adjusting method thereof

Technical Field

The invention relates to the technical field of RFID label reading and writing, in particular to an impedance self-adjusting ISO15693 label reading and writing device and an adjusting method thereof.

Background

RFID tags are widely used in the fields of libraries, archive management, logistics, and life services. The RFID is divided according to the working frequency band of the RFID, and mainly comprises microwave, ultrahigh frequency, High Frequency (HF), low frequency and the like, wherein the typical working frequency of the high frequency RFID is 13.56 Mhz.

In high frequency RFID system applications, it is usually necessary for the reader to first read the UID (i.e., unique serial number) of one or more tags within the antenna's sensing range, which is called "inventory", and then decide whether to read or write other data from or to the tag as needed.

In some application scenarios (such as access attendance, public transportation system, etc.), a tag holder actively brings the tag close to an antenna sensing area of the read-write device in sequence, and has no severe requirement on the performance of the device; however, in other applications (such as warehousing inventory and the like), the situation is quite complex, and the defects of label inventory omission and low data read-write success rate are always faced, so that a great problem is brought to the application. Objective factors causing tag inventory omission and data read-write failure are complex, for example: the electronic tag is far away from the antenna; the plane of the electronic tag is completely vertical to the plane of the antenna; a plurality of electronic tags are overlapped; the electronic tag is close to the metal; the electronic tag has low sensitivity and the like.

The above objective adverse conditions are difficult to avoid in many cases, and technicians are constantly trying to improve RFID tag reading and writing apparatuses, and it is desired to improve the performance.

Theoretical studies have shown that impedance matching is required for the RF system to perform optimally. Impedance matching is a basic concept in electronic technology, and refers to an operating state in which the load impedance and the internal impedance of the excitation source are matched with each other, and optimal transmission of energy and signals can be realized through matching. The conditions for impedance matching are: in the pure resistance circuit, the load resistance is equal to the internal resistance of the excitation source; in the complex impedance circuit, the load impedance and the internal impedance of the excitation source should be a pair of complex conjugates.

Specifically, in the RFID reader/writer, the radio frequency transmitting circuit may be regarded as an "excitation source", and the radio frequency antenna may be regarded as a "load", which need to implement impedance matching. In many cases, achieving a good impedance match is difficult because:

(1) in industrial production, components used for manufacturing electronic circuits have certain errors, so that the impedance value of an actual circuit is deviated from theoretical calculation;

(2) the circuit uses variable impedance devices such as a potentiometer and an adjustable capacitor, and the like to obtain a required impedance value by matching with manual debugging, which is a method, but has the problems of time and labor waste and low efficiency, and certain loads with complex topology (for example, a plurality of antennas are connected through a power divider) are difficult to obtain an accurate impedance value through manual adjustment;

(3) in some applications, the RFID reader and the antenna are physically separated (connected through a radio frequency coaxial line), and the field installation pairing of multiple sets of equipment is random, which brings another challenge to manual debugging of impedance matching;

(4) the antenna of the RFID reader is essentially a coil, and energy and signals are transmitted between the antenna and the RFID tag through near field coupling, so that in actual installation and use, the influence of the surrounding environment on the impedance of the antenna (such as a nearby metal cabinet) cannot be ignored, the surrounding environment is different from a laboratory for production and debugging of equipment, and the environment may even change at any time.

Due to the influence of the factors, good impedance matching cannot be guaranteed in practical use of many RFID read-write devices, the performance cannot be optimized, and the problems of 'inventory' omission and read-write failure still restrict the application of the high-frequency RFID technology in some occasions.

As an example of the application of the high-frequency RFID technology, the ISO15693 tag is one of the high-frequency RFID tags, and the tag chip has several models, which all conform to the ISO15693 protocol, and the above disadvantages are common in the prior art.

Disclosure of Invention

In view of this, the inventor has made a targeted study on an ISO15693 protocol, and has made the present invention to provide an impedance self-adjusting ISO15693 tag read-write apparatus and an adjusting method thereof, which significantly improve the accuracy of the inventory of an ISO15693 tag reader-writer and the success rate of reading and writing tag data, simplify the debugging process in the production of the read-write apparatus, and reduce the labor cost.

