2936IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 51, NO. 10, OCTOBER 2003
Microstrip Antennas Integrated With Electromagnetic
Band-Gap (EBG) Structures: A Low Mutual
Coupling Design for Array Applications
Fan Yang, Member, IEEE, and Yahya Rahmat-Samii, Fellow, IEEE
tures is becoming attractive in the electromagnetic and antenna
community. In this paper, a mushroom-like EBG structure is ana-
lyzed using the finite-difference time-domain (FDTD) method. Its
band-gap feature of surface-wave suppression is demonstrated by
The mutual coupling of microstrip antennas is parametrically in-
vestigated, including both the E and H coupling directions, dif-
ferent substrate thickness, and various dielectric constants. It is
observed that the E-plane coupled microstrip antenna array on a
thick and high permittivity substrate has a strong mutual coupling
duetothepronounced surfacewaves.Therefore, anEBGstructure
is inserted between array elements to reduce the mutual coupling.
This idea has been verified by both the FDTD simulations and ex-
perimental results. As a result, a significant 8 dB mutual coupling
reduction is noticed from the measurements.
Index Terms—Electromagnetic band-gap (EBG), finite-differ-
ence time-domain (FDTD) method, microstrip antennas, mutual
coupling, surface wave.
the electromagnetic and antenna community. The EBG ter-
minology has been suggested in  based on the photonic
band-gap (PBG) phenomena in optics  that are realized by
periodical structures.There are diverseforms ofEBG structures
, , and novel designs such as EBG structures integrated
with active device  and multilayer EBG structures  have
been proposed recently. This paper focuses on a mushroom-like
EBG structure, as shown in Fig. 1. Compared to other EBG
structures such as dielectric rods and holes, this structure has
a winning feature of compactness , , which is important
in communication antenna applications. Its band-gap features
are revealed in two ways: the suppression of surface-wave
propagation, and the in-phase reflection coefficient. The fea-
ture of surface-wave suppression helps to improve antenna’s
performance such as increasing the antenna gain and reducing
back radiation –. Meanwhile, the in-phase reflection
feature leads to low profile antenna designs –.
This paper concentrates on the surface-wave suppression ef-
fect of the EBG structure and its application to reduce the mu-
N RECENT years, there has been growing interest in
utilizing electromagnetic band-gap (EBG) structures in
Manuscript received January 29, 2002; revised November 25, 2002.
The authors are with the Department of Electrical Engineering, University
of California at Los Angeles, Los Angeles, CA 90095-1594 USA (e-mail:
Digital Object Identifier 10.1109/TAP.2003.817983
tual coupling of microstrip antennas, as shown in Fig. 1. To ex-
of an infinitesimal dipole source with and without the EBG
time-domain (FDTD) method , and a frequency stopband
for the field propagation is identified. Furthermore, the prop-
agating near fields at frequencies inside and outside the band
gap are graphically presented for a clear understanding of the
physics of the EBG structure. It is worthwhile to point out that
this band-gap study is closely associated with specific antenna
applications such as microstrip antennas and arrays.
Applications of microstrip antennas on high dielectric con-
stant substrates are of special interest due to their compact size
and conformability with the monolithic microwave integrated
circuit (MMIC). However, the utilization of a high dielectric
constant substrate has some drawbacks. Among these are
a narrower bandwidth and pronounced surface waves. The
bandwidth can be recovered using a thick substrate, yet this
excites severe surface waves. The generation of surface waves
decreases the antenna efficiency and degrades the antenna
pattern. Furthermore, it increases the mutual coupling of the
antenna array which causes the blind angle of a scanning array.
Several methods have been proposed to reduce the effects of
surface waves. One approach suggested is the synthesized
substrate that lowers the effective dielectric constant of the
substrate either under or around the patch –. Another
approach is to use a reduced surface wave patch antenna .
The EBG structures are also used to improve the antenna
performance. However, most researchers only study the EBG
effects on a single microstrip antenna element, and to the best
of our knowledge there are no comprehensive results reported
for antenna arrays.
The FDTD method is developed to analyze the mutual
coupling of probe-fed microstrip patch antenna arrays. The
simulated results agree well with the experimental results in
. Then, the mutual coupling of microstrip antennas is para-
metrically investigated, including both the E- and H-coupling
directions, different substrate thickness, and various dielectric
constants. In both coupling directions, increasing the substrate
thickness will increase the mutual coupling. However, the
effect of the dielectric constant on mutual coupling is different
at various coupling directions. It is found that for the E-plane
coupled cases the mutual coupling is stronger on a high
permittivity substrate than that on a low permittivity substrate.
