SmartX Launches Multilinear RFID Portals

The technology, which gathers multiple antennas in different positions, allows readings where the exact positions of tags cannot be guaranteed, and at a lower cost.
Published: October 2, 2019

SmartX Tags is launching in Brazil its line of special radio frequency identification (RFID) portals with multilinear technology, which allows for the controlled and efficient reading of tags arranged in different positions and at much lower deployment costs, the company reports. “No excess reading [is required], just the essentials,” says Pedro Moreira, SmartX’s CEO.

SmartX already has several customers adopting this new portal concept, though some of these clients, due to contractual issues, do not allow the disclosure of their projects. In addition to retail companies such as Havan, there are businesses in the white goods industry, as well as hospitals, that have adopted this technology.

Left: trucks at the docks with the SMTX portal in the background. Right: the side portal, with the trucks at the docks.

Multilinear technology consists of gathering, in a single antenna element, multiple linear antennas in series and positioned at different angles in order to favor greater reading coverage for complex environments, where one cannot, for example, guarantee the position of a single antenna. “No matter if the tag is positioned vertically, horizontally or perpendicular to the antenna, the reading will occur the same way,” Moreira says.

According to Alexsandro Eloi Venancio, Havan’s RFID product owner, for the company’s freight-forwarding project, “We performed tests with different portal designs, the major intricacies being reflections and a 100 percent guarantee of cages passing through the portal. The antenna model proposed by SmartX presented a good reading result, since the antenna projects the reading along the entire length of the portal, as though it were a curtain.”

“This way, it was possible to work with very low antenna power, reducing signal reflection problems to zero and, most importantly, ensuring 100 percent readability,” Venancio says. “Havan has an in-house software-development team and has opted for middleware and application development, but the support and exchange of experiences with the SmartX team was essential to the project’s success, including our partners in providing software, equipment and labels.”

Comparing the most popular RFID antenna polarization technologies with multilinear technology, linearly polarized antennas enable RFID tag readings over greater distances due to their directionality, allowing for a smaller reading angle. For the reading to take place successfully under these conditions, the RFID tag must be positioned horizontally or in the same plane as the antenna. One example of applications that use linearly polarized antennas is toll plazas, where tags must be read at long distances and in only one lane, with a smaller opening angle.

Circularly polarized antennas allow RFID tag readings at shorter distances and wider reading angles. For the reading to take place efficiently, the tag can be positioned vertically or horizontally, always in relation to the same antenna positioning.

However, Moreira explains, tags positioned perpendicular to the antenna plane (horizontal for top antennas or vertical for side antennas) may have their readings impaired. One commonly used technique for reading tags perpendicular to the plane of a portal’s side antennas is the adoption of antennas on the top, leaving the antennas positioned on the sides to ensure the coverage of tags positioned vertically and horizontally.

Havan’s Alexsandro Eloi Venancio

However, RFID tags positioned perpendicular to the plane of the side antennas and at the bottom of a goods pallet can still have their readings impaired. “With that, more antennas should be placed,” Moreira explains, “which makes it common to find portals with up to eight antennas to ensure 100 percent readability. This will still depend on the type of tag,” resulting in higher deployment costs.

Examples of applications using circular-polarization antennas include airport baggage-scanning solutions. “You never know the position of the RFID tag that should be read,” Moreira says. “Whether vertically or horizontally, the tag is likely to be read by one of the numerous strategically placed circularly polarized antennas.”

SmartX’s Pedro Moreira

Multilinear-polarization antennas enable RFID tag readings at shorter distances due to the small size of their multiple integrated antennas. That is, they have less gain over circular and linear antennas, but allow more efficient readings of a larger number of tags in a smaller space, thereby avoiding unwanted readings in the vicinity of the portals.

With the adoption of RF signal-confinement techniques, it becomes possible to limit the read zone and adopt higher signal strength in RFID interrogators without reading tags in neighboring read zones. Attempts to deploy this technology in the past have not been successful in Brazil, however.

“With the expertise and practical experience of SmartX’s technicians, we took the challenge,” Moreira states. “Now, the portals are offering results. Therefore, the adoption of multilinear antennas is not new in Brazil. The novelty is the implementation and proper manufacture of the portals.”

With the new portals, regardless of the tags’ positioning in the products, reading efficiency is practically the same due to the numerous planes present in a multilinear antenna, creating the possibility of segregating multiple reading zones, and adopting a single RFID reader. “This is possible because the technology of multilinear antennas allows the adoption of a small number of antennas—two per portal,” Moreira explains. Adopting a single reader also reduces the investment cost of the RFID portal, he adds.

RFID portals for receiving and shipping items at distribution center docks, due to the proximity between the docks, are an example of applications that will gain from the use of multilinear-polarization antennas. “Multilinear antenna technology was developed by Ohio State University’s Electro Science Laboratory, by Dr. Den Burnside, then the director and emeritus professor at the same university,” Moreira says.

A comparison of the patch antenna of the traditional portals (left) with the multilinear antennas used by SMTX portals (right)

This technology allows efficient reading only of products passing through the portal, which prevents the reading of products from outside the desired reading area—i.e., those already received and stored near the docks, or that are being loaded or unloaded at neighboring docks.

The portals, made by SmartX, are called SMTX Portals. They adopt multi-antenna antennas as components of exclusive agreements between SmartX and the Electro Science Laboratory, represented by Newave, also of Ohio. In this agreement, ESL supplies multilinear antennas and SmartX produces portals in Brazil, following the technical guidelines. “For logistical reasons, it makes no sense to import bulky and heavy U.S. portal structures,” Moreira explains. “Only the light and bulky elements of the antennas are imported, and the assembly of the portal structure becomes feasible in Brazil.”

Portals are intended for reading many items and in complex environments in which there are multiple reading zones nearby, due to their efficiency, without “spreading” the RF signal too much. They are not recommended, however, when reading distance is the most important requirement—even for its technical feature of close- and short-range reading—no more than 6 meters wide and up to 3 meters high, or a maximum RF curtain of 18 square meters.

Compared to conventional portals, the SMTX Portal has a lower price since it is possible to build up to two portals using only a four-door reader. Two reader ports are adopted for each portal: ports one and two for portal one and ports three and four for portal two.