KR20070022695A - Adaptable bandwidth rfid tags - Google Patents

Abstract

Provided are an RFID tag, a tag circuit, and a method for adapting a receive bandwidth. The tag has a decoder that decodes the first received wireless signal in accordance with the reception bandwidth setting. The tag also has a selector switch that transitions to a different setting, such as by switching using different filters. The received second signal is then decoded according to the new receive bandwidth setting.

RFID Tag, Receive Bandwidth, Decoder, Selector Switch, Receive Bandwidth Regulator

Description

Adaptive Bandwidth RDF Tag {ADAPTABLE BANDWIDTH RFID TAGS}

The present invention relates to a radio frequency identification tag, and more particularly to a tag that can adapt the reception bandwidth.

Radio Frequency Identification (RFID) tags can be used in a number of ways to locate the object to which the tag is attached and to identify the object. RFID tags are particularly useful in product-related and service-related industries that track the majority of objects being processed, cataloged, or handled. In such a case, the RFID tag is usually attached to an individual item or to its package.

In principle, RFID techniques involve sending signals to one or more RFID tags using a device called an RFID reader. Interrogation is performed by a reader that transmits radio frequency (RF) waves. The tag that detects the interrogation RF wave responds by sending another RF wave, a process known as backscatter. Backscattering may occur in a variety of ways. The response may also encode the number stored inside the tag. The response, if available, is decoded by the reader, thereby identifying, counting, or otherwise interacting with the related item. The number may indicate a serial number, price, date, destination, other attribute (s), any combination of attributes, and the like.

RFID tags typically include an antenna system, a radio section, a logic section and a memory. Advances in semiconductor technology have significantly miniaturized the electronics such that the RFID tag can generate backscattering while being powered only by the RF signal received by the RFID tag, allowing a plurality of RFID tags to operate without a battery.

The challenge in the operation of an RFID system arises from interference when other RF signals are also transmitted in the vicinity at the same time. Interfering RF signals may originate from other RFID readers and also from nearby wireless devices such as cellular telephones, personal digital assistants (PDAs), and the like. In such a case, the RFID tag cannot reliably detect the interrogation RF wave or analyze the command.

When the RFID reader detects that there is interference, it may lower the data rate of the transmission. This will allow the RFID receiving the transmission to more firmly analyze the transmission.

However, the challenge is that the RFID tag may not know the changed data rate of transmission by the RFID reader. Thus, the RFID tag may not be able to distinguish the interrogating RF wave from interfering RF signals. In such a case, the RFID tag may not be able to properly parse the query RF wave for the response.

<Overview of invention>

The present invention is an improvement over the prior art. In short, the present invention provides an RFID tag, a tag circuit, and a method for adapting a reception bandwidth. The tag according to the invention comprises a decoder for decoding the first received radio signal in accordance with the reception bandwidth setting. The tag also has a selector switch for transitioning to different settings, such as by switching to the use of different filters. The received second signal is then decoded according to the new receive bandwidth setting.

The present invention provides the advantage that the RFID tag receives data at the bandwidth most suitable for incoming transmission and the environment.

Other features and advantages other than these and advantages of the present invention will be better understood from the present specification, including the following detailed description and the accompanying drawings.

The present invention will become more apparent from the following detailed description with reference to the accompanying drawings.

1 is a block diagram of an RFID system in accordance with the present invention.

2A, 2B, and 2C show waveforms of the interrogation RF wave of FIG. 1 at three different data rates.

3 is a block diagram illustrating a component group of the RFID tag of FIG. 1 in accordance with an embodiment of the present invention.

4 is a conceptual state diagram illustrating the ability to control a reception bandwidth setting for decoding a wireless signal received at the RFID tag of FIG. 3 in accordance with the present invention.

FIG. 5 is a circuit schematic diagram of a portion of a first circuit for implementing the selection of FIG. 4 in accordance with the present invention. FIG.

