FAQ

Antennas

RF reader cannot detect antennas?

Keonn antennas may not be automatically detected by some readers. Antenna detection can be achieved through several approaches:

• Through a DC resistor.

• Through other methods that do not require a DC resistor.

Keonn antennas do not have a DC resistor. Whenever the reader uses this detection method, it will be necessary to disable automatic antenna detection:

• ThingMagic: by using the Mercury API, set the parameter /reader/antenna/checkPort to false.

Linear vs Circular polarized antennas

This is best understood by having a look at online resources

circular-polarization-vs-linear-polarization

To sum up:

• • Linear polarized antennas concentrate all energy in one orientation only

  • Linear polarized antennas can achieve higher read rates when using the right tag orientation

  • Linear polarized antennas cannot read tags in the wrong orientation

  • Circular polarized antennas diversified the energy in both orientations

  • Circular polarized antennas maximum read range will always be less than the maximum read range with a linear polarized antennas

  • Circular polarized antennas do not suffer from tag orientation.

Please note that tags also suffer from the polarization effect.

Antenna gain

The gain in the datasheets is referred to an isotropic circularly polarized antenna: dBi

Cables

Where can I find the cable specifications?

Cable specification can be found here.

What is the maximum cable length I can use?

Each application has certain power and sensitivity requirements, those are the main characteristics that define the maximum cable length.

The most simplistic approach to have an idea of the maximum cable length is:

• 1. Check your application with the shortest possible cables. Write down the minimum power and sensitivity that still works.

     • In case AdvanMuxes are used, also include them in this starting test.

  2. Take the minimum from powerMargin and sensitivityMargin

     • Power margin: (Max power-MinWorkPower)

     • Sensitivity margin: (MinWorkSensitivity-Min sensitivity)

  3. Take into account some margin

  4. The minimum value above will give you an idea of the maximum losses the cables may introduce.

  5. Given the cable you are using calculate the maximum distance. Keonn cable losses can be found here.

Example

Imagine you have a system with AdvanReader-m4-150 and 4 antennas. The application works okay at:

• • Read power: 26 dBm (MinWorkPower)

  • Sensitivity: -70 dBm (MinWorkSensitivity)

Taken that AdvanReader-m4-150 can work at 31.5 dBm and has a sensitivity around -80 dBm. The margins will be:

• • powerMargin: 31.5 dBm - 26 dBm = 5.5 dB

  • sensitivityMargin: -70 dBm -(-80dBm) = 10 dBm

In the example, the minimum is due to power and is 5.5 dB. In the most simplistic approach we could add cables up to a distance were they introduce 5.5 dB losses.

To be on the safe side we may decide to have some margin, so the maximum losses we allow are 3 dB.

Using LMR195 cables, 3 dB represent:

• • 100 m/ 42 dB *3 dB = 7.1 m

According to this approach, we could have cables of up to 7 m.

Now it would be time to verify that really works!

RF

What is the RSSI value?

RSSI stands for Received Signal Strength Indicator. It is a measurement of the signal received power level at the RFID reader from a certain RFID tag.

The RSSI gives a direct measure of how good a tag is being read.

RSSI depends on many factors:

• • Received power at the tag, which is related to conducted power

  • Tag inlay: larger tags have commonly larger RSSI values.

  • Tag tuning: it is related to the product material the tag is attached to

  • Tag density: very dense tag environment may reduce RSSI

  • Environment: reflections created by metal parts may also affect how the signal travels from the tag to the reader:

    • Constructive reflections may increase the received RSSI

    • Destructive reflections may create blind spots that prevent tag from being read.

  • Interference from other RFID or other electronic equipment

  • Other.

The RSSI is sometimes used as an indicator of the distance between the RFID reader to the RFID tag, although it is not a perfect indicator.

What is the Phase value?

The phase is the measure of the signal phase received at the reader by an RFID tag.

What is the Read count value?

The read count is the aggregation of the number of reads per the same EPC in a single inventory operation. 

When RFID data is received from the internal RFID module it may have suffered an aggregation process, so that, several low-level reads are transferred as a single read event with a Read Count value higher than 1.

Whether the Read Count has values higher than 1 will depend on many factors:

• • Operation mode: autonomous versus sequential

  • EPCGen2 session/target and RF settings: different settings will cause the tags to respond at certain periodicity, thus affecting the Read Count

It is important to use the Read Count any time the occurrences of a tag being read makes a difference. 

