Switchable Single/dual Notch Band Electromagnetic
Band Gap Structure
Dattaray S. Bade
Sudhakar. S. Mande
Department of Elect. and Telec. Engineering
Rajiv Gandhi Institute of Technology
University of Mumbai, Mumbai
Email:dattabade@gmail.com
Department of Elect. and Telec. Engineering
Don Bosco Institute of Technology,
University of Mumbai
Email: ssmande1@gmail.com
Abstract—In this letter, switchable single/dual bandgap electromagnetic bandgap (EBG) structure is presented. The proposed
EBG structure is developed using LC model.The EBG structure
developed in this work gives single bandgap when PIN diode is
in OFF state and dual bandgap when diode is in ON state. For
experimental validation, 5 × 5 cells of proposed EBG structures
are fabricated on FR4 substrate with open and short concept.
Applicability of EBG structure to obtain switchable single/dual
frequency notch in ultrawide band (UWB) band pass filter
(BPF) is also demonstrated using PINdiode SMP 1352. Our
results confirm the suitability of the proposed EBG structure
for microwave applications.
EBG cell. Proposed switchable EBG prototype is simulated in
HFSS and fabricated 5 × 5 EBG cells using suspended microstrip line (SML) for measurement of single/dual bandgap.
Application of proposed EBG structure to achieve switchable
single/dual notch in UWB filter is also presented.
II. S WITCHABLE EBG STRUCTURE
I. I NTRODUCTION
Electromagnetic band gap (EBG) structures plays an important role in microwave engineering due to their stop band
characteristics. Recently single layer, dual layer, polarization
dependent, and meta material based EBG structures are presented [1]. As per recent trends, switchable EBG structures are
widely used for microwave applications. In [2] fork like EBG
structure using micro-electromechanical switches (MEMS) is
presented for single bandgap application. In [3] single band
frequency re-configurable EBG, based on short circuited hair
pin resonators with periodic size 0.15λ is presented. Tunable
structure for switchable/tunable notch filter application is
reported in [4] using EBG where notch band is switched
by 450 MHz and tunable by 340 MHz. Latithendra Kurra et
al [5] reported bandwidth re-configurable bandstop filter using
electromagnetic bandgap (EBG) structure. Reconfiguration in
the bandwidth is achieved by connecting EBG cell using
PIN diodes. In [6] electromagnetic nondestructive material
characterization of dielectrics using EBG is presented based
on planar transmission line sensor. Complex permittivity of
dielectric material at 2.4 GHz is measured using EBG sensing
method. In [7] a tricycle nested electromagnetic bandgap
structure with dual bandgap characteristics for simultaneous
switching noise mitigation application is presented. In [8]
compact TVS EBG structure is presented with the periodic
structure and size of EBG cell 0.077λ at operating frequency.
It is observed that reported electromagnetic bandgap (EBG)
structures with single or dual bandgap characteristics are
limited to give switchable single/dual bandgap.
In this work we have proposed switchable single/dual
bandgap EBG structure by using single PIN diode per unit
Fig. 1. Geometry of proposed switchable EBG structure when (a) strip absent,
and (b) strip present.
Fig. 2. Microstrip-line-based model of proposed switchable EBG (a) Configuration schematic view, and (b) Equivalent-circuit model.
III. S WITCHABLE EBG STRUCTURE
The Proposed switchable EBG structure is shown in Fig. 1.
The open and short concept is applied to prove the switchable
characteristics of the proposed EBG structure [9]. The equivalent microstrip line based model [2] of proposed switchable
EBG structure is shown in Fig. 2.
When strip is present (diode ON) two LC resonant circuits
are present and therefore it gives dual band characteristics.
When strip is absent (diode OFF) two LC circuits with same
Airline
6
Mode 1
Mode 2
Mode 3
4
2
Frequency (GHz)
Frequency (GHz)
Airline
6
Mode 1
Mode 2
Mode 3
4
2
Band gap 1.52 GHz - 1.76 GHz
0
50
100
150
0
50
100
150
βd (deg.)
βd (deg.)
(a)
(b)
Fig. 3. Dispersion diagram of proposed switchable EBG when ( a ) strip
present, and ( b ) strip absent with ( E1 , E2 , E3 , E4 , g, r , h, tan δ) = (7
mm, 5 mm, 1 mm, 3 mm, 2 mm, 4.4, 1.50 mm, 0.02)
Epoxy substrate with (r ) = 4.4, substrate height (h) = 1.50
mm. The measurement was conducted with Agilent N9923A
network analyzer. The Suspended microstrip line method [2] is
used for bandgap measurement. The microstrip line of 50 Ω is
placed above the EBG surface with 0.8 mm FR4 substrate used
as supporting material, and 0.2 mm airgap is kept between
the supporting material and EBG surface to avoid the direct
contact. Other parameters are kept same as mentioned in Fig 3.