In contrast, for the H-plane coupled cases the mutual coupling
0018-926X/03$17.00 © 2003 IEEE
YANG AND RAHMAT-SAMII: MICROSTRIP ANTENNAS INTEGRATED WITH EBG STRUCTURES: FOR ARRAY APPLICATIONS 2937
Fig. 1.Integration of the EBG structure with microstrip antenna array for reduced mutual coupling.
is weaker on a high permittivity substrate than that on a low
permittivity substrate. This difference is due to surface waves
propagating along the E-plane direction, which can be easily
viewed from the provided near field plots.
To reduce the strong mutual coupling of the E-plane cou-
pled microstrip antennas on a thick and high permittivity sub-
strate, the mushroom-like EBG structure is inserted between
antenna elements. When the EBG parameters are properly de-
signed, the pronounced surface waves are suppressed, resulting
in a low mutual coupling. This method is compared with pre-
vious methods such as cavity back patch antennas. The EBG
structureexhibits a bettercapabilityin loweringthemutual cou-
pling than those approaches. Finally, several antennas with and
without the EBG structure are fabricated on Rogers RT/Duroid
6010 substrates (
). The measured results demonstrate
the utility of the EBG structure, and this approach is potentially
useful for a variety of array applications.
II. BAND GAP CHARACTERIZATION OF THE EBG STRUCTURE
The mushroom-like EBG structure was first proposed in .
It consists of four parts: a ground plane, a dielectric substrate,
metallic patches, and connecting vias. This EBG structure ex-
hibits a distinct stopband for surface-wave propagation.
The operation mechanism of this EBG structure can be ex-
plained by an LC filter array: the inductor
current flowing through the vias, and the capacitor
gap effect between the adjacent patches. For an EBG structure
with patch width
, gap width , substrate thickness
, the values of the inductor
are determined by the following formula :
results from the
due to the
and the capac-
2938 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 51, NO. 10, OCTOBER 2003
tivity of free space.
Reference  also predicts the frequency band gap as
is the permeability of free space and is the permit-
not very accurate. For example, this model does not consider
the via’s radius information. An accurate but complex model
using the theory of transmission lines and periodic circuits can
be found in . Some other methods such as reflection phase
characterization have also been utilized to identify theband-gap
In this paper, to accurately identify the band-gap region and
understand its properties comprehensively, the FDTD method
is used to analyze the band-gap features. The computational
code developed in UCLA is based on a Cartesian grid cell with
the perfectly matched layer (PML) boundary condition. A uni-
( is the free space wavelength at 6
GHz) discretization is used. An infinitesimal dipole source with
a Gaussian pulse waveform is utilized to activate the structure
in order to obtain a wide range of frequency responses.
Fig. 2(a) shows an FDTD simulation model: the infinitesimal
dipole source surrounded by the mushroom-like EBG structure.
The dipole is chosen to be vertically polarized because the E
field in microstrip antenna applications is vertical to the ground
plane. As an example, two rows of EBG patches are plotted in
Fig. 2(a). In FDTD simulations four rows, six rows, and eight
rows of EBG patches are all simulated and compared.
The EBG structure analyzed in this section has the following
is the free space impedance which is.
The vias’ radius is 0.005
outside the EBG structure, and the height of the reference plane
. For the sake of comparison, a conventional case
is also analyzed. This conventional (CONV.) case consists of a
perfect electric conductor (PEC) ground plane and a dielectric
substrate with the same thickness and permittivity as the EBG
The basic idea is to calculate and compare the E field at the
reference plane. Since the EBG structure can suppress the sur-
face waves in a certain band gap, the E field outside the EBG
quantify the surface-wave suppression effect, an average
calculated according to the following equation:
. The ground plane size is kept
. A reference plane is positioned
distance away from the edge, where it is located
model and (b) ??? at the reference plane. The ??? of various EBG cases are
normalized to the ??? of the conventional case.
EBG structure is analyzed using the FDTD method: (a) simulation
plotted by the dashed line in Fig. 2(a).
