Abstract:
An RFID security tag which changes its reflectivity after receiving an interrogation signal is provided. The RFID security tag changes its reflectivity so that it becomes transparent to RF power of the RFID reader interrogation signal once the RFID security tag responds, thereby permitting surrounding RFID security tags to absorb the interrogation signal and to respond thereto. These surrounding RFID security tags then, in turn, change their reflectivity so that RFID security tags surrounding that second set of RFID security tags can absorb the interrogation signal and can also respond thereto. In this manner, a large plurality of RFID security tags, such as those associated with merchandise loaded on a palette, can be interrogated accurately.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This utility application claims the benefit under 35 U.S.C. §119(e) of Provisional Application Ser. No. 61/249,843 filed on Oct. 8, 2009 entitled RFID REFLECTIVITY MODE POWER RATIONING and whose entire disclosure is incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention generally relates to the field of radio frequency identification (RFID) device communication protocols, and more particularly, to the management of power absorption and reflectivity of individual tags to facilitate reading of tags that are positioned close together and/or grouped in significant numbers. 
         [0004]    2. Description of Related Art 
         [0005]    RFID tags may be either backscatter or non-backscatter tags. Non-backscatter tags typically send information to readers by originating a carrier signal on which amplitude, frequency, or phase modulated data is impressed. Backscatter tags send information by modulating the reflectivity of the tag within a range that allows the tag to continue to be powered by the reader. Readers may detect such backscatter modulation a number ways, such as by sensing fluctuations in power of a resonant transmission antenna. 
         [0006]    With respect to 13 MHz RFID operation, the term used to describe RFID tags or labels is the “load modulation” of the magnetic field. However, in the UHF RFID operation (e.g., 900 MHz), the pertinent term used is the “delta radar cross section” (dRCS) or backscatter which forms the signaling mechanism. As a result, the term “reflectivity” is expressed in terms of the RCS in meter 2 . Thus, by way of example, the RCS of a ½ wavelength dipole in the 900 MHz range is approximately 0.01-0.02 m 2 . The dRCS is approximately 10-0.1% change of the RCS. 
         [0007]    Both backscatter and non-backscatter tags, especially those operating in the UHF or microwave ranges, are normally highly reflective whether or not they are actively communicating with a reader. If two tags are positioned along a line extending from the reader, the tag closer to the reader is fully illuminated by the reader. The tag further from the reader is not fully illuminated. Rather it is substantially occluded by the tag closer to the reader. Therefore the tag further from the reader receives less power than it would if the tag closer to the reader were absent. 
         [0008]    This is particularly problematic when large numbers of tags are present. The tags closer to the reader can act as a mirror, reflecting signals back to a reader, and thus casting a shadow on the tags further from the reader. This may result in a failure to read the tags in the shadow. 
         [0009]    In view of the foregoing, there still remains a need to allow security tags closest to a reader to respond to a reader&#39;s interrogation signal and then to become transparent or cloak itself to allow other security tags in the vicinity to respond. 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    A radio frequency identification (RFID) system is disclosed. The RFID system comprises: a reader for emitting an interrogation signal and for receiving response signals based thereon; and a first tag for emitting a respective response signal based upon receipt of the interrogation signal and defining a first reflectivity that casts a shadow on at least a second tag, wherein the first tag comprises circuitry that alters the first reflectivity state to a second reflectivity state that makes the first tag substantially transparent to the interrogation signal such that the interrogation signal can illuminate the second tag without physically moving either the first or second tag. 
         [0011]    A method of interrogating a group of RFID tags is disclosed. The method comprises the steps of: (a) emitting a first reader signal from a reader toward the group of RFID tags; (b) energizing a first tag having an RFID chip and tuned to a reader frequency for defining a first reflectivity state of the first tag; (c) listening to instructions within the first reader signal by the first tag to determine if the first reader signal is an initial encounter or a repeat encounter; (d) generating a reflected response signal from the first RFID tag if the first reader signal is an initial encounter; (e) temporarily altering the reflectivity of the first RFID tag to a second reflectivity state to render the first RFID tag substantially transparent to the first reader signal, thereby permitting a second tag located in a shadow of first RFID tag to receive the first reader signal, and wherein the second tag is in a first reflectivity state for receiving the first reader signal; and (f) the second tag comprising an RFID chip and generating its own reflected signal from the first reader signal; and (g) the first tag restoring itself to the first reflectivity state after temporarily altering the reflectivity. 
         [0012]    A radio frequency identification (RFID) tag is disclosed. The RFID tag comprises an antenna (e.g., a dipole antenna or a loop configuration), an RFID chip coupled to the antenna, wherein the RFID chip comprises tag reflectivity circuitry. The tag reflectivity circuitry permits the tag to become temporarily detuned from a first RFID reader signal emitted by an RFID reader once the RFID security tag has responded to the first RFID reader signal and then re-tunes the RFID tag to the RFID reader. 
         [0013]    A method of automatically altering the reflectivity of an RFID tag is disclosed, The method comprises: (a) providing an antenna coupled to an RFID chip to form the RFID tag and wherein the RFID tag is initially tuned to an RFID reader frequency, defining a first reflectivity state; (b) energizing the RFID tag upon receipt of an RFID reader signal having a frequency to which the RFID tag is tuned; (c) listening, by the RFID chip, to instructions within the RFID reader signal by to determine if the reader signal is an initial encounter or a repeat encounter; (d) generating a reflected response signal from the RFID tag if the first reader signal is an initial encounter; (e) temporarily altering the reflectivity of the RFID tag to a second reflectivity state to render the RFID tag substantially transparent to the RFID reader signal; and (f) restoring the RFID tag to the first reflectivity state. 
     
