RFID Arena


RFID shopping-cart level checkout is possible with technology that is available today

This guest blog was written by Jed Griffin and Scott Deuty. They describe how the elusive shopping-cart level checkout is now entirely possible offering the retail industry a real breakthrough in widespread use of RFID tags.

Authors: Jed Griffin and Scott Deuty

Despite many failed attempts, the elusive RFID based shopping-cart checkout is now entirely possible - a real breakthrough in RFID.  Both the technology and methodology now exist for making cost effective tags that have enough range to be read as the cart passes through a reader bay.  In order to overcome limitations of existing technology and allow for successful shopping-cart checkout, or item-level tagging, the following criteria must be met:

  • Cost, size, and power must all be significantly reduced to enable ubiquitous use of tags
  • Transmission ranges need to vastly increase from their current 15 cm to one meter

A new technology that enables RFID shopping-cart checkout has been created. The trick is to keep die size and antenna dimensions small while achieving a one meter transmit range with low transmit power. This new technology reduces current, comparable, tag die sizes to less than one tenth of comparable quadrature die, via a simpler architecture with much fewer stages, which also reduces power. By keeping the required Signal-to-Noise Ratio (SNR) small on the receiver (increased sensitivity), the antenna dimensions can also be kept equal to the small die size and lower transmit power to achieve comparable distances that RFID currently do with much larger antennae dimensions and higher power. Thus it will transmit roughly 10 times further than today's archaic solution, extending the current prohibitive 15 cm (6 inch) range (given small enough die and antenna dimensions to qualify as an item tag) well into the far-field range approaching one meter (several feet) required for item-level tagging or shopping-cart RFID - meeting both criteria.

This advancement will enable the shopping-cart checkout as well as receiving and instantaneous inventorying. The overall cost reduction over current methods of check out and inventory will be large. For instance, because of near instantaneous check out from RFID, the queues and manual operation inherent in current serial check out methods will be greatly reduced or effectively eliminated. Likewise, inventorying will eliminate manual operations and reduce to an almost simultaneous accounting for all tagged items.

In order to productize this technology, several things must happen. A modulation scheme needs to meet the criterion listed above and the industry must standardize on such a viable solution. Because the criteria cannot be met with existing methods, this new technology will be needed to create such a new market with item-level tagging.

Rest assured, a new industry standard won't be based on 802.11, nor any of the quadrature architectures commonly employed in RFID.  Gen 2 tags, the proposed Electronic Product Code (EPC) [1] Global Class 1 Generation 2 methods of transmission, also have flaws that limit the range and ability to keep tag and antenna size small while transmitting the required distance into far field. Overall, the currently proposed standards using quadrature architectures are notorious for superfluously large tag or antenna sizes and reduced transmission ranges (less than 15 cm) due to poor Signal to Noise Ratio (SNR) [2]. This is the reason, that after years of trying, current efforts have failed to realize the required criteria for a shopping-cart solution.

Using Ultra Phase Modulation (UPM), a fast two-constellation Frequency Shift Key (FSK modulation), the criteria for a shopping-cart application can be met.  FSK was once proposed as a possible transmission method for the 802.11 Wi-Fi standards yet it was abandoned in 1997 due to the limitations of the technology available at the time.  Ultra Phase Modulation has overcome these limitations to a point where a CTO at a large semiconductor design company with an extensive background in wireless communication (who was on the original 802.11 committee) confirmed that Ultra Phase Modulation, or very fast FSK, can indeed achieve the far superior wireless performance over existing quadrature architectures as touted and demonstrated via simulation results.

Ultra Phase Modulation architecture is shown in Figure 1. By eliminating stages of quadrature receivers, the down-convert, quadrature synchronization, and Digital Signal Processing (DSP), all of the corresponding noise, die area and power consumption are also eliminated. The eliminated noise, the dominant channel noise resulting in the high SNR of quadrature receivers that severely limit their transmission range, allows the SNR of Ultra Phase Modulation to now be kept much lower. At much lower SNR the antenna dimensions per given meter range can also be kept low and on the order of the die size which also reduces by roughly 90% (also reducing power). Thus Ultra Phase Modulation meets the criteria for shopping-cart checkout via RFID, smaller size and cost, and longer transmission range.

Gain IC_first

Figure 1. UPM eliminates noisy and area-consuming stages, to reduce size and power.

As a result of the advantages offered by this breakthrough technology, the RFID tag industry can now move towards longer transmission ranges that are roughly 10 times farther as depicted in Figure 2  The Ultra Phase Coordination produces much stronger signals (much less power dedicated to overcoming noise) thus enabling shopping-cart checkouts, and item-level tagging. The other criterion, the smaller die size can also be readily ascertained by the simplified architecture of Ultra Phase Modulation, which is roughly 10% of typical die area with correspondingly small antenna dimensions. This enables tags that are small enough for individualized tagging for massive inventories. Ultra Phase Modulation translates into greatly reduced cost, relative to the nickel per die cost of printing bar codes, keeping costs low as desired by the retail store economy [3]. Approaching these costs allows Ultra Phase Coordination to supplant the commonly used bar codes in inventorying and checkout.

Gain IC_2

Figure 2.  UPM improves transmission distances by orders of magnitude over quadrature architectures.


Ultra Phase Modulation has the inherent advantages needed to achieve the RFID shopping-cart checkout, or item-level tagging, as verified by longer transmission distances and significantly reduced size, cost, and power consumption versus existing methods. Such details can be further explained by contacting info@gainics.com.


