Impinj M700 RAIN RFID ICs: what’s new?

Improved read sensitivity

The read sensitivity of an RFID IC is the fundamental parameter defining the maximum reading distance you can achieve between an RFID label and a reader. The lower the sensitivity, the less power an IC needs to get turned, the longer the reading distance. Moreover, an improved sensitivity also leads to better readability of ‘stacked’ labels when they are close together.

The chart below shows the IC sensitivity versus the year of introduction. Roughly, there is a 0.5 dB improvement in IC sensitivity per year - and this trend is continued with the introduction of the M700 series. For reference, an improvement of 3 dB in label sensitivity results in a 40% increase in reading distance.

Reality is, unfortunately, a bit more complicated: the sensitivity of the whole RFID label (IC plus antenna) does not only depend on the IC, but also on a number of other factors (size of the label, antenna design, material the label is placed on, region of the world, etc.). With Monza R6, Impinj introduced a feature called 'Auto-tune' that automatically optimises sensitivity, even when conditions are sub-optimal. NXP has a similar technology in UCode8 called 'Self Adjust'. This ensures better performance, even in challenging conditions. Impinj M700 introduces 'enhanced' Auto-tune. What exactly 'enhanced' means (compared to 'regular' auto-tune in Monza R6) is unclear from public documentation, so we need to await mass-produced labels to understand the improvements.

For most applications in retail, the reading distance was not a limiting factor in applications before this generation of label ICs. It is therefore quite likely that the enhanced sensitivity will be used to reduce the typical size of an RFID label, which reduces cost and allows easier integration in existing tickets and packaging - and keeps reading distance consistent with the previous generation larger labels.

Privacy is getting a lot of attention

Impinj is putting a lot of attention to the privacy features of the M700 line of products. This is very understandable, with the increased public scrutiny over privacy and the introduction of GDPR in Europe and CCPA in California.

At the same time, more and more retailers are considering using deeply embedded RFID labels in their garments, instead of putting RFID labels in swing tickets (with obvious benefits for Loss Prevention and Grey Market reduction). But, it makes the RFID labels less trivial for consumers to remove, and therefore creates increased risk for consumer privacy invasions.

The good news is that privacy features have been part of the Gen2 standard for a few years now, and with the introduction of M700, both NXP and Impinj now offer a standardised feature to reduce the reading distance of an RFID label to a bare minimum at point-of-sale - after the item has been purchased. This ensures that it is much more challenging for bad actors to infringe on people's privacy.

In contrary to NXP, Impinj Impinj chose to not implement a standardised feature to hide (part of) the EPC and TID memory banks - at short or full reading range. Instead, it opted to implement a non-standard feature where you can render the complete IC inaccessible (even unreadable) when you don't provide the correct password (named 'Protected Mode'). This potentially provides even more privacy protection - but as this is not part of the Gen2 standard, it is challenging for retailers to consistently implement across all products.

Driving down cost: new production process and less memory

With M700, Impinj reduced the size of the label IC to 397x287 μm - which is a 45% reduction in the area compared to Monza R6. In combination with the usage of larger (300mm) silicon wafers, this will surely drive the price level of RAIN RFID labels further down.

To quote Impinj in their press release: "Impinj M700 series ICs are so small that roughly 30 million of them will fit in a single coffee cup", which is quite astonishing.

A new production process that allowed for smaller components was the main reason for the size reduction. In addition, Impinj opted to have only one password in the IC, instead of separate access and kill the password. As storage memory occupies most of the space on an IC, this also contributed to driving down the size of the IC. A consequence is that it is not possible anymore to distinguish between providing access to an IC (to e.g. enable privacy mode) and the ability to kill a tag. In practice, this will not have big consequences and seems like an interesting trade-off.

To compare sizes of modern RFID ICs, the image below puts it in perspective:

Feature comparison

In the chart below you can see all modern RFID ICs, and their respective features in one handy overview.

Product Developer

Danny Haak

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