What is the EPCGen2 modulation value?

This is the signal modulation used in the transmission between the RFID reader and the tags.

The different values provide different error detection and correction capabilities, and at the same time control the RFID Reader throughput:

• • FM0 is the fastest modulation without any error detection/correction. It should never be used as the red accuracy will drop significantly

  • M2 is the fastest modulation with error detection/correction

  • M4 represents a good compromise between speed and error detection/correction

  • M8 is the slowest modulation but the highest error detection//correction

In normal scenarios, the difference between the modulation values cannot be easily detected.

What is the EPCGen2 tari value?

This is the bit duration in microseconds used in the transmission between the RFID reader and the tags.

• • TARI_6_25: 6.25 us tari

  • TARI_12_5: 12.5 us tari

  • TARI_25: 25 us tari

In normal scenarios, the difference between tari values cannot be easily detected.

What is the EPCGen2 BLF value?

This is the backscatter link frequency (KHz), used by the tag to transmit back to the reader.

• • 250 KHz: normal value

  • 640 KHz: maximum value. It should never be used as the red accuracy will drop significantly

The BLF 640 can only be used with FM0 and TARI_6_25.

Maximum read distance

The maximum read distance expresses the absolute maximum distance some tag can be read by a certain reader and antenna.

The read distance seems to dominate market performance indicators. However, it is a term that may be misleading and can lead to false expectations. Read distance depends on several factors:

• • Tag type: chip and inlay

  • Tag orientation: tag RF properties change according to its orientation towards the antenna

  • Multipathing: that generates constructive and destructive reflections

  • RF interference

  • Etc.

Although it is true the maximum read distance may give an idea of an overall reader sensitivity, each application must be tested under their specific environmental conditions. That would result in the real effective read distance for each application.

What are ERP and EIRP?

ERP and EIRP are different ways to express how the conducted RF power is radiated by antennas.

Radiated power depends on:

• • Reader conducted/transmitted power

  • Internal reader losses (if exist)

  • Cable losses

  • Antenna gain

ERP stands for Effective Radiated Power and expresses radiated power compared against a dipole antenna.

EIRP stands for Effective Isotropic Radiated Power and expresses radiated power compared against an isotropic antenna.

There are different ways of calculate ERP and EIRP. We prefer:

EIRP (dBm)=Transmission Power (dBm)+Internal losses (neg. dB)+Cable loss (neg. dB)+Gain (dBi)+PLF (neg. dB), where PLF=-3dB

ERP (dBm)=Transmission Power (dBm)+Internal losses (neg. dB)+Cable loss (neg. dB)+Gain (dBi)-Gd (dBi), where Gd=2.15dBi (dipole)

Note:

If the Tx and Rx antennas are both of same-handed circular polarization, the usual formulas for power calculation can be used. If one of the antennas is linearly polarized (e.g. an RFID tag), then a Power Loss Factor (PLF) of -3dB must be applied. Some people, instead of using the PLF, use a different definition of gain, dBiC=dBi+PLF (PLF is negative), so that one can do power calculations with gain and without PLF. The logic behind using dBiC is that using it in the ERP or EIRP calculation, the value turns out smaller, and a higher (3dB higher) transmitted power may be used.

How can I change the RF duty cycle?

Whenever in Autonomous mode or derived modes it is possible to control the duty cycle of the RF operation. 

The duty cycle is controlled by the onTime and offTime parameters.

• • onTime (ms): this is the time the RF is ON

  • offTime (ms): after the onTime expires, the RF is OFF for offTime. After the offTime expires the RF is ON for onTime again, and etc

The duty cycle is calculated as 

DutyCycle (%) = onTime / (onTime+offTime)

Reducing the duty cycle is a convenient way to reduce heat generation on applications that can handle the RF to be stopped periodically.

Multiplexers and Splitters

What is a RFID multiplexer?

It's a device with:

• • One RF input line

  • N RF output lines

  • One or more control lines although some multiplexers use the RF cables for control

Multiplexers are switches that allows to connect the input to any of the available outputs.

At any given time there is only one active path between the input line and one of the outputs

Unused outputs can be left unconnected, it is important then to make sure those outputs are never addressed.

