DE102011103213B4 - Method and detection device for differentiating signals of moving and stationary signal transmitters - Google Patents

Abstract

Method for differentiating signals that are emitted by signal generators, which move through a detection path in a longitudinal direction, and signals from other signal generators, wherein at least one first antenna (A1.1, A1,2, to A1.n), the first Detection area in an initial area of the detection path (D), and at least one second antenna (A2.1, A2.2, to A2.n), which has a detection area in an end area of the detection path, can be provided with the following steps: a) Defining a period of observation (B), b) Defining a time limit within the period of observation (B), which divides the period of observation (B) into a first period of time (N) and a second period of time (K), c) Determination and recording of all of a signal transmitter (Day1, Day2) of received signals within the observation period separated according to antenna (A1.1, A1.2, A2.1, A2.2,) and time segment (N, K) in which the signal was measured, d) determination the number of signals (n1.1, n1.2, n1.) N received by the first antenna (A1.1, A1.2,) in the first time segment (N) and signals (n1. 1, n1.2, n1.3) K, e) Determination of the number of signals (n2.1, n2.2, n2) received by the second antenna (A2.1, A2.2,) in the first time segment (N) .3) N, and in the second time segment (K) received signals (n2.1, n2.2, n2.3) K, f) Determination of the total number (M) of the measured signals, including M = (n1.1 + n1 .2 + ...) N + (n1.1 + n1.2 + ...) K + (n2.1 + n2.2 + ...) N + (n2.1 + n2.2 + .. .) K g) Calculation of a first interference signal coefficient (P10) h) Calculation of a second interference signal coefficient (P01) i) Calculation of a useful signal coefficient (P11) j) Definition of the signal transmitter (day 1, day 2, up to day n) as a signal transmitter moving through the detection path if: P11> P10 and P11> P01.

Description

The invention relates to a method for distinguishing between useful signals and interference signals in the wireless, data transmission, wherein the useful signals are the signals of moving through a detection path transmitters and interference signals, the signals of all other stations.

While in general electrical engineering often specific filters are used, there are applications where such filters do not work, for example, because the characteristics of the useful signals and noise is too similar.

A typical application is the RFID technology:
The RFID tags send out signals in the UHF range that are recorded and evaluated by a usually permanently installed antenna of a reader.

RFID technology is used in logistics to control product flows.

The smaller the distance is, in which the RFID tag is guided past the antenna, the lower the performance of the RFID tags can be selected. Therefore, the sensitivity of the antennas can be set lower, whereby the recording of interference signals by the antenna is already greatly minimized.

However, in practice, there is a trend to increase the acceptable distance between the RFID tag and the antenna to simplify their use, thereby increasing the likelihood that interfering signals will be transmitted from the other unwanted transmitters within the receiving range of the antenna and from the antenna being received, getting bigger.

A typical application for RFID technology is the automatic checking of the flow of goods in a forwarding hall. For this purpose, RFID antennas are attached to the individual loading gates to which the delivering and picking trucks dock, and each stored and outsourced product, the respective pallet or each individual box stacked on a pallet carries an RFID tag. Tag whose passage is to be automatically determined by the RFID gate shown by means of the antenna and transmitted to the merchandise management system.

As soon as the antenna or most of the antennas present on an RFID gate are activated-which as a rule only takes place for the duration of the charging process-there is a risk that the respective antenna will not only receive signals from signal transmitters within its detection range, but also, for example, B. due to reflections of RFID tags that are in the vicinity of the antenna, or be moved through an adjacent gate, d. H. that are not within the detection range. Radio-frequency shielding measures to prevent this are often not possible with the UHF range used here.

In particular, signals from RFID tags that are stationary in the vicinity of the antenna pose a problem in practice since their distance from the antenna is generally much lower than from other moving RFID tags which pass through adjacent RFID gates to be moved.

The antennas are usually designed so that they do not record continuously, but at fixed short time intervals, for example, 1/10 seconds.

Since the function of entire logistics systems depends on the correct operation of such an RFID system, great efforts have already been made to solve this problem, but not yet with the desired result.

From the US2007 / 0280369A1 In addition, there is known a method of eliminating the noise received by antennas intended primarily to receive signals from an RFID tag. A clear distinction in such a signal generator, which are actually moved through the RFID gate and those that are out of the way, but this is not possible.

