# Technologies and Fabrication of Intelligent Packaging for Perishable Products
## 2 Intelligent Packaging Techniques
### Identification Techniques  
There are several stages of product identification. Writing the relevant product information or making marks on the package has been traditionally used for product identification. However, the absence of a single standard makes it a challenge to rapidly access the desired information on the product. In addition, it is challenging to record the information for all the parties of the supply chain. The barcode is the most commonly used method for identification in the packaging industry, which consists of a series of identification numbers and black bars. Barcodes can be easily printed on the product's packaging through economical printing techniques. However, there are two limitations of this technique: the first one is that it needs an optical device to read the barcode, and avoid being obstructed, the second one is that the technique can only store a limited amount of information, which makes it difficult to record additional information about the product, such as contamination or the prescribed temperature of the environment. Thus, people invented another more advanced technology, known as radio-frequency identification (RFID). RFID is a simple technique used for identification in intelligent packaging. In its read range, the RFID reader can automatically identify physical objects using radio-frequency signals by capturing the signal remotely from RFID tags. A typical RFID system is composed of an RFID tag, RFID reader, RFID antenna, and the backend system. The RFID tag is usually pasted on the packaging of the tracked item. The RFID reader and the antenna are usually connected by the cable. They function together to produce a magnetic field and to send and receive signals to and from RFID tags. The RFID reader can read and program the data stored on the RFID tags. A typical RFID system is illustrated in Figure 2.  
The Radio Frequency (RF) determines the type of applications that are best suited for an RFID system. RFs can be classified as listed in Table 2. A comparison between Barcodes and RFID is summarized in Table 3. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Frequency** & **Read Range** & **Data Speed** & **Applications** \\ \hline Low Frequency & 0–5 cm & Low & Emergency CardAccess Control \\ High Frequency, & 10 cm–1 m & Low to Moderate & ID CardsPayment \\ Ultra-High Frequency & 3 m–7 m & Moderate to High & Warehouse ManagementTracking \\  & 10 m–15 m (Passive) & & Electronic Toll Collection \\ Microwave & 20 m–40 m (Active) & High & Container Tracking \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Radio Frequency (RF) of an RFID System. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Barcode** & **RFID** \\ \hline Read Range & DirectlyWith no Obstacle & Longer \\ Price & Economical & Expensive \\ Read/Write Tag Data & No & Yes \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison between RFID and Barcodes. Figure 2: Schematic of atypical RFID System. **RFID Tags**: _RFID tags are devices that contain identification information remotely transferred to anRFIDreader. The tag is composed of a simple silicon microchip and a small flat antenna. The microchip and the antenna are connected and implemented on a substrate. Based on the sources of energy, there are three types of RFID tags_:  
1. Active tags--They contain built-in batteries. These batteries provide power for broad casting signals to RFID readers, and there is no need to utilize power from the readers. This also allows them to communicate over a much larger distance than the other two types of RFID tags. 2. Semi-passive tags--They also contain built-in batteries. Compared to active tags, semi-passive tags have two statuses: active and sleep. In sleep status, the batteries do not work. When the tags receive the request from the RFID readers, the status changes from sleep to active. Then, the batteries begin to power the transmitter and receiver to broadcast the signal over a long communication distance. 3. Passive tags--They do not have batteries.