The adopted technical scheme is as follows:

the invention relates to an impedance self-adjusting ISO15693 label reading and writing device, which is characterized by comprising the following components:

a microcontroller;

the transmitting circuit is provided with a microcontroller interface, the microcontroller interface is electrically connected with the microcontroller, and the microcontroller controls the transmitting circuit to be turned on or turned off;

the antenna load is used for coupling with the near field of the tag, transferring energy to the tag and exchanging data;

the impedance matching network is connected between the transmitting circuit and the antenna load and adjusts the input impedance and the output impedance of the impedance matching network through software on the microcontroller;

and the receiving circuit is used for receiving the data of the label, processing the radio frequency signal and outputting a digital signal to the microcontroller.

Furthermore, the circuit model of the impedance matching network is a T-shaped two-port network containing an adjustable capacitor, and the adjustable capacitor in the T-shaped two-port network is automatically adjusted through a microcontroller.

Further, a fixed capacitor and an adjustable capacitive module are connected in parallel to be equivalent to the adjustable capacitor, the adjustable capacitive module comprises m adjustable branches, and m is a natural number not less than 1; each adjustable branch comprises an electronic radio frequency switch and a branch two-terminal network, and the capacitance value of the adjustable branch is changed by opening and closing the electronic radio frequency switch.

Further, the electronic radio frequency switch is a PIN diode or a switching circuit integrated inside a dedicated chip.

Furthermore, the two-end network of the branch circuit is composed of a plurality of passive devices in series and parallel connection, and the whole impedance is capacitive.

Furthermore, the adjustable capacitive module further comprises an impedance control circuit which is provided with a microcontroller interface with the number equal to that of the adjustable branches and controls the electronic radio frequency switch to be switched on and switched off through software.

Further, the software is embedded software solidified in the microcontroller.

The invention relates to a method for adjusting an impedance self-adjusting ISO15693 label reading-writing device, which is characterized in that embedded software executes the following steps:

s1, firstly executing an initialization process and then entering a working stage of a circulation mode, wherein the initialization process comprises the operation of defining an impedance state table in a microcontroller, the impedance state table is a data table and is provided with J rows, each row corresponds to the on and off states which are set by m electronic radio frequency switches through m data with the value range of 0 or 1 so as to correspond to an impedance setting state of the impedance matching network, and J is a natural number larger than 1;

s2, in a working stage of a circulation mode, executing a label checking process according to needs;

and S3, in the working stage of the circulation mode, executing a flow of reading and writing the tag data as required.

Further, in S2, the process of performing label inventory includes the following steps:

s21, defining a tag number counter TagCount, and setting an initial value to be 0;

s22, preparing a data area BUFF for storing the checked label, and clearing 0 all data in the area; storing information of one label by using LEN bytes, wherein the maximum number of expected labels is NUM, the size of BUFF is not less than NUM multiplied by LEN bytes, LEN is a natural number, and NUM is a natural number;

s23, defining an integer variable Index for setting impedance, and setting an initial value to be 0, wherein the integer variable Index is only valid in the operation step of S2;

s24, opening a transmitting circuit;

s25, searching an Index row in the impedance state table, and setting the levels of m related pins of the microcontroller according to the values of m elements in the row so as to control the on-off of the m adjustable branch electronic radio frequency switches and adjust the input impedance and the output impedance of the impedance matching network;

s26, performing label checking, adding label information to the BUFF after one label is checked in each disc, sending a Stay Quiet instruction according with an ISO15693 protocol to the label, and performing a tag number counter TagCount adding operation; wherein the tag information comprises a UID of the tag;

when a Stay Quiet instruction is sent, the UID of the label is used as a parameter according to the specification of an ISO15693 protocol, and after the Stay Quiet is received, the label does not respond to the inventory any more unless the label is powered off;

s27, adding one to the variable Index;

s28, checking the value of the variable Index, if the number J of the rows of the impedance state table is reached, closing the transmitting circuit, ending the process, otherwise, jumping to the step S25 to continue the circulation.