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         [0014]    The invention will be described in conjunction with the following drawings in which like reference numerals designate like elements and wherein: 
           [0015]      FIG. 1A  is a schematic view of a first embodiment of the security tag comprising a UHF or microwave RFID tag which includes two dipole antenna elements and an RFID chip that is adapted to dramatically alter the reflectivity of the tag; 
           [0016]      FIG. 1B  is a plan view of an enlarged exemplary implementation of the first embodiment shown in  FIG. 1A ; 
           [0017]      FIG. 1C  is a schematic view of a second embodiment of the security tag comprising a UHF or microwave RFID which also includes two dipole elements but wherein a pair of switches is utilized by the RFID chip to dramatically alter the reflectivity of the tag; 
           [0018]      FIG. 2A  is a schematic view of a third embodiment of the security tag comprising a low frequency (LF) or high frequency (HF) RFID tag which includes a loop antenna, an RFID chip that is adapted to dramatically alter the reflectivity of the tag, a first capacitor for tuning the tag to the operational frequency, and a second capacitor for altering the reflectivity of tag; 
           [0019]      FIG. 2B  is a schematic view of a fourth embodiment of the security tag also comprising an LF or an HF RFID tag which includes a loop antenna and an RFID chip that is adapted to dramatically alter the reflectivity of the tag; 
           [0020]      FIG. 2C  is an enlarged plan view of a fifth and most preferred embodiment of the present invention showing an RFID tag that includes a loop antenna and an RFID chip that is also adaptable to dramatically alter the reflectivity of the security tag; 
           [0021]      FIG. 2D  is a functional diagram depicting the first reflectivity state (“tuned”) of the exemplary fifth embodiment of the security tag; and 
           [0022]      FIG. 2E  is a functional diagram depicting the second reflectivity state (“detuned”) of the exemplary fifth embodiment of the security tag; 
           [0023]      FIGS. 3A-3C  together depict the operation of a system and method using the security tags of the present invention; 
           [0024]      FIG. 4  is a flow diagram of the tag tuning/detuning process  600 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    A way to address the problem of security tags reflecting the reader&#39;s interrogation signal away from surrounding security tags is to enable individual tags to conditionally alter their reflectivity dramatically. Such alteration may occur in response to a particular operational status, such as: the receipt of a certain signal or command from a reader; the completion of a transmission to the reader; or the sensing of an input or condition unrelated to the communications protocol with the reader or with other tags. 
         [0026]    The alteration can be achieved by a number of means. For example, additional impedance could be introduced in parallel or in series with tag antenna elements. Alternatively, the antenna elements can be disconnected from either tuning elements of the tag or from the RFID integrated circuit (chip). 
         [0027]    The alteration can be permanent but is preferably temporary. Temporary alteration can be achieved by an analog and/or digital timing circuit which controls the reflectivity alteration mechanism. A digital timing circuit, for example, may include a real-time clock circuit, e.g. a timer that holds the reflectivity altered for a specific number of seconds. An analog timing circuit can include a floating gate MOSFET switch (e.g., EPROM) wherein the floating gate has a useful decay period. Such can be achieved by adding a high impedance leakage path to a floating gate element that is otherwise completely isolated during non-programming periods. 
         [0028]    Furthermore, the tuned range of the tag may be determined via the use of variable capacitors, as depicted in the figures of this application. It should be understood that the term “variable capacitors” is defined broadly. Dynamically variable capacitors may be achieved by any means but are preferably implemented on integrated circuit devices. For example, an n-bit variable capacitor could be implemented in a CMOS fabrication process using independent n-switches connected to n polysilicon to polysilicon, polysilicon to field, polysilicon to metal, or metal to metal plate capacitors with values of x, x/2, x/4 . . . x/n pF respectively. Other options include, but are not limited to, simple junction capacitors, voltage-controlled variable junction capacitors, MEMS devices, or even the use of active switched-capacitor methods. It is within the broadest scope of the invention to permit the signal processing unit (SPU, as discussed below) to configure the tag capacitances “on the fly”. The use of fixed capacitors is also within the broadest scope of the invention. 
         [0029]    The invention of the present application results in an increased detection based on respective detection probability for a large tag population. 
         [0030]    As shown in  FIG. 1A , a preferred embodiment of the invention is a tag  20  which comprises two dipole antenna elements  24  and an RFID chip  22  that is adapted to dramatically alter the reflectivity of the tag. The chip contains a signal processing unit (SPU)  26  which may optionally contain any convenient RFID functions such as, but not limited to: power conditioning, rectification, and/or regulation circuitry; digital memory; program code stored in memory; a computer processor; a received data signal demodulator; and a transmitted response data modulator. By way of example only, a chip similar to the NXP G2iL series chips may serve as the RFID chip  22 . In particular, the SPU  26  could be identical to the analogous portions of a NXP G2iL chip. However, preferably the RFID chip  22  is a “high Q” chip. Thus, for instance, such a chip operating in the UHF ranges approximately 860 MHz or 950 MHz would preferably present a stray capacitance at the antenna terminals of 1 pF or less, more preferably 0.7 pF or less, and most preferably approximately 0.5 pF or less. 
