COMMISSION C : Radio Signals and Systems (Nov. '01 Oct. '04)
Edited by Takashi Ohira
C1. Radio Communication Systems
Research and development activity in the field of radio communication systems, such as the fourthgeneration mobile/cellular radio and wireless LAN systems has been still high in Japan for these three
years. OFCDM or MC-CDM(A) systems which use multi-carrier transmission with multiplexing bothon time-domain and frequency-domain were well investigated for the 4G cellular systems [Atarashi et al.,2003]. Adaptive antenna or diversity techniques are also important issues for the systems [Ktaoka et al.,2004], [Mikami et al., 2004].
Studies on OFDM or multicarrier transmission for general radio systems including the cellular and
WLAN systems are also active. The PAPR (peak to average power ratio) and nonlinear distortion of
power amplifier are important problems for this kind of systems, and some PAPR reduction schemes[Tomisato et al., 2003], [Fujii et al., 2003] and distortion compensation techniques [Hosono et al., 2002]
were proposed.
Frequency domain equalization, which can be applied not only for multi-carrier but also for single
carrier, is one of the interesting research fields in these three years. Some applications on thosecombining with diversity reception [Adachi et al., 2003] were investigated. Another remarkable field isinterference cancellation. A unique adaptive algorithm for OFDM was proposed [Uesugi, 2003] andtheoretical expressions of the performance of those for CDMA receivers were derived [Suzuki, 2003].
Adaptive antenna and MIMO studies have been very active. Capacity and performance of MIMO
channel were measured in indoor environment [Sakaguchi et al., 2004], [Benjebbour et al., 2003].
Analog smart antennas and their theories were established [Ohira, 2003], and the adaptive beamforming
algorithms were developed [Sun, 2004]. Some adaptive array techniques were investigated on OFDM
systems to mitigate the interference due to delay spread longer than guard time [Hori et al., 2002],[Higuchi et al., 2004].
Wireless ad-hoc network [Ueda, 2002] and multi-hop radio system [Kishi, 2002] are other recently
studied interesting issues in these research fields and several papers have been published.
(M. Taromaru)
References
Atarashi, H., S. Abeta and M. Sawahashi [2003], Variable Spreading Factor-Orthogonal Frequency and
Code Division Multiplexing (VSF-OFCDM) for Broadband Packet Wireless Access, IEICE Trans. on
Commun.,Vol.E86-B, No.1, pp.291-299.
Kataoka, T., H. Taoka, K. Higuchi and M. Sawahashi [2004], Adaptive antenna array-beam formingwith simultaneous received path timing and DOA estimations based on two-dimensional power profilein broadband CDMA reverse link, Proc. ISSSE '04, Session 12-4, Linz.
Mikami, M. and T. Fujii [2004], An antenna weight control method of downlink for adaptive array
antenna at base station in DS-CDMA cellular system, IEICE Trans. Commun. (Japanese ed.), Vol. J87-B,
No.9, pp.1174-1184.

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Tomisato, S. and H. Suzuki [2003], A peak reduction scheme based on control signal insertion for
multi-carrier mobile communication systems, IEICE Trans. Commun., Vol. E86-B, No.6, pp.1910-1916.
Fujii,T. and M. Nakagawa [2003], Peak power reduction for MC-CDMA using cluster assigned code
selection, IEICE Trans. Commun., Vol. E86-B, No.9, pp.2637-2647.
Hosono, H., T. Hosokawa, T. Maeda, F. Maehara and F. Takahata [2002], A compensating method
based on recursive processing of nonlinear distortion for OFDM, IEICE Trans. Commun. (Japanese ed.),Vol. J85-B, No.1, pp.9-19.
Adachi, F., and T. Sao [2003], Joint Antenna Diversity and Frequency-Domain Equalization for MultiRate MC-CDMA, IEICE Trans. Commun., Vol. E86-B, No.11, pp.3217-3224.
Uesugi, M. [2003], An interference cancellation scheme for OFDM using adaptive algorithm, IEICE
Trans. Commun., Vol.E86-B, No.11, pp.3182 – 3191.