EPC™ Radio-Frequency Identity Protocols, Generation-2 UHF RFID, Specification for RFID Air Interface, Protocol for Communications at 860 MHz - 960 MHz, Version 2.0.0 Ratified

A New Technology Makes RFID Tags Much Less QAMplicated, Deuty and Griffin, RFID Journal White Papers Library, February 2014.

Item-level tagging in the grocery industry - are we there yet?, Hanna Östman, 02 April 2013,

Gain Ic _writers

[Right] Jed Griffin is currently the CTO and co-owner of Gain ICs, in Colorado Springs, Colorado. Gain ICS is an Analog Integrated Circuit (IC) Design House, developing ICs that are well beyond state of the art. His greatest innovation to date is the development of an ideal Phase-lock Loop (PLL), Ultra Phase Coordination (UPC) and a high-speed wireless link utilizing UPC which he has coined Ultra Phase Modulation (UPM). His current efforts are focused on bringing this technology to market. The performance gains of UPC and UPM are large and substantial enough to warrant the supplanting of ubiquitous quadrature architectures thus enhancing performance in all wireless applications. He has spent 20 years working as an Analog IC Design Engineer.

[Left] Scott Deuty is Director of Business Development for Gain ICs.  Scott is an accomplished technical writer with over 30 years of experience in analog circuitry.  He is a visionary who has a talent for recognizing new technologies such as synchronous rectifiers.  Scott wrote AN1520 an application note on this subject that has survived emerging technology and is still available on the internet twenty years after its first publication in 1994.  Scott is "enjoying the hell" out of promoting the Gain ICs ideal PLL, a disruptive technology that will surely impact the data transfer industry for the better.

22 comments on “RFID shopping-cart level checkout is possible with technology that is available today”

  1. Gravatar of Sergey DudnikovSergey Dudnikov
    Posted 15 May 2014 at 12:22:07

    FYI, the RFID future store with automatic checkout of the shopping basket (not cart) was realized in Moscow in 2012-2013 (http://futurestore.ru/en/).
    In our practice, we could not make a step from the basket to the cart. The reason is the size of near-field zone.
    Just try to make some experiments with the basket, full with radio-opaque and radio-absorbing food (ex. mixed cola, meat, chocolate, chips), using the magic abbreviations UPM, DSP and whatever else. I believe only in power of electric and magnetic field, and antenna+chip sensitivity. If RF does not exist in this area, you may use any modulation, it is useless.

  2. Posted 16 May 2014 at 02:49:52

    You bring up a valid point. We are aware of the efforts in Moscow. They used quadrature architecture as a modulation method which typically have poor signal to noise ratios. By the time you power the chip, you have virtually no signal power left with a quadrature architecture. That is not the case with this technology as shown in Figure 2.

  3. Gravatar of BillBill
    Posted 02 June 2014 at 10:46:10

    Interesting article. What impact do you expect UPM architecture to have on the readability of items containing metal and liquids?
    We produce steel items and it would be great to have a solution to tag them at item level even when stacked multiple units deep on a pallet. Could this be the solution?

  4. Posted 02 June 2014 at 17:50:28

    Yes, UPM can still keep signal strength high enough to overcome reflections from adjacent items like metal cans and transmission through containers with liquids, while achieving uninhibited tagging (transmitting well into the far field while keeping antennae dimensions smaller than a printed barcode). This cannot be achieved with current technology.

    While current technology with antennae dimensions smaller than a printed barcode can transit at most up to 15 centimeters, UPM at same dimensions is showing transmission distances beyond 4 meters by eliminating much of the noise common in current receivers -- the much lower required SNR of UPM means more transmitted power going to signal, which means greater receiver sensitivity and far greater transmission distances. This would definitely be a benefit in the item-level tagging environment you are describing.

    My email is jed.griffin@gainics.com. Feel free to contact us and we can provide you with more details into uninhibited tagging.

  5. Gravatar of Jared NewnamJared Newnam
    Posted 17 October 2014 at 20:42:36

    What measures are taken to prevent the cross signaling between two people, who might be standing next to each other?

  6. Gravatar of Kirsikka DrägerKirsikka Dräger
    Posted 20 October 2014 at 14:50:39

    Hello Jared, this article is a guest blog. If you would like to receive more details, please contact Jed for more information.

  7. Gravatar of sufri farouqsufri farouq
    Posted 09 August 2015 at 17:49:53

    give me more details about this project

  8. Gravatar of Suvi DalénSuvi Dalén
    Posted 11 August 2015 at 08:56:00

    Hi Sufri,

    in one of the comments above, you find Mr Griffin's e-mail address - you may ask him directly if you like, he is the other author of this blog.

    br, Suvi

  9. Posted 15 November 2016 at 20:45:37

    Hi, kirsikka would you please share his email address so that I can conduct with him?I found may errors whilst shopping here for many places.But this could be temporary which needs less attention to fix.

  10. Gravatar of KirsikkaKirsikka
    Posted 22 November 2016 at 11:17:36


    contact details are already disclosed above. Hope this helps!



  11. Posted 17 December 2016 at 07:30:00

    can you provide me more information on my email id so that i can take next step for this

  12. Gravatar of KirsikkaKirsikka
    Posted 20 December 2016 at 13:26:26

    Hello, what kind of further information were you looking for? BR, Kirsikka

  13. Posted 30 March 2017 at 22:18:09

    thanks for the info...

  14. Posted 31 March 2017 at 09:59:47


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