How a certain output is selected depends on the multiplexer model. Some use simple GPO lines, other use serial communication, while others use the same RF cable to transmit signals on the low band.

The following diagram helps understanding how a multiplexer works.

Advantages:

• • Expand the number of available antennas

  • Each antenna can be uniquely addresses by the reader. Applications using location based on antenna can benefit using multiplexers

  • The insertion losses of using multiplexers are limited. For example:

    • AdvanMux-4: Insertion losses are between 0.7 - 0.8 dB

    • AdvanMux-8: Insertion losses are between 1.4 - 1.5 dB

    • AdvanMux-16: Insertion losses are between 1.4 - 1.5 dB

Disadvantages:

• • The RFID reader configuration has to take care of the additional antennas

  • More time is needed to perform a complete inventory cycle.

Uses:

• • Applications that require a large number of antennas and location is based on antenna

  • Applications that require a large number of antennas without location, where power budget is tight

What is a RFID splitter?

It's a device with:

• • One RF input line

  • N RF output lines

Splitters are power dividers. The available signal at the input line is divided in equals parts on all N outputs.

All N outputs are active simultaneously. 

Unused outputs must be connected to a 50 ohm load, otherwise the power division will not work as expected.

Splitters are simple to use, do not require any control.

The following diagram helps understanding how a splitter works.

Advantages:

• • Expand the covered area without the need of addressing more antennas at the reader side.

  • No additional time is needed to perform a complete inventory cycle.

Disadvantages:

• • The Insertion losses are much higher than the multiplexers. For example:

    • AdvanSplitter-2:  Insertion losses are around  3.5 dB

    • AdvanSplitter-4:  Insertion losses are around  6.5 dB

    • AdvanSplitter-8:  Insertion losses are around  9.5 dB

Uses:

• • Applications that require a large number of antennas where: i) location based on antenna is not required and ii) there is enough power to absorb the splitter insertion losses.

When to use a multiplexer over a splitter?

• • Location based on antenna is needed

  • It's not possible to afford losing power.

For example, if for a certain application the power configuration is at 30 dBm, splitters could not be used as they add a minimum losses of 3.5 dB. In order to compensate the losses, the reader should be configured at 33.5 dBm, which is above it's maximum value.

When to use a splitter over multiplexer?

• • Location based on antenna is NOT needed

  • Read time must be kept to the minimum

  • The required power configuration allows for some additional losses.

For example, if for a certain application the power configuration is at 23 dBm, AdvanSplitter-2 or AdvanSplitter-4 could be used.

AdvanSplitter-2 adds 3.5 dB of losses, that means the reader would be set at 26.5 dBm to compensate those losses.

AdvanSplitter-4 adds 6.5 dB of losses, that means the reader would be set at 29.5 dBm to compensate those losses.

EAS systems

Can an RFID EAS system be used as an inventory system?

We strongly discourage the use of EAS systems as inventory systems.

EAS systems are designed with one goal in mind: maximize detection of legitimate alarmed tags

Achieving this goal includes HW and SW design, and configuration that may work in the opposite direction to what is needed for an inventory system: detect a large population of tags crossing a certain area.

Additionally, product simplicity always results in less system set up and fewer maintenance costs.

Regulation

What is the RF Region?

The Region value is the current value for the RF module UHF region. UHF stands for Ultra high frequency. It regulates the frequency band and other air protocol parameters.

Our readers support the following bands:

• ETSI

• FCC

• AUSTRALIA

• CHINA

• INDIA

• KOREA

  • JAPAN

• NEW_ZEALAND

• BRAZIL

• PERU

• TAIWAN

• CHILE

Whenever you change the band make sure that all the other system parts are compatible in the new band. In particular, antennas can be different for different bands.

Please check the exact regulation for each country in the document UHF Regulations at the end of this page.

If a reader has the RF Region set to one Region, it works in another?

For example, if a reader is working in France (EU member), the RF Region must be set to ETSI. If that reader is moved to the USA, the RF Region must be set to FCC.

Is Malaysian regulation supported?

Malaysian regulation follows FCC regulation in the sub-band 919 - 923 MHz. It is possible to conform to Malaysian regulation by using the channels in the Malaysian sub-band.

EPC encoding

How does BC encoding algorithm work?

