A Major Upgrade for Aerospace RFID Testing

May 15, 2020

About the author

I am the CEO and co-founder of Voyantic, a company that specializes in RFID test and measurement solutions. Before starting Voyantic in 2004, I worked as a researcher at the Helsinki University of Technology focusing on passive RFID sensing for moisture in building structures.

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中文版 Chinese version

日本語版 Japanese version

During this COVID-19 pandemic, as most airplanes are stuck on the ground and several large airplane orders have been canceled, aerospace is probably not considered the hottest market for RAIN RFID. However, eventually, this situation will pass, and more airplanes will be built. When that happens, the aerospace industry will be more ready than ever to use RAIN RFID, due to recent standardization work.

Back in 2015, I wrote about the aerospace industry as the pioneers of RFID:

“The aerospace industry realized that they need standardization for flyable tags as early as 2006. That is when a group of experts in the field decided to develop a standard under SAE International. SAE AS5678, “Passive RFID Tags Intended for Aircraft Use”, was born … In addition to environmental testing, the standard also describes RF performance tests for the tags. The standard described a very professional and well repeatable measurement methodology. But even more interestingly, the standard divided tag performance into performance grades, somewhat similarly to what the GS1 TIPP standard would do for the retail industry in 2015.”

Fast forward to 2020, in February, SAE published the third version of the standard, AS5678B Passive RFID Tags Intended for Airborne Equipment Use. So, what’s new in the standard revision?

The changes are mostly related to how the performance grades are defined. In earlier versions of the standard, tags were graded based on their read range, determined from their sensitivity. And that makes perfect sense: In 2006, the sensitivity of RFID chips wasn’t that great, and read range was nearly always limited by power delivery to the tag. Nowadays, that is not always the case. As the sensitivity of tags has improved, in more and more cases the return link from the tag to the reader may limit read range. This is reflected in the new standard revision; in AS5678B, the grades are determined by both minimum read sensitivity and minimum backscatter.

To give an example, for a tag to be classified for Grade X, the sensitivity of the tag on a metal plate has to be better than -12 dBm, and its backscatter strength needs to be at least -23 dBm. That corresponds to an expected read range of 6 m. But that’s not all. Because airplanes are expected to cross borders, and radio regulations are different in different parts of the world, this performance is required throughout the global RAIN RFID range of 865 to 930 MHz.

There is one more new element in the standard. It is no longer sufficient for one individual tag to pass a grade – a statistical element is introduced. A total of 30 tags needs to be tested, and their performance variation must be below a level defined in the standard.

Overall, I am quite happy with the new standard revision. With the new backscatter criteria, it is well in line with the development of the industry. The backscatter is required to be quite strong which means that most readers are able to read tags that meet the criteria – and that is probably a good approach. In addition, the statistical test brings a hint of a quality aspect to the standard.

As a final thought, there is one thing that I find curious about AS5678. No one is openly advertising to offer test services according to this standard. Customers often contact me to ask for a service provider. Some tag makers are obviously either testing their tags themselves or having them tested somewhere. Probably most of them use an external lab for the environmental testing and do the RFID part with their own Tagformance system).

But wouldn’t it make sense to have a one-stop-shop for AS5678B testing?

If you think that a lab that you know should start offering these tests, please let us know. If they already have the environmental part, we would be happy to help with the RFID part.

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Optimizing Counting Reliability With Well-Designed Reader Zoning

Feb 21, 2020

About the author

Teemu Ainasoja

I am Sales Director at Voyantic. I have over 15 years of experience from the RFID industry in Europe and the USA. I have two master's degrees: in industrial engineering and in marketing, and two patents in auto-ID technology. I am actively participating in RAIN RFID alliance activities.

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中文版 Chinese version

At RFID&WIoT Tomorrow 2019, Erik van Noort from Avery Dennison stopped by a Voyantic booth. He introduced a recently launched ShieldSense™ RFID blocking material. The material is for reader zoning and aimed to help system integrators in building better RAIN RFID systems.

After sharing some ideas, we decided to write an article explaining the reader zoning and how to use Voyantic Tagformance to check not only if the zoning works, but how well the zoning works. In this piece, we introduce the ShieldSense™ material with the Tagformance test results.

What Is Reader Zoning?

Reader zoning is a common challenge when building RAIN RFID systems. You want to scan tags in one area, but don’t want to read tags from another area nearby. For example, at a loading dock, it is essential to know that the item passes a specific gate and goes to the correct truck, and not to the next truck a few feet away.

Reader Zoning challenges

An apparel store has stock at the backroom
Every item in stock should be represented at the shop floor
With RAIN RFID it is possible to count and identify every item at the backroom and the shop floor, with a few minutes scan – quick enough to be done several times a day
The system can then generate an alert if an item type is not represented on the shop floor
Having each item represented on the shop floor is critical. If an item is forgotten, it would never be sold during the season and would have to be either heavily discounted afterward as the last season item, or even wasted

Reader Zoning – Test Without ShieldSense™

Conventional methods for reader zoning are

selecting reader antennas with different reading angles
planning reader placement
adjusting reader power levels
using the RSSI filter to prevent stray reads
applying RF shielding material aka RF blocking material

For testing the zoning challenge, I designed a simple test environment in our office. In one of our meeting rooms (“Front Room”), I had 100 tags placed on all sides of a cardboard box. In the next room (“Back Room”), behind a wall, there were another 100 tags placed on a similar box.

