Toshio Nishizawa

A miniaturized 3 /spl times/ 3-mm SAW antenna duplexer for the US-PCS band with temperature-compensated LiTaO/sub 3//sapphire substrate

This paper describes a temperature-stable and miniaturized SAW antenna duplexer for the 1.9 GHz US-PCS band that uses a temperature-compensated 42/spl deg/ Y-X:LiTaO/sub 3//sapphire bonded substrate. In this duplexer, the temperature coefficient of frequency is reduced to half or two-thirds of that of a conventional LiTaO/sub 3/ substrate. Also, it is shown that our new duplexer has a smaller insertion loss and offers sufficient power durability. These improvements are mainly due to the characteristics of sapphire, such as its larger thermal conductivity and smaller dielectric constant. Furthermore, the performance of our SAW duplexer is compared with that of two kinds of BAW duplexers, which are competitive technologies. As a result, it is shown that our newly developed SAW duplexer offers equal or better performance in a smaller package. This implies that our SAW duplexer is the best and the smallest PCS duplexer.

Realization of small and low profile Duplexer using a CSSD packaging technology

This paper presents the realization of Duplexer with small size, high reliability and excellent performance. Good heat radiation, hermetic performance and small frequency drift against temperature shift are essential to achieve small size and highly reliable Duplexers. In this paper, we will report on the advantage of the Chip Size SAW Devices (CSSD) structure for miniaturization and high reliability. In addition, we will discuss the possibility of further miniaturization.

A study of optimum material for SAW bonded wafer

We have proposed the use of a lithium tantalate (LiTaO3)/sapphire bonded substrate for compensation of temperature coefficient of frequency (TCF) in surface acoustic wave (SAW) duplexers. However, in the specific use case of a Band 8 SAW duplexer on Universal Mobile Telecommunications System (UMTS), this bonded substrate has exhibited spurious response in the pass-band. In this paper, we analyzed the spurious response by Finite Element Method (FEM) simulation and found that the spurious could be suppressed effectively by optimizing the cut angle of the LiTaO3 substrate. Moreover, we fabricated a Band 8 SAW duplexer with the optimized cut angle and obtained experimentally good insertion loss without degradation by the spurious response. The measured insertion losses of the duplexer were 2 dB and 2.5 dB at Tx and Rx bands, respectively.

Band3 Duplexer using ZERO TCF Love wave device

In this paper, a novel Love wave device which has Al₂O₃ under layer structure is proposed. Al₂O₃ under layer structure enables us to adjust the electromechanical coupling factor k² of Love wave. As a result, a suitable k² for Band3 Duplexer of about 10% was realized using 0°YX-LiNbO₃ substrate, Cu electrodes and thick SiO₂ film. In addition, the temperature coefficient of frequency (TCF) was improved especially at resonant frequency of 1-port resonator with Al₂O₃ under layer structure. Using this novel Love wave device with Al₂O₃ under layer structure a Band3 Duplexer was realized with excellent temperature characteristics. The TCF of the higher frequency side of pass band in Tx filter was -3.6 ppm/°C, that of the lower frequency side of pass band in Rx filter was -7.3 ppm/°C.