We proposed a new thchnique using saw wave modulation light to measure the thermal diffusivity of a transparent adhesive by photoacoustic microscope. In this technique, the time required for the measurement of it can be reduced by one-fifth compared with that of a conventional method.

Interdigital transducers (IDTs) with leaky-SAWs propagating on 36 YX-LiTaO3, and 41 and 64 YX-LiNbO3 were theoretically analyzed, providing a new equivalent circuit. This equivalent circuit included attenuation constant due to leakage as well as conductance caused by bulkwave radiation. All circuit parameters were derived by solving integral equations. Fundamental experiments showed fairly good agreement between theoretical and experimental results, which gave very accurate design tools for leaky-SAW devices.

Wide bandwidth of 30MHz was achieved by 3-IDT SAW resonator filters using 36Y-X LiTaO3 substrates at 800MHz. The filter, which has fractional bandwidth of 3.6%, can be applied for several mobile communication systems. Low insertion loss of 1.7 dB was obtained by taking parallel arranged configuration, which proved to be 0.4 dB better than simple cascade-connected configuration.

An asynchronous spread spectrum (SS) modem for 2.4-GHz wireless LAN has been implemented using an efficient ZnO-SiO2-Si surface acoustic wave (SAW) convolver. The design of the highly efficient SAW convolver was developed at Tohoku University and commercially manufactured by Clarion Co., Japan. The modem can operate under full-duplex transmission in the same frequency range of the 2.4-GHz SS band. The SS modem is based on a direct-sequence/code-shift-keying (DS/CSK) method for the modulation. Pseudo-noise (PN) codes are chosen from a preferred pair of 127-chip m-sequences and the code rate is 14MHz. The asynchronous demodulation is simply realized utilizing the coherent correlation characteristics of the SAW convolver. Under full-duplex transmission, the self-jamming caused by a transmitted signal in the modem itself is effectively reduced by an RF isolator and the SS processing gain. The implemented modem has been tested using a coaxial cable with attenuator. A bit error rate of 10-6 under full-duplex transmission is observed at 78.3dB of a desired to undesired signal ratio. The effective range is estimated on the basis of two-path propagation model. From self-jamming rejection of 78.3dB, the effective range under real-time full-duplex is estimated to be about 200m.

The spread spectrum system (abbreviated as SS system) is known to be an excellent communication system which resists jamming. Recently, its application to a simplified wireless communication system has been considered to be suited for consumer communication. In Japan, SS wireless LAN system has got the approval on 2.4GHz ISM band already. A compact SS transceiver for the SS wireless LAN is realized, whose data ratio is 230kbps. The SS transceiver is based on a direct sequence for the modulation, and the demodulation is carried out by a specially developed SAW device. In the first part of this paper, the technical conditions of the SS wireless LAN are mentioned. Then the SAW device and the principle of the demodulation are discussed. Finally, the configuration of the SS transceiver and the protocol of the SS wireless LAN are presented.

An asynchronous spread spectrum (SS) wireless modem has been implemented using an efficient ZnO-SiO2-Si surface acoustic wave (SAW) convolver. The modem is based on a direct-sequence/frequency-shift-keying (DS/FSK) method for the modulation. The demodulation is carried out asynchronously utilizing the coherent correlation characteristics of the SAW convolver. In order to improve the narrowband interference rejection capability, we propose a new technique based on the reference signal control. A notched-reference-signal circuit and a self-convolution canceler are implemented in the SS modem for the reference signal control. It was found that the antijam capability for narrowband interference is at least -24dB of desired-to-undesired power ratio (D/U); the improvement of the antijam capability is 16dB up as compared with our previous SS modem.

We applied a filip-chip-bonding technique to GHz-band SAW filters. The SAW filters mounted by the stud-bump-bonding (SBB) technique which is a kind of flip-chip-bonding technique showed almost the same frequency characteristics as those mounted by the conventional wire-bonding technique at 1.5 GHz. The SAW filter configuration, fabrication process using the SBB, and its electrical characteristics are described and discussed. The SBB technique has a lot of potential to reduce the size and weight even above GHz frequencies.

In the delayed regulation medel, X(t+1)=AX(t){1-X(t-1)}, new bifurcation regions which have been overlooked in the past studies were found out for -1.01A0 and 2.27563A2.2838. In the former fixed point lying at 0 is destabilized at A=-1, and new type bifurcation is induced for A-1, where oscillation with saw-tooth waveform is observed. In the latter the stability once lost for A2.271 is restored for A2.27563, and the stable region continues up to A=2.2838.