Selected Papers

Millimeter-wave High-Efficiency Multilayer Parasitic
Microstrip Antenna Array for System-on-package
Tomohiro Seki, Kenjiro Nishikawa†, Ichihiko Toyoda,
and Koichi Tsunekawa
Abstract
This paper describes the design and characteristics of a highly efficient multilayer parasitic microstrip
antenna array (MPMAA) constructed on a multilayer substrate for millimeter-wave system-on-package
modules. The antenna on a Teflon substrate achieved a radiation efficiency of greater than 91% and an
associated antenna gain of 11.1 dBi at 60 GHz. Its size is only 10 mm × 10 mm. We discuss MPMAAs
fabricated on both Teflon and low-temperature cofired ceramic (LTCC) substrates. The measured performances of prototype antennas are also presented. The MPMAA offers compactness and high efficiency and is easily integrated with the system-on-package design. It will lead to compact and cost-effective millimeter-wave RF modules.

1. Introduction
The strong demand for high-speed wireless applications has stimulated the development of millimeterwave and quasi-millimeter-wave wireless equipment[1]-[3]. V-band (50–75 GHz) wireless systems arevery interesting because they offer much higher
transmission rates, above 1 Gbit/s, due to their wider
bandwidths. These applications require compact,
high-performance, and cost-effective wireless equipment. A highly integrated RF (radio frequency) module, known as a system-on-package module, which
has a multilayer structure, is effective in meeting thethese requirements [4]-[7]. It is necessary to use
active integrated antenna technology to make a module integrated with antennas that consume little
power and have low-noise characteristics [8]-[10].
Several approaches to achieve an RF module integrated with antennas have been reported.
1) One approach is a semiconductor on-chip antenna such as a microstrip antenna (MSA) that is integrated with RF circuits on the same semiconductor
substrate [4]. However, in this approach it is difficult† NTT Network Innovation Laboratories
Yokosuka-shi, 239-0847 Japan
E-mail: nisikawa.kenjiro@lab.ntt.co.jp

Vol. 3 No. 9 Sep. 2005

to establish a high-gain antenna having an antenna
array configuration on a semiconductor substrate dueto the substrate’s size and loss. Therefore, high-gain
compact antennas have not yet been integrated withmonolithic microwave integrated circuits (MMICs).
2) A multi-chip module approach has also been
proposed for a module integrated with antennas [5],[6]. In this module, antennas and MMICs are connected by wire bonding or a ribbon, which results ina high connection loss. This approach also requires alow-loss feeding circuit.
3) A dielectric lens antenna has been used toachieve a high-gain antenna [7]. However, the commonly used lens antenna is constructed using an
expensive crystal material and it is difficult to mountit on the MMIC package. Thus, a dielectric lensantenna fabricated using resin was investigated as a
low cost alternative.
There are problems, however, in mounting theantenna on the MMIC package and achieving highefficiency. Moreover, it is difficult to construct anantenna array substrate on a single layer due to thelimitations of the manufacturing process for the millimeter-wave frequency band.
A technique for improving the radiation efficiency
by arranging parasitic elements above the feeding
microstrip antenna elements has been investigated33