Photo: Test setup: 100 tags on the box in the Front Room, and another 100 tags in Back Rroom

My goal was to find reader settings that would allow the inventory of the 100 tags in the Front Room without reading any tags from the Back Room. In the test, I used an antenna placed on different locations and orientations in the Front Room. I used the Tagformance population analysis as a test tool. A combination of several test positions would correspond with someone doing an inventory count with a handheld RFID reader.

Results Without RF Blocking Material

There was no antenna placement and orientation in the Front Room with which all of the tags in the Front Room could be read. In typical good positions, 85% – 95% of the tags were scanned. One apparent challenge was that the light wall between the Front Room and the Back Room did not block the RF signal. With antenna orientations that gave the best read results in the Front Room, a good number of tags from the Back Room were also found. In some antenna positions, more tags were found from the Back Room than from the Front Room.

Figure 1: antenna position 1, tags scanned from the Front Room with different power levels

Figure 2: antenna position 1, tags scanned from the Back Room with different power levels

No antenna placement would give a decent amount of readings from the Front Room without giving any readings from the Back Room

Figure 3: antenna position 11, tags scanned from the Front Room with different power levels

Figure 4: antenna position 11, tags scanned from the Back Room with different power levels

Even if 100% reading was not achieved from any single antenna position, a 100% read rate from the Front Room was achieved when two antenna positions were combined. In practice, a 100% read rate would be easy to achieve by a simple handheld reader sweep. But, the combination of two positions gave over 90% rate also from the Back Room.

No power level cut would enable efficient zoning. At any power level with which tags are found from the Front Room, some tags are also found from the Back Room.

There is no difference at backscatter signal strengths from tags in the Front Room and tags in the Back Room. RSSI filter would not be efficient for reader zoning in this scenario.

After the first tests, it was apparent that the task is hard. There was no reading angle where power adjustment or RSSI filter could separate the items. In the test scenario, antenna placement, adjusting reader power, RSSI filter, or any combination of those would not solve the zoning issue.

Reader Zoning – Test With ShieldSense™

For the delight of fellow Voyanticians, I wallpapered part of the Front Room with Avery Dennison’s ShieldSense™ material. After shaking of the numerous “do they make foil hats of that” comments, I did the second part of the testing. I again placed antenna to different positions and tried to find an antenna position where zoning would work. In this test, I also used the Voyantic High-Power kit to boost radiated power beyond normal power levels, up to 39 dB ERP radiated power (antenna in the test had about 8dB gain).

Photo: Test setup without and with temporarily mounted ShieldSense™ (and not the prettiest wallpapering
with test equipment)

Results With RF Blocking Material

The positive effect of ShieldSense™ was apparent immediately. In most antenna positions tags from Back Room were not found

It was also noticed that in the original test scenario, some tags were leaning against the wall, and after applying ShieldSense™, those tags were leaning against the metal surface, making the tags non-readable.

Figure 5: antenna position 1, tags scanned from the Front Room with different power levels, ShieldSense™ in use. Some tags leaning against the wall

Figure 6: antenna position 1, tags scanned from the Front Room with different power levels, ShieldSense™ in use. any tag 10cm from the wall

Figure 7: antenna position 1, tags scanned from Back Room with different power levels, ShieldSense™ in use

There were still read angles that gave some readings from the Back Room when the power level was high enough. Most likely, the read is from reflections, the Front Room was only partially shielded, and in some antenna orientations, the signals have some reflecting paths even if the direct paths are blocked.

Figure 8: antenna position 6, tags scanned from Back Room with different power levels, ShieldSense™ in use

When the power levels and backscatter signal strengths are analyzed, efficient zoning parameters can be found. Using 30dB radiated power and applying -65dBm RSSI filter with a handheld reader

would give 5dB safety margin before read rate would drop to below 100%
would give 5dB safety margin before tags in the Back Room would wake up
about 8dB margin in RSSI until reader would accept the response from Back Room

These safety margins are likely well sufficient for ensuring reliable system performance also in the long run.

I am also convinced that expanding the ShieldSense™ coverage a bit around the corner instead covering just one wall, and applying it permanently instead of the temporary mount I used, the safety margins would increase by some dBs

With ShieldSense™ it is easy to find reader power levels and RSSI filter values with which zoning works, and safety margins are good for getting reliable reads as well as for avoiding stray readings.

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Sensors, Healthcare IoT and Pigeon Races – Review of RAIN RFID Research in 2017

Feb 02, 2018

About the author

Teemu Ainasoja

Content

中文版 Chinese version

Following research activities of RFID is a nice way to keep up with the latest technology developments. Awareness of hot research topics also helps in anticipating the direction of commercial development and new product launches. Here is my take on the published RFID research in 2017. I have included short comments on the research topics, and a number of links to papers published in 2017 that have caught my attention – for one reason or another.

First, a disclaimer: the selection of the introduced research papers and overview is my own. Summaries of the articles are short and written from my personal perspective, the points I raise are not necessarily same as authors’ intentions. When the topic seems interesting, I recommend clicking the link and reading the whole article.