Fig. 2(b) plots the
normalized to the
study analyzing the number of EBG rows is carried out varying
the number of rows from two to eight. It is observed that when
less rows of EBG patches are used, the band-gap effect is not
significant. When the number of rows is increased, a clear band
gap can be noticed. Inside this band gap, the average E field
in the EBG case is much lower than that in the conventional
case. To determine the band-gap region, a criteria is used that
the average E field magnitude with the EBG is less than half
of that without the EBG (the CONV. case). This is equivalent to
the-6 dB (
) levelin Fig.2(b), thus a band gap from
5.8–7.0 GHz can be identified with a minimum of four rows of
The LC model [(1)–(4)] is also used to analyze this mush-
room-like EBG structure, and a band gap of 6.37–8.78 GHz is
obtained. It has some overlap with the band gap calculated by
the FDTD method, which means this model can be used to get
an initial engineering estimation. However, the LC model result
is the vertical reference plane whose boundary is
of various EBG cases and they are
of the conventional case. A parametric
YANG AND RAHMAT-SAMII: MICROSTRIP ANTENNAS INTEGRATED WITH EBG STRUCTURES: FOR ARRAY APPLICATIONS 2939
and (b) the CONV. case. The outside field of the EBG case is about 10 dB lower
than that of the CONV. case because of the surface-wave suppression.
Near fields at 6 GHz, which is inside the band gap. (a) The EBG case
is relatively higher than the FDTD results because it uses a sim-
the FDTD model here.
To visualize the band-gap feature of surface-wave suppres-
sion, the near field distributions of the eight row EBG case and
the conventional case are calculated and graphically presented.
Fig. 3 plots the near field of both cases at 6 GHz, which is in-
side theband gap.The fieldlevelis normalizedto1 Wdelivered
power and is shown in dB scale. The field level outside the EBG
and (b) the CONV. case. The outside field of the EBG case has a similar level
as that of the CONV. case.
Near fields at 5 GHz, which is outside the band gap. (a) The EBG case
structure is around 10 dB. In contrast, the field level of the
CONV. case is around 20 dB. The difference of field levels is
due to the existence of the EBG structure, which suppresses the
propagation of surface waves so that the field level in the EBG
case is much lower than in the conventional case. However, the
EBG structure cannot successfully suppress surface waves out-
side its frequency band gap. For example, Fig. 4 plots the near
field of both cases at 5 GHz, which is outside the band gap. The
field distribution of the CONV. case is similar to its distribution
at 6 GHz. However, the field value outside the EBG structure is
2940IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 51, NO. 10, OCTOBER 2003
FDTD model to calculate the mutual coupling of probe fed microstrip
case. This means that although there are some interactions be-
tween the dipole source and the EBG structure, the field can
still propagate through the EBG structure. These results corre-
late well with the results in Fig. 2(b). From this comparison it
can be concluded that as expected, the surface-wave suppres-
sion effect exists only inside the band gap of the EBG structure.
III. MUTUAL COUPLING COMPARISON OF VARIOUS
MICROSTRIP ANTENNA ARRAYS
A. FDTD Method for Mutual Coupling Simulation
The FDTD method is used to analyze the mutual coupling
of microstrip antennas. The mutual coupling of antennas fed by
and the probe fed antenna case is discussed herein.
Fig. 5 plots an FDTD model to calculate the mutual coupling
of two probe fed patch antennas. The reflection coefficients are
FDTD simulation, and the voltages and currents are recorded at
the ports . The relation between the waves and the recorded
,, , and are the normalized voltage waves. The
A Gaussian pulse type of voltage source is used to excite the
structure. For simplicity, only port one is activated during the
simulation and port two is matched to 50
cident wave at port two is zero,
and are characteristic impedances of the feeding
. Therefore, the in-
. Thus, (7) becomes
Substituting (12) and (13) into (8)–(11) and dividing (8) and
(10) by (9), one arrives at
Fig. 6. E- and H-plane coupled probe fed microstrip antennas.
GHz for 5 cm (radiating edge) ? 6 cm patches on a 0.305 cm thick substrate
with a dielectric constant of 2.5.
Measured  and FDTD simulated mutual coupling results at 1.56
and mutual coupling (
) can be derived from (14) and (15).