Suzuki, T. [2003], Analytical formulas for the overall performance of a linear parallel interference
canceller for asynchronous CDMA, IEICE Trans. Commun. (Japanese ed.), Vol. J86-B, No.4, pp.630644.
Sakaguchi, K., S. Ting and K. Araki [2004], Initial measurement on MIMO eigenmode communication
system, IEICE Trans. Commun. (Japanese ed.), Vol. J87-B, No.9, pp. 1454-1466.
Benjebbour, A. and S. Yoshida [2003], Performance improvement of ordered successive detection withimperfect channel estimates for MIMO systems, IEICE Trans. Commun., Vol. J86-B, No.11, pp.31923199.
Ohira, T. [2003], Reactance domain signal processing in parasite-array antennas, Asia-PacificMicrowave Conf., APMC2003, WD6-1, 1, pp.290-293, Seoul.
Sun, C., A. Hirata, T. Ohira and N. Karmakar [2004], Fast beamforming of electronically steerable
parasitic array radiator antennas: Theory and experiment, IEEE Trans. Antennas Propagat., Vo.52, No.7,
pp.1819-1832.
Hori, S., N. Kikuma and N. Inagaki [2002], MMSE adaptive array utilizing guard interval in the OFDM
systems, IEICE Trans. Commun. (Japanese ed.), Vol. J85-B, No.9, pp. 1608-1615.
Higuchi, K., and H. Sasaoka [2004], Adaptive array suppressing inter symbol interference based on
frequency spectrum in OFDM system, IEICE Trans. Commun. (Japanese ed.), Vol. J87-B, No.9, pp.
1222-1229.
Kishi, Y., K. Tabata, S. Konishi and S. Nomoto [2002], A proposal of multi-hop mesh networkarchitecture featuring adaptive network control for broadband fixed wireless access systems, IEICE
Trans. Commun. (Japanese ed.), Vol. J85-B, No.12, pp. 2025-2036.
Ueda, T., S. Bandyopadhyay and K. Hasuike [2002], An adaptive media access control protocol andsystem performance of wireless ad hoc network using smart antenna, IEICE Trans. Commun. (Japaneseed.), Vol. J85-B, No.12, pp. 2189-2197.
C2. Radio Circuits for Mobile Terminals

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The third-generation mobile communications (3G) system, W-CDMA, started in May 2001.
However it was only the system level launch. It was not enough miniaturization and cost for mass
subsribers. Today, 2005, W-CDMA is becoming real consumer mobile communication system as thesecond-generation (2G) mobile communication system. To reduce parts count and materials cost, radio
functionalities have been integrated rapidly toward System on Chip. For this objective, good technicalharmonization of semiconductor (SiGe, EF-CMOS less than quarter micron rule), radio architecture(direct conversion receiver) and radio circuits (integrated VCO, high power amplifier) make acontribution [Itoh et al. 2004].
Regarding to semiconductor techniques in Japan, lithography rule for large scale logics was shifting to
sub-micron [STARC, 2004]. This made radio digital baseband ICs small and inexpensive enough formobile terminals. Inflection from 0.13um to 0.09mm is one of the important technical drivers for the 3G
mobile terminals. In Japan, most of research efforts for high integrated RF-IC employ BiCMOS/SiGe
BiCMOS process thanks for its high RF performances [Yoshida et al. 2004]. With rapid progress of RF
performances of CMOS toward sub-micron rule, high gate/capacitor density of the standard CMOS
process make strong motivation for RF-CMOS techniques [Ugajin et al. 2004]. This RF-CMOS wasapplied for short distance communications as Bluetooth and WLAN [Komurasaki 2003], because oflower performance compared with SiGe circuits. However RF-CMOS circuits developments for 3G
mobile terminals are under high motivated efforts.
