Nobuhiko Shibagaki

Influence of Underlayer Materials on Preferred Orientations of Sputter-Deposited AlN/Mo Bilayers for Film Bulk Acoustic Wave Resonators

Highly c-axis-oriented aluminum nitride (AlN) films were deposited by reactive rf magnetron sputtering on molybdenum (Mo) films for film bulk acoustic wave resonators (FBARs). We investigated the effect of underlayer materials on the crystalline qualities of AlN/Mo bilayers. AlN/Mo bilayers were sputter-deposited on silicon, silicon dioxide and AlN underlayers under the same sputtering conditions. The results revealed that the AlN underlayer markedly improves Mo film quality, and this greatly affects the orientation of the upper AlN film. By applying the AlN underlayer, we obtained a full width at half maximum of 2.3° from the X-ray diffraction rocking curve of the AlN film grown on a Mo film. We propose that the large surface energy of AlN is the reason the AlN underlayer improves the quality of the Mo films. In the FBAR with the AlN underlayer, a quality factor of 800 and an effective electromechanical coupling coefficient of 5.7% were achieved.

New design procedures and experimental results of SAW filters for duplexers considering wide temperature range

New types of SAW filter called “extended SAW resonator coupled filter” using different substrates have been developed for 800 MHz cellular systems. Design and synthesis procedure for new SAW filters are discussed. Experimental frequency responses and temperature characteristics are also given for the filters used in an antenna duplexer of ETACS, EAMPS, and NTACS cellular systems

SAW front-end module for GSM-based dual-band cellular phones with direct-conversion demodulation

Assuming direct-conversion (DC) demodulation, the required characteristics for surface-acoustic-wave (SAW) front-end modules (FEMs) have been investigated. A new FEM configuration is described that consists of not only transmitter (Tx) switching p-i-n diodes and a diplexer with low-pass/high-pass filters, but also SAW filters and baluns. A direct parallel connection between a SAW filter and a p-i-n diode makes it possible to drastically reduce the number of circuit elements. A module developed for an extended global system for mobile communications (EGSM)/digital cellular system (DCS) dual-band cellular-phone transceiver achieved insertion losses in the receiver (Rx) portions as small as 3.0 and 3.3 dB for EGSM and DCS, respectively. The Rx portions had attenuation characteristics as high as 30-40 dB at harmonic frequencies up to several gigahertz and complete differential output signals with amplitude and phase imbalances less than /spl plusmn/0.5 dB and /spl plusmn/4/spl deg/, respectively. These characteristics are particularly required for DC demodulation. Small insertion losses in the Tx portions, 1.0 and 1.2 dB for EGSM and DCS, respectively, were also obtained.

SAW antenna duplexer module using SAW-resonator-coupled filter for PCN system

Surface Acoustic Wave (SAW) filters has been widely applied to radio personal communication to reduce size and volume of the radio terminals. In this paper, we discuss the application of SAW filters used in 1.8-GHz band antenna duplexer module for Personal Communications Network (PCN) systems. The module consisting of a receiver top filter (R1), a transmitter final stage filter (T1), lumped matching-circuit elements and lumped phase-shift circuits has been developed. The duplexer module has an insertion loss of less than 1.6 dB (1710-1785 MHz) in the Tx-to-antenna path and of less than 3.3 dB (1805-1880 MHz) in the antenna-to-Rx path, respectively. It also has a size of 14/spl times/8/spl times/1.8 mm and a weight of 0.4 g, which achieved about one-fifth reduction compared with the conventional dielectric-resonator filter duplexers.

Recent and future RF SAW technology for mobile communications

Surface acoustic wave (SAW) technology has been widely applied to VHF/UHF radio communications to reduce the volume of transceivers. In this paper, not only recent new SAW devices but also future SAW technology to achieve much higher-performance devices are investigated. First, the latest status of 0.8-1.5-GHz SAW antenna duplexers for cellular radios and a miniature SAW-VCO are presented. Second, new SAWs with extremely high velocities and fine submicron process techniques are examined. Finally, a future SAW-based chip-type receiver is discussed.