6 is a hybrid block diagram and a circuit schematic of a second circuit for implementing the selection of FIG. 4 in accordance with the present invention.

FIG. 7A is a block diagram illustrating a third circuit for implementing the selection of FIG. 4. FIG.

7B is a block diagram illustrating an alternative embodiment of the circuit of FIG. 7A.

8 is a flowchart illustrating a method according to an embodiment of the present invention.

9A is an intensity-frequency diagram illustrating the power spectral density of two RF signals arriving at the antenna of the RFID tag of FIG.

FIG. 9B is an intensity-frequency diagram illustrating the power spectral density of the interference signal of FIG. 9A when the interference signal of FIG. 9A appears from the envelope detector of FIG. 3.

9C is an intensity-frequency diagram illustrating the power spectral density of a signal emerging from the filter (s) block of FIG. 3 in response to the signal of FIG. 9B in an event where the first filter bandwidth selection is implemented.

FIG. 9D is an intensity-frequency diagram illustrating the power spectral density of the signal emerging from the filter (s) block of FIG. 3 in response to the signal of FIG. 9B in the event that the second filter bandwidth selection is implemented.

9E is an intensity-frequency diagram illustrating the power spectral density of a signal emerging from the filter (s) block of FIG. 3 in response to the signal of FIG. 9B in an event where a third filter bandwidth selection is implemented.

The present invention is now described. Although the present invention has been disclosed in its preferred form, the specific embodiments of the invention disclosed in this specification and shown in the drawings are not to be considered in a limiting sense. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Indeed, it will be readily apparent in light of this description that the present invention may be modified in various ways. In particular, the present invention may be implemented as a device, a method, software, or the like.

Thus, the present invention may take the form of a full hardware embodiment, a full software embodiment, or an embodiment combining software and hardware aspects. Therefore, the following detailed description is not to be interpreted in a limiting sense.

In addition, the present invention can be implemented in an RFID tag that can operate with or without a battery.

As mentioned above, the present invention provides a tag circuit and a method for adapting the reception bandwidth, such as by switching to the use of different filters. The present invention is now described in more detail.

1 is a diagram of an RFID system 100 in accordance with the present invention. The RFID reader 110 transmits an interrogation RF wave that may be continuous. The two RF signals 112 and 113 are shown as discontinuous to indicate processing that may be different from one another, but this is merely illustrative and they may actually be part of the same continuous signal. The RFID tag 120 near the RFID reader 110 may detect a query RF wave and generate backscatter (not shown). The RFID reader 110 detects and interprets any received backscatter.

Nearby, there is also interference shown here in the form of RF waves 122 from other other sources (not shown). The RF wave 122 arrives at the tag 120 simultaneously with the scheduled query signal 112. The RF wave 122 may not have the same carrier frequency as the interrogation signal 112 but may have a carrier frequency close enough to generate a beat frequency with that frequency. As can be seen below, the bit frequency then interferes with the reception.

2A, 2B, and 2C show sample waveforms 212-A, 212-B, 212-C of the interrogative RF signal 112 of FIG. 1, respectively, at three different data rates. Sample waveforms 212-A, 212-B, and 212-C start at four symbols for zero, followed by a predefined symbol called "violation", followed by another zero symbol. It is a waveform of a preamble. In all cases, the first low pulse has the same duration, which is at least 12.5 ms, which can be perceived and measured at time T1. However, the remaining transitions occur at different data rates. For example, waveforms 212-A, 212-B, 212-C may be generated at 40, 80, and 160 kbps, respectively.

3 is a block diagram illustrating a component group 320 of the RFID tag 120 of FIG. 1 in accordance with an embodiment of the present invention. It will be appreciated that group 320 is part of the demodulator of tag 120, and group 320 has additional components. Blocks of group 320 may be implemented in any manner known in the art, such as analog or digital components, microprocessors, application specific semiconductors (ASICs), and the like.