Regarding to radio architecture, the 3G direct conversion receiver (DCR) was firstly applied for thecommercial model in Japan [Itoh et al. 2002]. For realization of the DCR architecture, even harmonic
diode mixer for extreme low second order distortion, LTCC module integration and SiGe highperformance MMIC were developed. In addition to the diode configuration of the DCR, Gilbert typeactive mixer was developed for fully integration of the DCR [Yoshida 2004]. The fractional-PLL withdelta-sigma modulation is an important technique for randomization of periodical spurious that makes
interference of radio. However we can find less specific improvements in this field.
Regarding to circuit technique, the integrated VCO technique contribute miniaturization of mobile
terminals. For stabilization of phase noise in wider frequency range, variable current cell was developed
for the 3G utilization [Itoh 2002].
For next generation of radio communications like SDR (Software Defined Radio), broadband radio
circuits were developed for re-configurable radio architecture [Araki 2004]. In an aspect of radioarchitecture analog based approach is very saturated. Most of RF circuits except power amplifiers can be
integrated on LSI easily today. Under rapid evolution of sub-micron CMOS, research interests are
dedicated to paradigm shift on radio architecture from analog to digital. Digital oriented RF architecture
will be important research for the next several years.
(K. Itoh)
References
Itoh, K., M. Uesugi, S. Murakami, H. Joba [2004], Overview of the evolution of PLL synthesizers usedin mobile terminals, Digest of 2004 IEEE Radio and Wireless Conference, pp.471 - 474.
STARC [2004], http://www.starc.jp/univ/joint/roadmap-e.html
Yoshida, H., T. Toyoda, I. Seto, O. Fujimoto, T. Arai, T. Itakura, H. Tsurumi [2004], Fully Differential
Direct-Conversion Receiver for W-CDMA Reducing DC-Offset Variation, IEICE Trans. Electron.,
Vol.E87-C No.6 pp.901-908.
Ugajin, M., A. Yamagishi, J. Kodate, M. Harada, T. Tsukahara [2004], Design techniques for a 1-V
operation Bluetooth RF transceiver, Proceedings of the IEEE 2004 Custom Integrated Circuits
Conference, pp.393 - 400.

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Komurasaki, H., T. Sano, T. Heima, K. Yamamoto, H. Wakada, Yasui, I., M. Ono, T. Miwa, H. Sato, T.
Miki, N. Kato [2003], A 1.8-V operation RF CMOS transceiver for 2.4-GHz-band GFSK applications,
IEEE Journal of Solid-State Circuits, Vol.38, no. 5, pp.817 - 825.
Itoh, K., T. Yamaguchi, T. Katsura, K. Sadahiro, T. Ikushima, R. Hayashi, F. Ishizu, E. Taniguchi, T.
Nishino, M. Shimozawa, N. Suematsu, T. Takagi, O. Ishida [2002], Integrated even harmonic type directconversion receiver for W-CDMA mobile terminals, 2002 IEEE MTT-S International Microwave
Symposium Digest, pp.9-12.
Itoh, N., S. Ishizuka, [2002] 1200-MHz Fully Integrated VCO with "Turbo-Charger" Technique, IEICE
Trans. Electron., Vol.E85-C, no.8, pp.1569-1576.
Araki, K., T. Nakagawa, Kawashema, M., K. Kobayashi, K. Akabane, H. Sheba, H. Hayashi, [2004]
Implementation and performance of a multi-band transceiver for software defined radio, Digest of 2004
IEEE Radio and Wireless Conference, pp.207 - 210
C3. RF Integrated Circuits
The research interests of RF integrated circuits (ICs) for wireless terminals are moving from singleband / single-mode to multi-band /multi-mode transceiver ICs. Recent wireless LAN ICs weredeveloped as “Combo Chip” which covers 2.45GHz (IEEE 802.11b/g) and 5.2GHz (IEEE 802.11a)[McFarland, 2004], and Cellular phone ICs were developed as multi-band (0.8-2.1GHz) and multi-mode(GSM/PCS) chips [Kim, et al., 2004].