From the US2009 / 0079565 is a localization system for RFID tags with the help of multiple antennas known. However, a special procedure for removing the interference signals is not described there.

It is therefore the object of the invention to provide a method and a detection device for differentiating signals from moving through a detection path signal generator and signals of all other signal generator, which are feasible or manufacturable with less effort and work reliably.

This object is achieved by a method according to claim 1 and a detection device according to claim 8, by which a reliable Differnzierung in useful signals and interference signals is possible. Further embodiments emerge from the subclaims.

In order to be able to differentiate between signals and to distinguish signal transmitters which are moved by a detection path from other signal transmitters, at least one first and at least one second antenna are provided. The antennas are designed so that they can receive signals that are emitted by the signal generators. The first antenna has a first detection area, the z. B. comprises an initial portion of the detection path, and the second antenna has a second detection range, the z. B. includes an end portion of the detection path. The first and second detection areas are not identical, but both areas can overlap.

For the differentiation the following steps are carried out:
A period of observation is specified, in particular a beginning and an end of a period of observation. Furthermore, a time limit is set, which lies within the observation period. Due to the time limit, the observation period is divided into a first and a second time period.

Within the period of observation, all signals received by the first and second antennas of the signal generator to be checked are detected and recorded. In this case, the signal generator identification and information which antenna has received the signal, and the time, in particular the time period in which the signal was measured, stored.

From these data, the total number n _1.1N of the signals received by the first antenna in the first period N and the total number n _{1.1K of} the signals received by the first antenna in the second period K are determined. Analogously, the total number n _{2 . 1N determines} the signals received by the second antenna in the first period N and the total number n _{2.1K of} the signals received by the second antenna in the second period K. If a plurality of first or second antennas are used, the total number of received signals n _1.1 , n _1.2 or n _2.1 , n _{2.2 is} determined separately for each first or second antenna in each time segment.

Furthermore, the sum total M of all the signals received by all antennas of the signal generator to be checked is determined by summing up the numbers of the signals received by the respective first and second antennas. M = (n1.1 + n1.2 + ...) _N + (n1.1 + n1.2 + ...) _K + (n2.1 + n2.2 + ...) _N + (n2. 1 + n2.2 + ...) _K

In a further step, noise signal coefficients and useful signal coefficients are calculated. The calculation of the coefficients is based on the fact that, depending on the movement course of the signal generator, the first and second antennas receive certain temporal signal patterns.

A first spurious signal coefficient P ₁₀ is provided to identify transducers resting near the detection area of the first antenna. Such signal transmitters which are not moved through the detection path, according to the invention as "jamming". Signals of such a first "jammer" become predominantly of the first in both the first and the second time period Receive antennas. It is therefore to be expected that the first interfering signal coefficient P ₁₀ for such a jammer is close to one. The spurious signal coefficient P _{10 is} calculated as follows:

A second interference signal coefficient P ₀₁ is provided in order to be able to identify signal transmitters which are stationary or do not move through the detection path in the vicinity of the detection region of the second antenna. These signal generators also apply according to the invention as "jammers". Signals from such a first "jammer" are received primarily by the second antennas in both the first and second time slots. It is therefore to be expected that the second interference signal coefficient P ₀₁ for such a jammer is close to 1. The spurious signal coefficient P _{01 is} calculated as follows:

A Nutzsignalkoeffizient P ₁₁ is calculated for the identification of the useful signals.

The useful signals are signals which are received by signal transmitters moving through the detection path. Depending on the direction of movement of the signal generator whose signals are received in the first period N mainly from the first or the second antenna and in the second period K of the other, ie the second or the first antenna. It is to be expected for such a signal generator that the magnitude | P ₁₁ | of the Nutzsignalkoeffizienten P _{11 is} nearly 1.

Defining the signal transmitter as a signal transmitter moving through the detection path occurs when the magnitude of the useful signal coefficient P _{11 is} greater than both interference signal coefficients, ie | P ₁₁ | > P ₁₀ and | P ₁₁ | > P ₀₁ , is.