The antenna signal AS is generated from the antenna when the antenna (not shown) receives the signal 112 and the later signal 113. Antenna signal AS is input into envelope detector block 340, which then outputs envelope signal ES.

The filter (s) block 350 receives the envelope signal ES and in response outputs the filtered signal FS. Block 350 includes one or more filters, and the bandwidth of the filters can be made adjustable according to arrow 334.

Decoder 360 includes a single decoder 360 or group of decoders, as can be seen below. Decoder 360 receives the analog filtered signal FS and outputs a digitally decoded signal DS for subsequent processing. The reception bandwidth setting can be made controllable according to arrow 335. Further possible embodiments of the decoder 360 are described later with reference to FIG. 7.

Group 320 also includes a selector switch 333. The selector switch 333 controls the reception bandwidth setting of the group 320, as described below with reference to FIG. 4. Control can be done by operating in different blocks in accordance with the present invention. In the embodiment of FIG. 3, control is shown to operate at filter (s) block 350 via arrow 334, or at block 360 via arrow 335. If the setting is adjusted after signal 112 is decoded, a later received signal, such as signal 113, will be decoded differently than signal 112.

In some embodiments of the invention, selector switch 333 is adapted to adjust the setting in response to the decoded signal DS. In one embodiment, the decoder 360 generates a trigger signal TS from the decoded signal DS, and the selector switch 333 is adapted to be controlled from the trigger signal TS. Naturally, whether the trigger signal TS is provided, and its exact function depends on the specific embodiment. In some cases, the trigger signal TS is generated only when there is a decision to transition from one bandwidth to another.

In the embodiment of FIG. 3, group 320 also includes a receive bandwidth adjuster 380. The bandwidth adjuster 380 is also adapted to control the selector switch 333 in response to the trigger signal TS. The bandwidth adjuster 380 receives the trigger signal TS and generates a control signal CS for controlling the selector switch 333. In some embodiments, bandwidth adjuster 380 determines which setting to switch to. In another embodiment, bandwidth adjuster 380 also determines whether to transition to a different setting.

In some embodiments of the invention, the decoder 360 is adapted to compare the decoded signal DS to the preset code 768. In that case, the trigger signal TS is generated in response to the comparison. The preset code may be part of the preamble as shown in FIGS. 2A, 2B and 2C.

Comparison and the results can be implemented in several ways in accordance with the present invention. In many embodiments, the selector switch transitions to a new setting if the decoded signal does not match the preset code. For example, a tag may be waiting for a preamble and may try different settings while not receiving it. In some of such embodiments, the setting is changed if the decoded signal does not match the preset code after the preset time limit. The deadline may be, for example, two preamble durations or something equivalent. If the setting does not provide good results, other settings may be tried with a preferably lower bandwidth.

In many other embodiments, the selector switch transitions to a new setting once the decoded signal matches the preset code. For example, referring to Figures 2A, 2B, 2C, at time T1, if the first low pulse of the preamble was received at any of the three frequencies, the setting is skipped by default to the setting with the highest bandwidth. You can, and backtrack to the lower bandwidth there when trying to match the reader. In some embodiments, a tag may initially begin with the lowest bandwidth setting, transition to the highest bandwidth, and then end backtracking to the lowest bandwidth.

In some embodiments, the decoder 360 or other component of the tag 120 may determine the active data rate of the signal 112 that the reader 110 is transmitting. In a preferred embodiment, decoder 360 encodes the active data rate in the trigger signal for use by regulator 380.

The active data rate can be determined in any number of ways. In one embodiment, the bit period is determined between consecutively received symbols of the decoded first signal. For example, referring again to FIGS. 2A, 2B, 2C, the bit periods BP1, BP2, BP3 may be measured at each waveform 212-A, 212-B, 212-C, and then each The waveform can yield an active data rate. In other embodiments, different preambles may be previously associated with different data rates by convention. In such a case, the active data rate is determined from the identified preamble. In another embodiment of the present invention, the DATA RATE command is implemented by convention and signals 112 at the first data rate to warn of imminent changes to transmission at the second data rate for the next signal 113. Can be used during the transmission. In such a case, the preset code is a DATA RATE command and the decoded first signal is a DATA RATE command with an associated data rate command. In such a case, the active data rate is determined from the instruction.