Further, in S3, the process of reading and writing the tag data is executed, which includes the following steps:

s31, defining an integer variable Index for setting impedance, and setting an initial value to be 0, wherein the integer variable Index is only valid in the operation step of S3;

s32, opening a transmitting circuit;

s33, searching an Index row in the impedance state table, and setting the levels of m related pins of the microcontroller according to the values of m elements in the row so as to control the on-off of the m adjustable branch electronic radio frequency switches and adjust the input impedance and the output impedance of the impedance matching network;

s34, executing tag data read-write operation;

s35, if the tag data is successfully read and written, closing the transmitting circuit, ending the process, otherwise, continuing to execute downwards;

s36, adding one to the variable Index;

s37, checking the value of the variable Index, if the number of lines J of the impedance state table is reached, indicating that the operation of the process fails, executing the operation of closing the transmitting circuit and ending the process, otherwise, jumping to the step S33 to continue the circulation.

The invention has the beneficial effects that:

the impedance matching network in the impedance self-adjusting ISO15693 label reading and writing device is automatically adjusted to achieve the best matching effect, so that the checking accuracy of the ISO15693 label reading and writing device and the success rate of reading and writing label data are obviously improved, the debugging process in the production of the reading and writing device is simplified, and the labor cost is reduced.

Drawings

The drawings that accompany the detailed description can be briefly described as follows:

FIG. 1 is a circuit block diagram of an impedance self-adjusting ISO15693 tag reader/writer;

FIG. 2 is a circuit model of an impedance matching network;

FIG. 3 is a circuit block diagram of an impedance matching network;

FIG. 4 is a circuit block diagram of a tunable capacitive module;

FIG. 5 is a complete circuit block diagram of embodiment 1;

FIG. 6 is a complete circuit block diagram of embodiment 2;

FIG. 7 is a software flow diagram of tag inventory;

fig. 8 is a software flow diagram of tag read and write.

Detailed Description

The technical scheme of the invention is more clearly described below by combining the accompanying drawings.

As shown in fig. 1, the impedance self-adjusting ISO15693 tag reader/writer includes a microcontroller 1, a transmission circuit 2, an antenna load 3, an impedance matching network 4, and a reception circuit 5. The transmitting circuit 2 is provided with a microcontroller interface, is electrically connected with the microcontroller 1, can control the output of the microcontroller through software of the microcontroller, and controls the on or off operation of the transmitting circuit through the software of the microcontroller; the receiving circuit 5 is used for receiving the data of the label, processing the radio frequency signal and outputting a digital signal to the microcontroller 1; the antenna load 3 is used for near-field coupling with a tag, transferring energy to the tag and exchanging data, and can be a single high-frequency RFID antenna coil or a complex module comprising a plurality of high-frequency RFID antenna coils, a radio-frequency signal distributor, a power divider and other active or passive devices; the main circuit and the antenna load of the tag reading and writing device can be integrated together or physically separated and connected through a radio frequency coaxial cable; the impedance matching network 4 is connected between the transmitting circuit 2 and the antenna load 3, and self-adjusts the input and output impedance through software on the microcontroller, so as to achieve the effect of impedance matching.

As shown in fig. 2, the circuit model of the impedance matching network 4 is a T-type two-port network, the input impedance of the receiving circuit 5 is high, and the theoretical parameters can be ignored when calculating, and after the output impedance of the transmitting circuit 2 and the input impedance of the antenna load 3 are known, those skilled in the art can easily obtain the circuit parameters of the T-type network by theoretical calculation or computer simulation (the result is not unique).

In order to realize impedance self-adjustment, the adjustable capacitor C in the T-shaped two-port network shown in FIG. 2 is automatically adjusted by a method of combining software and hardware.

As shown in fig. 3, the fixed capacitor C1 and the tunable capacitive module 42 are connected in parallel to be equivalent to the tunable capacitor C, and the capacitance value of the fixed capacitor C1 should be slightly smaller than the theoretical value of the tunable capacitor C. The fixed capacitor C1, the inductor L1, the inductor L2, and the resistor R1 constitute a basic impedance circuit 41.