Sensor Tags

RFID sensors continue to be one of the main research areas. The topic is wide – there are a lot of parameters that can be sensed, and the ways to sense ambient conditions are vast. New materials provide new possibilities for sensing, and existing methods have been fine-tuned to solve specific problems.

Graphene seems to offer a way to amplify ambient conditions’ effect on RFID tag tuning. This effect can be used in sensor tags. Research paper “Graphene oxide dielectric permittivity at GHz and its applications for wireless humidity sensing” introduces a printed graphene tag antenna coated with graphene oxide. The antenna changes properties when graphene oxide bonds with water molecules. The changing properties can be detected as a changed backscatter signal strength and phase.
Another approach to detect ambient conditions utilizes bimetal strips. Research paper “A Passive Temperature-Sensing Antenna Based on a Bimetal Strip Coil” presents a tag antenna combined with bi-metal strip. Antenna changes its’ tuning when ambient temperature changes.
Another research project “UHF passive RFID‐based sensor‐less system to detect humidity for irrigation monitoring” starts from a practical application. The paper describes a tag and a method for monitoring soil humidity. The tag is designed and tuned to provide high read range when buried to dry soil. In properly irrigated soil the read range drops. Farmers can thus monitor field condition just by checking whether tags buried to soil can be read or not.
In my mind, I associate energy harvesting with sensor tags. This paper “Performance Evaluation of a Long-Range RFID Tag Powered by a Vibration Energy Harvester” describes a vibration energy harvesting component used to boost read range of a semi-passive tag. Even though in the described application the harvested energy is used to boost the tag’s read range, I could see the component applied to RFID sensors logging data.

Healthcare and Wellness

Healthcare and wellness related sensor tag applications is a wide research area on its own. Research is aiming to fulfill the potential of RAIN RFID technology in healthcare. Amount of research related to RFID in healthcare is significant. I expect already growing RAIN RFID use in healthcare to grow even faster in the coming years.

The healthcare RFID sensor applications seem to fall into one of three application categories: implantable, partially implantable and wearable RFID sensors.

This paper “Effect of skin dielectric properties on the read range of epidermal ultra-high frequency radio-frequency identification tags” describes effects of human skin dielectric properties on UHF RFID tag operation. The report includes information of di-electricity variation between individuals, and the results provide some basic guidance for implantable and on skin tag designs. Another paper “A Tightly Integrated Multilayer Battery Antenna for RFID Epidermal Applications” describes an implantable and chargeable battery assisted tag design. The tag could be used as a data interface for various implanted devices.
A tag design consisting of a split ring antenna and a separate resonating element can be used as a partially implantable RFID tag. Part of the tag is implanted; the implanted part does not backscatter on its own and therefore the effect to a person is minimized. Another, non-implantable part completes the tag and enables data transmission when needed. “Wearable passive UHF RFID tag based on a split ring antenna“.
Separate papers describe specific applications on this topic: “Split ring resonator antenna system with implantable and wearable parts for far field readable backscattering implants“, “Split Ring Resonator Inspired Passive UHF RFID Antenna System For Wireless Intra-Abdominal Pressure Sensor” and “Split Ring Resonator Inspired Implantable Platform for Wireless Brain Care“.
Wearable tags can be used as humidity sensors. Embroidering tags from conductive yarns seems to be a promising manufacturing method from both cost and performance point of view: “The possibilities of embroidered passive UHF RFID textile tags as wearable moisture sensors“. Reliability of embroidering has also been studied and a comparison to conductive paint method has been presented.
An application of wearable humidity sensors is presented for reducing risks of inflammations of injuries covered with bandages: “Experimental study on UHF RFID tags integrated in medical bandage and paper-based materials“. A humidity sensing tag integrated to a bandage can be used to monitor condition of the bandage covered injury without removing the bandage.

Printed Antennas and Tags

Research of printable antennas is in my opinion shifting from basics towards studying mass production possibilities and reliability, although new methods and ink types are also being studied.

Inkjet printing is an interesting method from cost and accessibility point of view and studied in a few papers: “Inkjet-printed antenna-electronics interconnections in passive UHF RFID tags“; “Capability assessment of inkjet printing for reliable RFID applications” and “Possibilities of Fabricating Copper-based RFID Tags with Photonic-sintered Inkjet Printing and Thermal Transfer Printing“.
3D printing of graphene antennas provides new possibilities: “3D Printed and Photonically Cured Graphene UHF RFID Tags on Textile, Wood, and Cardboard Substrates“; “3D-Printed Graphene Antennas and Interconnections for Textile RFID Tags: Fabrication and Reliability towards Humidity“.