For the next generation systems (Beyond 3G or 4G), SDR (Software Defined Radio) and/or cognitive
radio transceiver were discussed and the transceiver ICs for these application were reported [Madihian,2002], [Araki, et al., 2004], [Abe, et al., 2001]. For these applications, a quadrature-mixer IC having
0.8-5.2GHz broad-band characteristic was reported [Kageyama, et al., 2004]. Direct conversion
configuration became common for these Tx/Rx ICs [Nakajima, et al., 2004].
CMOS has been widely used for these ICs but SiGe still be used especially for narrow-band / wide
dynamic range applications (i.e. Cellular phone/DTV) to achieve lower 1/f noise and higher saturation
characteristics.
(N. Suematsu)
References
McFarland, W.J. [2004], “WLAN system trends and the implications for WLAN RFICs,” 2004 IEEE
RFIC symposium, MO3C-1.
Kim, Y., Y.Son, V.N.Parkhomenko, I. Hwang, K Nah, H.Lee, J.Cho, A.Sergeev and B.Park [2004], “A
GSM/EGSM/DCS/PCS direct conversion receiver with integrated synthesizer,” 2004 IEEE RFIC
symposium, MO3B-1.
Madihian, M.[2002], “Reconfigurable Si-RF Front-End Chips for Software Defined Radio,” 2002 AsiaPacific Microwave Conference Proceeding, pp.1659-1663.
Araki K., T. Nakagawa, M. Kawashimi, K. Kobayashi, K. Akabane, H. Shiba. H. Hayashi [2004]“Implementation and performance of a multi-band transceiver for software defined radio,” 2004 IEEE
Radio and Wireless Conference (RAWCON), T3B.1.

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Abe M., N. Sasho, R. Morelos-Zaragoza, S. Haruyama [2001], “An RF Architecture for Software
Defined Receivers,” Microwave Workshop & Exhibition 2001 (MWE2001).
Kageyama C., K. Nakajima, K. Tsutsumi, E. Taniguchi, M. Shimozawa, N. Suematsu [2004], "0.85.2GHz band SiGe-MMIC Q-MIX for a multi-band multi-mode direct conversion receiver," 2004 IEEE
Radio and Wireless Conference (RAWCON), T3B.2.
Nakajima K., T. Sugano, N. Suematsu [2004], "A 5-GHz-band SiGe-MMIC direct quadrature modulator
using a doubly stacked polyphase filter," 2004 IEEE Radio Frequency Integrated Circuits Symp. Dig. ,TU3C-3.
C4. Direction of Arrival Estimation
Research activities for direction of arrival (DOA) estimation in Japan were very active in the past
three years. The research topics expand to include experimental verification and system calibration of
the test-bed for high-resolution DOA estimation systems, which is the feature to be mentioned. Many
researches were reported in annual conference of IEICE, monthly technical meetings of Antennas andPropagation (AP) and Radio Communication System (RCS) technical group of IEICE, and so forth. Also
we can see their high activities through two international conferences held in Japan, ISAP-i02 andISAP2004 sponsored by IEICE, which had several sessions for DOA estimation.
As the trends of DOA estimation researches in these three years, implementation problems of DOA
estimation techniques and their performance evaluation were highlighted. NTT began the field
experiment of adaptive beamforming techniques by using DOA estimation results for the next generation
base-station of the cellular phone in the spring of 2003. It was a promising event. Effects of fabrication
error and mutual coupling of array elements were studied [Inoue, et al., 2001], [Inoue, et al., 2003]. To
realize high resulution DOA estimation, several new array calibration techniques have been proposed;
mutual coupling compensation by using generalized mode-vector [Yuan, et. al., 2004], the technique forarray with coupled objects [Yamada, et al., 2004], and so forth. For progress in researches of DOA
estimation algorithms, the following researches would be mentioned; New signal subspace method
without eigen-decomposition [Xin, et al., 2004] that can successfully reduce computational burden
without performance degradation, improved DOA tracking algorithm based on the signal subspacemethod [Kikuma, et al., 2004], DOA and angular spread estimation by using extended mode vectors[Hotta, et al., 2004], and so forth.