Due to the definition described above, signal transmitters that move through the detection path (useful signal generators) are distinguished from the other signal transmitters (interference signal transmitters). In the context of the invention, noise detectors which are preferably stationary for the purposes of the invention and which are not moved through the detection path, preferably include signal transmitters which are moved.

In addition to the above distinction, it is preferable that the noise detectors which are stopped near the detection area of the first antenna are recognized as such when P ₁₀ > | P ₁₁ | and P ₁₀ > P ₀₁ .

Further, it is preferable that auto switches which are recognized near the detection area of the second antennas can be recognized as such when P ₀₁ > | P ₁₁ | and P ₀₁ > P ₁₀ .

The determination of the observation period can be done by setting its beginning and / or end by signals from separate sensors. In this case, for example, a first sensor detects when an object moves into the detection path and a second sensor when the object moves out of the detection path.

The time limit by which the observation period is divided into the first and second time periods may be chosen to be the time center of the observation period.

Alternatively, the time limit can be determined by means of a sensor unit. For this purpose, for example, a light barrier can be used, which is located at a certain point, in particular the middle, of the detection path and is interrupted by an object moving through the detection path.

In this method of determining the time limit, the start of the observation period may be defined as a time which is a certain period of time (eg four seconds) before the time limit, and as the end of the period of observation a time later than the same time period Time limit is what is only possible if the antenna are continuously active.

According to the invention, it can be provided that the useful signal coefficient P _{11 is} equal to 0 if either the first or the second antenna does not receive any signal of the signal generator to be defined in both periods. Thus, another possible false indication source of a noise signal transmitter is avoided.

In the following, the detection device according to the invention will be described.

The detection device for detecting whether or not signal transmitters move through a detection path comprises at least one first antenna a detection area, the z. B. comprises a first region of the detection path. Furthermore, the detection device comprises a second antenna with a detection range, the z. B. comprises a second portion of the detection path, wherein the first and the second region are not identical in the longitudinal direction, but both areas can overlap.

The first and second antenna can receive signals from the signal transmitters and be designed, for example, as RFID antennas.

The detection device further comprises a control unit which carries out the method according to the invention and also defines the signal transmitters as "moving through the detection path".

Preferably, the detection device comprises a sensor which is arranged in the detection path and whose activation defines the time limit. The sensor is preferably designed as a light barrier, which detects when an object is located at a certain point in the detection path. In this case, the specific location may be in an area in which the first and the second area overlap or in an area that lies between the first and second area.

Preferably, the detection device comprises sensors which detect when an object moves into and / or out of the detection path. The sensors can be designed as motion sensors or light barriers.

The signal transmitters can be embodied as RFID signal transmitters and the receivers as RFID antennas.

Furthermore, the detection device may comprise at least one RFID gate on which the receiver, the sensor unit and / or the sensors are arranged.

Embodiments according to the invention are described in more detail below by way of example. Show it:

1 : schematic embodiment of a detection device according to the invention, which is integrated in a logistics system,

2 : a schematic representation of the in 1 shown embodiment of a detection device and

3a : a schematic representation of a first receiving pattern,

3b : a schematic representation of a second receiving pattern,

3c FIG. 2 is a schematic representation of a third receiving pattern, FIG.

4a FIG. 4 is an evaluation diagram of the signals received by antennas of an embodiment of the invention. FIG.

4b : Receiving pattern of the signal generator Day 1 and

4c : Receiving pattern of the signal generator Day 2.

In the 1 is a detection device shown in a logistics system in a warehouse 7 integrated with the pallets in a truck 2 be discharged from this. Several boxes 4a . 4b are on the pallet three each loaded with a signal generator (eg Day 2), wherein the signalers are RFID tags. The detection device should read information from those signal generator, which are moved into or out of the truck.

The signals of the RFID tags can be information such. B. Type of product in the box, quantity, size, etc. included. To read the signal generator, the detection device comprises first antennas A1.1, A1.2 and second antennas A2.1 and A2.2, which are each RFID antennas and the RFID gate 1 are arranged.

The signaler Day 2 of a box on the pallet three moves along with the pallet three along a detection path D which extends from a distance beginning d1 to a distance end d2. In this case, the signal generator day 2 by a first and a second region a1, a2 of the detection path D moves. In the first area a1, the signal generator day 2 is located in the detection area of the first antenna groups, ie the antennas A1.1, A1.2 and in the second area a2 in the detection area of the second antenna groups, ie the antennas A2.1 and A2.2.