Selected Papers[11]-[15]. However, obtaining a sufficient absolute
gain was difficult in these studies [11]-[14]. A highgain antenna using a low-permittivity layer or an air
layer has been investigated, but only the directional
gain was described and it was difficult to use thisantenna in a system-on-package design due to theparasitic element substrates.
To overcome the above problems, we are studying
a multilayer parasitic microstrip antenna array(MPMAA) structure based on a parasitic antennaconfiguration [16], [17]. This paper describes a highly efficient MPMAA structure for a system-on-package module at millimeter-wave frequency bands. At
60 GHz, the antenna on a Teflon substrate achieves
high radiation efficiency of greater than 91% andhigh gain of greater than 11.1 dBi. The rest of thispaper is organized as follows. Section 2 describe theconcept of the system-on-package module and thedesign of the antenna. Section 3 presents the effect of
the alignment precision of the manufacturing
process. Finally, Section 4 presents measurement
results for prototype 60-GHz band antennas fabricated on Teflon and low-temperature cofired ceramic(LTCC)* substrates. Our MPMAA offers compactness and high-efficiency performance for millimeterwave system-on-package modules.
2. Design of parasitic element arrangement on
Teflon substrate
2.1 Concept of millimeter-wave system-onpackage
The concept of a system-on-package module integrated with an antenna is shown in Fig. 1. An
MPMAA and a highly integrated transceiver MMIC
are mounted on a multilayer structure, in a verticalstacking configuration. Two types of feeding methods
for the MPMAA are considered. In the first method,a feeding element is constructed on the MMIC chip,and the MPMAA is fed by electromagnetic coupling
without a feeding line. In the other, a feeding element
is constructed where the multilayer substrate of the
MPMAA and the element are connected to the terminal of the MMIC using flip-chip technology. As indicated in Fig. 1, the MPMAA uses two parasitic layerswith four parasitic elements on each layer.
2.2 MPMAA design
This antenna achieves high gain because it increases the antenna aperture by utilizing the coupling* LTCC is a glass ceramics to be fired at around 900°C.

34

between the layers of the multilayer substrate. Here,
we describe the MPMAA design for the 60-GHz
band. We use the moment method as the calculation
method and assume that the ground plane is infinite.
To clarify the MPMAA’s characteristics, we use a
multilayer Teflon substrate (εr = 2.2, tanδ = 0.0007 at
10 GHz) as the antenna substrate. The MPMAA on
the Teflon substrate also exhibits excellent characteristics such as a high gain and a wide bandwidth. A
simulation model for the MPMAA is shown in Fig. 2.
Here, we use the via-fed method for the feeding
method. The size of the feeding element is 0.30 λ 0 ×
0.30 λ 0 and the feeding point is 0.01 λ 0 away from thecenter of the patch, where λ 0 is the free-space wavelength. The size of the parasitic elements mounted on
the first parasitic layer is 0.32 λ 0 × 0.32 λ 0 and thepatch size of the second parasitic layer is 0.28 λ 0 ×
0.28 λ 0. The four parasitic elements mounted on the
Proposed multilayer
parasitic
microstrip array antenna

Parasitic
elements

Bump
Multilayer
TeflonMultilayer
LTCC

Via hole
Motherboard
Highly-integrated
MMIC chip

Feeding elements

Bump

Fig. 1. Novel structure of system-on-package integrated
with antenna.

w2
Second layer

w1

Feeding
element
Feeding
point

First layer
Feeding linet2
t1
0.25 mm0.05 mmFig. 2. Antenna model.

NTT Technical Review

Selected Papers

first parasitic layer are arranged so that they are
equidistant from the center of the feeding MSA. For
convenience, the width (horizontal direction) is
expressed so that the widths of the first and second
parasitic layers are w1 and w2, respectively. In addition, t1 and t2 represent the substrate thicknesses ofthe first and second parasitic layers, respectively. The
relationship between w1 and w2 that yields the maximum absolute gain is shown in Fig. 3. Here, t1 andt2 were set to 0.25 and 0.55 mm, respectively. In thisfigure, it is clear that w1 is proportional to w2. The
relationships between maximum absolute gain andw2 and between radiation efficiency and w2 areshown in Fig. 4. Here, the substrate thickness parameters were the same. In this figure, it is clear that the
maximum absolute gain is 11.1 dBi and that the radiation efficiency is 91% when w1 is 0.22 λ 0 and w2 is
0.28 λ 0. The antenna achieves the maximum radiation efficiency of 97% when w2 is 0.32 λ 0. We

believe that, in this case, the peak of the absolute gain
is obtained by increasing the antenna aperture as thenumber of parasitic elements increases and the efficiency degrades due to the decrease in the coupling
between the feed element and the parasitic elements.
Additionally, it is necessary to clarify the effect of
substrate thickness on the parasitic elements. The
dependence of the absolute gain on the substrate
thicknesses, t1 and t2, is shown in Fig. 5. When t1 andt2 are 0.25 and 0.55 mm, respectively, the absolute
gain has the maximum value of 11.1 dBi. Additionally, it is clear that the manufacturing margins of t1 andt2 are approximately 150 and 100 µm, respectively,
and the gain reduction is less than 0.5 dB. Furthermore, it is clear that the precision of the substrate
thickness of the conventional multilayer Teflon substrate process is sufficient to construct this proposed
antenna. The antenna’s frequency characteristics(Fig. 6) show that the bandwidth is 2.6% when the S11