         [0031]    The chip  22  also includes a variable impedance device  28 . In  FIG. 1A , the device  28  is depicted as being in parallel with the SPU  26 , but it could optionally be positioned in series between dipole antenna element  24  and the SPU  26 . The device  28  may comprise any circuitry useful to accomplishing the function of dramatic altering the reflectivity of the tag so as to allow more power from the reader to reach the other tags that are positioned further from the reader. In general, passive tags lack power pickup when they are present in a large tag population. Thus, by dramatically altering reflectivity of the tag this, in effect, reduces the extent to which the tag blocks reader signals by allowing more reader power to reach the other tags that are further from the reader. Preferably, the device  28  uses an analog and/or digital control circuit to effect the dramatic altering of the reflectivity of the tag for a limited period of time as described above. As shown in  FIG. 1A , the variable impedance device  28  is preferably triggered by a control signal  30  from the SPU  26 . 
         [0032]      FIG. 1B  depicts an actual implementation of an RFID UHF security tag using the variable impedance device  28  controlled by an SPU  26  all of which are electrically coupled to dipole antenna elements  24 . 
         [0033]      FIG. 1C  depicts another embodiment of the RFID UHF security tag which can alter its impedance. In particular, this configuration uses a pair of switches that are controlled by the SPU  26  in opposition using the control signal  30 . Therefore, when switch SW 1  is closed, the variable impedance device  28  is shorted out and when switch SW 1  is opened, switch SW 2  is closed, thereby introducing the variable impedance device  28  into the antenna circuit. 
         [0034]      FIG. 2A  illustrates some of the options for implementing embodiments of the invention.  FIG. 2  shows a low frequency (LF) or high frequency (HF) RFID tag  120  which includes: a loop antenna  124 ; an RFID chip  122 ; a first variable capacitor (C 1 )  132  for tuning the tag to the operational frequency; and a second variable capacitor (C 2 )  134  for altering the reflectivity of tag. For example, to create an HF tag, C 1  may be varied so that together C 1   132 , the loop antenna  124 , and the chip  122  together form a resonant system with a peak response at 13.56 MHz for optimum performance using the ISO 15693 protocol. The SPU  126  of chip  122  is analogous the SPU  26  of chip  22 , and control signal  130  performs the same function as control signal  30 . 
         [0035]    SW 1   128  in  FIG. 2A  is somewhat different from the variable impedance devices  28  of  FIGS. 1A-1C  in that SW 1   128  does not itself comprise the necessary impedance to effect the required alteration of reflectivity. Instead, SW 1   128  switches the impedance of the second capacitor (C 2 )  134  into or out of connection with the resonant system (of loop antenna  124 , C 1   132 , and chip  122 ) as prompted by control signal  130 . 
         [0036]      FIG. 2B  depicts another variation wherein the security tag coil W 1 /W 2  is open-circuited by the SPU  26  via the switch to remain temporarily non-reflective and then switch is closed to restore the tag&#39;s reflectivity. This configuration is most applicable in the low RF frequency regime (e.g., 13 MHz) rather than the UHF frequency bands since reflectivity of this tag is highly dependent upon current flow through the coil and the switch operates to permit current flow (i.e., when the switch is closed) or terminate current flow (i.e., when switch is open). 
         [0037]    It should be noted that the switches may be implemented in a variety of ways, MEMs microswitches or solid state switches (JFETs, MOSFETs, etc.), etc. and any other type of switch known in the art. 
         [0038]      FIG. 2C  depicts a plan view of an enlarged plan view of a fifth embodiment  420  of the security tag of the present invention. As shown, the tag  420  comprises a loop  424  and an RFID chip  22  (as discussed previously with regard to the other embodiments). It should be understood that the RFID chip  22  shown is by way of example only and that any of the other RFID chip  22  configurations can be used. The preferred design is a single loop  424  which, by way of example only, may comprise dimensions 8 mm×50 mm or may be even be circular (e.g., 10 mm diameter such that the circumference is shorter than ⅓ wavelength in air at the applied RFID reader frequency). 
         [0039]    By way of example only, the following discussion (and associated Table I) provides an explanation of the advantages of using temporary alteration of tag reflectivity based on the following scenario. The propagation of energy is in two dimensions through a set of tags with ideal half wavelength UHF dipole antennas, where the tags are arranged in rows and where the dipoles are aligned perpendicular to the direction of the propagation of the radio energy from a reader. It is assumed that all energy from the reader reaches the first row of tags. A fully resonant, tuned antenna ideally re-radiates 100% of the energy impinging upon it: 50% of the energy is reflected back toward to the reader antenna and 50% is radiated toward the next row of tags, and so on. Thus, each row will receive 50% of the energy impinging upon the prior row. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE I 
               