Specialty Tags

Embedded and other specialty tags are a continuous and versatile project area. The amazing versatility of the research topics tells about the potential of the RAIN RFID technology, and about the world we live in. Here are some examples:

Using RAIN RFID tags for Automatic Vehicle Identification (AVI) / Electronic Vehicle Identification (EVI) / Electronic Vehicle Registration (EVR) is an increasingly interesting topic. The amount of vehicles on roads may rise to intolerable amounts in some areas. Road tolls and other methods to limit vehicle quantities can be based on RAIN RFID. “Passive UHF RFID tag designs for automatic vehicle identification“.
Wearable tags have applications also outside of healthcare. Smart clothes may connect to personal electronics to form Wireless Body Area Networks (WBAN) in addition to WPAN (Wireless Personal Area) and WLAN (Wireless Local Area) networks. “Small square-shaped slot antenna for wearable passive UHF RFID tags“; “Wearable Passive E-Textile UHF RFID Tag Based on a Slotted Patch Antenna with Sewn Ground and Microchip Interconnections“.
Hard to tag items require continuously new specialty tags. These papers describe tag designs to be used on both on-metal and non-metal applications: “A Hybrid UHF RFID Tag Robust to Host Material“; “Compact Folded Dipole With Embedded Matching Loop for Universal Tag Applications” and “A compact dual band RFID metal tag with orthogonal polarizations at ETSI and FCC bands“.
Some specialty tag needs are not universal, but rather specific. Finding the need and realizing RAIN RFID’s potential requires a combination of RFID knowledge and understanding the application. As an example: Pigeon races are held 3 times a year in Taiwan. Thousands of pigeons race back home from the middle of the ocean – and the fastest bird wins. This paper describes design, characteristics and design process of a special RAIN RFID tag designed for pigeon race timing application.

Contact us and let me hear what you think of the above studies! I would also be happy to guide you how Voyantic test systems can be used in various RFID research projects.

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Testing Against RFID Immunity Makes Medical Devices Future Proof

Dec 15, 2017

About the author

Teemu Ainasoja

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中文版 Chinese version

Healthcare spending raises steadily as the silver tsunami rolls over societies in East and West. Tightening cost, quality of care and efficiency requirements are some of the drivers that highlight healthcare as one of the strongly growing RFID application areas. RFID improves patient safety, raises operational efficiency and reduces shrinkage.

Healthcare organizations have expressed concerns about medical device immunity against RFID, and the RFID technology vendors and regulatory authorities have been quick to respond. A new immunity test standard has been developed in cooperation with RFID and healthcare stakeholders, and released by AIM. This standard has been recognized by FDA and the first test laboratories are already offering Immunity Testing as a service for Medical Device manufacturers.

Interference May Effect Medical Devices

Healthcare organizations are understandably very cautious about any new RF systems that could risk the functionality or reliability of various medical testing and treatment devices. Research projects were commissioned and some studies – for example van Lieshout et al. – found that RFID can induce incidents with medical equipment.

Solution – Standardized RFID Immunity Testing for Medical Devices

To remove possible RFID related risks and uncertainties, RFID industry took action. With the help of industry organization AIM, a new test standard was created: AIM 7351731. This standard describes methods for testing Medical Electric Equipment and System Electromagnetic Immunity against RFID readers.

U.S. Food and Drug Administration FDA soon recognized the standard. FDA has also started to endorse it for medical device manufacturers submitting new equipment to Premarket notification (PMN) process according to section 510(k) of the FDA rules.

Voyantic was quick to release a solution that conveniently extends EMC laboratories’ existing EMC hardware to support the new AIM standard. Voyantic approach is based on creating the required test commands on a PC software and loading them over Ethernet to vector signal generator (VSG) already in use at the EMC labs. This approach, called Voyantic RFID Immunity Interface, is a quick and cost-efficient way to implement RFID immunity testing, utilizing the facilities and equipment already available.

Do you have any thoughts or questions about the RFID immunity testing? Contact us – I would be happy to discuss this in more detail!

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Vehicle RFID Tags – Big Benefits with Some Challenges

Nov 30, 2016

About the author

Teemu Ainasoja

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中文版 Chinese version

Electronic Vehicle Identification (EVI) is a perfect match for RAIN RFID (UHF RFID) technology. Once a vehicle is tagged, the possibility to identify the vehicle remotely enables a lot of applications and services. While vehicle tagging is of high interest, it is not the easiest task. In the past few months I have worked with some vehicle tagging projects and learned that the application requires some special attention from technology providers.

EVI Tag Types

The EVI tags come in different forms. Most common EVI tag types are

windshield tags attached to the windshield inside the car; and
license plate tags mounted on license plates outside the vehicle.

There are some specific design issues related to both of these tag types.

License plate tags must be on-metal tags, and very durable. They must survive weather conditions and car washing. Also, the position and the mounting angle are rarely ideal for readers. The natural best reading direction is straight backward (or forward), and at low height. In many applications the goal is to identify a vehicle approaching an identification point, for example an access gate or a road toll collection point. Reading would preferably be done from above or from side with an angle.

Windshield tags provide better reading angle. The challenge is to design a tag that works well with all possible windshields, regardless of the windshield’s angle, thickness, material, embedded technologies and type and proximity of the windshield frame to the tag position.

Both passive and semi-passive tags are commonly used. The semi-passive tags are battery powered; more of those can be read in earlier Voyantic Blog post.

EVI Tag Applications

Once the tagging is successful, it is easy to find use for the tags. Applications include road toll collection, tracking vehicle registrations and inspections, tracking tax payments, and parking control. Many of the applications are initially set for government purposes. Once the tags are in place, they can also be used in various value added applications of the private sector. Even if the tag is initially placed for registration, it can be used as a parking permit and gate access permit of a housing community.