Moreover, it is one of the features in Japan that high-resolution DOA estimation techniques withparasitic antenna array were intensively studied. Hand-held DOA finder with electronically steerable
parasitic array radiator (ESPAR) was developed [Ohira, et al., 2001]. High-resolution techniques such as
the MUSIC algorithm were found applicable to the ESPAR system [Plapous, et al., 2004], and spatialsmoothing preprocessing scheme for coherent wave detection became also available [Hirata, et al., 2004].
Besides the ESPAR antenna with varactor, beam steering antenna with MEMS [Tran, et al., 2003] and2D-DOA estimation algorithm for switched parasitic antenna was also considered [Matsumoto, et al.,2004].
Furthermore, DOA estimation techniques as wireless propagation channel sounding for coming
wireless systems, such as MIMO system [Takada, et al., 2001] and UWB system [Haneda, et al., 2003],
were also extensively studied.
(H.Yamada)
References
Ohira, T., K. Gyoda [2001], "Hand-held microwave direction-of-arrival finder based on varactor-tuned

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analog aerial beamforming," 2001 Asia-Pacific Microwave Conference, vol.2, pp.585-588
Inoue, Y., K. Mori and H. Arai [2001], "DOA error estimation using 2.6 GHz DBF array antenna," 2001
Asia-Pacific Microwave Conference, vol.2, pp.701 - 704.
Takada, J., K. Sakaguchi, K. Araki [2001], "Development of high resolution MIMO channel sounder forthe advanced modeling of wireless channels," 2001 Asia-Pacific Microwave Conference, vol.2, pp.563 568.
Haneda, K., J. Takada [2003], "An application of SAGE algorithm for UWB propagation channel
estimation," 2003 IEEE Conference on Ultra Wideband Systems and Technologies, pp. 483 - 487
Inoue, H., H. Arai [2003], "Effect of mutual coupling and manufactural error of array for DOA
estimation of ESPRIT algorithm," IEICE Trans. Commun. (Japanese Edition), Vol.J86-B, No.10,
pp.2145-2152.
Xin, J., A. Sano [2004], "Computationally efficient subspace-based method for direction-of-arrival
estimation without eigendecomposition, "IEEE Trans. on Signal Processing, vol.52, no.4, pp.876 - 893
Matsumoto T., Y. Kuwahara, [2004], “2D DOA estimation using beam steering antenna by the switchedparasitic elements," International Symposium on Antennas and Propagation 2004 (ISAP2004), Vol.3,
pp.916 - 919.
Yamada, H., R. Hara, Y. Yamaguchi [2004], "Calibration of dipole array with reflector using method ofimages, "2004 International Symposium on Multi-Dimensional Mobile Communications, Vol.2, pp.660664.
Tran, O., Y. Irie, S. Hara, Y. Nakaya, T. Toda, Y. Oishi [2004], "A Beamforming Algorithm for ESPAR
Antenna with RF-MEMS Variable Reactors, "IEICE Annual Conference, Fall, B-1-59
Hirata, A., E. Taillefer, T. Aono, H. Yamada, T. Ohira [2004], "Reactance-Domain SSP MUSIC for
DOA estimation of coherent waves with a 7-element circular Espar antenna, "IEICE Trans. Commun.
(Japanese Edition), Vol.J87-B No.9 pp.1405-1413.
Hotta, H., N. Kikuma, K. Sakakibara, H. Hirayama [2004], "Comparison of MUSIC algorithms using
gradient- and integral-type mode vectors for direction of arrival and angular spread estimation, "IEICE
Trans. Commun. (Japanese Edition), Vol.J87-B, no.9, pp.1414-1423.
Kikuma, N. [2004], "Iterative DOA estimation using subspace tracking methods and adaptive
beamforming, "IEICE Trans. Commun. (Japanese Edition), Vol.J87-B, no.9, pp.1149-1161.