0.35
0.40
Thickness t2 (mm)Width w1 (xλ0)

0.3

0.25

0.2

8

6

10

8

0.50

10

0.60

11
0.70

11

10

0.80

0.25

0.35

0.3

0.90
0.10

0.4

0.15

Width w2 (xλ0)

Fig. 3. Relationship between w1 and w2 that achieves
the maximum absolute gain.
12

15

80
6
70
4
60

2
0
0.2

0.25

0.3
Width w2 (xλ0)

0.35

50
0.4

Fig. 4. Absolute gain and radiation efficiency
characteristics versus w2.

Vol. 3 No. 9 Sep. 2005

Absolute gain (dBi)

8

Radiation efficiency (%)

Absolute gain (dBi)

90

0.20
0.25
Thickness t1 (mm)

0.30

0.35

Fig. 5. Absolute gain characteristics versus substrate
thicknesses t1 and t2.

100

10

8

10

0

–5
10
–10

S11 (dB)

0.15
0.2

5
–15

0
59

60

61
Frequency (GHz)

62

–20
63

Fig. 6. Calculated frequency characteristics of theabsolute gain and S11.

35

Selected Papers

characteristics are less than –10 dB. To consider themechanism of this antenna, we calculated the current
distribution using the moment method analysis. The
results in Fig. 7 show that in the feeding element, thecurrent is distributed to the first layer parasitic elements and via them to the second-layer parasitic elements. The RF signal can be effectively separated
from the feeding element and passed to the secondlayer parasitic elements without using a power
divider circuit, so array operation can been achieved.
2.3 Effect of the substrate on MPMAA
To make the system-on-package module, we investigated several substrates. In this section, we describe
the dependence of the antenna’s performance on the
key substrate characteristic: the effective dielectric
constant. Figure 8 shows the positions of the parasitic elements that give maximum antenna gain as afunction of the effective dielectric constant of a sub-strate. The corresponding maximum antenna gain isplotted in Fig. 9. As the effective dielectric constantof the substrate increased, w1 and w2 decreased.
They saturated when the effective dielectric constant
was more than 7.5. On the other hand, the corresponding maximum gain continuously decreased.
However, the MPMAA fabricated on an LTCC substrate (εr = 7.7, tanδ = 0.002 at 10 GHz) achieved
antenna gain of more than 8 dBi. These results indicate that our MPMAA can offer reasonable antenna
gain even if we use low-cost materials, such as LTCC
or high-temperature cofired ceramic (HTCC), for thesubstrate.
3. Effect of alignment precision
The antenna constructed on a multilayered Teflon
substrate that binds the substrates using a bonding
0.5

TeflonLTCC
Feeding
element

w2
w1

w1, w2 (λ0)

0.4

HTCC

Second
layer
First
layer

w2
0.3
Feeding line
0.2

0.1

w1

Y
0

X

2

3

4
5
6
7
8
Effective dielectric constant910(a) Front viewFig. 8. Positions of parasitic elements for maximum
antenna gain versus effective dielectric constant.

12

Teflon

LTCC

HTCC

Y
X

Antenna gain (dBi)

10
8
6
4
2

(b) Rear view
Current density

0
2

Low

High

Fig. 7. Current distribution of the proposed antenna.

36

3

4
5
6
7
8
Effective dielectric constant9

10

Fig. 9. Antenna gain versus effective dielectric constant.