The validity of these formulations has been demonstrated by
the E-plane and H-plane coupled microstrip antennas illustrated
in Fig. 6. A comparison of FDTD simulation results and ex-
perimental results  is shown in Fig. 7. The antenna has a
patch size of 5 cm (radiation edge)
a 0.305 cm substrate with a dielectric constant of 2.5. The mu-
tual coupling is calculated and measured at 1.56 GHz, and good
agreements are observed. This method can also be used to ana-
lyze the mutual coupling of microstrip antennas with arbitrary
6 cm, and is mounted on
B. Mutual Coupling Comparison
The developed FDTD method is next used to analyze the
mutual coupling features of microstrip antennas at different
thicknesses and permittivities , . Both the E-plane and
H-plane couplings are investigated, and four patch antennas are
compared as follows:
YANG AND RAHMAT-SAMII: MICROSTRIP ANTENNAS INTEGRATED WITH EBG STRUCTURES: FOR ARRAY APPLICATIONS 2941
dielectric constants and different thickness substrates: (a) ?
frequency (distance ? 0.5 ?
Comparisons of the E-plane coupled microstrip antennas on different
), (b) ?
versus patch distance (? ?
1) patch antennas on a thin and low dielectric constant sub-
, mm, and the patch size is 16 mm
2) patch antennas on a thick and low dielectric constant sub-
,mm, and the patch size is 15.5 mm
3) patch antennas on a thin and high dielectric constant sub-
,mm, and the patch size is 7.5 mm
4) patchantennasonathickandhighdielectric constantsub-
,mm, and the patch size is 7 mm
picted in Fig. 8. Fig. 8(a) plots the return loss results of the four
antenna cases. All the antennas are designed to resonate around
5.8 GHz. This frequency range is chosen for the ease of mea-
surements to be presented in the next section. The impedance
bandwidths (according to
for the first case, 2.40% for the second case, 0.61% for the third
case, and 1.71% for the last case. It can be observed that the
dB criterion) are 1.38%
dielectric constants and different thickness substrates: (a) ?
frequency (distance ? 0.5 ?
Comparisons of the H-plane coupled microstrip antennas on different
), (b) ?
versus patch distance (? ?
bandwidth increases with increasing thickness and decreases
while the permittivity increases. It’s worthwhile to point out
that the bandwidth of case 4 is even larger than that of case 1,
which means the bandwidth of microstrip antennas on a high
permittivity substrate can be recovered by increasing the sub-
strate thickness. Similar observations were also made in ,
which emphasized on a single element’s performance, espe-
cially on the improvement of radiation patterns.
pled microstrip antennas with a 0.50
is the free space wavelength at the resonant frequency
5.8 GHz. The first case has the lowest mutual coupling level,
while the last case shows the strongest. This is because the mi-
crostrip antenna on a high permittivity and thick substrate ac-
tivate the most severe surface waves. Fig. 8(b) plots the mu-
tual coupling varying with the patch distance at the resonant
frequency. The mutual coupling of all cases decreases as the
antenna distance increases. It is observed that both increasing
the substrate thickness and permittivity will increase the mutual
2942 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 51, NO. 10, OCTOBER 2003
thick substrate: (a) ?
activated and the mutual coupling is measured at the feeding port of the right
Near fields of the E-plane coupled microstrip antennas on a 2 mm
? ???? and (b) ?
? ?????. The left antennas are
In Fig. 9, the H-plane coupled microstrip antennas results
are depicted. Fig. 9(a) plots the return loss and mutual cou-
pling versus frequency with a 0.50
and Fig. 9(b) plots the mutual coupling varying with antenna
distance at the resonant frequency 5.8 GHz. In contrast to the
E-plane coupled results,the strongest mutual coupling occurs at
the second case, which has a low dielectric constant and a thick
substrate thickness, and the weakest mutual coupling happens
at the third case, which has a high dielectric constant and a thin
substrate thickness. It is observed that increasing the substrate
thickness still increases the mutual coupling, while increasing
the permittivity decreases it.
thick substrate: (a) ?
activated and the mutual coupling is measured at the feeding port of the right
Near fields of the H-plane coupled microstrip antennas on a 2 mm
? ???? and (b) ?
