Nanjing University of Aeronautics and Astronautics, Nanjing
211106, China
lycloud1978@163.com*
Abstract—A novel 3-bit frequency-reconfigurable antenna (FRA) with
miniaturized dimensions is realized with a meander line. The frequency
reconfiguration of the antenna is achieved by introducing N RF
p-i-n diodes into the meander line. The related parts of the meander
line with different lengths are bypassed or included into the antenna by
switching on or off the diodes, resulting in 2Nswitchable size lengths of the antenna and equally spaced operating
frequencies. A 3-bit meander-line reconfigurable antenna (N=3) is
designed, and the simulated and measured results agree well. The antenna
provides 23=8 independent switchable states, with the
operating frequencies covering a wide switchable frequency range from
1.04 GHz to 1.51 GHz and the working bandwidths varying from 80 MHz to
150 MHz. The number of working states is optimally large, considering
the number of switches used. Besides, this work has an acceptable peak
gain of 1.59 dBi regarding the miniaturized total dimension of 0.17 λ ×
0.07 λ (λ is the wavelength of the lowest working frequency), which is
more compact than many published FRAs.
Introduction: With the rapid development of modern wireless
communication systems, RF front-ends are required to operate at multiple
frequency bands, and the number of integrated antenna and total
dimensions is highly increased. To solve the problems, reconfigurable
antennas have been extensively studied recently.
Reconfigurable antennas can be classified into three types, namely,
frequency-reconfigurable antennas (FRAs) [1]-[10],
polarization-reconfigurable antennas [11], and radiation pattern
reconfigurable antennas [12]. Among them, FRAs have attracted
substantial attention and been intensively studied. The frequency of an
FRA can be continuously tuned using varactors [1]-[5] or
discretely switched using RF-switches [6]-[10]. Frequency
reconfigurability has been achieved on various types of antennas, such
as microstrip patch antennas (MSAs) [1], [2], [9], dipole
antennas [3], patch-slot antennas (PSAs) [6], microstrip
monopole antennas (MMAs) [7], microstrip slot antenna (MSA) [8],
and planar inverted-F antennas (PIFAs) [10]. Majority of FRAs
tune/switch the resonant frequencies by reconfiguring the current flow
path on the antenna or reshaping the antenna structure, changing the
equivalent electrical lengths of antennas in addition.
Nonetheless,
many of these published FRAs fail to take miniaturization into account,
which is critical especially when FRAs are used in handheld devices.
Typically, antenna miniaturization is accomplished by folding the
radiation branch of the antenna [13], [14], by selecting an
antenna patch loaded with a specialized shape [15] or a shorting
wall [16], and by introducing metasurfaces [17] or metamaterial
structures [18]. The most common method of antenna miniaturization
is to use a meander line. In [14], a miniaturized monopole chip
antenna with meander lines on the first and third layers is presented,
greatly reducing the antenna’s size at lower and upper bands.
Furthermore, many published FRAs load too many switches while only
providing a limited number of operational states. Fortunately, binary
reconfiguration can successfully resolve this problem by realizing
2N switchable states with N switches. A
3-bit binary reconfigurable PIFA with eight independent states covering
a working frequency range from 1.52 GHz to 2.25 GHz is developed by
using three MEMS switches in [10]. The presented FRA is miniaturized
by the meander line in [7], and only three states are achieved using
two diodes.
In this study, a miniature 3-bit frequency-reconfiguring monopole
antenna with a meander-line is proposed. It employs three switches to
achieve 23 states, which is the maximum number
of states. The structure can be extended for achieving binary FRA with
larger number of bits.