Furthermore, the first and second antennas also receive "spurious signals", i. H. Signals from z. Eg stationary signalers (eg day1, day3). The "interfering signals" also include signals received from "detectors moving through the detection path" (eg, Tag2) but received at a time when the signaler is not in the first and second areas a1, respectively , a2, d. H. the detection range of the respective antenna is located. However, this type of "jamming" signal of the moving through the detection path D signal generator day 2 are received much less than the "useful signals" of the same signal generator, if this is in the area a1 or a2.

In order to be able to distinguish useful signals from interference signals, a period of observation B is determined within which the signal generator 2 to be detected moves through the detection path D (see FIG three ). The observation period B is divided by a time limit Z into a first time period N and a second time period K.

The determination of the observation period B and the time limit Z by means of the sensors 5a . 5b and 5c is described below on the basis of 1 shown example one in the direction of movement 10 through the detection path D moving pallet three described.

Once a palette three moves to the beginning of the distance d1 of the detection path D, detects the direction to the start d1 sensor directed 5b the pallet three , Triggered by this signal, the observation period B is started.

At the RFID gate 1 is another sensor 5c , which can be configured as a light barrier or motion sensor, attached and detected when the pallet three in the area of the RFID gate 1 located. If the sensor 5c the pallet three detected, a signal is transmitted to a controller and determines a time limit Z.

The sensor 5a detected when the pallet three leaves the detection path D at the end of travel d2. This determines the end of the viewing period.

Schematic diagrams for the "optimum reception patterns" of the useful and disturbing signal coefficients P ₁₀ , P ₀₁ and P ₁₁ are given in FIGS 3a to 3c shown. For the "optimal reception patterns" of the diagrams, it was simplifiedly assumed that a TagX, TagY or TagZ is detected at most once per time segment N, K from the first or second antenna A1.1 or A2.1 and the antennas exclusively in the respective detection areas Signals from the signalers TagX, TagY and TagZ received.

In the 3a is the "optimal reception pattern" of a signal generator TagX shown, which is stationary and is in the detection range of the antenna A1.1. The signals from the signal generator TagX are received once each of the antenna A1.1 in both periods. The first Störsignalkoeffizient P ₁₀ of in 3a signal shown is TagX

The second parasitic coefficient P ₁₀ of in 3a signaler TagX shown is:

The effective signal coefficient P ₁₁ of in 3a signaler TagX shown is:

This results in the following relationship: | P _{11, TagX} | <P _{10, TagX} and | P _{11, TagX} | > P _{0,1, TagX} .

Thus, the signal generator TagX in evaluation of the reception pattern according to the 3a recorded as a "silent signal generator".

In the 3b is the "optimal reception pattern" of a signal generator TagY shown, which is stationary and is in the detection range of the antenna A2.1. The signals of the signal generator TagY are received once each time by the antenna A2.1 in both periods. The first Störsignalkoeffizient P ₁₀ of in 3b signaled TagY is:

The second parasitic coefficient P ₁₀ of in 3b signaled TagY is:

The effective signal coefficient P ₁₁ of in 3a signaled TagY is:

This results in the following relationship for the TagY: | P _{11, TagY} | > P _{10, TagY} and | P _{11, TagY} | < _{P01, TagY} .

Thus, the signal generator TagY is detected when evaluating the reception pattern as a "stationary signal generator".

In the 3b the "optimal reception pattern" of a signal generator TagZ is shown, which moves through the detection path and is in the detection range of the first antenna A1.1 in the first time period N and in the second period in the detection range of the second antenna A2.1. The signals of the signal generator TagZ are received once in each of the two time periods, namely in the first time segment N from the first antenna A1.1 and in the second period from the antenna A2.1. The first Störsignalkoeffizient P ₁₀ of in 3b Signaler TagZ shown is:

The second parasitic coefficient P ₁₀ of in 3b signaled TagY is:

The effective signal coefficient P ₁₁ of in 3a Signaler TagZ shown is:

This results in the following relationship for the TagY: | P _{11, TagZ} | > P _{10, daytime} and | P _{11, daytime} | <P _{01, dayZ} .