             
             
               
                   
               
               
                 Propagation through Rows of Ideal Tuned Resonant Tags 
               
             
          
           
               
                 % of original energy 
                 1st 
                 2nd 
                 3rd 
                 4th 
               
               
                 from the reader 
                 Row 
                 Row 
                 Row 
                 Row 
               
               
                   
               
               
                 % impinging on row 
                 100%  
                 50% 
                   25% 
                 12.50%  
               
               
                 % reflected by the row back 
                 50% 
                 25% 
                 12.50% 
                 6.25% 
               
               
                 to the reader 
               
               
                 % re-radiated to the next row 
                 50% 
                 25% 
                 12.50% 
                 6.25% 
               
               
                 further from the reader 
               
               
                 % of energy from reader not 
                  0% 
                  0% 
                    0% 
                   0% 
               
               
                 absorbed/re-radiated, and therefore 
               
               
                 propagating to the next row 
                   
               
               
                 total energy reaching the next row 
                 50% 
                 25% 
                 12.50% 
                 6.25% 
               
               
                   
               
             
          
         
       
     
         [0040]    This should now be compared to the detuned tag condition, i.e., the propagation in the same array of tags where the tag antennas are instead not tuned to the frequency of the reader. See Table II below. It is assumed that reflectivity therefore drops by 3 dB, i.e., 50%. (Simulations indicate that decreases of 3 to 4 dB in reflectivity may also be obtained in tags using, for instance, practical UHF loop antennas.) An interesting effect occurs with the detuned tags. As stated, the energy reflected back to the reader from the first row of tags drops by half, therefore to 25% of the original energy from the reader. Similarly, the amount of energy re-radiated to the next row also drops by half, to 25%. However, the remaining 50% of the original energy from the reader is not lost. It propagates uninterrupted to the second row of readers. The total energy reaching the second row is 75%, a 50% increase over the case where the tags in the row closet to the reader are tuned. The effect is more significant in rows further from the reader. For instance, the energy impinging the 4 th  row is 400% higher than it is in the case where all the tags are tuned. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE II 
               
             
             
               
                   
               
               
                 Propagation through rows of ideal detuned 
               
               
                 resonant tags (with −3 dB reflectivity) 
               
             
          
           
               
                 % of original energy 
                 1st 
                 2nd 
                 3rd 
                 4 th   
               
               
                 from the reader 
                 Row 
                 Row 
                 Row 
                 Row 
               
               
                   
               
               
                 % impinging on row 
                 100%  
                   75% 
                 56.25% 
                 42.19% 
               
               
                 % reflected by the row back 
                 25% 
                 18.75% 
                 14.06% 
                 10.55% 
               
               
                 to the reader 
               
               
                 % re-radiated to the next row 
                 25% 
                 18.75% 
                 14.06% 
                 10.55% 
               
               
                 further from the reader 
               
               
                 % of energy from reader not 
                 50% 
                  37.5% 
                 28.13% 
                 21.09% 
               
               
                 absorbed/re-radiated, and therefore 
               
               
                 propagating to the next row 
                   
               
               
                 total energy reaching the next row 
                 75% 
                 56.25% 
                 42.19% 
                 31.64% 
               
               
                   
               
             
          
         
       
     