As shown in fig. 4, the tunable capacitive module 42 is mainly composed of m tunable branches 421, each of which includes an electronic rf switch (denoted by s1.... Sm in fig. 4) and a two-terminal branch network. The electronic radio frequency switch may be a PIN diode or a switching circuit integrated inside a dedicated chip. The two-end network of the branch circuit can be formed by connecting a plurality of passive devices in series and in parallel, and the integral impedance is capacitive. And the capacitance value of the adjustable branch can be changed by switching on and off the electronic radio frequency switch.

In the above, m is a natural number of not less than 1.

As a preferred embodiment, a high power PIN diode is used as the electronic radio frequency switch.

Still referring to fig. 4, the tunable capacitive module 42 further comprises an impedance control circuit 442 having a microcontroller interface equal to the number of tunable branches 421, and the microcontroller 1 can control the on/off of the electronic rf switch through software. According to the characteristics of the selected electronic radio frequency switch, the related technical personnel can realize the impedance control circuit without creative labor, which is not described in detail.

The present invention also includes embedded software that is solidified in the microcontroller 1, and the following describes a software processing method and a related process. For convenience of description, the C language is taken as an example, and those skilled in the art can naturally implement other programming languages, and the names of related variables, constants and functions in the description are only used to help describe the software.

An impedance self-adjusting method for adjusting an ISO15693 label reading and writing device comprises the following steps of:

s1, after the device is powered on, an initialization process is executed first and then a cycle mode working stage is entered, wherein the initialization process comprises the operation of defining a global data table in a microcontroller, and the table is called an impedance state table for convenience of description. The "impedance state table" will be described in detail in embodiment 1.

And S2, in a working stage of a circulation mode, executing a label checking process as required, wherein the process can be initiated by a timing trigger, an upper computer command trigger, a sensor trigger and the like. Referring to fig. 7, the process includes the following steps in sequence:

s21, defining an integer variable TagCount for recording the number of labels, and setting an initial value to be 0.

S22, preparing a data area BUFF for storing the checked label, and clearing 0 all data in the area. The information of one label is stored by LEN bytes, the maximum number of expected labels is NUM, and the size of BUFF is not less than NUM multiplied by LEN bytes.

In the above, LEN is a natural number, and the value is generally 8 to 12 depending on the application scenario.

In the above, NUM is a natural number, and the numerical value depends on the application scenario.

S23, in order to set the impedance, a local integer variable Index is defined, and an initial value is set to 0.

S24, opening a transmitting circuit.

S25, an Index row is searched in the impedance state table, and the levels of m related pins of the microcontroller are set according to the values of m elements in the row, so that the on-off of the m adjustable branch electronic radio frequency switches is controlled, and the input impedance and the output impedance of the impedance matching network are adjusted.

S26, performing label checking, adding label information to the BUFF after one label is checked in each disc, sending a Stay Quiet instruction conforming to the ISO15693 protocol to the label, and performing an operation of adding one to the number of labels TagCount.

In the above, the tag information is customized according to the application scenario, but must include a UID (unique serial number) of the tag.

In the above, when sending the Stay Quiet command, according to the ISO15693 protocol, the UID of the tag must be used as a parameter, and after receiving the Stay Quiet, the tag will not respond to the inventory unless the tag is powered off, and sending the Stay Quiet is an essential link for processing data collision in the ISO15693 protocol.

In the above, other technical details of the inventory are the means of the prior art in the field and are not described in detail.

S27, adding one to the variable Index.

S28, checking the value of the variable Index, if the number J of the rows of the impedance state table is reached, executing the operation of closing the transmitting circuit and ending the process, otherwise, jumping to the step S25 to continue the circulation.

Please note the following points:

(1) in the above checking process, steps S25-S28 execute J times of loop operations altogether, the impedance matching network has J states altogether, and as long as the circuit design is reasonable, even if there is a certain error in the impedance parameters due to various reasons, the J states inevitably include an optimal impedance matching state closer to the ideal state, so that the use effect of the present invention can be ensured.