Performance Testing of EVI Tags

A car is a special case of a tagged item. There are components that reflect RFID signals, absorb or block the signals, and may even resonate with RFID frequencies. These effects are different to different reading angles, they vary when a tag is attached to different position in a vehicle, and may even change when a tag’s mounting orientation changes. At Voyantic we have assisted several companies in defining test methods and processes for optimizing the EVI tag performance.

With the Voyantic Tagformance Pro system it is possible to test the sensitivity, tuning and backscatter signal strength of the car tag. The Tagformance system is an essential tool for evaluating effects of reading angles and mounting positions. The system can also be used for optimizing the EVI tag performance, finding optimal tag positions in the cars, and for finding optimal reader antenna positions for the applications.

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RAIN RFID Tag Read Range: Opinion or Fact?

Oct 31, 2016

About the author

Lasse Saarinen

I have been working for Voyantic as a Product Specialist since March 2014 mainly focusing on technical support. Before joining Voyantic I have 15 years' experience in customer support on telecommunications industry.

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中文版 Chinese version

Creating a tagging solution for passive RAIN RFID tags to a particular application starts with understanding the application specific requirements. That involves plenty of process engineering, but also typically discussions around the expected read range between tagged items and reader antennas. The read range is impacted by several factors and many start the cooking process by looking at the properties of RAIN RFID tags.

Tag datasheets carry plenty of information: protocol, operating frequency, chip type, memory utilization, physical size and much more. Amongst all information on datasheet, I reckon tag dimensions and read range are typically the first ones checked. Both are relatively easy values to understand, although the first one is a fact, and the second more an opinion. In the following I explain how to interpret the tag read range right.

Classic Approach: Take a Tag and Walk Away

The simplest way to get an idea of the read range is to place a reader to the end of a hall, take a tag and walk away from the reader antenna to see how far the tag can still be successfully read. In this kind of empirical test the result is not a fixed distance under which the reading would always be successful, but instead the result typically varies as below:

Result of a “walk away” read range measurement using a lower end RFID reader. What would you choose for a read range value?

Obviously such a result leaves a problem: how to interpret the results? What in fact is the read range in this case? A bigger problem is that the result is actually a synthesis of so many factors, such as reader properties, tag alignment, other objects in the environment, illumination in the hall, settings in the reader… So, what was it again you wanted to see?

Very few halls, office spaces or basements are stable enough to reproduce the test from day to another with the same test result. Therefore, key delivered value of this approach is merely the physical exercise, and most vendors don’t use these results in their tag datasheets.

Laboratory vs. Real Life Performance

RFID measurement systems characterize tags at high precision after which read range is calculated based on a few assumptions. Laboratory measurements themselves are often performed in shielded and anechoic chambers to remove other variables from the test results, which greatly improves the value of the data and the repeatability of the test process.

Theoretical read range of two RAIN RFID tags designed for different applications. Tag 2 shows better max read range at the FCC band, but is too highly tuned to efficiently cover the whole band. Despite of its shorter read range, Tag 1 as a broadband design seems like a more reliable choice.

This kind of measurement does not emulate effects of environment where tags are used. Experts talk of multipath propagation and path loss, and some others may talk of reflections, shadowing and interior design. No matter which definition is used, the environment is the grand source of differences between laboratory and real life performance.

Practical Difference of ERP and EIRP

Theoretical read range values plotted by the Tagformance system are based on the Tag Performance Parameters and Test Methods Version 1.1.2, 2008, EPCGlobal Inc. For the read range standard specifies 35dBm EIRP transmit power to be used in the calculation. 35dBm EIRP transmit power equals 33dBm ERP power. 33dBm ERP equals 2W and 35dBm EIRP equals 3.28W. If maximum power 4W EIRP is allowed, as in the FCC band, theoretical read range results can be obtained by adding 11% on the figures shown in the Tagformance software.

Forward Limited Read Range Is Not a Safe Assumption Anymore

As tag dimensions shrink and tag ICs become more sensitive, readers often become the limiting factor of read range. A reader with more sensitive receiver is able to pick up a tag’s reply from greater distance. When read range is analyzed it is typical to separate read range to forward (up) and reverse (down) links.

Picture below shows forward and reverse read range curves, which are calculated using 1W ERP transmit power, 2dBi antenna gain and -65dBm receiver sensitivity.

Separated forward, reverse and resulting read range curves. For ETSI range forward and reverse curves are equal, but for FCC range read range is reverse link limited – a reader with more sensitive receiver would improve read range on FCC band.

Tag Close Coupling Issues to Be Addressed by TIPP

As tagging spreads to new product categories in the retail industry, small tagged items are often brought into close proximity to each other. Just think about items boxed for transport. Especially when the distance between tags is less than 3 cm, the tags start to couple with each other.

The close coupling effects will be considered in the upcoming GS1 TIPP global standard. Stay put for Juho Partanen’s upcoming blog post regarding these issues!

From Opinions Back to the Facts

As you saw from the above, the read range is a factor of many issues. As you work yourself through the tag and reader datasheets with the aid of expert tools and good standards, you can connect the dots with relative ease. This process transforms opinions into facts.

I’d appreciate your comments and suggestions around these topics. New perspectives are always welcome.

