Differences between UHF Gen 2 RFID and HF RFID

At present, the performance of UHF Gen 2RFID on small monomers on high-speed production lines is comparable to that on box pallets in freight centers. Due to the low cost, UHF RFID has caused the old, slow and expensive HF 13.56 MHz RFID technology to become obsolete. Before deciding which RFID technology to deploy, it is necessary to understand the basic concepts of UHF and HF.

Radio frequency waves contain two components: magnetic waves and electric waves. Generally, HF RFID 13.56 MHz relies on the "near-field" magnetic field in the electromagnetic field, while UHF RFID 860-960 MHz is far-field radiation, which includes both magnetic field and electric field. The kind of wave that responds in the UHF tag depends on two aspects: the distance between the RFID tag antenna and the RFID Reader.

Since the strength of the magnetic field component in the wave will decrease rapidly with distance, it can only work in the near field. Its effective range is limited by the antenna structure to about one or two wavelengths. Since the HF tag uses inductive coupling to sense the magnetic field in order to receive energy. HF tag antennas are usually inductive type antennas that act somewhat like coils and therefore require more conductive material and a more complex manufacturing process than equivalent UHF tag antennas. Fortunately, HF tags do not have a dead spot above the magnetic field, and with a suitable antenna, UHF tags can easily capture the same near-field energy, much more efficiently and cost-effectively.

Maxwell's four equations are the basis for the analysis and design of electromagnetic fields. Faraday's law is one of these four equations: "The voltage induced by a coil in a magnetic field is proportional to the strength and frequency of the magnetic field". This reveals an extremely simple concept: the higher the frequency, the higher the efficiency. The frequency of UHF is 60 times that of HF, which means that for the energy coupling efficiency between the RFID tag and the RFID reader antenna, UHF is about 60 times that of HF.

The traditional concept is that UHF RFID is not suitable for item-level tags: the tag is too large, and UHF RFID cannot work on liquids, metals, and small single-item packages that are close to each other. And UHF is too far away, all of which ignores the fact that UHF Gen 2 can be used in the near field much more easily and efficiently than HF. This means that UHF systems can read a lot more things that HF can read, including liquids and items with a high metal content. More importantly, this means that item-level applications have been able to balance the various benefits brought by the UHF Gen 2 standard to the supply chain. The key is how to control the near field of UHF. This component in the radio frequency wave is especially suitable for the item-level RFID work at a very short distance. Applications using near-field UHF Gen 2 solutions are growing.

In December 2004, EPC global approved the UHF Gen 2 protocol, resulting in the first global RFID standard. Since then, the market has seen many products that meet this standard. This popularity proves the ubiquity from single items, containers to pallets, objects used in both near field and far field, and materials covering liquids, metals, tightly packed and packaged items, etc.

Three years later, HF product developers had to endorse the standard. On the contrary, the latest HF specification has disillusioned the drafters. According to Ken Laing, standard writer for HF "V2" (the HF version of UHF Gen 2), work has so far been limited, with limited improvements to existing standards and some commercial products emerging.

Laing believes companies encoding EPC on Gen 2 HF tags will see performance improvements relative to encoding EPC on the currently popular HF standard ISO 15693. He said that according to the results of RFID Update, although the improvement is not earth-shattering, it is still much better than the HF products currently on the market. Perhaps the important point is that even though the standard has been approved, the so-called qualified V2 products will not meet it in the first place. It will take a long time, and even if it is available now, it will not reach the current performance of UHF Gen 2.

However, this article returns to continue to look at the frequency debate, because it is related to the actual deployment.

Consider the following factors:

* UHF Gen 2 covers various applications in all global supply chains;

* UHF Gen 2 is effective on all types of product materials, including liquids and metal materials.

So as far as UHF Gen 2 is concerned, it is redundant in HF RFID technology because:

* There is nothing that HF can achieve but UHF cannot;

* Many things that HF cannot achieve but UHF can achieve. HF can only address a small part of the vast field of UHF RFID.

For RFID applications, UHF is a "superset" of RFID. Products compliant to this standard are capable of handling a wide variety of items, containers, pallets, all materials and packaging types, as well as offering much higher throughput rates than HF.