(2) In the checking process, after the label is checked every time, a Stay Quiet instruction conforming to an ISO15693 protocol is sent to the label, the interference of the known label can be eliminated in the next checking, and a large amount of time is saved. Therefore, although the above flow performs J loop operations in total, the total execution time is not J times of that of a single loop, but is slightly longer than that of the single loop.

(3) Because the checked labels in each state are stored indiscriminately, the invention does not need to determine the optimal impedance matching state appearing in the cycle of the number of times, the deviation between the actual impedance parameter and the theoretical calculated value and the reason causing the deviation between the actual impedance parameter and the theoretical value, thereby having good adaptability and obtaining good effect even if the environmental factors suddenly change.

And S3, in the working stage of the circulation mode, executing a flow of reading and writing the tag data as required, wherein the flow can be initiated by a timing trigger, an upper computer command trigger, a sensor trigger and the like.

Referring to fig. 8, the process includes the following steps in sequence:

s31, in order to set the impedance, a local integer variable Index is defined, and an initial value is set to 0.

S32, opening a transmitting circuit.

S33, an Index row is searched in the impedance state table, and the levels of m related pins of the microcontroller are set according to the values of m elements in the row, so that the on-off of the m adjustable branch electronic radio frequency switches is controlled, and the input impedance and the output impedance of the impedance matching network are adjusted.

And S34, executing tag data read-write operation.

In the above, the tag data read/write operation needs to specify specific parameters (e.g. storage address, etc.), and the technical details thereof are the means in the prior art and are not described herein again.

And S35, if the reading and writing of the tag data are successful, executing the operation of closing the transmitting circuit and ending the process, otherwise, continuing to execute the next step.

In the above, the technical details for checking whether the reading and writing of the tag data are successful are the means in the prior art in the field and are not described in detail.

S36, adding one to the variable Index.

The following is a further description by way of example.

Example 1

Fig. 5 is a complete circuit block diagram of the present embodiment.

Referring to fig. 2, the ideal value of the T-type network equivalent capacitance C of the impedance matching network 4 is 350pF, which is obtained by computer simulation. Referring again to fig. 3, the same effect as that of capacitor C is achieved by connecting a fixed capacitor C1 in parallel with the tunable capacitive module 42, the fixed capacitor C1 having a nominal value of 300pF and the tunable capacitive module 42 having a desired value of 50 pF. In order to adjust the tunable capacitive module 42 by a method of combining software and hardware to adapt to the influence of various factors on the actual effect of impedance matching, the following scheme is adopted:

referring again to fig. 5, the tunable capacitive module 42 has 3 tunable branches 421, each of which includes an electronic rf switch and a two-terminal branch network, the electronic rf switch is a PIN diode (denoted by S1, S2, S3 in fig. 5) and is of the type MA4P7104-1072T of MACOM corporation, each of the two-terminal branch networks is composed of two capacitors connected in series, and the capacitance value of the tunable branch can be changed by turning on and off the electronic rf switch. When the PIN diode is used as a radio frequency switch, the minimum working frequency and the maximum working frequency of a radio frequency signal are limited to a certain extent, the radio frequency signal of the embodiment is 13.56Mhz, and MA4P7104-1072T can meet the requirements. According to the characteristics of the PIN diode, when enough forward direct current voltage is applied to the two ends of the PIN diode, the low impedance characteristic is presented to the radio frequency signal, the radio frequency signal can be regarded as the on state of the radio frequency switch, and when the direct current voltage is not applied to the two ends of the PIN diode or the reverse direct current voltage is applied to the two ends of the PIN diode, the high impedance characteristic is presented to the radio frequency signal, and the radio frequency signal can be regarded as the off state of the radio frequency switch. The tunable capacitive module 42 further comprises an impedance control circuit 442 having a microcontroller interface equal to the number of tunable branches 421, and the microcontroller can control the on and off of the electronic rf switch through software.

