Reconfigurable RFID Antennas and Applications

Reconfigurable RFID antennas and applications
Name of the Student
Name of the University
Abstract- This paper has been focused on the concept of
reconfigurable antennas and its application at various
fields. There have been various development in the field
of communication. A tuning circuit including radio
frequency (RF) switch, passive components have been
integrated with antenna element with DC wires. A
varactor diode that is surface mount has been applied
with a frequency-tuning element at various places of slots
in compact antenna.
Keywords- RFID, Frequency Tuning, Reconfigurable
dipole antenna, Active Antenna
I. INTRODUCTION
Wireless communication has been enhanced by
growing rapidly in the market in recent years. The
collaboration of RFID with various technology has
been including computer technique, integrated circuit
technique and communication technique. There has
been a working range of Radio Frequency
Identification (RFID) technology that covers 13.6
MHz in high band range 100-500 KHz in the low
band range and microwave band range including 860-
960 MHz and 2.45 GHz. RFID technology has been
developing by using Radio Frequency (RF) signals
for automation in identifying objects. In RFID
systems, performance has been the maximum read
range by which RFID reader can be detected.
Therefore, the read range has been sensitive in order
to tag orientation on which tag has been placed. The
antenna helps in determining performance of tag
stuck into a object. The antenna has been determining
performance of tag stuck in the object. The tag
antenna needs to be small in size and low in profile.
The range of frequency from 120-150 KHz is used
for factory data collection and animal detection, the
range of frequency in 13.56 MHz is compatible with
smart cards and ISO compatible memory cards. The
ultra high frequency of 433 MHz is applied in
defense that has active tags in it. The microwave
range is used in WLAN and in Bluetooth standards.
The frequencies in Giga Hertz range requires either
active or semi-active tags. A Radio Frequency
Identification tag has been an antenna compromise
with microchip in a package.
II. RFID SYSTEM OVERVIEW WITH
THEORETICAL CONSIDERATION
A. Antenna equations
The communication in various microwave RFID and
passive UHF systems has been based on
backscattering. RFID tag include an antenna and
microchip that helps in sending information back to
reader and switches between two states. Signals that
RFID reader antenna receives has been forwarded
and reversed by different communication. RFID has
been using simple modulations including amplitude-
shift keying frequency shift keying and phase shift
keying.
Figure 1: Generic backscattered RFID system.
(Source: Nikitin, 2017)
The power density at distance R1 from the
transmitting antenna in the direction (θ trans , φ
trans) is:
Wtrans= {PtransGtrans(θtrans,φtrans)}/4πR2
where Ptrans is the input power of transmitting antenna
and Gtrans is the gain of transmitting reader antenna.
PtransGtrans is called reader-transmitted equivalent
isotropic radiated power (EIRP). The power received
by the RFID tag antenna is expressed by the
following antenna formula:
Ptag=WtransGtag(θtag, φtag) λ2 /4π |ρ trans.ρ tag| 2
The surface waves has been flowing on antenna can
be excited by travelling across dielectric substrate.
However, these waves have reached to edges of
substrate as reflected, diffracted and scattered. This
also help in increasing cross-coupling between array
elements. This excitation of surface waves has been a
function of εr and h. The loss in power of surface
waves has been increased with increase in thickness,
h/ λ0 of the substrate. The loss can be neglected when
h satisfies below criterion:
h /λ0 ≤ 0.3 /2π √εr
B. Varacter-loaded active compact antenna
The equivalent circuit of a rectangular microstrip
antenna has been a parallel combination of resistance

R, inductance L and capacitor C. According to modal
expansion cavity model, the values of R, L and C are
mentioned below:
C = (ε0εelω /2h) cos−2(πd/l)
L = 1 /ω2C
R = Qr /ωC
Qr = C√εr/ 4fh
Here, c is velocity of light, d is the feed-point
location, ω = 2πfr, f r is the design frequency, Qr is
the radiation quality factor, and εe is the effective
permittivity of the medium. The varacter diode when
reverse-biased.
C. Tag antenna structure
This study has been simulated on an FR4 substrate
having relative permittivity of 4.6, width of 1.6 mm
and dimensions of 103*33mm2. This antenna consists
of loop for feeding and meandered dipole. There has
been a proposed RFID diagram, given below:
Figure 2: Schematic of the proposed varactor-
loaded antenna for RFID tag
(Source: Amendola et al. 2018)
The fractal dipole antenna has a rectangular compact
shape and pair of meander patches with a metal
length of 23 mm and a width of 1 mm. There has
been an end gap distance of 2 mm between meander
patch end and microstrip line. The optimal
dimensions of the proposed antenna are W1 = 33
mm, L1 = 41.5 mm, W2 = 3 mm, W3 = 2 mm, L2 =
9.3 mm, L3 = 23 mm, and L4 = 15.2 mm. The
dimensions of the antenna were first studied with
AWR Microwave Office simulation electromagnetic
software and then verified by the experiment.
Figure 3: Radiation pattern comparisons of
proposed antenna: a) radiation patterns of
proposed antenna with all varactors OFF at 2.4
GHz, b) radiation patterns of proposed antenna
with all varactors ON at 2.4 GHz
(Source: Ji et al. 2016)
The authority IEEE meaning of a radio wire as given
by Stutzman Microstrip radio wires are notable for
their highlights, for example, low profile, light
weight, minimal effort, comparability to planar and
non-planar surfaces, inflexible, and simple
establishment. They are most normally fused into
portable, specialized gadgets due to minimal effort
and flexible structures. An accentuation has been
given in microstrip radio wire and reconfigurable
gap, with the end goal to accomplish different octave
tunability. Reconfigurable multiband space radio
wires are accepting a considerable measure of
consideration of late because of the development of
RF-MEMS switches (Chen & Wong 2018).
Regularly microstrip radio wires are additionally
alluded to as fix reception apparatuses (Ji et al. 2016).
The element of self-comparability of a fractal
recieving wire can likewise give a premise to the plan
of various recurrence radio wires. These reception
apparatuses have the preferred standpoint that they
emanate comparable examples in an assortment of
recurrence groups. The significant antecedent is the
broadly examined Sierpinski gasket. The different
fractals shape that gang self-likeness have been
connected to multi-band or scaled down radio wire
structure. There are numerous fractal geometries, for
example, Sierpinski gasket, Sierpinski cover, Koch
Island, Hilbert bend and Minskowsi and so on has
been utilized in fractal radio wires. Reconfigurable
antenna has been demonstrated in various research
papers in the way to switching from single band to
narrow band. The range of frequency from 120-150
KHz is used for factory data collection and animal
detection, the range of frequency in 13.56 MHz is
compatible with smart cards and ISO compatible
memory cards. The ultra high frequency of 433 MHz
is applied in defense that has active tags in it. The