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ISSN: 2278 – 1323
International Journal of Advanced Research in Computer Engineering & Technology
Volume 1, Issue 4, June 2012

13.5 MHz RFID(NFC) ANTENNA DESIGN FOR DEDICATED MOBILE
APPLICATIONS WITH IMPROVED RESULTS
1 2 3
1
Amit Gupta , Sudeep Baudha , Shrikant Pandey
2 3
amit1113@hotmail.com., sudeepbaudha@gmail.com, @shrikantpandey2009@gmail.com
Department of Electronics & Communication, Gyan Ganga College of technology, Jabalpur (M.P)

Abstract—First part of the paper discusses antennas can be created by exploiting real
about the latest trend within RFID is to use life metallic structures. In this paper, a
the technology for more advanced applications shopping trolley is taken as an example. The
that can replace the magnet cards used today first part of this paper will focus upon the
for payment and electronic key cards. The design of NFC antennas for communication
more advanced types of these cards, called
between two devices within proximity less
proximity cards. This standard, named Near
Field Communication (NFC) can therefore be than 10cm apart. Such example in the case
used to replace key cards and of contactless payments would be a mobile
Visa/MasterCard. At the same time, a small handset communicating with a vending
NFC reader integrated in the phone opens up device, such as a ticket machine or credit
for many new possibilities. If this idea is card payment terminal in a café. Applying
accepted by consumers and companies, the cell theory analysed for such antennas, the paper
phone could be the only device needed when a will then go on to analyse the potential use
person leaves the house, since it in addition to of a shopping trolley to act as a rogue
being a phone also is a set of keys, an ID card antenna from which information could
and a wallet. potentially be eaves dropped.
Later part of paper discuss about the RFID
antenna and its revolutions. New designs with
new results and all other parameters to
describe the antenna design in detail. 2. NFC ANTENNA DESIGN THEORY:-

A typical example of magnetic coupling
INTRODUCTION:- loop ntennas, otherwise known as “H-
The increasing interest in using Near Field antennas”, is illustrated in figure 1. The two
Communications (NFC) technology at ends of such an antenna are connected to a
13.5MHz is growing rapidly in the area of radio frequency (RF) transceiver with a
contactless payments, as well as numerous capacitor placed across in parallel. The DC
other applications, between devices that are resistance at the input can be assumed to be
within 10cm distance apart. However, there zero while as the frequency increases, it will
is growing concern that the use of such create an inductance such that a circuit
devices for contactless payments invites model for such an antenna can be
problems with regards to using metallic represented as that shown in figure 2 where
objects in the vicinity of the two devices to the
act as “rogue” antennas, which eavesdrop Antenna is represented as an inductor [2].
information during a financial transaction is The parallel capacitor is then connected to
taking place. This paper presents aspects of the load of the transceiver, which will in this
designing H-antennas both for the two case be assumed to be purely resistive. Were
devices communicating while also there to be a reactive component at the
identifying the means by which rogue transceiver input, it can be easily cancelled
out by applying a series, negative reactance

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ISSN: 2278 – 1323

so therefore need not be considered. Many
publications in the literature assume the
inductance to be constant over frequency,
though observations from measurement
using a network analyzer find it to be the
case that inductance will change at lower
frequencies.

Figure 3 shows measured results using a
Fig.2 circuit model of H antenna
vector network analyzer, where the
inductance reduces to a constant value after
about 1MHz. Where the frequency is low,
the loop effectively resembles a short circuit
where the inductance would be expected to
fall to zero. However, due to precision
required in such circumstances, an accurate
value of inductance cannot be resolved. In
this paper the inductance will be considered
as frequency dependent and is therefore Fig. 3 Measured values of inductance over
denoted, L(f) or L(w) where relevant, where frequency
f is the frequency and w is the angular
frequency equal to 2pf. This will become At the resonant frequency, the transceiver
more important when the inductance values connected to the antenna has a load
for a rogue antenna are considered. For any resistance, RL, where in receive mode it will
loop antenna to resonate, it is well known have the following system frequency
that the parallel capacitance to be applied response function, based on the ratio of the
can be derived as follows: load voltage, VL, across the load resistance
compared to the input voltage effectively
resulting from the current flowing in the
loop antenna, Vin, is defined as follows:

One important point to realize from this is
that maximum power transfer at the resonant
frequency, w0, will reduce to:

Fig.1 Coil Antenna
thus requiring a low inductance in order to
maximize gain with as high load resistance
as possible. The magnitude of this equation

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is also equal to the Q factor of the system, transmitting RF signal when operating
that will depend on a low value of L and a active and passive NFC mode and RFID
high value of RL. For transmit mode, the reader mode. The Tag part is both for target
transfer function relating the voltage across operation of NFC protocol and passive
the antenna, VA, which is now a reactive RFID tag mode. The conventional NFC
load, to the source voltage, VS, that is now chipset could not support RFID tag mode
in parallel with RL, is as follows: when external power is not supplied,
because it has only one antenna both for
NFC mode and RFID mode [5]. RFID tag
mode must support standard of 13.56MHz
smartcard such as ISO/IEC14443 type A/B,
or ISO/IEC15693[1-4]. The key differences
between target of passive NFC mode and
3. BLOCK DIAGRAM OF THE RFID tag is operating distance, data rate,
PROPOSED NFC TRANSCEIVER. and host interface.
To realize NFC devices, implementation of 4. SIMULATION USING ADS:-
active and passive mode of NFC protocol
with passive RFID protocols is required. An The designed coil antenna has 10 numbers
NFC chipset consists of a digital block of turns in units of 100x50.
including digital controller and host
interface, and an analog front end part with
external antenna matching circuit as shown
in figure:

Fig. 5 Schematic diagram of the antenna
coil
It has got lumped ports to deal with power
supply. The gap between the coils is 1 mm
and the thickness of the coil is also 1 mm.
ADS view of designed coil:-

Fig.4 Block dig of NFC transceiver

The host interface of the chipset should be
designed to support maximum baud rate of
424kbps. The analog front end part is
composed of two analog/RF circuits and
matching circuits for Initiator and Target
antennas. The reader/writer part is for Fig. 6 ADS coil design

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The Input impedance (ZL) in the schematic
Return losses achieved by simulation:- of the ADS with lumped elements:-

Fig. 10 S-parameter matching circuit
Fig.7 Return losses
Gain parameter achieved:-
-16.78dB is achieved at 13.5 MHz
frequency. This is almost the double of
existing system of NFC.

Smith chart:-

Fig. 11 Gain & directivity

Fig 8 Smith chart for the coil antenna
5. CONCLUSION:-
3-D plot:-
This paper shows the basic parameters of
NFC system and antenna design, including
all the circuits and values required for
designing the antenna.
In later part the simulation work has been
shown which was done using ADS software.
With the help of this software many
parameters have been taken out eg. Antenna
design, Return losses, S-Parameters, Gain,
Fig. 9. 3 dimensional view Directivity & 3-D plot. The existing NFC
system provides a distance of 3-4 Cms.

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Maximum between two NFC tags with About Authors:-
return losses in range of -8 dB.
With this new design of 13.5 Mhz RFID
About Authors:-
antenna, it will double the distance than
before that means two NFC tags can
communicate with more than double AMIT GUPTA: BE (EC) from GGITS,
distance as compared to what they are JABALPUR.M.Tech. (UnderPersuation)
currently using. This will be helpful in DigitalCommunication, GGCT, JABALPUR.
several NFC applications which enhance the Research Work:-Antenna Designing.
transmission and overall efficiency of the
system.

6. REFERENCES:- Sudeep Baudha: B.E. (EC)
GEC,Ujjain.M.Tech. (Microwave EnggIIT
[1] Near Field Communication-White paper, Kharagpur. search Work :- Antenna
ECMA Designing
International, Jan. 2004.
[2] International standard ISO/IEC 18092,
International
Standardization Organization, April 2004.
[3] Standard ECMA-340, “Near Field Shrikant Pankey : BE (EC)
Communication - TIETECH,JABALPUR.
Interface and Protocol (NFCIP-1)”, ECMA M.Tech. (Under Persuasion)
International,
DIGITAL COMMUNICATION, GGCT,
December 2002.
[4] Standard ECMA-352, “Near Field JABALPUR.

Communication Interface Research Work :- Antenna Designing.
and Protocol -2 (NFCIP-2)”, ECMA
International, December
2003.
[5] Short Form Specification, “Near Field
Communication PN531- μC based
Transmission module”, Philips
Semiconductors, February 2004.
[6] David M. Pozar, Microwave Engineering
3rd ed, Publishing House of Electronics
Industry , pp. 223-235, September 2006.
[7] Antenna Theory and Design by Balanis,
3rd edition.

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