Still referring to fig. 5, a specific manner in which the impedance control circuit 442 controls the PIN diode is described by taking one of the ways as an example: an NPN triode T421, a resistor R421 and a resistor R422 form a typical triode switching circuit to control the grid voltage of a PMOS tube Q421, the source electrode of the PMOS tube Q421 is connected with a direct-current voltage source VCC, the drain electrode is connected with the positive electrode of a PIN diode S1 after being connected with a resistor R423 and an inductor L421 in series, and the negative electrode of the PIN diode S1 is grounded. When the interface of the microcontroller is at a high level, the triode T421 is turned on, a voltage difference is formed between the source and the gate of the PMOS transistor Q421, the source and the drain of the Q421 are turned on, current flows to the ground from a power supply VCC through the PMOS transistor Q421, the resistor R423, the inductor L421 and the PIN diode S1, and the PIN diode S1 has a positive direct current voltage meeting requirements at both ends, has a low impedance characteristic for radio frequency signals, and can be regarded as a conduction state of the radio frequency switch; when the microcontroller interface is at a low level, the triode T421 and the PMOS transistor Q421 are both in a cut-off state, and the two ends of the PIN diode S1 have no dc bias, and exhibit a high impedance characteristic to the radio frequency signal, which can be regarded as a cut-off state of the radio frequency switch. Please note that the inductor L421 plays a role in this embodiment, because the inductor has the characteristics of "direct current and alternating current resistance", and under the condition that the parameters are reasonably selected, the impedance of the branch in which the inductor L421 is located is very high in the 13.56Mhz operating frequency band, and can be ignored when analyzing the rf impedance. In this embodiment, VCC voltage is 4.5 volts, inductor L421 is 22uH, resistor R423 is 15 ohms, and Q421 is model SI7313DN from VISHAY.

Still referring to fig. 5, the values of the capacitors in the tunable capacitive module 42 are shown in table 1 below:

TABLE 1

Capacitor label

C4A1

C4B1

C4A2

C4B2

C4A3

C4B3

Volume value

10pF

20pF

40pF

The present embodiment further includes embedded software solidified in the microcontroller 1, and the following describes a software processing method and a related flow, where the software of the present embodiment is written in C language:

p1. after the device of the invention is powered on, an initialization process is performed before entering the cycle mode operating phase, the initialization process including the operation of defining an "impedance state table" within the microcontroller.

In order to understand the impedance state table, a simple review of the relevant contents of the hardware circuit is needed: the tunable capacitive module 42 comprises m tunable branches 421 and an impedance control circuit 442, and the impedance control circuit 442 has m microcontroller interfaces connected to m pins of the microcontroller 1. Therefore, the embedded software can control the level of m relevant pins of the microcontroller 1 to be high or low; thereby controlling the on and off of the electronic switches of the m adjustable branches 421; thereby controlling the equivalent capacitance of the tunable capacitive module 42; thereby controlling the input and output impedances of the impedance matching network 4.

M is a natural number not less than 1, and in the present embodiment, m is 3.

The steps of establishing the "impedance state table" are as follows:

(1) determining an ideal capacitance value of the tunable capacitive module 42 according to the circuit specific parameters, which is 50pF in this embodiment;

(2) listing all combinations of high and low levels of m pins of the microcontroller, wherein the total power is m of 2, and calculating the theoretical capacitance value of the adjustable capacitive module corresponding to each combination. Referring to fig. 5, considering the PIN diode as an ideal switching element, it is easy to analyze that all states of the tunable capacitive module 42 in this embodiment are shown in table 2 below:

TABLE 2

(3) In the above 2 m-th power combinations, the theoretical capacitance of the tunable capacitive module 42 may be out of range and greatly deviate from the ideal value in a state corresponding to a part of the combinations, and after the part of the combinations is deleted, the remaining part is the available combination. In this embodiment, two combinations corresponding to the serial numbers "1" and "8" are deleted to obtain 6 available combinations.

(4) Depending on the specific circuit parameters, some of the available combinations may exist, and the theoretical capacitance values of the tunable capacitive modules 42 are equal in the corresponding states, and after the redundant combinations are deleted, the remaining combinations are valid combinations. In this embodiment, after checking, the theoretical capacitance values of the tunable capacitive modules 42 in the corresponding states of the combinations are not equal, so that the effective combinations are still 6.