All of these functions of the decoder 360 may also be performed equivalently in a distributed fashion, such as by other components of the tag 120.

4 is a conceptual state diagram 400 for illustrating reception bandwidth selection in accordance with the present invention. State diagram 400 operates inferred from an electrical concept.

State diagram 400 includes blocks 451,..., 459 representing different receive bandwidth selections for filtering actions performed in group 320. In one embodiment of the present invention, as many bandwidth selections are provided as are available data rates, but are not necessary to practice the present invention. In another embodiment, state diagram 400 provides for continuously adjustable bandwidth selection over at least one range.

State diagram 400 also includes a concept selector switch 433. The concept switch 433 controls which of the blocks 451,... 459 sets the receive bandwidth selection of the group 320. The circuit may transition from one bandwidth to another by a switch 433 that changes any block that the block points to.

The conceptual state diagram of FIG. 4 may be implemented in a number of ways. Examples are described immediately below.

In one group of embodiments, where a selector switch adjusts its bandwidth, a single filter may be used. The filter can be passive or active. The bandwidth can be continuously adjustable over a range or can be adjusted with discrete values. The latter can be implemented by switching on and off additional components, as in the example below.

FIG. 5 is a circuit schematic of the first filter circuit 520 that is part of the filter (s) block 350 of the group 320 in FIG. 3. The circuit 520 implements a filter that receives the envelope signal ES and outputs the filtered signal FS. The two control signals CS1 and CS2 operate selector switches 533A and 533B, respectively, to switch on and switch off additional resistors to the already existing resistors. Therefore, the control signals CS1 and CS2 adjust the bandwidth of the filter circuit 520.

In addition to the example of FIG. 5, the filter may include at least two of resistors, capacitance, and inductance, or may include all three. At least one of the resistors, capacitances and inductances included can be switched on and off. In another embodiment, the filter includes a resonator such as made of a cavity, crystal, or the like. In yet another embodiment, the filter may consist of a switch and a capacitor switched at variable speeds. In other embodiments, Surface Acoustic Wave (SAW) implementations may be used and the like.

In another group of embodiments, multiple filters may be placed in the possible paths of the received signal. The selector switch can route the received first and second signals through different ones of the paths.

FIG. 6 is a hybrid block diagram and circuit schematic diagram of a second filter circuit 620 that is a replacement for filter (s) block 350 of group 320 in FIG. 3. The circuit 620 implements a filter that receives the envelope signal ES and outputs the filtered signal FS. Multiple filters 651, 652, 653 are disposed within the possible paths of envelope signal ES, and selector switches 633A, 633B transition the circuit to different bandwidths by routing the envelope signal ES to be filtered through different paths. Since the selector switches 633A and 633B operate according to the control signals CSA and CSB, the selector switches 633A and 633B control the overall bandwidth of the filter circuit 620.

In another group of embodiments, filtering occurs according to different bandwidths to produce differently filtered signals, and then the selector switch selects one of the filtered signals. Such an embodiment is described immediately below.

FIG. 7A is a block diagram 720-illustrating a filter (s) block 750 and a decoder 760-A similar to the filter (s) block 350 and decoder 360 of the group 320 in FIG. 3. A) Filter (s) block 750 includes individual filters 751, 752, 753 of different bandwidths. These filters 751, 752, 753 receive all of the envelope signals ES and in response output respective individually filtered signals FS1, FS2, FS3. The selector switch 734 is controlled by the control signal CS and selects the individual filtered signal to be the filtered signal FS from the individual filtered signals FS1, FS2, FS3. In another embodiment, the selector switch 734 is not provided separately from the filter (s) block 750, but is provided as part of it. In all such embodiments, control signal CS is directed to selector switch 733.