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Battery Assisted Passive (BAP) Tags – Do You Know Your Reader Receiver Sensitivity?

Jul 29, 2016

About the author

Smoos Peng

Smoos started his RFID business in 2002. Currently, he manages METAG's daily activities to promote RFID measurement and testing solutions as a Voyantic distributor in Taiwan. In the meanwhile, Smoos also handles Voyantic business in Asia-Pacific region as APAC Director since 2014.

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One of my customers in Taiwan is developing battery-assisted passive (BAP) tags. He called me recently and asked why the read range that they reach with their RFID reader is only a quarter (1/4) of the distance that they measure with their Tagformance RFID measurement system. I answered him with another question: “Do you know your reader receiver sensitivity…?”

What Is a BAP Tag?

A BAP tag has an on-board battery to power its IC, but like a passive tag, it does not have an active transmitter. BAP tags are generally used to reach longer read ranges than what passive tags can provide, or for logging some physical quantity when a reader is not present. As known, the typical limiting factor for the read range of a passive tag is the forward link. In other words, the read range of a normal passive tag is determined by how far the passive tag can be powered or activated, i.e., the tag sensitivity is the limiting factor. Therefore, by default designing the passive tag to receive power from an on-board battery as a BAP tag, read range could be increased.

However, since the on-board battery is only used to power-on the RFID IC or to increase the BAP tag sensitivity, the battery does not really increase the tag backscatter power. As a result, the return link will become the limiting factor for the read range of a BAP tag. In order to fully realize the maximum read range of a BAP tag, the reader receiver sensitivity becomes crucial.

The Performance of a BAP Tag

When evaluating the performance of an RFID tag, the starting point is usually measuring the sensitivity of the tag as a function of frequency. The graph below shows the Tagformance Pro’s Threshold Sweep measurement results of one BAP tag. As can be seen, the theoretical read range for this BAP tag is close to 37 meters at 930 MHz. That is a lot; the read range of a good passive tag is around 10 meters.

Sensitivity of a BAP RFID Tag Measured with Tagformance Pro

But the forward link read range above is only the theoretical upper limit of the read range that can be reached. Below we use the Tagformance Pro’s Read Range measurement functionality to test the BAP tag with different reader parameter settings. The radiated power is set at 2W ERP. The yellow curve below shows that the read range is about 19 meters at 930 MHz if the reader receiver (RX) sensitivity is -85 dBm.

Read Range of a BAP Tag Measured with Tagformance Pro; 2W ERP & -85 dBm Sensitivity

By changing the reader sensitivity in the Tagformance software, we can see what reader sensitivity would be needed to reach the theoretical read range maximum. This situation is shown in the yellow curve below. The reader sensitivity required to reach the 37-meter read range is -97 dBm.

Read Range of a BAP Tag Measured with Tagformance Pro; 2W ERP & -97 dBm Sensitivity

From my experiences, it may not be easy nowadays to find a reader with the RX sensitivity of -97 dBm. Therefore, in order to reach the read range of 37 meters, I have suggested my customer redesign the BAP tag’s antenna to make the tag having stronger backscatter power and use a higher sensitivity reader if possible.

Reader receiver sensitivity is getting more attention in the RFID market after the increase of tag sensitivity both in BAP tags and normal passive tags. This means that the limiting factor for the read range is the return link. Receiver sensitivity is the key to optimizing the read range. Interestingly, most system integrators and even UHF reader suppliers do not know how to measure the receiver sensitivity.

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Designing a RAIN RFID Sensor. Simple, or Is It?

Mar 23, 2016

About the author

Jesse Tuominen

I joined Voyantic as a partner in 2005 to design Voyantic's first commercial product, and I've had a front-row seat since then to see how the RAIN technology has evolved and matured while bringing my own contribution to it. As a background, I have a MSc level in electronics after which I made my PhD in the field of photonics. UHF RFID slots nicely between these two worlds and they offer a lot of perspective into my work. Currently, as the CTO of RFID technology, I work with new measurement methods, RF design, proofs of concept, standards, protocols, industry collaboration and IPR.

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Combine identification, sensors, low cost and years of life time together and you certainly end up with a disruptive mixture that is set to boil over in the near future. RAIN RFID sensors may not be a huge market just yet, but we can see many companies putting a lot of development effort on them. Read on to see an introduction to the six topologies that I’ve seen utilized so far.

1) Affecting Antenna to Chip Matching

Right from the beginning of the UHF RFID, engineers have been aware of the inlay antenna’s sensitive nature to change its parameters whenever just about anything changes in its proximity. So, it didn’t take long for scientists to call it a sensor. No added energy was wasted on sensing electronics, therefore potentially long sensing ranges were expected. In practice, however, these type of sensors never got too much of a foothold on the market, as the tags were still sensitive to many measurable parameters, and not just one.

The impedance of the antenna is affected, making a detectable change in frequency tuning, activation power, or RSSI.

2) The Dual Tag Relative Approach

To address the real world problems of the previous approach, a simple improvement was soon used. This time, two similar inlays were encapsulated into one physical tag casing, but one of the antennas is made more sensitive to one particular property. For example, if salt impregnated foam is placed over one of the inlay antennas, it doesn’t affect the antenna when dry. However, when humidity rises, it will deteriorate the performance of this antenna at a much faster rate. The reader would poll both of these tags, typically of a sequential EPC code, and monitor the difference between the two RSSI levels.

