Osamu Hikino

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.

Saw duplexer design for WCDMA system

Some relations between sensitivity performances and duplexer performances (losses, isolations between Tx and Rx terminals) are obtained. We simulate system noise figure levels from duplexer performances and low noise amplifier parameters by using a nonlinear NF model at the viewpoint of a system design.

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.

Code optimization for direct sequence spread spectrum and SAW-matched filter implementation

This paper introduces a new optimization algorithm for the minimization of the time sidelobes of the correlation function of a pseudonoise (PN) sequence by applying dynamic weighting to the sequence. The resulting optimized time sidelobe level sequences are to be used in direct sequence spread spectrum (DS-SS) systems with digital modulations such as BPSK, DPSK, QPSK, etc. The new optimization algorithm starts with a PN sequence. It first optimizes the correlation time sidelobes for the case where the consecutive data bits are identical (11 or 00). It then optimizes the correlation time sidelobes for the case of alternating consecutive data bits (10 or 01). The suppressed time sidelobe level sequences are derived by iterating these algorithms alternately starting from the initial PN sequence. The derived suppressed time sidelobe sequences show excellent correlation characteristics when compared to conventional PN sequences such as maximal length sequences, Gold sequences and Barker codes. Surface acoustic wave (SAW) devices were used to implement the optimized time sidelobe level sequences in a matched filter pair. The design of the apodized SAW-matched filters and their predicted second order effects are presented. The experimental results for the SAW-matched filters for the optimized time sidelobe level sequences derived from a Barker code were found to be in good agreement with the theoretical predictions from this new algorithm.

New low-distortion band-switching techniques for SAW antenna duplexers used in ultra-wide-band cellular phone

A new low-distortion band-switching technique for a surface-acoustic-wave (SAW) antenna duplexer used in ultra-wide-band cellular-phone systems has been developed. Both a transmitter (Tx) portion and a receiver (Rx) portion of the duplexer consist of not only wide-band SAW bandpass filters (BPFs), but also band-rejection SAW filters (BRFs) whose rejection bands can be shifted by switching circuits. The spurious-response sensitivity caused by the third-order nonlinear distortion of the switching circuits was dramatically improved by the new above configurations, i.e., the combination of BPFs and BRFs. The developed duplexer for the 900-MHz Japanese cdmaOne system has a size of 10 /spl times/ 8 /spl times/ 2 mm. It also has frequency characteristics of equivalent transmitted/received frequency bands as wide as 38 MHz and the guard band as narrow as 17 MHz. The insertion losses in both the low and high bands of the Tx portion are less than 2 dB, and those of the Rx portion are less than 3.3 dB. The other required specifications, e.g., attenuation at harmonic frequencies, attenuation at the image frequency, etc. are also satisfied.

Measurements of SAW effective velocity angular-variation under metal strip gratings and their application to ASPW analysis

Measurements of SAW effective velocity angular-variation under metal strip gratings, using a comb-filter method are described. A distinctive characteristic was newly observed at higher frequency; the minimum observed at propagation angle 0° of the above angular-variation of LiNbO3-128° rotYX single crystal. The minimum is originated by SAW dispersion considered to be mainly due to stored energy effect. Moreover, as an example to utilize the above measurement results for an analysis of SAW second order effects, the frequency response of a 480 MHz SAW filter was calculated including SAW diffraction effect using angular spectrum of plane wave (ASPW) method. The simulation result was in good agreement with the experimental one

6J-2 Study of High Isolation and Miniature SAW Duplexer

Finite element methods for integrated circuits of LTCC and equivalent circuit models for SAW chips are applied to SAW duplexer analysis. We improve this composite method with considering feed through. A good agreement with this improved composite simulation and experiment is obtained. We have found that magnetic interaction between a phase-shifter and a matching element for Tx circuit becomes a worse of Tx-Rx isolation. We have also found an improved shape of element to suppress the magnetic interaction between these circuits by try and error method. An isolation value of 48 dB in Rx band is observed at an improved duplexer. Consequently it is verified that a improved composite model is effective for analyzing Tx-Rx isolation of a miniature SAW duplexer. And high isolation characteristic for SAW duplexer is also obtained by using improved structure

New band-switching SAW antenna duplexer used in 800-MHz Japanese cdmaOne systems

Japanese 800-MHz cdmaOne systems have not only reverse frequency allocations for the transmitted and received frequency bands, but also the very wide frequency bandwidth of 38 MHz for each band and the narrow frequency spacing of 17 MHz between two bands. We have developed a new band-switching SAW antenna duplexer for these systems. Each of the transmitter-line and receiver-line filter consists of a wide-band SAW bandpass filter and an SAW band-rejection filter of which rejection band can be shifted by switching circuits corresponding to low (L) and high (H) bands. The duplexer module size is as small as 10/spl times/8/spl times/2 mm3 and the required specifications for cdmaOne were satisfied.

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.

Automatic design technique based on nonlinear optimization for SAW devices

An improved automatic design technique based on nonlinear optimization method will be reported. The number of interdigital transducer (IDT) electrodes are treated as continuous function vector with the other design parameters, the IDT position, the IDT aperture and the external element constants etc. The procedure is applied to the interstage filter for digital mobile terminals which consists of two different substrates. We also apply the technique to high performance SAW antenna duplexers for digital mobile terminals and miniature SAW IF filters for automatic electrical toll collection systems. The performance of these devices is found to be in good agreement with the design predictions.