The Keonn BC encoding algorithm is free and proprietary. Clients are granted to use it unlimited but the details of the implementation itself belong to Keonn. 

BC encoding does require a set of parameters to run. Each encoding/decoding scheme may use a different set depending on the original SKU codes.

The encoding/decoding of the BC scheme is integrated into each Keonn device, in the form each device requires:

• • AdvanScan/AdvanStation can read barcodes and encode them according to the client BC parameters.

  • AdvanReader/AdvanPay can decode EPC codes but cannot by default encode barcodes into EPCs.

Operation

What is the maximum operating altitude?

The altitude operation is basically limited by power supplies and screens. As a general rule, the maximum operating altitude is 3048 m (10.000 feet).

In case the operation is required at higher altitudes please contact support@keonn.com

Configuration

What is the difference between Power and Sensitivity?

The power level defines the conducted power from the RF module to the antenna. Its is defined in logarithmic scale:

• 30 dBm (1 Watt)

• 27 dBm (0.5 Watt)

• etc.

The tags have a wake-up level that is only reached when there is enough received power. Higher conducted power generally results in higher received power in tags.

The sensitivity is a software filter applied at the reader side.

Part of the energy power received by each tag is backscattered back to the reader. The power returned by the tag and received back at the reader is measured (RSSI), the sensitivity threshold applied at that time.

The RSSI - Received Signal Strength Indicator- depends on many factors:

• • Received power at the tag, which is related to conducted power

  • Tag inlay: larger tags have commonly larger RSSI values.

  • Tag tuning: it is related to the product material the tag is attached to

  • Tag density: very dense tag environment may reduce RSSI

  • Environment: reflections created by metal parts may also affect how the signal travels from the tag to the reader:

  • Constructive reflections may increase the received RSSI

  • Destructive reflections may create blind spots that prevent tag from being read.

  • Interference from other RFID or other electronic equipment

  • Other.

Example

Imagine that you have an AdvanSafe-100, 10 meters from the floor, and two tags below it, one in the floor and one at 5 meters of AdvanSafe-100. 

• The power establishes if the signal will "hit" one or two tags. If we set AdvanSafe-100 power to 10 dBm, it will "hit" only the nearest tag with enough energy to respond. But if we set it to 30 dBm it will "hit" with enough energy to respond the two tags.

• The sensitivity establishes a threshold that the signal coming from each tag has to surpass. Setting the power to 30 dBm, AdvanSafe-100 will get the respond of each tag with an RSSI (e.g. -45 dBm and -58 dBm), you can see the RSSI number in the Monitor tab. If we set the sensitivity to -50 dBm, AdvanSafe-100 will discard the second tag.

If the power is increased, is the sensitivity affected?

In general, the transmitted power does not affect the sensitivity. The reader conducted power goes from 5 dBm (3.16 mW) to 31.5 dBm (1.41 W).

The power received at the reader hardware is related to the tag backscattered power, the minimum power the reader can detect as a read is called the sensitivity. It is usually in the range of -80 dBm (10 pW) to -85 dBm (3.16 pW).

What is the best combination of power and sensitivity?

The answer depends on many factors, general recommendations are:

• • Adjust the RF power to achieve the desired read field.

  • Adjust sensitivity to reduce unwanted reads due to reflections.

What do target and session options mean?

Session and target are specific parameters from the EpcGen2 protocol.

Session and Target settings control whether, and how often, a tag participates in an inventory round. When doing an inventory, the reader also sends two other pieces of information to all tags:

1. How long they should delay until they re-respond (called the “session” value) and 

2. What state (“A” or “B”) they should be in to participate in the inventory round. The “A” state indicates that the tag has not yet responded to an inventory round. The “B” state indicates that it has.

During an inventory round, the reader attempts to read all tags within the field. The reader operates in only one session for the duration of an inventory round.

The “Session” setting, which controls how often tags respond to inventory rounds, has 4 options, but two behave identically.

• Session “0”: tags respond immediately after they have been inventoried.

• Session “1”: once inventoried a tag stays quiet between 0.5 and 5 seconds.

• Session “2” or “3”: Do not respond any more while in the read field.

The “target” setting determines which tag set will respond a certain query:

• • Target A: only tags currently in state A will respond to the query. They will switch immediately to state B.

  • Target B: only tags currently in state B will respond to the query. They will switch immediately to state A.