In the embodiment of FIG. 7, it will be appreciated that the selector switch 734 is disposed behind the filters 751, 752, 753. It is desirable for practical embodiments, as it allows some additional settling time for all filters 751, 752, 753, and allows more reliable filtered signals FS1, FS2, FS3 to be selected from this. However, it is also an equivalent embodiment of the present invention to have a selector switch 734 disposed in front of filters 751, 752, 753.

In the embodiment of FIG. 7A, the decoder 760 -A includes a detection decision maker 764 -A that generates a digital signal MS from the filtered signal FS. The detection decision maker 764 -A preferably includes a comparator that generates a digital signal having high (H) and low (L) values from the analog signal. Decoder 760-A also includes an interpreter 766-A for outputting the decoded signal DS from the digital signal MS.

FIG. 7B is a block diagram 720-illustrating a filter (s) block 750 and a decoder 760 -B similar to the filter (s) block 350 and decoder 360 of the group 320 in FIG. 3. B). In practice, filter (s) block 750 is the same as shown in group 720-A and outputs individual filter signals FS1, FS2, FS3.

In the embodiment of FIG. 7B, the decoder 760-B includes a group 764-B of detection decision makers 761, 762, 763, each of which is similar to the detection decision maker 764 of FIG. 7A. Is made. The detection decision makers 761, 762, 763 generate the respective digital signals MS1, MS2, MS3 from the outputted individual filter signals FS1, FS2, FS3.

The selector switch 735 is positioned to select a digital signal to be selected to be the signal MS among the digital signals MS1, MS2, MS3. In another embodiment, the selector switch 735 is not provided separately from block 764 -B, but is provided as part of it.

Decoder 760-B also includes an interpreter 766-A similar to that described in group 720-A. The interpreter 766-A outputs the decoded signal DS from the digital signal MS. In other embodiments, three interpreters are provided, one output is selected, and so forth.

8 is a flowchart 800 illustrating a method according to one embodiment of the present invention. The method of flowchart 800 includes, but is not limited to, RFID tags 120, which are RFID tags including component groups 320, 520, 620, 720-A, and 720-B. It can be carried out by.

In block 810, a receive bandwidth setting is provided. This can be implemented as a setting from the factory or as a setting programmed to occur at power up. The settings provided in this block remain at their current settings unless and until they change. The remaining blocks of flowchart 800 can be executed at this setting or at other settings.

At a next block 820, a signal is received. This may be an RF radio signal, such as from a reader, or a signal generated in response to receiving an RF radio signal at different parts of the circuit.

In a next block 830, the received signal is filtered. This may occur after the envelope signal is extracted from the received signal. It may occur only once depending on the current reception bandwidth setting or multiple times as one of the signals to be selected later.

In a next block 840, the signal is decoded according to the current receive bandwidth setting. This may occur after the signal is filtered. As above, decoding may occur only once from the filter and / or the selected signal, depending on the current reception bandwidth setting. Alternatively, decoding may be performed on a number of filtered signals, and then selecting one of them may be performed according to the current reception bandwidth setting, either before or after interpretation.

In a next block 850, it is determined whether to transition to a new receive bandwidth setting, such as one of the settings shown in FIG. 4. In some embodiments, the determination is made at block 840 according to the decoded signal at the current setting. In some embodiments, the transition is performed in response to the decoded signal.

The determination can be made by comparing the decoded signal with a preset code, such as code 768 in FIGS. 7A and 7B. In some embodiments, code 768 is at least a portion of a preamble. Then, determining whether to transition to the second setting depends on the comparison.

If at block 850 it is determined not to transition, execution returns to block 820. Then, another signal or part of the signal is received and processed at the same current setting without transitioning as above.

In some embodiments, in the comparison of block 850, it is determined that the decoded signal transitions if it does not match the preset code. That is, the RFID tag will try to set a new bandwidth without recognizing what it received at the current setting. In some of such embodiments, the tag will listen (or “will stay”) for the current setting for a predetermined wait time before transitioning. Such latency may be any suitable time, such as two preamble durations.

In another embodiment, in a comparison of block 850, it is determined to transition if the decoded signal matches the preset code. For example, referring to Figures 2A, 2B, 2C, at time T1, the matching preset code is the first of the plurality of preambles. From there, it can be determined to transition anyway.

If it is determined at block 850 to transition, then at optional next block 860, it is determined which new setting to transition to. In some cases, multiple receive bandwidth settings are provided, each corresponding to a different receive bandwidth. In some of these cases, the bandwidth is continuous. The choice is based on bandwidth.

In some embodiments, the new setting is the setting with the largest bandwidth. For example, referring to Figures 2A, 2B, 2C, listening to the time T1 to know the start of the preamble may be done at a fixed bandwidth, such as about 50 Hz. Then, upon detection, the new setting may be the setting with the highest bandwidth by default.

In another embodiment, the new setting depends on the current setting. For example, the new setting may be a setting that gradually reduces bandwidth. If a discrete bandwidth option is provided, it decreases to the next smaller option and so on. In that case, the RFID tag can sequentially reduce the bandwidth until the lowest value is reached. In some of such embodiments, the RFID tag may start at the highest value.

In another embodiment, the active data rate of the transmission is determined from the decoded signal. Then, although not necessarily a sequential attempt, the new setting can be a setting with the bandwidth that best fits the active data rate.

The active data rate of the transmission can be determined in several ways. In one embodiment, the active data rate is determined by determining the bit period between successive received symbols of the decoded signal. In another embodiment, the decoded signal is a preamble having a pre-associated data rate, and the active data rate is determined from the pre-related data rate. In another embodiment, the decoded first signal is a DATA RATE command followed by an associated data rate command. The DATA RATE command can be agreed by agreement. The active data rate is determined from the command.

In optional next block 870, there is a transition to the next decoded setting. The transition can be accomplished in several ways, such as by adjusting the bandwidth of the filter or by changing the path of the received signal. The signal path can include a first filter and the switching can route the following signal through a second filter or the like.

Execution then returns to block 820. Then, as above, another signal or part of the signal is received, processed at the new setting, and so on.

The effects and advantages of switching receive bandwidth settings are now described.

9A is an intensity-frequency diagram illustrating the power spectral densities of two RF signals arriving at the antenna of the RFID tag in FIG. 1 simultaneously. Signal 112 has carrier S112, with the remainder of this carrier signal being distributed around it, and signal 122 having carrier S122. To simplify this description, the signal 122 need not be, but is assumed to have only a carrier wave. These signals together form the antenna signal AS.

FIG. 9B is an intensity-frequency plot showing the power spectral density of the interference signal of FIG. 9A when the interference signal of FIG. 9A appears from the envelope detector of FIG. 3. It will be appreciated that for reasons of attenuation, arbitrary amplification, etc., the drawings are not necessarily drawn to scale along the vertical axis. The signal 122 remains as a carrier S112 and its surroundings, and is also repeated around the DC frequency carrier S0. Carrier S122 also appears. In addition, the interference also generates the difference bit frequency SD1 by subtraction and the sum bit frequency SS1 by the addition of the carriers S112 and S122. Moreover, each frequency of the difference bit frequency SD1 and the sum bit frequency SS1 has a signal around it. All these signals form the envelope signal ES.

The filtering of the signal is advantageously performed around the DC frequency carrier SO. This is desirable because only the low pass filter needs to be used instead of the band pass filter. Corresponding to the continuous setting of decreasing bandwidth, three choices are presented below.