NTT Technical Review

Selected Papers

Feeding element
First layer
Second layer

Feeding element
First layer
Second layer
12

Absolute gain (dBi)

Absolute gain (dBi)

12

10
y

x

8

6

10
y

8
x

6
0

0.1

0.2
0.3
Offset length (mm)

0.4

0.5

Fig. 10. Absolute gain reduction versus alignment
precision of x-axis direction.

film is more sensitive to alignment precision thanantennas on other substrates such as an aluminaceramic substrate. Therefore, we need to clarify theeffect of alignment error due to the binding substrates. We used the moment method for the calculation. The size of the feeding element was 0.30 λ 0 ×
0.30 λ 0 and the feeding point was 0.01 λ 0 away fromthe center of the patch. The size of the parasitic elements mounted on the first parasitic layer was 0.32 λ 0× 0.32 λ 0 and the patch size of the second parasitic
layer was 0.28 λ 0 × 0.28 λ 0. Furthermore, the positionof the first parasitic layer was x: ±0.22 λ 0, y: ±0.22 λ 0
and the position of the second parasitic layer was x:±0.28 λ 0, y: ±0.28 λ 0. The calculated absolute gain
reductions when alignment errors occur in the direction of the x- and y-axes are shown in Figs. 10 and 11,
respectively. Alignment errors in the y-axis direction
clearly had a greater effect than those in the x-axis
direction. We believe this is because there was a standing wave in the direction of the y-axis of each patch.
Moreover, it is clear that the alignment margins of thefirst-and second-layer parasitic substrate are approximately ±100 and ±50 µm, respectively, and that thegain reduction is less than 0.5 dB. Furthermore, thesimulation results indicate that the alignment precision of the conventional multilayer Teflon substrate
process is sufficient to construct this antenna.
4. Measured performance
4.1 Measurement system
In the millimeter-wave frequency range, one imporVol. 3 No. 9 Sep. 2005

0

0.1

0.2
0.3
Offset length (mm)

0.4

0.5

Fig. 11. Absolute gain reduction versus alignment
precision of y-axis direction.

Anechoic chamber

Horn antenna

Test antenna

Coupler
Mixer
Mixer

Lo

Lo

Network analyzer
Agilent 8510C
Port 1

Port 2mm wavesourceFig. 12. Antenna pattern measuring system.

tant issue is the effect on measured values of soldering errors and differences in the connecting torque.
To eliminate this deviation, we developed a novel
antenna-probing fixture based on an RF on-wafer
probing system. As a result, we obtained the samemeasurement accuracy as for MMIC chip measurements for the radiation pattern of miniaturized antennas in the millimeter-wave frequency band. Our millimeter-wave radiation pattern measuring system isshown in Fig. 12. The configuration using an RF
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Selected Papers

probe is shown in Fig. 13 and a photograph of the system is shown in Fig. 14. These on-wafer probes canbe directly connected to an antenna terminal formedon the planar substrate. This system can measure theantenna radiation without the need to mount RF connectors on the antenna substrate. This method yields
higher accuracy and higher efficiency. This fixture
has two probe heads. One probe is used to feed the RF
signal to the antenna terminal and the other is used tofeed the control signal and DC power to the devices
mounted on the antenna substrate.

RF connector
Probe head
Mounting board

Antennasubstrate

Control and bias terminal

4.2 MPMAA on Teflon substrate
We manufactured a prototype antenna with a Teflon
substrate to confirm the design for the 60-GHz band.
We used a microstrip line (MSL) and a via hole tofeed the MSA, which acted as the feeding element
shown in Fig. 2. Two parasitic layers were arranged
so that the size and location of the MSA and parasitic
elements, the substrate thickness, and the location of
the feeding points yielded the maximum absolute
gain as described in the previous section. A photograph of the prototype antenna is shown in Fig. 15.
The left side shows a side view of the antenna element and the right side shows the feeding line. The
fabricated prototype antenna chip size is 10.0 mm ×10.0 mm × 1.1 mm. The E-plane and H-plane radiation patterns are shown in Fig. 16. The measured andcalculated radiation patterns had fairly similar main
lobes.
Next, we discuss the bandwidth of this antenna.
The frequency characteristics of the measured maximum gain and the S11 characteristics are shown in
Fig. 17. The frequency bandwidth for the gain that is
3 dB below the peak gain for this antenna is from 59.3
to 62.6 GHz. Therefore, the bandwidth comparedwith the center frequency is 5.5%. The S11 frequency
characteristics and the gain are in good agreementwith the calculated results shown in Fig. 6. Moreover,
we can see that the estimated absolute gain is greaterthan 8.5 dBi because the measured absolute gain of
this antenna is greater than 7.4 dBi including the RFprobe loss, which is approximately 1.1 dB at 60 GHz.
The difference between the calculated and measured
gains is approximately 3 dB. Here, we discuss threepossible causes for this gain reduction: 1) loss in the
microstrip line or coplanar line transition, 2) a discrepancy between the designed and actual values ofthe bonding film thickness resulting from the manufacturing process, and 3) the fabrication accuracy inthe antenna manufacturing process. More specifically, the gain reduction due to the change in bonding
38