  • Target AB: each inventory round takes two cycles:

    • An inventory in A state. Will move A tags to B state.

    • An inventory in B state. Will move B tags to A state.

  • Target BA: each inventory round takes two cycles:

    • An inventory in B state. Will move B tags to A state.

    • An inventory in A state. Will move A tags to B state.

Examples of Session and Target configurations

• AdvanSafe-100: the most performant configuration is Session 1 and Target A

• AdvanShelf: in case location is an important factor, we recommend using Session 0 and Target AB. That will provide the largest amount of data. 

What is the meaning of the mask (EPCGen2 filter)?

Each tag contains an EPC (Electronic Product Code), this is a number between 96 to 512 bits.

The mask is just a means to express a filter that will be applied to any tag read. The EPCGen2 standard defines a filter that may be used during the singulation process, it is the most efficient filter.

The mask is composed of:

• Mask value (hexadecimal): number expressed as a hexadecimal number.

• Mask length (bytes): is the size of the mask that the reader is going to use. 

If the mask is defined, any tag EPC  that does not match the filter will be ignored. This is for example used in the alarm mode: EAS-EPC.

Examples of mask expressions

To filter all tags with an EPC that starts with 8080h:

• • Mask: 8080

  • Mask length: 2

To filter all tags with an EPC that starts with 808023h:

• • Mask: 80802300

  • Mask length:4

What is the SW filter?

SW filter stands for Software Filter, it is a filter applied at a software level. Under some circumstances, the mask filter applied at EPCGen2 level may not work as expected. For those cases the SW filter out unwanted tags.

By default, set it always to true.

What is the SW filter only?

The EPCGen2 filter silences completely non-matching tags. For some scenarios it may be required to read all possible tags and do a software processing.

The SW filter only option disables the EPCGen2 filter and processes all tags once they are received. This may lead to a degraded performance in read intensive applications.

For example in AdvanSafe, that allows saving all reads in a CSV file while reacting only to alarmed tags.

How to configure systems when EAS Serial Number is used?

EAS Serial Number is a method to encode EAS information into the SGTIN-96 serial number. It takes advantage of the fact the SGTIN-96 is divided into three parts:

• • Header + flags

  • EAN/GTIN number

  • Serial number

EAS Serial Number uses part of the serial number bits in SGTIN96, from 4 to 16 bits of the available 58 bits.

It is an option available in AdvanStation and AdvanPay.

When the EAS Serial Number is used, that forces certain configuration in some systems. In particular: AdvanSafe/AdvanGuard and AdvanPay.

AdvanSafe/AdvanGuard

When the EAS EPC operation mode is used, please select the EPCGen2 filter as follows

AdvanPay

Payment mode

• • Selects only alarmed tags

  • Disable alarm (re-write) on payment

Return mode

• • Selects only non-alarmed tags

  • Re-enable alarm (re-write) on return

What is the antenna orientation?

Antenna orientation is a configuration setting used only in the tag direction detection algorithm1.

It can be left empty when the tag direction algorithm is not in use.

Contact support@keonn.com to learn more about the tag direction algorithm

Speaker output

Which speakers can be used?

Any 2 Watt or superior 8 Ohm speaker can be connected to AdvanReader and derived systems. 

What is the maximum speaker cable length?

Almost any cable pair can be used up to 10 m.

The following is a short list with different cables AWG (conductor inverse square diameter) and the maximum distance

• • AWG24: up to 12 m

  • AWG21: up to 24 m

  • AWG18: up to 48 m

Is it possible to connect directly to a second speaker?

It is not possible, AdvanReader only has one audio amplifier.

How can I connect a second audio device?

The preferred way to connect an additional speaker/audio device is to use an industrial sounder.

For example:

Please check the sounder page.

Race timing

Antenna orientation

Antennas must be placed perpendicularly to the finish/start line. That is, antennas must cross the road.

Antenna polarization

All Pxx antennas are circularly polarized. In particular, antennas used for race timing: P13, P13 and P16 are circularly polarized.

Tag orientation

As antennas are circularly polarized, tag orientation does not cause major differences. However, for the best possible read rate, it is important to ensure the following:

• • Tag surface and antenna surface shouldn't be perpendicular, perpendicular orientation would be the worst. Meaning that when antenna surface and tag surface are perpendicular read distance will be reduced.

