**5.2 Passive mode**

In passive mode, the initiator sends the RF field to power the target. In turn, target used the RF field and sends back the stored data via a process called load modulation (Manchester coding) [52]. It is the most common mode for NFC, as it requires no battery and it is less expensive [53].

Three different combinations of communications are possible when two NFC device communicates with each other wirelessly, active-active, active-passive and passive-active. These are listed in **Table 3** [53].

While working in active and passive modes, the NFC devices perform different operation during communication. This means NFC device 1(initiator) must send signal first to NFC device 2 (target) to get the response back from device 2 (target). It is not possible for NFC device 2 (Target) to send data to device 1 without receiving any initial signal. All the possible interaction styles of NFC devices are listed in **Table 4** [14].

According to the NFC forum's device requirement, a device must have the functionality i.e., device needs to operate in reader/writer mode and in peer mode in order to be NFC-compliant [54]. i.e., a device must behave as an initiator during passive communication and an initiator or target during active communication. Initially, the NFC operating frequency of 13.56 MHz was unregulated. In 2004, NFC forum was established to standardize the tags and their operating protocols. There were three tasks standardized by the NFC Forum: including transferring power from a NFC device to a NFC tag, sending information from a NFC device to a NFC tag via signal modulation, and sensing the modulation by the load created on the NFC tag while performing load modulation to receive information from a NFC device. These three operation modes were designated by the NFC forum as reader/ writer, peer-to-peer, and card emulation communications, as depicted in **Figure 9**. These are three main modes, under which a NFC device can operate [14]:


#### **Table 3.**

*Various possible communication arrangements between two NFC devices [53].*


**Table 4.**

*Various possible interaction styles of NFC devices [14].*

**5.5 Card emulation mode**

*DOI: http://dx.doi.org/10.5772/intechopen.96345*

**6. NFC tags**

**6.1 Type 1 NFC tags**

**6.2 Type 2 NFC tags**

**6.3 Type 3 NFC tags**

**6.4 Type 4 NFC tags**

**107**

high; between 106 to 424 Kbps.

tags have read/re-write capability.

In card emulation mode, a NFC device behaves as an external reader traditional contactless smart card. This enables contactless payments through credit cards, debit cards, loyalty cards, etc. by using NFC device without changing the existing infrastructure. For example, NFC enabled mobile device can even store multiple contactless smart card applications in one phone. Card emulation mode supports

*Near-Field Communications (NFC) for Wireless Power Transfer (WPT): An Overview*

In an NFC system, there is always an element which functions as the receptor in passive mode, such as NFC tag. NFC tag, also known as the smart tag or information tag, is a small, printed circuit which act as a bit of storage memory along with a radio chip attached to an antenna [18]. It works in a passive mode, during which it does not have its own power source but uses power from the NFC device that communicates with it via magnetic induction. NFC tags have a few inches of working distance, NFC device must be very close to read the tag. NFC tags are used for a variety of applications in our day-to-day life, such as payments, launching websites, virtual visiting cards, lock/unlock doors, pet animals tagging, share photos, videos, and other information, etc. To ensure interoperability, a classification has been established for NFC tags by NFC-Forum that provides necessary specifications between different tag providers and the manufacturers of devices. Currently, there are five different types of NFC tags, depending on storage

Type 1 tags are based on standard ISO14443A with a memory of 96 bytes, expandable up to 2 Kbytes. The rate of data transfer is 106 Kbps and type 1 NFC

Like Type 1 tags, Type 2 tags are also based on ISO 14443A standard. It has a memory of 48 bytes, expandable up to 2 Kbytes. The rate of data transfer is 106

Type 3 tags are Japanese Sony FeliCa standard (JIS X 6319–4). It has more memory and faster data transfer speed as compare to type 1 & 2 tags. The memory

Type 4 tags work on both ISO 14443 A & B communications. These are manufactured either in read only or read/re-write modes. Unlike other tags, a user cannot decide the mode. The memory is up to 32 Kbytes and, transmission rates are

is 2 Kbyte, expandable up to 1 Mbyte with a transfer rate of 212 Kbps.

ISO/IEC 14443 Type A and B, and Felica standards [14].

capacity, data transfer rate and read/write ability [1].

Kbps and type 2 NFC tags have read/re-write capability.

**Figure 9.** *Three different communication modes of a NFC device [14].*