FIG. 9C is an intensity-frequency plot showing the power spectral density of the signal emerging from the filter (s) block of FIG. 3 in response to the signal of FIG. 9B. First filter bandwidth selection 951 is implemented. It will be appreciated that the filtered signal FS1 includes the desired component FS0, but also includes the difference bit frequency SD1 and the signal around it. It will also be appreciated that all other signals have been rejected.

9D is an intensity-frequency plot showing the power spectral density of the signal emerging from the filter (s) block of FIG. 3 in response to the signal of FIG. 9B. Second filter bandwidth selection 952 is implemented. It will be appreciated that the filtered signal FS2 is much more successful than the filtered signal FS1 in that part of the signal around the difference bit frequency SD1 is also rejected.

FIG. 9E is an intensity-frequency plot showing the power spectral density of the signal emerging from the filter (s) block of FIG. 3 in response to the signal of FIG. 9B. Third filter bandwidth selection 953 is implemented. It will be appreciated that the filtered signal FS3 is much more successful than the filtered signal FS2 in that all signals around the difference bit frequency SD1 are rejected.

Many details are set forth in this specification, which may be referred to in its entirety, to provide a more complete understanding of the invention. In other instances, well known features have not been described in detail in order not to unnecessarily obscure the present invention.

The invention includes combinations and subcombinations of the various components, features, functions, and / or features disclosed herein. The following claims set forth certain combinations and subcombinations that are considered new and unclear. Additional claims for other combinations and subcombinations of features, functions, components, and / or features may appear in this specification or related documents.

Claims (62)

RFID tag, A decoder for decoding the first received wireless signal in accordance with the reception bandwidth setting, and Then a selector switch for transitioning to a second different setting to control decoding of the second received second signal by the decoder as well RFID tag comprising a. The method of claim 1, Further includes a filter, And the selector switch adjusts the bandwidth of the filter. The method of claim 2, And said filter is an active filter. The method of claim 2, And said filter is a passive filter. The method of claim 2, And the bandwidth is continuously adjustable over a range. The method of claim 2, The filter comprises at least two of resistance, capacitance and inductance, RFID tag wherein at least one of resistance, capacitance and inductance can be switched on and off. The method of claim 2, The filter includes a capacitor and a switch switched at a variable speed. The method of claim 2, And the filter includes a resonator. The method of claim 1, Further comprising a plurality of filters in possible paths of the received signal, And the selector switch routes the received first and second signals through different ones of the paths. The method of claim 1, The decoder is adapted to generate a decoded signal in response to the decoding of the first signal, And the selector switch is adapted to transition to a different setting in response to the first decoded signal. The method of claim 10, The decoder is further adapted to generate a trigger signal from the decoded signal, And a filter bandwidth adjuster adapted to control the selector switch in response to the trigger signal. The method of claim 11, The decoder is further adapted to compare the decoded signal to a preset code and to generate a trigger signal in response to the comparison. The method of claim 12, And the preset code is at least part of a preamble. The method of claim 13, And the selector switch is adapted to transition to a different setting if the decoded signal matches the preset code. The method of claim 12, And the selector switch is adapted to transition to a different setting if the decoded signal does not match the preset code. The method of claim 12, The selector switch is adapted to transition to a different setting if the decoded signal does not match the preset code after a preset time limit. The method of claim 16, The preset deadline is two preamble duration RFID tag. The method of claim 12, The decoder further determines an active data rate of the first signal, RFID tag that encodes an active data rate in the trigger signal. The method of claim 18, And the active data rate is determined by determining a bit period between successive received symbols of the decoded first signal. The method of claim 18, The decoded first signal is a preamble having a pre-associated data rate, And the active data rate is determined from the pre-related data rate. The method of claim 18, The preset code is a DATA RATE command, The decoded first signal is a DATA RATE command with an associated data rate command, The active data rate is determined from the command. As a device, Means for receiving first and second wireless signals, Means for decoding the first signal in accordance with a first reception bandwidth setting, and decoding the second signal in accordance with a second reception bandwidth setting that is different from the first setting, and Means for transitioning from the first setting to the second setting Device comprising a. The method of claim 22, And the transition is performed in response to the first decoded signal. The method of claim 23, wherein Means for comparing the decoded first signal with a preset code, and Means for determining whether to transition to the second setting depending on the comparison The device further comprising. The method of claim 24, And if determined not to transition, the second signal is decoded according to the first setting instead of the second setting. The method of claim 24, And the preset code is at least part of a preamble. The method of claim 24, The device is determined to transition if the decoded first signal does not match the preset code. The method of claim 27, And if the first decoded signal does not conform to the preset code after a preset wait time, it is determined to transition. The method of claim 28, And said preset wait time is about two preamble durations. The method of claim 24, The device is determined to transition if the decoded first signal matches the preset code. The method of claim 22, Multiple receive bandwidth settings are provided, And said second setting is one of a number of settings that are related to the largest available reception bandwidth. The method of claim 31, wherein And the first setting is associated with a bandwidth of about 50 Hz. The method of claim 22, The second setting is dependent on the first setting. The method of claim 33, wherein Multiple receive bandwidth settings are provided, And said second setting is one of a plurality of settings associated with an available bandwidth that is progressively smaller than said first setting. The method of claim 22, Means for determining an active data rate from the decoded first signal, Multiple receive bandwidth settings are provided, And said second setting is one of a number of settings associated with a bandwidth that best fits said active data rate. 36. The method of claim 35 wherein And wherein the active data rate is determined by determining a bit period between successive received symbols of the decoded first signal. (none) (none) (none) (none) (none) Decoding the second signal in accordance with the second setting How to include. The method of claim 42, wherein Transitioning step is performed in response to the first decoded signal. The method of claim 34, wherein Comparing the decoded first signal with a preset code, and Determining whether to transition to the second setting depending on the comparison How to include more. The method of claim 44, And if determined not to transition, the second signal is decoded according to the first setting instead of the second setting. The method of claim 44, The preset code is at least part of a preamble. The method of claim 44, And if it is determined that the decoded first signal does not match the preset code. The method of claim 47, And if it is determined that the decoded first signal does not conform to the preset code after a preset wait time. The method of claim 48, And said preset wait time is about two preamble durations. The method of claim 44, And if it is determined that the decoded first signal matches the preset code. 51. The method of claim 50, Transitioning to a third receive bandwidth setting different from the second setting, Receiving a third signal, and Decoding the third signal according to the third setting How to include more. The method of claim 42, wherein Multiple receive bandwidth settings are provided, Wherein the second setting is one of a number of settings that are related to the largest available reception bandwidth. The method of claim 52, wherein The first setting is associated with a bandwidth of about 50 Hz. The method of claim 42, wherein The second setting is dependent on the first setting. The method of claim 54, Multiple receive bandwidth settings are provided, Wherein the second setting is one of a plurality of settings associated with an available bandwidth that is progressively smaller than the first setting. The method of claim 42, wherein Determining an active data rate from the decoded first signal, Multiple receive bandwidth settings are provided, The second setting is one of a number of settings associated with a bandwidth that best fits the active data rate. The method of claim 56, wherein Wherein the active data rate is determined by determining a bit period between successive received symbols of the decoded first signal. The method of claim 56, wherein The decoded first signal is a preamble having a pre-associated data rate, The active data rate is determined from the pre-related data rate. The method of claim 56, wherein The decoded first signal is a DATA RATE command with an associated data rate command, The active data rate is determined from the instruction. The method of claim 42, wherein The transition step is performed by adjusting the bandwidth of the filter. The method of claim 42, wherein And the transitioning step is performed by changing the path of the second received signal compared to the first received signal. 62. The method of claim 61, The signal path comprises a first filter, The transitioning step routes the signal through a second filter.

Images