Thus, the signal generator TagZ is also detected when evaluating the reception pattern as "signal transmitter moving through the detection path".

After the description of the detection of signal generators based on "optimal reception patterns", the detection of the signal generators by means of real reception patterns will be described below. This is in 4a a diagram with all received signals of the signal generator Tag1 and Tag2 shown.

In the diagram, the time points at which the signals of the respective signal generator were received, and a time limit Z, which divides the observation period into a first and second time period N, K are shown. The vertical axis of the in the 4a The diagram shown corresponds to the signal strength of the received signal. However, signal strength is not used in the present method to define the Day 1, Day 2, and Day 3 signal generators.

In the diagram, the times of the received signals according to signal generator Tag1, Tag2 and Tag3 and antennas A1.1 and A2.1 are shown divided.

Hereinafter, for the signalers Tag1 and Tag2, the definition will be explained as "signal transmitters moving through the detection path" and "jamming transmitter".

First, it is checked whether the signal generator Tag1 was moved in the observation period B through the detection path D, and evaluated its signals.

As shown in Table 4b, the number n1.1 _N is the signal received from the first antenna A1.1 in the first period N 15 N1.1 and the number _K in the second time section K received signals 14 , The number n2.1 _{N of} the signals received in the first period N by the second antenna 2.1 is two and the number n2.1 _K of the signals of the same signal generator received in the second time period K is one.

The total sum of all signals is: M _day1 = n1.1 _N + n1.1 _K + n2.1 _N n2.1 _K = 15 + 14 + 2 + 1 = 32

The first interfering signal coefficient P ₁₀ is

The second interfering signal coefficient P ₀₁ is

The effective signal coefficient P ₁₁ is

The control unit recognizes that the conditions for a useful signal signal generator are not met, since | P _{11, Tag1} | <P _{10, day1} . As a result, the controller recognizes that tag 1 was not moved through the detection path in the observation period B.

Subsequently, the same check is carried out for the signal generator Tag2. The according to the diagram three The numbers of received signals in the respective time segments from the respective antennas are: n1.1 _N = 9 n1.1 _K = 1 n2.1 _N = 1 n2.1 _K = 5.

The total sum of all signals is: M _day2 = n1.1 _N + n1.1 _K + n2.1 _N n2.1 _K = 9 + 1 + 1 + 5 = 16

The first interfering signal _coefficient is R _{10, day 2}

The second interfering signal _coefficient P _{01, day 2} is

The _effective signal _coefficient P _{11, day 2} is

In the next step, the controller compares the _{payload coefficient} P _{11, day 2} with the disturbance signal _coefficients P _{10, day 2} and P _{11, day 2} . Since | P _{11, day2} | > P _{10, day 2} and | P _{11, day 2} | > P _{01, Tag2} recognizes the control that the signal generator Tag2 was moved through the detection distance D in the observation period.

LIST OF REFERENCE NUMBERS

1

RFID gate

2

truck

3

moving pallet

4a, b

carton

5a, b, c

sensor

6

loading ramp

7

storage hall

8th

The period

9

Third-range

10

movement direction

11

threshold

S1, S2, ...

signal

A1.1, A1.2, A2.1, A2.2

antennas

Day1, 2

Day, transmitter

B

The period

D

detection distance

K

period

N

period

d1

route beginning

d2

route finish

a1

first area

a2

second area

Z

time limit

n1.1, n1.2

signal

Claims (16)