The impedance of one of the antennas is made much more sensitive to the parameter to be measured.

3) The Embedded Tag

A few years ago the most common type of sensor tag was the embedded type of tag. In this form one or several sensors and inputs can be monitored, logged into memory and read from there when needed. Practically any type of sensoring can be performed in this way, but the solution requires a battery. Although the battery does not sound like a too bad thing to have inside, however the advantage to other technologies, like Bluetooth LE, is rapidly lost. There are also several RFID chips that work with the same principle, but alone without a separate microcontroller.

The RAIN tag uses an I2C interface to interact with a separate sensing circuitry. All this requires more power that the tag can harvest from the RF field, thus a battery is added.

4) Using Automatic Chip Impedance Tuning

Adaptive chip impedance tuning was long awaited, and finally RF Micron was among the first to arrive to the market with a chip with that capability built-in. It didn’t take long till it was used to detect changes in the antennas proximity just like in the case 1. The biggest difference is that now the sensing result can simply be read from the tag memory and not from the RF properties of the tag.

An RAIN RFID IC with automatic chip impedance tuning capability stores the data in the tag memory where it can simply be read with a reader.

5) Binary Sensing

Several ICs have a special pin called the tamper detection pin. Whether this pin is in contact with ground or not can be polled by the reader. It is thus not so difficult to turn this tamper function into a sensor with a bimetallic strip, mercury switch, level float, magnetic switch, NTC resistor, etc. The fact remains that this topology of sensor remains binary.

ICs with tamper detection can be turned into a binary sensor with relative ease.

6) Inbuilt Sensing Capability

To bring potential cost down and optimize the energy consumption of the tag, the sensor is best integrated into the RFID IC itself. As no busses, microcontrollers, sensors, etc. need to be powered externally, the reading range can be potentially close to that of industry standard tags. The range of measured properties are more limited with this approach, temperature being the simplest candidate.

Built-in sensors can be powered from the RF field without a battery.

All this is to say that RFID sensoring can, in fact, be really simple. However, to get the solution working right also on-site with a known level of sensing accuracy requires advanced methods and a correct set of tools.

Getting It Right With Proper Tools

A number of RFID sensor developers are already using diverse functionalities in the Voyantic Tagformance systemto accelerate tag development cycles, optimize designs and to characterize their products. The more data there is in the sensor tag datasheet, the easier it is for anyone to take it into use!

If there is a particular type of testing you need to get done, but cannot find that particular function in our software GUI, please do not hesitate to contact us! Check out also our earlier blog post of passive RFID sensing!

Learn How to Design Passive Sensor Tags

Download our application note “Utilizing Voyantic Tagformance to Speed Up Development of UHF RAIN RFID Sensor Tags” to learn how to design passive sensor tags!

Download Now

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How to Win Sales with Good RAIN RFID Test Data

Dec 29, 2015

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Teemu Ainasoja

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When selling RAIN RFID tags: wouldn’t it be great to prove that the proposed tag is the best possible one for the customer’s application instead of just sending out loads of free samples hoping that the customer tests them properly? And when purchasing: wouldn’t it be great to have comparable data of how each tag works in your application instead of “our tags are the best ones, you can trust us” statements?

Guess what: it is possible, and in most cases, the salesperson or the buyer just needs to know what to ask. Tag developers have a lot of characterization data ready. Read on to see how to leverage that data following the 3-step approach!

Step 1: Extract Tag Characterization Data from the Production Quality Log

Useful RAIN RFID tag data combines production quality information with detailed laboratory test results. Production quality data is a good starting point since it shows the overall quality variation. With Voyantic’s Sweep Data Analyzer, it is easy to identify the typical and the worst acceptable tag and to quantify variation. Variation can be described, for example, as each tag having a sensitivity of -8 dBm +/-2.5 dB. With the Tagformance viewer software, the sensitivity values can also be translated into read ranges.

RAIN RFID tag quality – variance in RFID production quality

Step 2: Connect RAIN RFID Tag Performance Data to the Use Case

Detailed information about the performance of a RAIN RFID tag can be generated by testing the selected sample tag (typical tag or weakest tag) in a laboratory environment. The goal of the laboratory tests is to show how the tag would perform in different applications. Simply place the tag or tags on Voyantic Reference Materials in different arrangements and run the tests on Tagformance.

When proper test data is available, there is no need for extensive field tests with various tag and reader combinations. Shortening the field tests saves time and money significantly – both for the seller and the buyer.

Typical test results include RAIN RFID read ranges and orientation patterns on various materials and within diverse tag populations. When the tags are attached to different materials, their tuning, and performance level change, with the test results, it is possible to evaluate what the read range would be with varying models of readers. The results predict how the real-life RAIN RFID system will work. With proper tag data, even RAIN RFID readers can be easily compared, and the bottleneck of the system performance can be identified.

Step 3: Let the Customer Play with the Data

Utilizing RAIN RFID tag test data is really simple. As a result, you are able to assist your customer efficiently, and most likely, also to shorten tag sales cycles. If you want to learn the specifics related to RAIN RFID tag data crunching utilizing the Tagformance software, please read on.