? ?????. The left antennas are
pled microstrip antenna arrays, the near fields of different cou-
plots the near fields of the E-plane coupled microstrip antennas
The left antennas (M1 in Fig. 6) are activated and the mutual
coupling is measured at the feeding port of the right antennas
(M2 in Fig. 6). The field is normalized to 1 W delivered power,
and plotted in dB scale. The surface waves propagate along the
direction and a strong mutual coupling can be observed for
the antennas on the high permittivity substrate. Fig. 11 shows
the near fields of the H-plane coupled microstrip antennas. As
YANG AND RAHMAT-SAMII: MICROSTRIP ANTENNAS INTEGRATED WITH EBG STRUCTURES: FOR ARRAY APPLICATIONS 2943
Fig. 12.Microstrip antennas separated by the mushroom-like EBG structure for a low mutual coupling. Four columns EBG patches are used.
shown inFig.11(a), theantennasona lowpermittivitysubstrate
have a larger patch size and their fringing fields couple to each
other, resulting in a strong mutual coupling. However, for the
antennas on a high permittivity substrate, there is less coupling
between theirfringingfieldsdue toitssmall patch sizeshownin
tual coupling of the E-plane coupled case have less effect now
because they do not propagate along the
concluded from the above discussion that the mutual coupling
behaviors of microstrip antennas are determined by both the di-
rectional surface waves and antenna size.
direction. It can be
IV. MUTUAL COUPLING REDUCTION USING THE
A. FDTD Simulation Results
From the above comparison, it is found that the E-plane cou-
pled microstrip antennas on a thick and high permittivity sub-
surface waves. Since the EBG structure has already demon-
strated its ability to suppress surface waves, four columns of
EBG patches are inserted between the antennas to reduce the
mutual coupling, as shown in Fig. 12.
microstrip antennas on a dielectric substrate with
. The antenna’s size is 7mm
distance between the antennas is 38.8 mm (
mushroom-like EBG structure is inserted between the antennas
to reduce the mutual coupling. Three different EBG cases are
analyzed and their mushroom-like patch sizes are 2, 3, and 4
mm, respectively. The gap between mushroom-like patches is
constant at 0.5 mm for all three cases.
antennas resonate around 5.8 GHz. Although the existence of
the EBG structure has some effects on the input matches of the
The mutual coupling results are shown in Fig. 13(b). Without
the EBG structure, the antennas show a strong mutual coupling
16.15 dB. If the EBG structures are employed, the mutual
mutual coupling is not reduced and a strong coupling of
5.8 GHz falls inside theEBG band gap so that thesurface waves
4 mm, and the
4 mm): (a) return loss and (b) mutual coupling.
FDTD simulated results of the E-plane coupled microstrip antennas
still as strong as
2944 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 51, NO. 10, OCTOBER 2003
antenna structures. (a) Four different patch antenna structures: (1) normal
microstrip antennas, (2) substrate between antennas is removed, (3) cavity back
microstrip antennas, and (4) microstrip antennas with the EBG structure in
between. (b) Mutual coupling results of four antenna structures. Patch antennas
resonate at 5.8 GHz.
Comparison of E-plane mutual coupling using different microstrip
B. Comparison of the EBG Structure With Other Approaches
tures also used to reduce the mutual coupling. Fig. 14(a) plots
four E-plane coupled antenna structures to be compared:
1) normal microstrip antennas,
2) the substrate between antennas are removed,
3) cavity back microstrip antennas, and
4) microstrip antennas with the EBG structure in between.
and antenna distance in all the structures are kept the same as
in the EBG case. In structure 2), a 13.5 mm width substrate is
removed between the patch antennas. This width is chosen to
be the same as the total width of four rows of the EBG patches.
When the cavity structure is used, the distance between the ad-
jacent PEC wall is also selected to be 13.5 mm.
Fig. 14(b) displays the mutual coupling results of four
different structures. The normal microstrip antennas show the
highest mutual coupling. The substrate removal case and the
cavity back case have some effects on reducing the mutual
coupling. A 1.5 dB mutual coupling reduction is noticed for the
former case and a 2 dB reduction is observed for the latter case.