(5) The effective combinations are sorted according to the principle that the closer the theoretical value of the adjustable capacitive module 42 is to the ideal value, the smaller the serial number is, and J kinds of optimized combinations are obtained. In this example, J has a value of 6, and the optimized combination table is shown in table 3 below:

TABLE 3

(6) Defining a plurality of one-dimensional arrays with the length of m, wherein each element of the array takes the value of 1 or 0, 1 represents that the pin of the microcontroller outputs high level, and 0 represents that the pin of the microcontroller outputs low level. Each one-dimensional array corresponds to a high and low level combination of m relevant pins of the microcontroller; so as to correspond to a combination of on and off states of the electronic switches of the m adjustable branches 421; corresponding to a theoretical capacitance value of the tunable capacitive module 42; corresponding to a set of input and output impedance values of the impedance matching network 4. A total of J one-dimensional arrays are needed to represent all the optimized combinations obtained in step (5). A global two-dimensional constant array is established in embedded software, the number of rows is J, the number of columns is m, the number of m elements of each row corresponds to the output level of the relevant pins of the microcontroller, and for convenience of description, the two-dimensional array is called an impedance state table.

In this example, m is 3, J is 6, and "impedance state table" is written in C language as follows:

const unsigned char Table[6][3]＝\

{{1,1,0},{0,1,0},{0,0,1},{1,0,0},{1,0,1},{0,1,1}}；

and P2, the embedded software executes the label checking process as required in the working stage of the circulation mode, and the embodiment triggers the label checking by sending a communication command through the upper computer. Referring to fig. 7, the process includes the following steps in sequence:

p2_1, the following statement is executed:

signaled int TagCount ═ 0; // tag number set to 0

P2_2. execute the following statement:

unused char BUFF [200 x 10 ]; // define data area, prepare to store tag information

memset (BUFF,0,200 × 10); // BUFF data clear 0

The present embodiment stores information of one tag with 10 bytes, and the expected maximum number of tags is 200.

P2_3. execute the following statement:

the signed char Index is 0; // define local variables for setting impedance

P2_4. turn on the transmit circuit.

P2_5, looking up the Index row in the impedance state table, and setting the level of the 3 related pins of the microcontroller according to the values of the 3 elements in the row, thereby controlling the on-off of the electronic radio frequency switches of the 3 adjustable branches, and adjusting the input and output impedance of the impedance matching network.

P2_6. perform label inventory, add label information to BUFF after one label per disk, and send a Stay query instruction conforming to ISO15693 protocol to the label, and perform the following statements:

TagCount++；

in this embodiment, the tag information includes 8 bytes UID and 1 byte DSFID (data storage format identification code) of the tag, and also includes 1 byte AFI (application family identifier), which is 10 bytes in total.

P2_7, the following statement is executed:

Index++；

p2_8, checking the value of the variable Index, if reaching the row number 6 of the impedance state table, closing the transmitting circuit, ending the flow, otherwise, jumping to the step P2_5 to continue the circulation.

P3, in the working stage of the loop mode, the embedded software of the present invention executes the flow of reading and writing the tag data as needed, in this embodiment, the upper computer sends the communication command to specify the relevant parameters and trigger the flow, please refer to fig. 8, and the flow sequentially includes the following steps:

p3_1, the following statement is executed:

the signed char Index is 0; // define local variables for setting impedance

P3_2. turn on the transmit circuit.

P3_3, looking up the Index row in the impedance state table, and setting the level of the 3 related pins of the microcontroller according to the values of the 3 elements in the row, thereby controlling the on-off of the electronic radio frequency switches of the 3 adjustable branches, and adjusting the input and output impedance of the impedance matching network.

P3_4, executing label data read-write operation.

P3_5. if the reading and writing of the label data are successful, the transmitting circuit is closed, the flow is ended, otherwise, the next execution is continued.

