What Is a UHF RFID Tag?
A UHF RFID Tag is a type of passive or active RF tag that operates at the ultra high frequency (UHF) band. It has a long range, is able to transmit a large amount of data and is used for many different applications including asset tracking and inventory management.
UHF-RFID labels can be negatively affected by a number of metal and liquid surfaces, as they generate strong reflections that disrupt the transmitted signal. This can be either constructive or destructive and can result in reduced reading intervals.
RF Antennas
Radio-Frequency Antennas communicate with the other components of a UHF RFID Tag by sending and receiving electromagnetic waves that are created when an electric current is passed through them. RF antennas can be made from various materials, which have different properties. Antennas also have to be designed to support a wide range of frequencies. Using a radio frequency to communicate with other devices is a complicated process, so it’s important to design and test the antennas before they are used.
Antennas are typically designed to have a certain gain. This gain is measured by measuring the amplitude of the radio waves that they transmit. Generally speaking, higher amplitude means that the antenna can send more radiated energy in a single beam. This can be useful when multiple tags need to be detected in close proximity, as it allows them to cover a larger area with their signals.
However, this increase in gain can also cause the antenna to become overloaded and unable to receive as many signals as it should. It can also make the antennas unsuitable for a wide variety of applications. Fortunately, there are several ways to reduce the amplitude of an antenna and maintain a high RF signal strength.
One of these is miniaturization, which can reduce the length of an antenna without negatively affecting its performance. For example, a meandered monopole antenna can be miniaturized into a serpentine pattern that’s much shorter than the original monopole.
Another area of antenna miniaturization is printed flexible antennas. These antennas are often small and have good antenna gain. But they are typically not suitable for large form-factors because they have a large diameter relative to their operating wavelength (D/(lambda)).
Therefore, our goal was to find an antenna that has small linear dimensions while preserving reasonable gain. In addition, we sought an antenna that could be fabricated using a variety of printing techniques to ensure a consistent production process.
The results of our studies show that screen-printed antennas are the best option for fabricating flexible dipoles with moderate gain and small linear dimensions. We have also investigated stencil printing, which is UHF RFID Tag a technique that can be used to produce antennas whose thickness, impedance, and S-parameters are comparable to those of screen-printed antennas.
RF Circuits
RFID (radio frequency identification) technology is used in a variety of applications, such as asset management and apparel retail. Recently, it is also being used in unmanned supermarkets and for the electronic identification of motor vehicles.
UHF (ultra high-frequency) RFID tags are small, flexible, and can be integrated on packaging and other objects, making them ideal for supply chain management. However, these tags require antennas with reasonable gain and RF circuits that can be powered wirelessly via the RFID technology.
To make these tags, RF circuits are typically mounted on the printed antenna’s substrate with solder. The mounting of these components is problematic for flexible antennas because reflow temperatures exceed the glass transition temperature of plastic substrates, which leads to brittle joints and erosion of silver, resulting in poor electrical connection.
A number of different RF circuits are available, with each designed to meet the specific requirements of an application. They may be designed to power the tag, communicate with the reader, or both.
These circuits may be designed to operate with a specific radio frequency, such as UHF, LF or HF. They also may be designed to operate at a specific voltage, such as 5 V or 12 V.
Choosing a circuit can be an important decision for a UHF RFID tag, as it determines the type of sensor it will have and how it will function. It can also affect how the tag interacts with other devices, such as a camera or smartphone.
As a result, it is vital to understand the needs of your project before designing the circuits. This will help you to choose the most appropriate RF circuits for your UHF RFID tag.
We have developed an antenna miniaturization method that allows for the fabrication of compact and flexible UHF RFID sensor tags. This technique enables these tags to be integrated onto a variety of objects, such as packaging for sensitive products.
We have then used this method to produce a printed capacitive touch sensor. We have incorporated the sensor into a flexible antenna that has been printed with a silver nanowire ink.
RF Integrated Circuits
RF Integrated Circuits (ICs) are used in a variety of applications from wireless communications to medical imaging. They are a low-cost solution to many electronic systems. Compared to traditional microchips, ICs are smaller and use lower power. Moreover, they can integrate more functions into a single chip.
Using ICs in RFID tags is becoming an attractive alternative to passive antennas. Printed ICs have a small footprint and can be mounted on flexible substrates to withstand bending or reorientation. However, integrating them in textiles is challenging due to the geometric constraints.
This is particularly true of UHF RFID Tags which have to be long and thin to fit on a textile and require a low-profile design. This means that the footprint of the IC needs to be minimal in order for the tag to be concealed within the fabric without degrading the impedance match between the IC and the antenna after integration.
There are a number of ways to accomplish this, including direct digital synthesis and phase-locked loops. Both have their advantages, but the multiplicity of sources, mixers, and dividers in direct digital synthesis can result in high DC power consumption. PLL solutions, on the other hand, can offer a very compact solution.
Another way to improve the efficiency of a passive RF tag is to use a voltage multiplier. This reduces the threshold voltage of the active element and improves power conversion efficiency. It also increases the frequency range of the tag and can be tuned to suit different environments.
These techniques can be employed in a variety of RFID applications, including tags for wearable devices. For example, the use of voltage multipliers and a low-profile IC in sensor tags can allow them to be worn under the skin or under clothing.
Alternatively, the use of a capacitive touch sensor can enhance the functionality of an RFID tag. Capacitive sensors are based on interdigidated electrodes that have some capacitance between them. When a finger touches the sensor, the capacitance of each electrode increases. This capacitance is detected by a microchip or a RFIC.
Sensors
Sensors are devices that detect a physical quantity or property and convert it into a readable signal that is sent for reading, processing, or further logging. They are found in a wide variety of products, from night vision and radar equipment to medical imaging and digital cameras to cars.
Sensing technologies enable a variety of applications in industry, including process monitoring and control, inventory management, asset tracking, security, and more. They detect physical, chemical, or biological quantities and then convert them into a readable signal.
RFID tags with sensors are used for a variety of industrial applications, such as inventory management, supply chain management, and asset tracking. They are also being used in consumer goods, UHF RFID Tag such as toys, to identify items and provide information about their status.
UHF-RFID sensor tags require flexible antennas with compact dimensions and reasonable gain. This is a challenge for many reasons, including the fact that solder reflow temperatures exceed the glass transition temperature of plastic substrates. This prevents conventional antenna-integration methods from being suitable for printed tags.
Moreover, standard antennas with large D are not suited for integration on small packages. This is especially true of a typical dipole antenna that has to protrude from the plane of the print and be attached to a flexible substrate.
This is why we focused on miniaturizing antennas, achieving lower D/(lambda). We achieved this by utilizing meander monopoles with ground pads on the front side of the substrate, in place of traditional dipoles that must protrude from the substrate. This resulted in antennas with much smaller D/(lambda) and moderate gains (see Fig. 1b).
To validate the wireless readouts, we placed the same interrogator antenna described above and two screen-printed tags inside an environmental chamber, which went through three temperature cycles and relative humidity levels at different sensitivity levels (Fig. 4b). The resulting readouts were comparable to those of the rigid reference boards.
These results demonstrate the ability of a combination of flexible antennas and printed sensors to produce UHF-RFID sensor tags that are more scalable, easy to manufacture, and integrate into objects. This method is applicable to a wide variety of objects and will lead to the development of new applications for RFID.
