Masafumi Iwaki

A triple-beat-free PCS SAW duplexer

In general, surface acoustic wave (SAW) duplexers have the lower 3rd order linearity compared to bulk acoustic wave (BAW) duplexers. Actually, the specification for the inband 3rd order nonlinear distortion, triple beat, required for 1.9 GHz Personal Communications Service (PCS) band in CDMA2000 can be satisfied only by BAW duplexers. The objective of this work is to propose the design methodology for extremely high-linear SAW duplexers and to develop the triplebeat-free PCS SAW duplexers. The nonlinear elastic model, which we have proposed last year for predicting the triple beat, is applied to design the highly linear PCS SAW duplexers. The developed SAW duplexer achieves the extremely high linearity of approximately -90 dBc in the triple beat test, which is 20 dB better than the conventional duplexer keeping the equivalent filter characteristics and same packaging size. To the best of our knowledge, this is the first PCS SAW duplexer which satisfies the triple beat specification required in CDMA2000.

A design technique to enhance isolation of duplexer in single-ended and differential modes

This paper describes a design technique to enhance isolation of acoustic duplexers in the single-ended and the differential modes for a so-called “inter-stage SAW-less” radio frequency (RF) front-end of cellular phones. The leakage signal from the Tx to the Rx ports existing inside the duplexer, which degrades the isolation characteristics, is cancelled out by utilizing a proposed circuit topology and by performing careful design of the whole duplexer structure. The principle directly enhances the single-ended isolation, but it also contributes to improve the differential mode isolation. The prototypes for the single-ended and differential duplexers exhibit isolation higher than 70 dB and 65 dB, respectively, in the Tx band for UMTS Band 1 application.

A converged Rx SAW duplexer module with embedded substrate for multi-band RF front-end

A novel surface acoustic wave (SAW) duplexer module called a converged Rx duplexer module is proposed. The Rx ports of two duplexers for different frequency bands are combined using passive matching components in the module, which reduces the number of Rx pins by half. A feasibility study including the issue of isolation between the bands is discussed and a prototype composed of four duplexers (two converged-Rx ports) is fabricated using the stacked-duplexer layout. The fabricated module features reduced Rx Pins, an area reduced by about 40%, and a sufficient isolation of 55 dB between the converged frequency bands.

Design Consideration on Converged Rx SAW Duplexer Module for Multiband RF Front End

This paper presents the design consideration on a converged Rx surface acoustic wave (SAW) duplexer module for integrated RF front end. Two different matching-circuit and notch-circuit configurations were examined with importance placed on electrical characteristics (insertion loss and isolation of duplexer) and simplification of module, respectively. From circuit simulations and examinations, we verified that a simplified design was best in terms of both characteristics and space in the case of a finite inductor’s Q. We also fabricate a quad-band converged Rx module (Band I + II, V + VIII) using an SAW duplexer and verified that its electrical characteristics agree well with our simulation results.

Co-design of SAW duplexer and LNA in RF transceiver IC for reducing total noise figure in RF front-end of cellular systems

The co-design of a SAW duplexer and a low-noise amplifier (LNA) for reducing the total noise figure of the Rx chain in the RF front-end of current multi-band cellular handsets is presented in this paper. The co-design procedure is proposed and one case study for the UMTS Band2 is demonstrated. The key point of the co-design is designing a duplexer and an LNA at the optimum impedance, instead of the standard 50 Ω impedance interface, while taking the matching circuit loss into account. The possibility of reducing the total noise figure is shown in the case study simulation.