Investigation of merged Rx-differential output for multi-band saw front-end module

A quad-band SAW FEM used together with conventional triple-band RFICs was developed. To reduce number of Rx output ports of the FEM, we examined several types of merging methods for GSM850 and EGSM, and showed the feature comparisons among them. RFICs with direct-conversion demodulation circuits require not only differential Rx-output ports from the FEM but also very accurate balanced characteristics especially when demodulating 3/spl pi//8-rotated-8PSK signals used in the future EDGE system. We also proposed new wideband and accurate balun circuits for merged Rx-differential output ports to achieve required characteristics. Investigated and experimental results for the new FEM are presented.

90-GHz radio-on-radio-over-fiber system for linearly located distributed antenna systems

To realize a high-speed and high-capacity transmission link for fast mobile vehicles such as a bullet train, we propose a wavelength-division-multiplexing radio-on-radio-over-fiber (WDM-RoRoF) system with a linearly located distributed antenna system (DAS) on the 90-GHz band. All the conventional microwave (MW) radio signals such as mobile telecommunication and broadcast signals are encapsulated in a single millimeter-wave (MMW) carrier radio. Centralized control at a central office using the information of the position of a car can optimize and distribute the suitable RoRoF signal to each remote cell over optical fibers. An optical two-tone generator with an optical modulator can easily generate a 90-GHz RoRoF signal, and then, a high-speed photomixer directly converts from an RoRoF signal to an MMW RoR signal, which is composed of an MW signal with a 90-GHz carrier component, for irradiation over air. Heterodyne frequency down-conversion performs the direct frequency conversion from the MMW signal to an MW signal available to consumers.

Miniature SAW antenna duplexer module for 1.9 GHz PCN systems using SAW-resonator-coupled filters

Surface Acoustic Wave (SAW) filters has been widely applied to radio personal communication to reduce size and volume of the radio terminals. In this paper, we discuss the application of SAW filters used in a 1.8 GHz band antenna duplexer module for Personal Communications Network (PCN) systems. The module consisting of a receiver top filter, a transmitter final stage filter, lumped matching-circuit elements and lumped phase-shift circuits has been developed. The duplexer module has an insertion loss of less than 1.6 dB (1710-1785 MHz) in the Tx-to-antenna path and of less than 3.3 dB (1805-1880 MHz) in the antenna-to-Rx path, respectively. It also has the size of 14/spl times/8/spl times/1.8 mm/sup 3/ and the weight of 0.4 g, which achieved about one-fifth reduction compared with the conventional dielectric-resonator filter duplexers.

New high-performance and low-loss SAW filters used in ultra-wideband cellular radio systems

Several new technologies are reported for the design of high-performance and low-loss surface acoustic wave (SAW) filters used in ultra-wideband cellular radios. Among them, new configurations for wideband bandpass filters applicable as receiver filters have been developed. These configurations allow 3- or 4-dB insertion loss and sharp-cutoff frequency responses. New structures for wideband band-rejection filters applicable as transmitter final stage filters have also been developed. Their use results in loss as low as 1.4 dB as well as high-power characteristics. A SAW front-end module constructed with SAW filters, with a low-noise amplifier, and with a single balanced mixer is described.<<ETX>>

Investigation of SAW W-CDMA antenna duplexer and GSM-based FEM including duplexer

GSM/W-CDMA dual-mode phones will be required in Europe and elsewhere. Therefore, we must not only develop a SAW antenna duplexer for W-CDMA but also combine the duplexer with a GSM-based SAW FEM (front-end module). First, we show characteristics of a W-CDMA duplexer developed using conventional hybrid-ceramics multi-layered technologies. Next, we investigate configurations of the GSM-based FEM which includes the W-CDMA duplexer. We also examine the non-linear characteristics of the SAW duplexer, because very high off-band blocking characteristics are required by 3GPP specifications. Not only performance improvement of the SAW filters but also miniaturization of the duplexer are presented to achieve the future multi-band/multi-mode FEMs.