         [0041]    In this much simplified illustration, it should be emphasized that non-ideal factors such as power consumption by the tags, multiple reflections between rows, phase effects, etc., have been neglected. Nonetheless, the principle of the advantage of selectively detuning a tag nearer the reader for purposes of enabling propagation of reader energy to a tag further from the reader along a pathway through the detuned tag is readily appreciated. 
         [0042]      FIG. 2D  depicts the first reflectivity state of the security tag  420  when the tag  420  is tuned to the frequency of the RFID reader  202 . In particular, with the tag  420  “tuned,” the tag  420  forms an effective reflector, indicated by the dotted line  421  (also referred to as the radar cross section, RCS), of the incoming reader signal power  204  by generating a reflected signal  426 . Thus, during this “tuned” state, a reduced reader signal power  204  is making its way past the security tag  420 . However, as shown in  FIG. 2E , once the tag  420  detunes itself (as also discussed previously with regard to the other embodiments), the tag  420  becomes substantially “transparent,” by permitting the incoming signal  204  to “pass through” the tag  420  and impinge on the tags  420 A- 420 C located “in the shadow”  11  of the tag  420  (e.g., behind tag  420 ). The phrase “in the shadow of the tag” is meant to describe the relative position of at least two security tags where the presence of one tag effectively hides the other tag from receiving a reader signal  204 . Thus, the only way to permit the other tag to receive the reader signal  204 , other than physically displacing the tags, is to make the tag “creating the shadow” substantially transparent. It should be noted that there is some residual reflection  205  from the detuned tag  20  ( FIG. 2E ) due to the presence of the tag&#39;s metal loop  424  but the effect is that the overall tag  420  is rendered effectively transparent (hence the phrase “substantially transparent”). 
         [0043]    By way of example only, there is shown in  FIGS. 3A-3C  a system and method  500  for utilizing the security tags of the present invention therein. In particular, in  FIG. 3A , there is shown an RFID reader  202  (e.g., 915 MHz) and a target box or pallet  10  containing a plurality of items each having a corresponding security tag ST of the present invention attached thereto. It should be noted that the security tags ST can be any of the security tags  20 - 420  discussed above. As shown in  FIG. 3A , an interrogation signal  204  of the corresponding RF frequency is emitted by the RFID reader  202 . When the first column of security tags ST absorbs a portion of the interrogation signal  204 , each security tag ST emits its corresponding data D 1 -D 4  back to the reader  202 . In accordance with the RFID reflectivity operation discussed above, each security tag ST in the first column then changes its impedance to reflect a reduced portion of the interrogation signal  204 ; thus, the tag temporarily changes its reflectivity from a first reflectivity state to a second reflectivity state that makes the tag appear “substantially transparent” to the reader interrogation signal  204 , which continues onto the next column, as shown in  FIG. 3B . The second column of the security tags ST, then reflects a portion of the interrogation signal  204  and to form their corresponding signals D 5 -D 8  back to the reader  204 ; these security tags ST in the second column then change their impedances to reflect a reduced portion of the interrogation signal  204 . Next, the third column of security tags ST then reflect a portion of the interrogation signal  204  and to form their corresponding signals D 9 -D 12 . After a predetermined period, each security tag ST then restores its original impedance in preparation for the next interrogation signal. Should a security tag that has already responded to the interrogation signal  204  restore its original impedance prematurely, e.g., while the interrogation signal  204  is still interrogating other security tags ST in other columns, that particular security tag ST will recognize the particular interrogation signal  204  and alter its impedance to become substantially transparent again. 
