D3.7 A Structured Collection on Information and Literature on Technological and Usability Aspects of Radio Frequency Identification (RFID)

Untitled PHYSICAL PROPERTIES

Physical properties

In this section, we shall elaborate on some of the key aspects of the RFID system design to highlight some of the important methodological differences between systems. An understanding of these different facets is essential to the appreciation of the fundamental limitations to RFID technologies. 

Generally speaking, the variances between RFID systems can be broken down into eight key areas. Although this is not a comprehensive detailing of all potential differences between any two given systems, it does account for the major variants which have a significant bearing on the operating principles of the system. 

These eight key areas are: 

1. Operation type: 

The basic operation of the RFID system is for the RFID tag to communicate some piece of information back to the reader. However, by what protocol the RFID tag and the reader communicate to each other varies between systems. 

1. Data Quantity: 

Although the basic premise is for the RFID tag to transfer information to the reader, the amount of data transferred varies from system to system from only one bit to several bytes. 

1. Programmability: 

In some cases, the RFID tag can actually be programmed to run a sequence of instructions. This differs from the very basic tags in the sense that they are hard-wired to perform only one basic function. 

1. Data carrier’s operating principle: 

There is a choice of transport methodology by which data can be transferred between the RFID tag and its reader. This aspect has a direct bearing on the range of frequencies which can be utilised, which in turn sets other system limits. Typical implementations use either surface acoustic wave (SAW) or, more usually, inductively coupled (IC) solutions. 

1. Sequence: 

The sequence refers to the principles governing the RFID tag’s mode of operation. Essentially, this can either be a complex microprocessor (µP), as is required in programmable tags, or a simpler ‘state-machine’. 

1. Power supply: 

This aspect is undoubtedly the driving force behind the design of the majority of RFID systems. Ideally, the RFID tag will not require its own power source, but will be given its power through some contactless means from the reader. However, in cases where this is not practical, such as with higher power microprocessor based tags, a supply internal to the tag is needed. 

1. Frequency range: 

The operating frequency of the transport media between the RFID tag and reader is another key design aspect which sets limits on other aspects of the RFID system. 

1. Data transfer: 

The data transfer from the RFID tag to the reader will be through some form of manipulation of the data carrier which is directly related to the ‘response frequency’ of the RFID system. 

The interdependencies of these important factors and the resulting design methodologies can be derived from .

Figure : A flow diagram representing the major basic combinations of RFID systems

The design of an RFID system, and thus the operation of its component parts is very much application specific. In most cases there will be fixed requirements which have to be catered for, and typically these will dictate the other aspects of the system. In the next section we will further describe the variations within the key areas of RFID system design.