Kim, M., K. Ichige, H. Arai, [2004], "Implementation of FPGA Based Fast Unitary MUSIC DOA
Estimator," IEICE Trans.Electronics, Vol.E87-C, No.9, pp.1485-1494.
Plapous, C., J. Cheng, E. Taillefer, A. Hirata, T. Ohira [2004], "Reactance domain MUSIC algorithm forelectronically steerable parasitic array radiator," IEEE Trans. on Antennas and Propagation, vol.52,
no.12, pp.3257 – 3264
Yuan Q., Q.Chen, K.Sawaya [2004], "Mutual coupling effect on performance of dataptive array
antenna," International Symposium on Antennas and Propagation 2004 (ISAP2004), Vol.2, pp.625-628.

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C5. Base Station for Cellular Phone System
NTT DoCoMo commercially began the FOMA service that was the third generation cellular phonesystem on October 1, 2001. The FOMA service enabled high-speed packet transmission in the mobile
environment. The modulation method become digital from the second generation cellular phone. In thethird generation cellular phone system, some base station employs not only the modulation scheme but
also the digital modulation circuits. In addition, the digital signal processing technology was applied tothe transmission amplifier. The transmission amplifier of the digital pre-distortion technology was built
in the FOMA base station sub system in July, 2002 [Oishi, et al., 2002]. The digital pre-distortion
technology is a highly efficient transmitting power amplification technology that also compensates for
signal distortion in third-generation cellular phone systems. A large capacity base station with more than2880 user being accommodated was achieved by the low power consumption LSI technology and thedigital processing high efficiency amplifiers. Recently, there is a movement to try to share the interface
between wireless front end by a digital method with the base station such as CPRI (Common PublicRadio Interface) and OBSAI (Open Base Station Architecture Initiative). This tendency will give an
impetus to the digitalization of the transmission amplifier further. Therefore, some people forecast thatthe digital pre-distortion method becomes a main current though the feed forward type amplifier was amain current as the method of the base station amplifier up to now. [Vasillakis, 2003](T. Maniwa)
References
Oishi Y. et al., “Highly Efficient Power Amplifier for IMT-2000 BTS Equipment,” Fujitsu Scientific &Technical Journal, Vol. 38, No.2, pp.201-208., December 2002.
Or http://magazine.fujitsu.com/us/vol38-2/paper11.pdf
http://www.cpri.info
http://www.obsai.org/
Vasillakis W., “Evolution of Power Amplifiers for Base station Application,” IEEE Topical Workshop
on Power Amplifiers for Wireless Communications 2003, Sept.2003. in San Diego
C6.Space Time Domain Processing
Space-time signal processing techniques have been playing an important role, particularly as demands
for mobile communications increase. The space domain signal processing brought by the application ofarray antennas enables us to add one more dimension on the time domain signal processing. It results infurther performance improvement under serious multipath fading environments in wirelesscommunication systems.
Recently, in addition to the conventional concept of the space-time signal processing, some newconcepts combining space-domain signal processing with time-domain coding so called as Space Time
Block Code (STBC) have attracted much attention of researchers. Particularly in the last three years,
many practical researches have been conducted towards its implementation and practical use in the realsystems. For example, STBC is applied to multi-carrier systems that are employed in digital
broadcastings, wireless local area networks (WLAN) and so on. In these systems, Orthogonal Frequency
Division Multiplexing (OFDM) is combined with STBC by using multiple antennas to obtain thediversity gain effectively in rich multipath fading environments [X.N.Tran et al, 2005],[M. Fujii, 2003].

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Multi-carrier systems such as OFDM, Multi-Carrier Code Division Multiple Access (MC-CDMA) are
widely paid attention for the applications in mobile systems. Naturally, these schemes are extended overthe space domain in order to obtain further performance improvement. However, in these systems, spacetime signal processing causes heavy computational load. Some researches try to reduce the complexity
by using a frequency-domain signal processing technique [F. Adachi et al, 2003], [T. Itagaki et al, 2004].