The lowest mutual coupling is obtained in the EBG case as an
8.8 dB reduction is achieved. This comparison demonstrates
substrate thickness is 1.92 mm and its dielectric constant is 10.2. The antenna
size is 6.8 mm ? 5 mm with a distance of 38.8 mm. The EBG mushroom-like
patch size is 3 mm and the gap width is 0.5 mm.
structure. An 8 dB mutual coupling reduction is observed at the resonant
Measured results of microstrip antennas with and without the EBG
the unique capability of the EBG structure to reduce the mutual
C. Experimental Demonstration
To verify the conclusions drawn from the FDTD simulation,
two pairs of microstrip antennas are fabricated on Roger
RT/Duroid 6010 substrates. The permittivity of the substrate is
10.2, and the substrate thickness is 1.92 mm (75 mil). Fig. 15
shows a photograph of the fabricated antennas with and without
the EBG structure. The antenna’s size is 6.8 mm
the distance between the antennas’ edges is 38.8 mm (0.75
). The antennas are fabricated on a ground plane of
50 mm. For the EBG structures, the mushroom-like
5 mm, and
YANG AND RAHMAT-SAMII: MICROSTRIP ANTENNAS INTEGRATED WITH EBG STRUCTURES: FOR ARRAY APPLICATIONS2945
patch size is 3 mm and the gap between the patches is 0.5 mm.
Four columns of mushroom-like patches are inserted between
the antennas to reduce the mutual coupling.
The measured results are shown in Fig. 16. It is observed that
both antennas resonate at 5.86 GHz with return loss better than
10 dB. For the antennas without the EBG structure, the mu-
tual coupling at 5.86 GHz is
16.8 dB. In comparison, the mu-
tual coupling of the antennas with the EBG structure is only
24.6 dB. An approximately 8 dB reduction of mutual cou-
pling is achieved at the resonant frequency of 5.86 GHz. This
result agrees well with the simulated result shown in Fig. 13(b).
From this experimental demonstration, it can be concluded that
the EBG structure can be utilized to reduce the antenna mutual
coupling between array elements.
Inthispaper,amushroom-like EBGstructureis implemented
in the design of microstrip antenna arrays to reduce the strong
mutual coupling caused by the thick and high permittivity
substrate without sacrificing the compact size or bandwidth of
the antenna elements. The EBG structure is analyzed using the
FDTD method. The near field distribution of the EBG structure
waves. Also compared is the mutual coupling of microstrip
antennas on various thickness and permittivities substrates.
The strongest mutual coupling happens in the E-plane coupled
antennas on a thick and high permittivity substrate due to
the pronounced surface waves. The EBG structure is then
inserted between the antenna elements to reduce the mutual
coupling. Compared to other approaches such as cavity back
structure, the EBG structure demonstrates a better performance
to improve the mutual coupling. Several microstrip antennas
are fabricated to validate this observation, and an 8 dB mutual
coupling reduction is observed at the resonant frequency. This
mutual coupling reduction technique can be used in various
antenna array applications.
 Y. Rahmat-Samii and H. Mosallaei, “Electromagnetic band-gap struc-
tures: Classification, characterization and applications,” in Proc. Inst.
Elect. Eng.-ICAP Symp., Apr. 2001, pp. 560–564.
 E. Yablonovitch, “Photonic crystals,” J. Modern Opt., vol. 41, no. 2, pp.
 D. Sievenpiper, L. Zhang, R. F. J. Broas, N. G. Alexopolus, and E.
Yablonovitch, “High-impedance electromagnetic surfaces with a for-
bidden frequency band,” IEEE Trans. Microwave Theory Tech., vol. 47,
pp. 2059–2074, Nov. 1999.
 D. Sievenpiper, J. Schaffner, B. Loo, G. Tangonan, R. Harold, J.
Pikulski, and R. Garcia, “Electronic beam steering using a var-
actor-tuned impedance surface,” in Proc. IEEE AP-S Dig., vol. 1, July
2001, pp. 174–177.
 A. S. Barlevy and Y. Rahmat-Samii, “Characterization of electro-
magnetic band-gaps composed of multiple periodic tripods with
interconnecting vias: Concept, analysis, and design,” IEEE Trans.
Antennas Propagat., vol. 49, pp. 343–353, Mar. 2001.
 F. Yang and Y. Rahmat-Samii, “Step-Like structure and EBG Structure
to improve the performance of patch antennas on high dielectric sub-
strate,” in Proc. IEEE AP-S Dig., vol. 2, July 2001, pp. 482–485.
 R. Gonzalo, P. Maagt, and M. Sorolla, “Enhanced patch-antenna per-
formance by suppressing surface waves using photonic-bandgap sub-
strates,” IEEE Trans. Microwave Theory Tech., vol. 47, pp. 2131–2138,
 F. Yang and Y. Rahmat-Samii, “Mutual coupling reduction of microstrip
Dig., vol. 2, July 2001, pp. 478–481.