A properly deployed UHF Gen 2 system will work just fine on large or small items, liquids or metals, as well as on containers and pallets, effectively eliminating the HF that existed before near-field UHF Gen 2. It has advantages at the item level. Yes, liquids can absorb RF energy, and metals can reflect RF energy, but these are all things to consider in the far field, not in the near field. In fact, since a properly designed UHF tag antenna can be used in both the near field and the far field, it can actually use the attached metal as an extension of the antenna! But HF tags cannot, because they lack the means of electric field coupling. Nevertheless, let's delve a little further into the practical implications of deploying an HF RFID system.

At first, HF was unable to achieve far-field applications, which meant that it could not be used for containers and pallets that required RFID to work remotely in warehouses and logistics centers. Therefore, the application distance of HF was limited to near-field.

Therefore, companies that choose HF for item-level tag identification must also deploy UHF Gen 2 for container and pallet identification. Today, multiple complex factors such as multi-channel data bearing architecture, cost, complexity, efficiency, and maintenance must be considered at the same time. Therefore, if you think digital logistics is not difficult, you will hit a wall. These also require us to consider some economic factors: UHF Gen 2 tags will always be cheaper than HF tags.

In fact, since UHF tags are easy to manufacture, they will be 2-3 times cheaper. Unlike HF tags, UHF Gen 2 tags are particularly well-suited for simple, high-speed manufacturing technologies where process upgrades are particularly good. Thanks to the simplicity of UHF Gen 2 and the single-layer antenna structure, it can be fabricated using an inexpensive conductive ink process. UHF is a very practical and economical band for standards compliance. In fact, the same UHF Gen 2 chip designed for long range and used on a large tray can also be used with a near-field antenna as small as 6mm or so - such tags are much smaller and cheaper than previously widely adopted HF tags Much more, plus better performance.

Another advantage of the UHF antenna structure is that when items are stacked very close together, the UHF tags do not cast an RF "shadow" on adjacent items. The HF tag antenna is not the case. The antenna is composed of a thick metal coil, which can form a magnetic shield for adjacent tags, so that the reader can read it. Therefore, UHF has more reliable performance.

The continuous development of UHF Gen 2 technology will further widen the cost, performance and function gap between it and HF technology, and this gap will never be bridged by HF. This is the fundamental point, because the economics of UHF Gen 2 actually benefit from the physics of the UHF band. For RFID operation, the efficiency of the UHF frequency band is 60 times that of the HF frequency band.

If the goal is coupled communication between RFID tags and RFID readers, UHF has many advantages over less capable HF solutions. Because UHF Gen 2 has high speed, high reliability, and flexibility of operation. This is why Blue Vector's CEO - Nancy Anderson concluded, "We don't use HF much anymore because it is not as flexible as UHF."

Julie Kuhn of Cardinal Health, manager of Pedigree, explained this to me. "You can't achieve the read speeds of UHF tags with HF tags. That means our conveyor belts can't go any faster than the slowest read rate." This is a big limitation that will impact order throughput for distributors. "Right now," she continued, "we pick up orders until 8:00 p.m. and dispatch them from 5:30 a.m. This complex UF/UHF architecture will limit our ability to maintain the bill of lading refill time" .

This exacerbates the problem with multi-protocol architectures. And unfortunately, solving these problems with devices capable of reading both HF and UHF tags—ie, multiprotocol RFID readers—only creates more problems. These issues include more complex, more costly, and more sophisticated interrogators with lower read rates and less reliable reads because the interrogator must periodically cover multiple It is a compromise. These issues arise along the supply chain when multiple data-carrying protocols are employed.

While Gen 2 solves these problems of competition and incompatibility with UHF standards, HF technology itself also has these problems. The relevant standards currently in use include ISO 14443, ISO 15693, and EPCglobal HF Class 1. Depending on the technology and standard chosen, for deploying, maintaining and upgrading a hybrid system architecture, it goes without saying that there is a need to manage the respective data formats, even economically and logistically, there is no need to support separate UHF and HF architectures What's the point.

The continuity strategy ultimately adopted by the enterprise has a major impact on downstream trading partners and will gradually penetrate the entire supply chain. This scenario is happening in some areas of medicine today, where the mixed protocol system used here is hindering the reliable throughput of goods. Julie Kuhn added, “Our focus is on how we can combine all the technologies into a single technology, forming a highly automated environment where we can capture the genealogy information of an item at the item and container level and maintain our existing high Throughput."