Naoki Matsuura

Rigorous treatment of leaky SAWs and new equivalent circuit representation for interdigital transducers

Leaky surface acoustic wave (SAW) interdigital transducers (LDTs) formed on 36/spl deg/ YX-LiTaO/sub 3/ and 41/spl deg/ and 64/spl deg/ YX-LiNbO/sub 3/ are theoretically analyzed, and a new equivalent circuit representation is proposed. The influence of the attenuation constant due to leakage as well as conductance caused by bulk wave radiation are taken into account. A new treatment based on an integral equation approach provides all circuit parameters. Fundamental experiments show fairly good agreement between theoretical and experimental results, confirming that this treatment provides very accurate tools for designing leaky-SAW devices.

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.

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.

New rigorous treatment of leaky SAWs and its application to high-performance filters used in mobile pocket phones

Leaky-SAW IDTs formed on 36° YX-LiTaO3, and 41° and 64° YX-LiNbO3 are theoretically analyzed, providing a new equivalent circuit. Fundamental experiments show fairly good agreement between theoretical and experimental results. New high-performance SAW filters using this equivalent circuit satisfy all the specifications for cellular pocket phones, incorporating the characteristics of a SAW antenna duplexer also proposed recently

New SAW antenna duplexers for single- and dual-band handy phones used in 800-MHz and 1.8-GHz cellular-radio systems

New SAW antenna duplexers used in EGSM/PCN dual-band handy phones have been developed. The differences between the single- and dual-band RF-circuit configurations are taken into considerations. Direct-parallel connection between the receiver SAW filter and the transmitter diode switch makes it possible to reduce the number of circuit elements and to achieve a small module size. The required frequency characteristics were also achieved.

SAW FEMs for GSM-based multi-band cellular phones with direct-conversion demodulation

Assuming DC demodulation, the required characteristics and new configurations for SAW front-end modules (FEMs) were investigated. Parallel connections between SAW filters and the pin diode reduce the number of circuit elements drastically. The developed module for EGSM/DCS dual-band achieved Tx insertion losses as small as 1.0 dB and 1.2 dB, and Rx insertion losses of 3.0 dB and 3.3 dB for EGSM and DCS, respectively. 30-40 dB attenuation particularly required for DC demodulation up to several GHz was achieved. Multi-band FEMs such as triple-band FEMs and so on were also investigated.

Multi-band SAW front-end module considering impedance matching between FEM and direct-conversion RF-IC

Assuming a direct-conversion demodulation method, a triple-band SAW front-end module was investigated. Based on the blocking requirements given by GSM regulation, we proposed a new FEM structure, which included three Rx-SAW filters. Low-loss and sharp-cutoff frequency characteristics was designed, especially for PR SAW filter. Differential Rx-output ports with small amplitude- and phase-imbalances were achieved by developing lumped-element baluns within the FEM. A new evaluation procedure were discussed taking into consideration not only differential-mode impedance matching at the-pass band but also impedance miss-matching at the out-of band between the FEM and a RF-IC. Experimental results are also presented.

An integrated SAW antenna duplexer for EGSM/DCS1800/PCS triple-band cellular systems

New surface acoustic wave (SAW) antenna duplexer used in EGSM/DCS1800/PCS triple-band cellular phones has been developed. Unique configurations to achieve miniaturization are demonstrated. Direct-parallel connection between the EGSM receiver SAW filter and the transmitter diode switch, and direct-parallel connection between the DCS and PCS receiver SAW filters make it possible to reduce the number of circuit elements and to achieve a small module size. We also realize balance-mode output capability at receiver port with unbalance-balance transformation circuit on the module. The measurement procedure, balance-mode frequency characteristics for receiver path and unbalance-mode frequency characteristics for transmitter path are also presented.

The new approach to realize small imbalances in differential Rx-outputs for SAW front end module

A balun circuit which has unique structure has been studied for accurate balanced characteristics and minimization of front end module (FEM) device size having differential Rx outputs. The procedure to design the balun has been derived and shown. The balun has been implemented in LTCC packages of 5.6/spl times/5.5/spl times/1.25 mm Typ. (triple band) and 7.2/spl times/5.5/spl times/1.25 mmTyp. (quad band) FEM and the amplitude and the phase imbalance of dB and degree has been derived, respectively.

RF-circuit configurations and new SAW duplexers for single- and dual-band cellular radios

Single-band and dual-band SAW antenna duplexers have been developed. The former constructed with R1 and T1 filters can be used in 800-MHz EGSM or 1.8-GHz PCN single-band system. The latter constructed with R1s anti-diode switches can be used in the EGSM/PCN dual-band system. The required frequency characteristics as well as the module miniaturization have been achieved.