 M. Rahman and M. Stuchly, “Wide-band microstrip patch antenna with
planar PBG structure,” in Proc. IEEE AP-S Dig., vol. 2, July 2001, pp.
 R. Coccioli, F. R. Yang, K. P. Ma, and T. Itoh, “Aperture-coupled patch
antenna on UC-PBG substrate,” IEEE Trans. Microwave Theory Tech.,
vol. 47, pp. 2123–2130, Nov. 1999.
 S. Sharma and L. Shafai, “Enhanced performance of an aperture-cou-
pled rectangular microstrip antenna on a simplified unipolar compact
photonic bandgap (UCPBG) structure,” in Proc. IEEE AP-S Dig., vol.
2, July 2001, pp. 498–501.
 Z. Li and Y. Rahmat-Samii, “PBG, PMC and PEC surface for antenna
 F. Yang and Y. Rahmat-Samii, “A low profile circularly polarized curl
antenna over Electromagnetic Band-Gap (EBG) surface,” Microw. Opt.
Tech. Lett., vol. 31, no. 4, pp. 478–481, Nov. 2001.
 J. Y. Park, C. C. Chang, Y. Qian, and T. Itoh, “An improved low-profile
cavity-backed slot antenna loaded with 2D UC-PBG reflector,” in Proc.
IEEE AP-S Dig., vol. 4, July 2001, pp. 194–197.
 M. A. Jensen and Y. Rahmat-Samii, “Performance analysis of antennas
for hand-held transceivers using FDTD,” IEEE Trans. Antennas Prop-
agat., vol. 42, pp. 1106–1113, Aug. 1994.
 G. P. Gauthier, A. Courtay, and G. H. Rebeiz, “Microstrip antennas on
synthesized low dielectric-constant substrate,” IEEE Trans. Antennas
Propagat., vol. 45, pp. 1310–1314, Aug. 1997.
 I. Papapolymerou, R. F. Frayton, and L. P. B. Katehi, “Micromachined
rated high dielectric constant substrates,” IEEE Trans. Antennas Prop-
agat., vol. 47, pp. 1785–1794, Dec. 1999.
 D. R. Jackson, J. T. Williams, A. K. Bhattacharyya, R. L. Smith, S. J.
Buchheit, and S. A. Long, “Microstrip patch antenna designs that do
not excite surface waves,” IEEE Trans. Antennas Propagat., vol. 41, pp.
1026–1037, Aug. 1993.
 R. P. Jedlicka, M. T. Poe, and K. R. Carver, “Measured mutual coupling
pp. 147–149, Jan. 1981.
 D. F. Sievenpiper, “High-impedance electromagnetic surfaces,” Ph.D.
dissertation, UCLA, 1999.
 M. Rahman and M. A. Stuchly, “Transmission line-periodic circuit
representation of planar microwave photonic bandgap structures,”
Microwave Opt. Technol. Lett., vol. 30, no. 1, pp. 15–19, July 2001.
 F. Yang and Y. Rahmat-Samii, “Reflection phase characterization of an
3, June 2002, pp. 744–747.
 Y. X. Guo, K. M. Luk, and K. W. Leung, “Mutual coupling between
rectangular dielectric resonator antennas by FDTD,” Proc. Inst. Elect.
Eng.- Microwave Antennas Propagation, vol. 146, no. 4, pp. 292–294,
 D. E. Humphrey and V. F. Fusco, “A mutual coupling model for mi-
crostrip patch antenna pairs with arbitrary orientation,” Microw. Opt.
Tech. Lett., vol. 18, pp. 230–233, June 1998.
 D. H. Schaubert and K. S. Yngvesson, “Experimental study of a mi-
crostrip array on high permittivity substrate,” IEEE Trans. Antennas
Propagat., vol. 34, pp. 92–97, Jan. 1986.
 D. H. Schaubert, D. M. Pozar, and A. Adrian, “Effect of microstrip an-
tenna substrate thickness and permittivity: Comparison of theories with
experiment,” IEEE Trans. Antennas Propagat., vol. 37, pp. 677–682,
Fan Yang (S’96–M’03) received the B.S. and M.S.
degrees from Tsinghua University, Beijing, China
and the Ph.D. degree from University of California,
Los Angeles, all in electric engineering, in 1997,
1999, and 2002, respectively.