Non-linear signal processing techniques applied on the space- and time-domain signal processing
yields quite interesting new features. Some of such applications allows us to demodulate DirectSequence Spread Spectrum (DS/SS) signals without any knowledge of the signal even the spreadingcode [Y. Kamiya et al, 2001], [Y. Kamiya et al, 2003]. It demodulate DS/SS signal asynchronously andblindly while it accomplishes the equalization of delayed signals and beamforming, simultaneously.
These features are advantageous because of the following reason. In DS/SS systems, conventionally,
space-time signal processors require a training sequence inserted in communication signals. In otherwords, the processors require the bit-timing synchronization. However, it should be noted that this fact
implies that the processors cannot perform the signal processing until the synchronization is acquired
even though the space-time signal processing is performed to enable the demodulation under severe
environments. These new configurations based on non-linear signal processing solve this paradoxical
problem.
Although space-time signal processing improves the performance of the receiver significantly, itcauses large-scale configuration due to the usage of multiple antennas. Multiple antennas results in
multiple RF front-ends and A/D converters. In order for reducing the hardware complexity of the spacetime signal processing, combination with ESPAR antenna is attractive solution. ESPAR antennaachieves beamforming in the analog domain so that it enables us to reduce the RF front-ends and A/Dconverters. Its adaptive control scheme has been proposed in [J. Cheng, 2001]. After that, it is combinedwith the above-mentioned non-linear signal processing schemes [Y. Kamiya et al, 2003].
(Y. Kamiya)
ReferencesTran, X. N., T. Fujino and Y. Karasawa [2005] “Spatio-Temporal Equalization for Space-Time Block
Coded Transmission over Frequency Selective Fading Channel with Co-channel Interference,” IEICE
Trans., Fundamentals, Vol.E88-A No.3 pp.660-668.
M. Fujii [2003], “Beamspace-Time Transmit Diversity for Time-Domain Spreading OFDM-CDM
Systems,” IEICE Trans., Commun., Vol. E86-B, No. 1.
Adachi F. and T. Sao [2003], “Joint Antenna Diversity and Frequency-Domain Equalization for MultiRate MC-CDMA,” IEICE Trans., Commun., Vol. E86-B, No. 11.
Itagaki T. and F. Adachi [2004] “Joint Frequency-Domain Equalization and Antenna Diversity
Combining for Orthogonal Multicode DS-CDMA Signal Transmissions in a Frequency-Selective Fading
Channel,” IEICE Trans., Commun., Vol.E87-B No.7, pp.1954-1963
Kamiya Y., S. Denno, Y. Mizuguchi, M. Katayama, A. Ogawa [2001], Y. Karasawa: “Novel
Configuration of CMA Adaptive Array for Beamforming, Equalization and Despreading of SS signals,”
IEICE Trans., Fundamentals, Vol. J85-A, No. 1, pp. 31-41.
Kamiya Y., K. Ochiai, Y. Karasawa [2003], “A Multistage Blind Adaptive Array Antenna for Multiuser
Signal Detection in Asynchronous SS Sysmtes,” IEICE Transactions on Communications, Vol. E86-B.
No. 8, pp. 2414-2424.

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Cheng J., Y. Kamiya, and T. Ohira [2001], “Adaptive beamforming of ESPAR antenna based on
steepest gradient algorithm,” IEICE Transactions on Communications, Vol. E84-B, No. 7, pp.1790-1800.
Kamiya Y. and T. Ohira [2003] “A New Concurrent Reactance- and Time-domain Signal Processing
Approach for the ESPAR Antenna in Wireless Ad Hoc Networks,” Proceeding of The 6th International
Symposium on Wireless Personal Multimedia Communications (WPMC'03), Yokosuka Japan .
C7. Metamaterials
Interests on metamaterials in Japan have been growing rapidly among microwave engineers/scientists
in the past three years. Novel RF devices and antennas based on left-handed materials or negativerefractive index materials, PBG/EBG structures, artificial dielectrics, chiral materials, and the like havebeen proposed for potential applications in wideband communication and radar systems from microwave
to optics frequency range. Domestic activities on metamaterial study in Japan have also been stimulated.