Antenna substrate fixer
Mounting board fixer

Fig. 13. Configuration of measuring system using an
RF probe.

RF probe
Radiationside

Antennasubstrate
Probe holder

Mixer module

Fig. 14. Photograph of measuring system using an RFprobe.

Parasitic element

MSL

Ground plane

Fig. 15. Photograph of MPMAA fabricated on Teflon
substrate.

NTT Technical Review

Selected Papers

010Measured
Calculated

–10

–5
5
–10

S11 (dB)

Absolute gain (dBi)

Relative power (dB)

0

0
–15

–20
–5
59
–30
–180

–90

0
Angle (deg)

90

180

(a) E-plane

Measured
Calculated

60

61Frequency (GHz)

–20
63

62

Fig. 17. Absolute gain and S11 of MPMAA on Teflon
substrate.

Parasitic element

MS lineRelative power (dB)0–10CPW line
–20

–30
–180

–90

0
Angle (deg)

90

180

Fig. 18. Photograph of MPMAA fabricated on LTCC
substrate.

(b) H-plane

Fig. 16. Measured radiation pattern of MPMAA on Teflon
substrate.

film thickness was at least 1 dB, even when the antenna’s alignment accuracy at the time of manufacture
was approximately 100 µm. One topic for future
study is to find a bonding film material that has electrical characteristics similar to the Teflon substrate.
Furthermore, it seems that the alignment binding
accuracy of the multilayer Teflon substrate needs tobe improved to approximately 50 µm.
4.3 MPMAA on LTCC substrate
A photograph of the prototype antenna fabricatedon an LTCC substrate is shown in Fig. 18. The left
side shows a side view of the antenna element and theright side shows the feeding line. The radiation characteristics of the prototype antenna are shown in Fig.
Vol. 3 No. 9 Sep. 2005

19. The measured and calculated main lobe characteristics are in good agreement. Furthermore, we clarified that the measured absolute gain of this antennais 7.17 dBi including the RF probe loss, which isapproximately 1.2 dB at 60 GHz. The frequency
bandwidth for the gain that is 3 dB below the peak
gain for this antenna is from 59.3 to 61.3 GHz. Therefore, the bandwidth compared with the center frequency is 3.3%.
5. Conclusion
We described a highly efficient multilayer parasitic
microstrip antenna array (MPMAA) constructed on amultilayer substrate for millimeter-wave system-onpackage modules. The basic design and performanceof the array antenna were described when a Teflon
substrate was used. We also described the effects ofthe substrate and the alignment of parasitic elements
39

Selected Papers

References

Measured
Calculated[1]

Relative power (dB)

0

–10

–20

–30
–180

–90

0
Angle (deg)

90

180

90

180

(a) E-plane
Measured
Calculated

Relative power (dB)

0

–10

–20

–30
–180

–90

0
Angle (deg)(b) H-plane

Fig. 19. Measured radiation pattern of MPMAA on LTCC
substrate.

on antenna performance. The radiation efficiency andassociated antenna gain of the antenna on a Teflon
substrate were greater than 91% and 11.1 dBi, respectively. We discussed fabricated 60-GHz-band
MPMAAs on both Teflon and LTCC substrates andpresented performance measurement results. The
MPMAA offers compactness and high efficiency andis suitable for system-on-package modules. Thus, itenables us to make compact and cost-effective millimeter-wave RF modules.