From 1994 to 1999, he was a Research Assistant
with the State Key Laboratory of Microwave and
China. From 1999 to 2002, he was a Graduate
Student Researcher in the Antenna Research, Ap-
plications, and Measurement Laboratory (ARAM),
University of California, Los Angeles. Since September 2002, he has been a
Research Engineer in the UCLA Antenna Laboratory. His research interests
include microstrip antenna and reconfigurable antenna designs, electromag-
netic band-gap structures, numerical methods in electromagnetics, and antenna
Dr. Yang is Secretary of the IEEE AP Society, Los Angeles chapter.
2946 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 51, NO. 10, OCTOBER 2003
Yahya Rahmat-Samii (S’73–M’75–SM’79–F’85)
received the M.S. and Ph.D. degrees in electrical
engineering from the University of Illinois, Ur-
He is a Professor and the Chairman of the
Electrical Engineering Department, University of
California, Los Angeles (UCLA). He was a Senior
Research Scientist at NASA’s Jet Propulsion Labo-
ratory/California Institute of Technology, Pasadena,
before joining UCLA in 1989. He was a Guest
Professor with the Technical University of Denmark
(TUD) during the summer of 1986. He has also been a consultant to many
aerospace companies. He has been Editor and Guest Editor of many technical
journals and book publication entities. He has Authored and Coauthored more
than 500 technical journal articles and conference papers and has written 17
book chapters. He is the Coauthor of two books entitled, Electromagnetic
Optimization by Genetic Algorithms, and Impedance Boundary Conditions in
of several patents. He has had pioneering research contributions in diverse
areas of electromagnetics, antennas, measurement and diagnostics techniques,
numerical and asymptotic methods, satellite and personal communications,
human/antenna interactions, frequency selective surfaces, electromagnetic
band-gap structures and the applications of the genetic algorithms, etc., (visit
http://www.antlab.ee.ucla.edu). On several occasions, his work has made the
cover of many magazines and has been featured on several TV newscasts.
Dr. Rahmat-Samii was the elected 1995 President and 1994 Vice-President
of the IEEE Antennas and Propagation Society. He was appointed an IEEE An-
tennas and Propagation Society Distinguished Lecturer and presented lectures
internationally. He was elected as a Fellow of the Institute of Advances in En-
gineering (IAE) in 1986. He was also a member of the Strategic Planning and
Review Committee (SPARC) of the IEEE. He was the IEEE AP-S Los Angeles
two consecutive years. He has been the plenary and millennium session speaker
at many national and international symposia. He was one of the directors and
Vice President of the Antennas Measurement Techniques Association (AMTA)
for three years. He has also served as Chairman and Co-Chairman of several
national and international symposia. He was also a member of UCLA’s Grad-
uate council for a period of three years. For his contributions, he has received
numerous NASA and JPL Certificates of Recognition. In 1984, he received
the coveted Henry Booker Award of the International Scientific Radio Union
(URSI) which is given triennially to the Most Outstanding Young Radio Sci-
entist in North America. Since 1987, he has been designated every three years
as one of the Academy of Science’s Research Council Representatives to the
URSI General Assemblies held in various parts of the world. In 1992 and 1995,
for papers published in the 1991 and 1993 IEEE ANTENNAS AND PROPAGATION.
In 1993, 1994, and 1995, three of his Ph.D. students were named the Most Out-
standing Ph.D. Students at UCLA’s School of Engineering and Applied Sci-
ence. Seven others received various Student Paper Awards at the 1993–2002
IEEE AP-S/URSI Symposiums. He is a Member of Commissions A, B, J, and
K of USNC/URSI, AMTA, Sigma Xi, Eta Kappa Nu, and the Electromagnetics
Academy. HeislistedinWho’s WhoinAmerica,Who’s WhoinFrontiersofSci-
ient of the University of Illinois ECE Distinguished Alumni Award. In 2000, he
was the recipient of IEEE Third Millennium Medal and AMTA Distinguished
Achievement Award.In 2001, he wasthe recipientof the Honorary Doctorate in
physics from the University of Santiago de Compostela, Spain. In 2001, he was
elected as the Foreign Member of the Royal Academy of Belgium for Science
and the Arts. He is the designer of the IEEE Antennas and Propagation Society
logo that is displayed on all IEEE ANTENNAS AND PROPAGATION publications.