Technical workshops on metamaterials have been organized in Microwave Workshop and Exhibition(MWE) 2003 in Yokohama, one of the biggest annual microwave workshops in Japan, which covers
fundamentals and applications of the left-handed materials artificial dielectrics, periodic PBG/EBG
structures and chiral materials. The Optics and Radio Wave Workshop has also been held in Sapporo in2004 jointly by the four technical groups on microwaves, antennas and propagation, optelectronics, andsatellite communication of the Institute of Electronics, Information and Communication Engineers(IEICE) and a focusing session entitled “Recent advances of PBG/EBG structures and metamaterials”
has been held.
Extensive studies on left-handed materials and applications have been carried out. Zeroth-orderresonance in the composite right/left-handed transmission line has been studied [Sanada et al., 2003],
and radiation characteristics of the zeroth-order resonator have further been studied for antenna
applications [Sanada et al., 2004]. The characteristics of the right/left-handed transmission line havebeen theoretically summarized in [Sanada et al., 2004] and purely distributed negative refractive index
lenses have also been demonstrated experimentally [Sanada et al, 2004] based on the 2-dimensional
planar composite right/left-handed transmission line structure. Wideband planar backward couplers havealso been proposed [Caloz et al., 2004]. In addition, novel microwave devices and antennas have been
proposed and demonstrated; nonreciprocal left-handed transmission lines using ferrite substrates[Tsutsumi et al., 2004], novel via-free planar left-handed transmission line structure and antenna
applications [Sanada, et al., 2004], left handed transmission lines using gyrator [Okubo et al., 2004],
ferrite left-handed transmission line circulators [Tsutsumi et al., 2004], ferrite loaded left-handed
waveguides [Ueda et al., 2004], compact multi-layered left-handed transmission line structures [Horii etal., 2004], novel planar left-handed transmission line structures using enhanced capacitors with built-in
shunt inductor on the ground plane [Sahara et al., 2004], planar left-handed dual-band branch line
couplers [Matsunaga et al., 2004], and 2D beam scanning left-handed leaky-wave antennas [Aso et al.,2004].
Besides the left-handed materials, right-handed metamaterials and periodic PBG/EBG structures havealso been studied. Compact artificial dielectric resonators with spurious suppression have been
demonstrated [Awai et al., 2004] exploiting its huge permittivity and resonant mode control functionality.
Loss study of artificial dielectrics based on metal strips has also been carried out [Kubo et al., 2004]. In
optics frequency, studies on PBG structures [Hangyo et al, 2004] and optical fiber applications of PBG
structures [Koshiba 2004] have successfully been carried out. In addition, photonic crystals in THz
regions have been demonstrated [Takeda 2004] as well as in microwave regions [Kawasaki 2004].
(A.Sanada)
References
Sanada, A., C. Caloz, and T. Itoh [2003], “Novel zeroth-order resonance in composite right/left-handed
transmission line resonators,” 2003 Asia-Pacific Microwave Conference Proceedings, pp. 1588-1591.

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Sanada, A., M. Kimura, I. Awai, H. Kubo, C. Caloz, and T. Itoh [2004], “A planar zeroth-orderresonator antenna using a left-handed transmission line,” 2004 European Microwave Conference
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EditorTakashi Ohira
ATR Wave Engineering Laboratories
Contributors
Makoto Taromaru
ATR Wave Engineering Laboratories
Kenji Itoh
Mitsubishi Electric
Noriharu Suematsu
Mitsubishi Electric
Hiroyoshi Yamada
Niigata University
Toru Maniwa
Fujitsu Laboratories
Yukihiro Kamiya
Tokyo University of Agriculture and Technology
Atsushi Sanada
Yamaguchi University
This work is part of "Research and development of ultra-high speed giga-bit rate wireless LAN
systems" supported by National Institute of Information and Communication Technology (NICT).

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