40

Y. Takimoto, “Recent activities on millimeter wave indoor LAN system development in Japan,” in 1995 IEEE MTT-S Int. Microwave
Symp. Dig., pp. 405-408, June 1995.
[2] N. Morinaga and A. Hashimoto, “Technical trend of multimedia
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E82-B, No. 12, pp. 1897-1905, Dec. 1999.
[3] T. Ihara and K. Fujimura, “Research and development of millimeterwave short-range application systems,” IEICE Trans. B, Vol. E79-B,
No. 12, pp. 1741-1753, Dec. 1996.
[4] T. Nakagawa, K. Nishikawa, B. Piernas, T. Seki, and K. Araki, “60GHz antenna and 5-GHz demodulator MMICs for more than 1-Gbps
FSK transceivers,” in Proc. 32nd European Microwave Conf., pp.
929-932, Sep. 2002.
[5] Y. Hirachi, H. Nakano, and A. Kato, “A cost-effective RF-modulewith built-in patch antenna for millimeter-wave wireless systems,” inProc. 29th European Microwave Conf., pp. 347-350, Oct. 1999.
[6] M. Tentzeris, N. Bushyager, J. Laskar, G. Zheng, and J. Papapolymerou, “Analysis and design of MEMS and embedded components in
Silicon/LTCC packages using FDTD/MRTD for system-on-package(SOP),” in Proc. Silicon Monolithic Integrated Circuits in RF Systems, 2003 Topical Meeting, pp. 138-141, Apr. 2003.
[7] U. Sangawa, T. Urabe, Y. Kudoh, A. Omote, and K. Takahashi, “A
study on a 60 GHz low profile dielectric lens antenna using high-permittivity ceramics -toward a low profile antenna,” Technical report of
IEICE, MW2002-116, pp. 57-62, Nov. 2002.
[8] J. Lin and T. Itoh, “Active integrated antennas,” IEEE Trans.
Microwave Theory and Tech., Vol. 42, pp. 2186-2194, Dec. 1994.
[9] T. Seki, H. Yamamoto, T. Hori, and M. Nakatsugawa, “Active antenna using multilayer ceramic-polyimide substrates for wireless communication systems,” in 2001 IEEE MTT-S Int. Microwave Symp.
Dig., pp. 385-388, May 2001.
[10] T. Seki, K. Cho, and H. Mizuno, “Novel active integrated antennaconfiguration using multilayer Teflon substrate and solder bumpinterconnection,” in Proc. 32nd European Microwave Conf., pp. 605608, Sep. 2002.
[11] H. Legay and L. Shafai, “A new stacked microstrip antenna with large
bandwidth and high gain,” in Proc. 1993 IEEE AP-S Int. Symp., pp.
948-951, July 1993.
[12] S. D. Targonski, R. B. Waterhouse, and D. M. Pozar, “Design ofwide-band aperture-stacked patch microstrip antennas,” IEEE Transactions on Antennas and Propagation, Vol. 46, pp. 1245-1251, Sep.
1998.
[13] R. B. Waterhouse, “Stacked patches using high and low dielectric
constant material combinations,” IEEE Transactions on Antennas andPropagation, Vol. 47, pp. 1767-1771, Dec. 1999.
[14] R. Li, G. Dejean, M. Maeng, K. Lim, S. Pinel, M. M. Tentzeris, andJ. Laskar, “Design of compact stacked-patch antennas in LTCC multilayer packaging modules for wireless applications,” IEEE Transactions on Advanced Packaging, Vol. 27, No. 4, pp. 581-589, Nov.
2004.
[15] E. Nishiyama, M. Aikawa, and S. Egashira, “Three-Element stacked
microstrip antenna with wide-band and high-gain performances,”2003 Int. IEEE AP-S Symp. Dig., Vol. 2, pp. 900-903, June 2003.
[16] T. Seki, K. Nishikawa, and K. Cho, “Multilayer parasitic microstrip
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[17] T. Seki, N. Honma, K. Nishikawa, and K. Tsunekawa, “High efficiency multilayer parasitic microstrip array antenna on Teflon substrate,” in Proc. 34th European Microwave Conf., pp. 829-832, Oct.
2004.