Tagformance Read Range test results are an excellent way to compare tags. Choose test data with the tag population and material corresponding to the RAIN system use, and enter reader the information.

The graphs show the read range of one RAIN RFID tag with two different readers.

When the tag is tested with the RAIN RFID reader parameters entered into the system, the test results show the overall system performance.

In the first case, the system level read range bottleneck is tag sensitivity, and the resulting read range is 8 meters (26 feet) in the FCC frequency range.

RAIN RFID tag read range and reader sensitivity

In the second scenario, the reader has lower sensitivity, read range decreases to 5 meters (16 feet), and the system level bottleneck is reader sensitivity.

It is also easy to tie production variation to the test results. With production, variation included the read range variation is 3.5 meters to 7 meters (12 feet to 23 feet).

RAIN RFID tag read range and production variation

Producing the same information with tag samples and a reader is difficult and uncertain. Depending on the selected sample tag, the expected read range may be anything between 12 feet and 23 feet, and there is no information about the variation. Surprises await in implementation, and counting accuracy is likely to be well below 100%.

Other test results show, for example, the orientation pattern – how the read range changes when the tag and the reader are not facing each other directly, and how the tag performance changes when there are multiple tags in front of the reader.

Good RAIN RFID Tag Performance Data is a Powerful Sales Tool

There is a lot of tag test data available, and the Tagformance viewer software is an excellent tool for presenting the data to the customers.

Tagformance Viewer is Available and Can Be Used by Anyone

With the viewer software, it is easy to choose results from RAIN RFID tag tests corresponding with the customer’s intended use scenario, input reader information, and see the actual system-level performance.

Download a Sample Datasheet Showing RAIN RFID Tag Performance and Quality Information

Download here an excerpt from a sample datasheet showing how to tag data could be presented in a datasheet. The sample shows how the tag performance and quality information is presented in a format that is useful for the customer in tag selection.

Download Sample Test Data and Tagformance Viewer Software

The Tagformance viewer software can be used to view test data. By inputting different reader parameters, such as reader power, to the software, the application shows how the read range changes. By inputting tag variation information, read range variation can be seen. The viewer software can be used for viewing and analyzing data from the tag developers and manufacturers. Would you like to try? Contact us and I will be happy to send you the software installer with demo results!

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This Doesn’t Look Right – Should I Contact Technical Support?

Dec 11, 2015

About the author

Lasse Saarinen

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What do you do if, one morning, a new light with some strange symbol is suddenly lit on your car’s dashboard? You probably pull over and start browsing the car owner manual. You may be a little worried. Did I do something wrong? Can I fix this myself, or does the car need to be serviced? How long will I need to survive without my car?
In the same way, your Tagformance, the RFID test system that you typically use every day may have a problem you need to solve. You may already be an experienced user, or maybe you have just recently started to work with the system. When a new error message pops up or you get unexpected measurement results, it’s just like with your car. What’s wrong? Should I contact Voyantic Technical Support?

The answer to the last question is yes. You should.

*‘No such thing as a stupid question’ is a common phrase with a long history, and it makes perfect sense to me. *

If you have a problem with anything, and there is a possibility to get it solved quickly by asking someone who can help you, why shouldn’t you? The one who asks the “stupid question” may be doing a service to everyone, including the vendor, by pointing out a visible improvement to the product.

Here are some more or less typical situations where you might wonder if you should contact the vendor or just carry on. Uncertainty: You are performing measurements that look nice and smooth, but deep down, you are still wondering whether the results are correct? Is there some bias in the device? Am I measuring the right way? By contacting Voyantic Technical Support, we can verify if the device is OK by comparing the reference tag measurement results with the same measurement setup. We can also measure your sample tags and give a second opinion of the results and maybe give pointers on what else you can measure from your tags.

Differences between sites: You may have a colleague in the next room or on the other side of the globe doing the same measurements that you are. The equipment may be the same, the setup may be identical, but still, your results don’t match completely. For example, you get a theoretical read range value of 11 meters, and your colleague measures 10 meters. One meter sounds like a lot, but is it after all? By looking at the measurement data, we can verify whether the difference is something to worry about, or if it fits into production variation and typical measurement accuracy. Other factors, such as temperature, may cause a difference. The effect of temperature is described in more detail in an Application Note, which can be downloaded here. While visiting the site, you may find other Application Notes worth reading too.

Missing features: Different Tagformance measurement options are enabled with the license file. We can create license files where any measurement option can be enabled for a given time. So, if you think that one or more options could be useful for your work, we can enable the option for a trial period. To name a few;

Scripter is a great tool to automate your daily measurement routines and reduce the human error from the results.
The Tagformance has two Application Programming Interfaces, APIs, that enable you to write your software that uses the Tagformance device. The LabVIEW API is a perfect match for LabVIEW users, and the DLL API serves users of other programming languages.
Memory management is a brand new tool for one of the hot topics, sensor tags, for example. With Memory management, it is possible to verify changes of any memory address content within seconds.

All this said, do not hesitate to contact us! In most cases, it is a win-win situation where you will get your problem solved or a question answered, and we get valuable feedback, which will help us in making our products even better. We are here to help you – send us a message!

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