         [0044]    The RFID chip  22  comprises, among other things, non-volatile memory such that when power is removed (e.g., the RFID reader  202  is silent), the RFID chip  22  forms a state machine that knows its prior response history. 
         [0045]      FIG. 4  is an exemplary flow diagram of the operation of the tag tuning/detuning process  600 . The tag&#39;s initial state  602  is in its tuned condition so that when the original RFID reader signal  204  impinges on the tag  20 - 420 , the tag is energized (step  604 ) and then the RFID chip  22  can then listen to the instructions from the RFID reader  202  (step  606 ). At step  608 , the RFID chip  22  then determines whether it has already responded to the instructions from the RFID reader  202  or not. If this is a first time encounter with respect to these instructions, the RFID chip  22  moves to step  610  and reflects the response signal  426 . The RFID chip  22  then moves to the second reflectivity state by detuning the tag for a predetermined period of time at step  612 . The RFID chip  22  then utilizes its remaining power to monitor the time elapsed during the predetermined period in step  614 . If the period has not elapsed, the RFID chip  22  continues to monitor; if the period has expired, in step  616 , the RFID chip  22  uses whatever remaining power there is to retune the tag into the first reflectivity state. This re-energizes the tag so that it can move to step  606  and listen to the RFID reader instructions. If the RFID chip  22  determines that this is the previous set of instructions that it has already responded to, then the RFID chip  22  moves to step  612  and detunes again; if, on the other hand, these are new RFID reader instructions, the RFID chip  22  moves to step  610  and reflects a response signal  426  and then moves to step  612 , as discussed previously. 
         [0046]    It should be noted that process  600  is by way of example only and that other processes can be used. In any of the processes, the completion of the second reflectivity state must always place the security tag  20 - 420  into the first reflectivity state so that the security tag can be re-energized. Thus, if step  612  involves detuning the tag until all power runs out, the default mechanism in the RFID chip  22  is to power off such that the tag  20 - 420  is placed into the tuned or first reflectivity state. 
         [0047]    It should be also noted that the predetermined period of time can be defined in any number of ways. If the physical layout of items having the tags associated therewith are known, the predetermine period can be the time it takes the reader to complete communications with all of the tags in the reader field. 
         [0048]    For wide adaptability of the security tag  20 - 420 , it may be desirable to have the tags  20 - 420  detune to a frequency that RFID readers in other jurisdictions are tuned (e.g., 860 MHz). That way, the RFID chip  22  in the tags  20 - 420  can be programmed to simply reverse the tune/detune process from the other jurisdiction. 
         [0049]    While the invention has been described in detail and with reference to specific examples thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.