NTT Technical Review

Selected Papers

Tomohiro Seki
Research Engineer, Wireless Systems Innovation Laboratory, NTT Network Innovation Laboratories.
He received the B.E. and M.E. degrees in electrical engineering from Tokyo University of Science, Tokyo in 1991 and 1993, respectively. In
1993, he joined NTT Radio Communication Systems Laboratories (now NTT Network Innovation Laboratories), Kanagawa. He has been
engaged in the development of array antennas
and active antennas for the millimeter-wave andmicrowave bands. He received the Young Engineer Award from the Institute of Electronics,
Information and Communication Engineers(IEICE) in 1999. He is a member of IEEE and
IEICE.

Kenjiro Nishikawa
Senior Research Engineer, Wireless System
Innovation Laboratory, NTT Network Innovation Laboratories.
He received the B.E. and M.E. degrees in welding engineering and Dr. Eng. degree in communication engineering from Osaka University,
Suita, Osaka in 1989, 1991, and 2004, respectively. In 1991, he joined NTT Radio Communication Systems Laboratories (now NTT Network
Innovation Laboratories), Kanagawa, where hehas been engaged in R&D of three-dimensional
and uniplanar monolithic MMICs on Si and
GaAs and their applications. He is currently
interested in millimeter-wave transceivers, system-on-package technologies, active integrated
antennas, and high-speed communication systems. He is a Technical Program Committee
member of the IEEE Compound Semiconductor
Integrated Circuit Symposium and the IEEE
Radio and Wireless Symposium. He is a memberof IEEE and IEICE of Japan. He received the1996 Young Engineer Award from IEICE.

Vol. 3 No. 9 Sep. 2005

Ichihiko Toyoda
Senior Research Engineer, Wireless Systems
Innovation Laboratory, NTT Network Innovation Laboratories.
He received the B.E., M.E., and Dr. Eng.
degrees in communication engineering from
Osaka University, Suita, Osaka in 1985, 1987,
and 1990, respectively. In 1990, he joined NTT
Radio Communication Systems Laboratories,
Kanagawa, where he was engaged in developmental research based on electromagnetic analysis for three-dimensional and uniplanar MMICs.
From 1994 to 1996, he was with NTT Electronics
Technology Corporation, Kanagawa, where he
was engaged in the development of wireless communication equipment and MMICs. From 1996
to 1997, he was with NTT Wireless Systems Laboratories, Kanagawa, where he performed R&D of highly integrated multifunctional MMICs, high-frequency Si MMICs, and MMIC design software based on 3-D
masterslice MMIC technology. From 1997 to 2001, he was engaged in the development of ultrahigh-speed digital ICs and MMICs for optical and wireless communication systems as Engineering Director of IC Design at NTT Electronics Corporation, Kanagawa. His current interests concern millimeter-wave and quasi-millimeter-wave high-speed wireless access systems and their applications. Since 2004, he
has also been a Visiting Associate Professor at Niigata University. He received the1993 IEICE Young Engineer Award, the Japan Microwave Prize presented at the
1994 Asia-Pacific Microwave Conference in Tokyo, the 18th Telecom System
Technology Award from the Telecommunications Advancement Foundation, andthe 2005 IEICE Electronics Society Award. He is a member of IEICE and IEEE.

Koichi Tsunekawa
Senior Manager, Executive Research Engineer, Wireless Systems Innovation Laboratory,
NTT Network Innovation Laboratories.
He received the B.S., M.S., and Ph.D. degrees
in engineering science from the University ofTsukuba, Tsukuba, Ibaraki in 1981, 1983, and1992, respectively. He joined the ElectricalCommunications Laboratories of Nippon Telegraph and Telephone Public Corporation (nowNTT), Tokyo in 1983. Since 1984, he has been
engaged in R&D of portable telephone antennas
in land mobile communication systems. From1993 to 2003, he was with NTT DoCoMo, Inc.
where he worked on radio propagation research,
intelligent antenna systems for wireless communications, and the development of IMT-2000
antenna systems. His research interests are antenna systems for MIMO transmission, millimeterwave broadband access, and ubiquitous wirelesssystems. He is a member of IEICE and IEEE.

41