A television IF acoustic surface wave filter on bismuth silicon oxide
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A brief account is given of a television IF acoustic surface wave filter made on bismuth silicon oxide. The potential advantages of this substrate material are pointed out, the filter design techniques used are explained, and the device construction is described. Measured responses of filters for two television systems are given.Keywords:
Bismuth
Electronic filter
Electronic filter
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Abstract Currently, surface acoustic wave (SAW) filters are widely used in RF stages as well as IF stages of modern telecommunication systems. With successful research and development of SAW devices since the early 1960s, the growth of mobile phone markets has accelerated, with surprising advances in SAW device technologies since the early 1990s. This article discusses how the filtering function of SAW devices is realized using various SAW propagation phenomena, and reviews the performance of current commercial SAW filters. First, SAW transversal filters are discussed. Starting from a brief discussion of their fundamentals, we describe achievable performance, impact of the substrate selection and the most recent advances of this type of filter. Next, filters based on SAW resonators are discussed. After giving basic ideas of SAW resonators, it is shown how SAW resonator filters are composed and designed using SAW resonators.
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In this work, we study the design and implementation of a parallel-IDT surface acoustic wave (SAW) filter for telecommunication applications. The equivalent circuit and 3D model are established to understand acoustoelectric interactions. The 128 0 Y-Z rotated LiNbO 3 which has high electromechanical coupling constant is used as the piezoelectric material to generate the acoustic waves. The single-IDT and parallel IDT SAW filters were implemented in 122 MHz. The parallel-IDT SAW filter has an insertion loss to -5.515 dB, larger than the single-IDT SAW filter.
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Abstract It was found that the surface acoustic wave (SAW) amplitudes in SAW filters made of ZnO films vary from filter to filter even when the center frequencies are the same and the deviation of amplitudes must be reduced. It was found also that the frequency and amplitude characteristics could be improved by mirror polishing of the ZnO film surface. In an SAW filter with a ZnO/interdigital transducer (IDT)/glass substrate structure, periodic convex areas due to the thickness of the finger electrode of IDT and fine roughness were present on the device surface. As a result of investigating the influence of the surface structure on the amplitude deviation, it was found that the convex areas did not influence the electromechanical coupling coefficient; but they reduced the acoustic velocity of SAW. In addition, it was clarified that the convex areas due to the finger electrode and fine roughness on the ZnO surface caused deviations in the acoustic velocity of SAW and reflections of SAW, causing a deviation in the amplitude characteristics.
Electronic filter
Electromechanical coupling coefficient
Center frequency
Interdigital transducer
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Fabricated the interdigitated electrodes and the circuit elements via the MOS IC processing on AlN piezoelectric thin film, the active surface acoustic wave (SAW) filter was produced and studied, which centre frequency was 320 MHz. Results show it’s insertion loss is smaller than 10 dB, and above 45 dB the decay is in out of the band.
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The power durability of the ZnO/diamond surface acoustic wave (SAW) filter was investigated and compared with the LiTaO/sub 3/ SAW filter. The ZnO/diamond SAW filter maintained linearity of the input-output relation up to the input power of 36 dBm at 2.90 GHz, whereas the LiTaO/sub 3/ SAW filter, which operated at 822 MHz, was nonlinear above the input power of 23 dBm and degraded significantly at 27.7 dBm. The input power dependence of the time to failure was also investigated for both SAW filters. It was found that the ZnO/diamond SAW filter was durable for 8 dB higher input power than that of the LiTaO/sub 3/ SAW filter even at 3.5 times higher frequency. These results indicate the extremely high power durability of the ZnO/diamond SAW filter.
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Abstract A multi-channel surface acoustic wave filter with narrow bandwidth is realized by using an output interdigital transducer composed of multiple electrode groups. The filter characteristics are related to the number of the electrode group and the apodization of the overlap length of the interdigital electrodes. A Z-Y propagating LiNbO3 SAW multi-channel filter around 495 MHz is demonstrated which is in good accordance with a simulated result.
Narrowband
Apodization
Electronic filter
Interdigital transducer
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A 250 MHz Li 2 B 4 O 7 surface acoustic wave (SAW) filter was successfully designed using a newly developed program for double-mode SAW (DMS) filters. The elastic, piezoelectric and dielectric constants of Li 2 B 4 O 7 grown by the resistance-furnace heating Czochralski method were measured precisely to determine the accurete phase velocity and the electromechanical coupling coefficient of SAW. The mode coupling coefficients were determined as a function of the electrode thickness as well. These coefficients were introduced in the simulation program, and the SAW filter was designed. The DMS filter fabricated in this study had almost the same characteristics as those expected from the design.
Electronic filter
Electromechanical coupling coefficient
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This paper reports the specifications of RF surface acoustic wave (SAW)filter forGSM moble communication systems, and discusses the disigning principle of SAW filter with ladder-type structure. SAW filter experimental results based on this new configuration are also given.
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GSM
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The acoustic-surface-wave filter for the use of video intermediate frequency at 58 MHz was fabricated using an rf-sputtered ZnO film overlying the interdigital electrodes and the wave path on a glass substrate, and its fundamental properties for practical application were studied. The average and easily reproducible insertion loss characteristics are as follows: 16 dB at the minimum, 5(+16) dB at chromatic and picture signal carrier frequencies, 15(+16) dB at sound signal carrier frequency, more than 55(+16) dB at trap frequencies for adjacent channels, and 35(+16) dB at the maximum side lobe. The triple transit echo suppression is more than 30 dB. The temperature coefficient of the frequency characteristic is 30 ppm/°C. 400 days of aging has shown no significant change in the filter.
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Center frequency
SIGNAL (programming language)
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