P3_6 the following statement is executed:

Index++；

p3_7, checking the value of the variable Index, if reaching the row number 6 of the impedance state table, indicating that the operation of the flow fails, executing the operation of closing the transmitting circuit and ending the flow, otherwise, jumping to the step P3_3 to continue the circulation.

Example 2

Referring to fig. 6, the tunable capacitive module 42 of this embodiment has only 1 tunable branch 421, which includes an electronic rf switch S1 and a two-terminal branch network, where the electronic rf switch is a PIN diode and is MA4P7104-1072T of MACOM corporation, the two-terminal branch network is composed of two capacitors C4a1 and C4B1 connected in series, the electronic rf switch S1 is connected in parallel with the capacitor C4B1, and the capacitance value of the tunable branch can be changed by turning on and off the electronic rf switch. The tunable capacitive module 42 further comprises an impedance control circuit 442 having a microcontroller interface, which is capable of controlling the electronic rf switch to be turned on and off according to software, and corresponding to the two states of the impedance transforming network 4.

The workflow and software method of this embodiment is similar to that of embodiment 1, because the tunable capacitive module 42 has only one electronic switch, the process of creating the impedance state table is simple, and the final table is represented by a two-dimensional array with the row number J of 2 and the column number m of 1, and is written in C language as follows:

const unsigned char Table[2][1]＝{{0},{1}}；

regardless of the specific details of the circuit, example 2 is the simplest implementation of the invention. Since the impedance state table has only two rows, the impedance matching effect of embodiment 2 may be worse than that of embodiment 1, the accuracy of the tag inventory and the success rate of data read/write may be worse than that of embodiment 1, and the related procedure is performed slightly faster than that of embodiment 1.

The above-listed detailed description is only a specific description of a possible embodiment of the present invention, and they are not intended to limit the scope of the present invention, and equivalent embodiments or modifications made without departing from the technical spirit of the present invention should be included in the scope of the present invention.

Claims

1. An impedance self-adjusting ISO15693 label reader-writer device, characterized by comprising:

a microcontroller;

2. The impedance self-adjusting ISO15693 tag reader/writer as claimed in claim 1, wherein the circuit model of the impedance matching network is a T-type two-port network with adjustable capacitance, and the adjustable capacitance in the T-type two-port network is automatically adjusted by the microcontroller.

3. The impedance self-adjusting ISO15693 tag reader-writer device of claim 2 characterized in that the adjustable capacitance is equivalent by connecting a fixed capacitance and an adjustable capacitive module in parallel, the adjustable capacitive module comprises m adjustable branches, m is a natural number not less than 1; each adjustable branch comprises an electronic radio frequency switch and a branch two-terminal network, and the capacitance value of the adjustable branch is changed by opening and closing the electronic radio frequency switch.

4. The impedance self-adjusting ISO15693 tag reader/writer of claim 3 wherein said electronic radio frequency switch is a PIN diode or a switching circuit integrated inside a dedicated chip.

5. The impedance self-adjusting ISO15693 tag reader-writer device of claim 3 characterized in that said two-terminal branch network is composed of several passive devices connected in series and parallel, and the whole impedance is capacitive.

6. The impedance self-adjusting ISO15693 tag reader/writer as claimed in claim 3 wherein said tunable capacitive module further comprises an impedance control circuit having a microcontroller interface equal to the number of tunable branches, said electronic rf switch being software controlled to close and open.

7. The impedance self-adjusting ISO15693 tag reader of claim 6 wherein said software is embedded software that is resident within said microcontroller.

8. The method for adjusting the impedance self-adjusting ISO15693 tag reader/writer of claim 7, wherein the embedded software performs the following steps:

9. The method for adjusting the impedance self-adjusting ISO15693 tag reader/writer according to claim 8, wherein in S2, the process of performing tag inventory is performed, which comprises the following steps:

s24, opening a transmitting circuit;

s27, adding one to the variable Index;

10. The method for adjusting the impedance self-adjusting ISO15693 tag reader/writer according to claim 8, wherein in S3, the process of reading/writing the tag data is executed, comprising the following steps:

s32, opening a transmitting circuit;

s34, executing tag data read-write operation;

s36, adding one to the variable Index;