Atsushi Sumioka

800 Mhz Low Loss Saw Filter Using New Phase Weighting

A new high performance SAW filter for a mobile telephone is presented here. New technologies - - low loss weighting in an IDT, and a new resonant filter configuration - - are described. Experimental results with 3.5~4.0 dB insertion loss at 830 MHz are presented.

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.

Grating-mode-type wide-band SAW resonators for VCOs

Grating-mode-type surface acoustic waves (SAWs) that are particularly suitable for wide-band SAW resonators were found. Their bandwidths are larger than 13%. Their spurious responses originating from Rayleigh waves are almost negligible when the Al-grating thickness is optimized for the cut angle of substrate. For example, the ratio of the Al-grating thickness to the SAW wavelength must be required within 0.125/spl plusmn/0.007 for 15/spl deg/-rotated Y-cut X-propagating lithium niobate. These SAW resonators were applied to UHF-band voltage-controlled oscillators. They achieved a high control-voltage sensitivity of 13.5 MHz/V (3.2%/V) and a high phase-noise performance of <-115 dBc/Hz offset 25 kHz from the carrier.

Miniaturized SAW devices for radio communication transceivers

Various applications of surface-acoustic-wave (SAW) technologies are investigated in which the use of SAW devices would result in reduced volume and weight for VHF/UHF radio communication transceivers. Attention is given to improved insertion loss and power requirements reported for SAW filters. In particular, by analyzing the loss mechanisms of a previously developed high-performance SAW filter for mobile telephones, a new extremely low-loss SAW filter (loss of as low as 1.2-2.0 dB at 600 MHz) has been developed. The results of fundamental experiments for a SAW antenna duplexer using this new SAW filter as the transmitter filter with a semicoaxial filter as the receiver filter at 800 MHz 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

A miniature high-Q grating-mode-type SAW resonator and a wide-band 1-GHz SAW-VCO for mobile communications

We have designed and tested a compact high-Q SAW resonator for wide-band VCOs that oscillate in the 1-GHz band. This was achieved by optimizing the SAW propagation in the Al-grating structure, especially by changing the shape of the structure. The resonator chip size was 0.8 /spl times/ 0.8 mm and the Q value of the SAW resonator exceeded 200. Its spurious response originating from Rayleigh waves was almost negligible when the Al-grating thickness was optimized for the cut angle of the substrate. A 1-GHz VCO that used the SAW resonator showed a high control-voltage sensitivity of 25.0 MHz/V (2.3%/V) and a high phase-noise performance of <-106.0 dBc/Hz when offset 25 kHz from the carrier.

A wideband SAW resonator and its application to a VCO for mobile radio transceivers

A new wideband SAW resonator has been developed for SAW-VCOs used in mobile radio communication transceivers. The resonator is based on a repeated structure of pairs of electrically connected IDTs, which provides a high Q and a wide frequency bandwidth. An experimental SAW-VCO module measuring 8/spl times/8 mm/sup 2/ offers a frequency-variation bandwidth of about 20 MHz, a C/N of 75 dB, and an output power of 3-4 dBm at 900 MHz, satisfying the specifications for Japanese MCA and business-use radio transceivers. >

New miniature SAW antenna duplexer used in GHz-band digital mobile cellular radios

New filters used in an antenna duplexer which is applied to GHz-band digital cellular radios were developed. Taking 1.5 GHz PDC, we have achieved low insertion losses of 0.8 and 1.6 dB for T1 and R1 filters, respectively. The developed duplexer is 1.4/spl times/0.6/spl times/0.2 cm/sup 3/, several-time smaller than a conventional dielectric-filter duplexer. It also satisfied all required specifications and provided sufficient power-handling capabilities.

Computer-Aided Design of Parametric Amplifiers

A computer-aided design approach is developed for the analysis and design of single-tuned parametric amplifiers. An 18 GHz single-tuned amplifier is designed and experimented for an illustration.

Spurious suppression technique for edge-trap-type SAW resonators and their application to 1-GHz wide-band SAW-VCOs for mobile communications

1-GHz wide-band VCOs using SAW resonators have been successfully developed. A control-voltage sensitivity of over 5%/V has been achieved by using new edge-trap-type SAW-resonators. Optimizing the reflectors of SAW resonators is very effective for suppressing the spurious resonance of the Rayleigh wave in the oscillation band. Two types of VCOs are compared. One uses a Si bipolar junction transistor as a feedback amplifier and the other uses a GaAs MESFET. Both VCOs achieved a control-voltage sensitivity of over 5%/V and a phase noise of less than -107 dBc/Hz at a 25 kHz offset frequency from the carrier frequency. The GaAs MESFET VCO showed better phase noise performance than the Si transistor VCO at a 30-kHz or greater offset frequency. By changing the amplifier elements, it is possible to achieve the requirements for both local VCOs and transmission VCOs for wireless communication terminals.