  • The tag does not touch the skin.

RFID facts

RFID tag detuning

RFID tags are designed for maximum matching, and therefore performance, for a certain use: air, cartoon, metal, etc.

When the RFID tags are applied to a different material the tags get detuned, causing a loss in performance.

Another cause for loss of performance is the fact RFID tags are surrounded by RFID absorbing or reflective materials.

Such materials absorb the RF energy or reflect it, reducing the tag performance. 

Connectors

12 V - 24 V connector

The AdvanReader-100, AdvanReader-150.03 and AdvanReader-150.04 use a locking jack connector for the auxiliary power supply. 

The jack connector in the PCB is

Switchcraft L712RA

The mating jack connector should be compatible with

Switchcraft 761K

Positive voltage at center pin.

The required dimensions are

In particular, Keonn Technologies can provide a 24 V power supply that mates the PCB connector.

CSV files

Change tag read limit

When using the keepAllReads setting there is an internal limit: for each tag only 512 read events are stored.

It is easy to change that limit by adding a line in connectors.xml

Locate the connectors.xml and at the beginning of the file locate a configuration block that starts with <CONFIGURATION>. Add the following line (in bold)

<?xml version='1.0' encoding='utf-8'?>

<aliases>

<load-order-scope>default</load-order-scope>

<load-order>20000</load-order>

<CONFIGURATION>

<com.keonn.model.TagDataMaxLayers>1024</com.keonn.model.TagDataMaxLayers>

...

</CONFIGURATION>

...

</aliases>

TroubleShooting

Reader assert error

Reader assert errors can be identified as follows:

Reader assert errors originate at the RFID module. In general, they are the result of hardware damage.

The most common cause of hardware damage is ESD (Electrostatic discharge). To avoid them, please have a look at the ESD handling chapter.

Possible causes for such problems are:

• • Connecting/disconnecting antennas while the readers are operating

  • Connecting antennas that have an electrostatic charge. When antennas are in contact with certain materials they can be charged.

However, there are a few easy things you can check to discard potential installation problems:

• 1. Make sure all the cables are properly tightened.

  2. Make sure the antennas are not causing a high reflection to the reader. For example when antennas face large metallic pieces.

In case the error persists after adjusting the points before, please contact support@keonn.com

Other

What ports do I need to open in the router/firewall/request to IT?

Keonn readers and derived systems may use the following ports:

• • TCP 443: used by AdvanCloud agent to upload data. Allow it for the host your_cloud_instance.keonn.com

  • TCP 4443: used only when the AdvanCloud is used to remotely access readers and systems. Allow it for the host remote.keonn.com

  • UDP 123: used by the NTP client for time synchronization. Allow it for the host pool.ntp.org

If I'm doing port-forwarding, what ports do I need to configure?

Keonn readers and derived systems may use the following ports:

• • TCP 80 (HTTP): this is the used by the AdvanNet Bee UI

  • TCP 3161 : this is used by the AdvanNet legacy UI (pre-2.5.5)

  • TCP 8080: this provides access to the Keonn Bootloader, used to upgrade the unit FW

  • TCP 11987: WebSocket server required for both AdvanNet UIs

  • TCP 22 (SSH): for remote maintenance 

Why Keonn Readers do not support LLRP?

Having and using standards is always the best approach, and Keonn Technologies strongly encourage its use.

The question is then, why we do not support LLRP?

• • Our higher level vision when designing RFID readers and systems put focus on higher level standards: HTTP, SQL, MQTT, etc.

  • Our reader FW works at a higher software level than LLRP. It provides unique out-of-the-box features:

    • Advanced Operation modes: payment, alarms, tracking, etc

    • Advanced integration using widely used standards: HTTP, SQL, MQTT, etc

  • LLRP extensions bound applications to manufacturers, breaking the theoretical compatibility between different hardware.

That said, we have preferred to use our own HTTP REST API when managing the RFID hardware:

• • This goes along with our vision of RFID, as a hardware ready to connect to common IT standards.

  • This avoids creating LLRP extensions to support some of our features:

    • Higher level read modes.

    • Built-in audio amplifier.

    • Analogue GPI lines, etc.

  • HTTP REST is a commonly understood paradigm.

  • HTTP REST reduces the time to market for new developments.

Downloads