Method for differentiating signals emitted by signal transmitters which move in a longitudinal direction through a detection path and signals from other signal transmitters, wherein at least one first antenna (A1.1, A1.2, to A1.n) has a first antenna Detection area in an initial region of the detection path (D), and at least one second antenna (A2.1, A2.2, A2.n), which has a detection area in an end portion of the detection path, are provided with the following steps: Defining a period of observation (B), b) setting a time limit within the observation period (B) that subdivides the observation period (B) into a first time period (N) and a second time period (K); c) detecting and recording all signals received from a signal generator (day1, day2) within the observation period separated by antenna (A1.1, A1.2, A2.1, A2.2,) and time period (N, K) in which the signal was measured, d) determination of the number of times the antenna ( A1.1, A1.2,) in the first time segment (N) received signals (n _1.1 , n _1.2, n _1. ) _N and in the second period (K) received signals (n _1.1 , n _1.2 , n _1.3 ) _K , e) determination of the number of signals received by the second antenna (A2.1, A2.2,) in the first time segment (N) (n _2.1 , n _2.2 , n _2.3 ) _N , and signals received in the second time segment (K) ( n _2.1 n _2.2 n _{2.3) K,} f) determine the total number (M) of the measured signals, comprising M = (n1.1 + n1.2 + ...) _N + (n1.1 + n1.2 + ...) _K + (n2.1 + n2.2 + ...) _N + (n2. 1 + n2.2 + ...) _K g) calculation of a first interfering signal coefficient (P ₁₀ )

h) calculation of a second interfering signal coefficient (P ₀₁ )

i) calculation of a useful signal coefficient (P ₁₁ )

j) Defining the signal generator (Day1, Day2, through Day n) as a signal transmitter moving through the detection path if: P ₁₁ > P ₁₀ and P ₁₁ > P ₀₁ . A method according to claim 1, characterized in that signal generators are detected as spurious emitting, which are closer to the detection range of the first antenna (A1.1) than at the detection range of the second antenna (A2.1), if P ₁₀ > | P ₁₁ | and P ₁₀ > P ₀₁ and Signalers are detected as spurious signals that are closer to the detection range of the second antenna (A2.1) than at the detection range of the first antenna (A1.1), in which P ₀₁ > | P ₁₁ | and P ₀₁ > P ₁₀ . Method according to one of the preceding claims, characterized in that the beginning or the end of the observation period (B) by signals of at least one separate sensor ( 5a . 5b ). Method according to claim 3, characterized in that a sensor ( 5a . 5b ) detected when an object with a signal generator, in the detection path (D) into or out of the detection path (D) is moved out. Method according to one of the preceding claims, characterized in that the temporal center of the period under consideration (B) is selected as the time limit (Z). Method according to one of the preceding claims 1 to 4, characterized in that the time limit (Z) is determined by a sensor ( 5c ) is used, which detects when an object is in the middle region of the detection path (D). A method according to claim 6, characterized in that a time is set as the beginning of the observation period (B), which is a predetermined period of time before the time limit (Z), and as the end of a time which is a predetermined period of time after the time limit (Z) , Method according to one of the preceding claims, characterized in that the useful signal coefficient (P ₁₁ ) is set to zero if (n1.1 + n1.2 + ...) _N = 0 or (n2.1 + n2.2 +. ..) _K = 0. Detection device for detecting signal transmitters moving through a detection path (D) a) at least one first antenna (A1.1, A1.2) having a detection region which comprises a first region (a1) of the detection path (D), b) at least one second antenna (A2.1, A2.2) having a detection region which comprises a second region (a2) of the detection path (D), wherein the second region (a2) is not identical to the first region (a1) , wherein the first and second antenna (A1.1, A1.2, A2.1, A2.2,) can receive signals from the signal generator, and c) a control unit, which performs a method according to any one of claims 1 to 7. Detection device according to claim 9, characterized in that a middle sensor ( 5c ) is arranged in the detection path (D), which detects the time of the time limit (Z) when a predetermined event occurs. Detection device according to one of claims 9 to 10, characterized in that the sensor ( 5c ) is a light barrier which detects when an object is located at a certain position in the detection path (D). Detection device according to one of claims 9 to 11, characterized in that the detection device sensors ( 5a . 5b ) which can detect when an object moves into and / or out of the detection path (D). Detection device according to one of claims 9 to 12, characterized in that the sensors ( 5a . 5b . 5c ) Are motion sensors or light barriers. Detection device according to one of Claims 9 to 13, characterized in that the signal transmitters are RFID signal transmitters and the antennas are RFID antennas. Detection device according to one of claims 9 to 14, characterized in that the detection device at least one RFID gate ( 1 ), on which first (A1.1, A1.2) and second antennas (A2.1, A2.2) are arranged. Detection device according to claim 15, characterized in that the detection device at least one RFID gate ( 1 ), to which a middle sensor ( 5c ) or a motion detecting sensors ( 5a . 5b ) are arranged.

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