Band gap 1.52 GHz - 1.76 GHz
Photograph and measured S12 of proposed EBG structure is
demonstrated in Fig. 4. When strip is present dual bandgap are
observed with bandgap center frequency (fc1 ) = 2.84 GHz and
(fc2 ) = 5.31 GHz. When strip is absent a single bandgap is
observed with center frequency (fc1 ) = 2.84 GHz.
resonance are presents which gives single band characteristics.
To validated the switchable properties of proposed EBG structure is simulated in Ansys high frequency structure simulator
(HFSS) and dispersion diagram for with and without strip are
shown in Figs. 3 (a) and (b) respectively. The Parameters
are taken as: dielectric constant (r ) = 4.4, substrate height
(h) = 1.50 mm. Due to the fabrication limitation (25 EBG
cells), open and short concept is applied in the experimental
measurements [9]. The gap between two adjacent EBG cells
is (g) = 2 mm. Other parameters are mentioned in Fig. 3.
From dispersion diagram as shown in Fig. 3 (a), when strip
is absent (diode off) only single bandgap is present between
mode 1 and mode 2 with center frequency (fc ) at 2.73
GHz, the bandgap lower cutoff frequency (fl ) is 2.50 GHz
and higher cutoff frequency is 2.95 GHz. From dispersion
diagram as shown in Fig. 3 (b), when strip is present dual
bandgap are observed with center frequency 2.73 GHz and
5.25 GHz between mode 1 and mode 2, and mode 2 and mode
3 respectively , which proves that, proposed EBG structure
exhibits switchable single/dual bandgap characteristics.
Fig. 5. Geometry of UWB Filter with proposed switchable EBG with PIN
diode (a) top view, and (b) back view with ( E1 , E2 , E3 , E4 , L1 , L2 , L3 ,
L4 , L5 , W1 , W2 , W3 , W4 , W5 , W6 , r , h, tan δ) = (5.5 mm, 3.8 mm,
1.32 mm, 3.4 mm, 8 mm, 1.9 mm, 9.6 mm, 1.85 mm, 10.8 mm, 3.4 mm, 0.5
mm, 1.47 mm, 1.4 mm, 0.5 mm, 3.9 mm, 4.4, 0.8 mm, 0.02)
S12 (dB)
0
−20
0
0
2
3
4
5
6
Frequency (GHz)
Fig. 4. Photograph, and measured S12 of proposed switchable EBG using
suspended microstrip line method.
S12 (dB)
Strip absent ( D off )
Strip present ( D on )
S12 (dB)
−40
−20
−40
−60
To validate the switchable bandgap properties of proposed
EBG structure, 5 × 5 cell of EBG structures fabricated on FR4
−40
−60
0
IV. E XPERIMENTAL RESULTS
−20
5
10
0
5
10
Frequency (GHz)
Frequency (GHz)
(a)
(b)
Fig. 6. Measured, and photograph of UWB BPF (a) PIN diode off, and (b)
PIN diode on
V. A PPLICATION
In this section, application of proposed EBG structure to get
switchable single/dual band notch in UWB filter is presented.
In 2002, the FCC release the unlicensed use of UWB (3.1 10.6 GHz) band for commercial use but due to ISM bands
like WLAN, WiFi etc. gives strong interference [8]. Therefore
it is desired to design UWB BPF with band notch rejections.
There are several UWB BPF are proposed [10] [11] [12] in
past years. But they are limited to give suitable single/dual
band notch with less number of active devices. In this section
UWB BPF [12] as shown in Fig. 5 is used. The parameters
of UWB BPF are (r )= 4.4, Substrate height (h) = 0.8 mm.
Other parameters are mentioned in Fig. 5. UWB BPF with
proposed EBG structure using PIN diode SMP 1352 is also
implanted as shown in Fig. 5. The parameters of switchable
EBG structure are mention in Fig 5. From measured results
as shown in Figs. 6 (a) and (b), it is observed that when PIN
diode is ‘on’ ,two band notches with center frequency 3.55
GHz (S12 > −10 dB) and 5.34 GHz (S12 > −10 dB) are
present and when PIN diode is OFF only single band notch
observed with center frequency 3.50 GHz (S12 > −10 dB).
When switchable EBG is absent near to feed line of UWB
BPF, band notch is not observed [12]. From experimental
result, by using single PIN diode, proposed EBG structure
can easily switch over single to dual band characteristics.
VI. C ONCLUSION
In this letter proposed switchable EBG structure is successfully simulated as well fabricated with good match between
simulation and experimental results. Applicability of the EBG
structure to get switchable notch-bands on UWB BP filter is
also demonstrated. Good matching between experimental and
simulation results validated the usefulness of the proposed
EBG structure for microwave applications.
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