INTRODUCTION TO NEAR FIELD COMMUNICATION
Near Field Communication (NFC) is a technology for contactless short-range communication. Based on the Radio Frequency Identification (RFID), it uses magnetic field induction to enable communication between electronic devices. The number of short-range applications for NFC technology is growing continuously, appearing in all areas of life. Especially the use in conjunction with mobile phones offers great opportunities. One of the main goals of NFC technology has been to make the benefits of short-range contactless communications available to consumers globally. The existing radio frequency (RF) technology base has so far been driven by various business needs, such as logistics and item tracking. While the technology behind NFC is found in existing applications, there has been a shift in focus — most notably, in how the technology is used and what it offers to consumers. With just a point or a touch, NFC enables effortless use of the devices and gadgets we use daily. Here are some examples of what a user can do with an NFC mobile phone in an NFC-enabled environment: * Download music or video from a smart poster.
* Exchange business cards with another phone.
* Pay bus or train fare.
* Print an image on a printer.
* Use a point-of-sale terminal to pay for a purchase, the same way as with a standard contactless credit card. * Pair two Bluetooth devices.
An NFC-enabled phone functions much like standard contactless smart cards that are used worldwide in credit cards and in tickets for public transit systems. Once an application, such as a credit card application, has been securely provisioned to the NFC-enabled phone, the customer can pay by simply waving the phone at a point-of-sale reader. The NFC phone also offers enhanced security, enabling the user to protect the secure applications through the phone's user interface features.
NEAR FIELD AND FAR FIELD
The terms “far field” and “near field” describe the fields around an antenna or, more generally, any electromagnetic-radiation source .The names imply that two regions with a boundary between them exist around an antenna. Actually, as many as three regions and two boundaries exist. These boundaries are not fixed in space. Instead, the boundaries move closer to or farther from an antenna, depending on both the radiation frequency and the amount of error an application can tolerate. To talk about these quantities, we need a way to describe these regions and boundaries. A brief scan of reference literature yields the terminology in Figure 1. The terms apply to the two- and three-region models.
USING AN ELEMENTAL DIPOLE’S FIELD
Defining a near-field/far-field boundary, we use a strictly algebraic approach .We need equations that describe two important concepts: the fields from an elemental—that is, small—electric dipole antenna and from an elemental magnetic loop antenna. SK Schelkunoff derived these equations using Maxwell’s equations. We can represent an ideal electric dipole antenna by a short uniform current element of a certain length,
l. The fields from an electric dipole are:
2.The fields for a magnetic dipole loop are: