A design method of fir filters suitable for SAW filters

As an example of evolutionary computation technique in the real-world application, we presented an optimum design method for balanced SAW filters. First of all, in order to evaluate the performances of balanced SAW filters based on the computer simulation, we derived the network model of balanced SAW filters from the equivalent circuit model of them according to the balanced network theory. Then we formulated the structural design of balanced SAW filters as an optimization problem for improving their performances in both the balance characteristics and the filter characteristics. For solving the optimization problem, or the optimum design problem of balanced SAW filters, we employed DE. DE is a recent EA for solving real-parameter optimization problems. However, in the optimum design problem of balanced SAW filters, some design parameters take discrete values while others take continuous values. Therefore, in order to apply DE to the optimum design problem, we proposed a technique to insert the various design parameters of balanced SAW filters into the regularized continuous search space of DE. Finally, through the computational experiments conducted on a practical balanced SAW filter, we demonstrated the usefulness of the proposed optimum design method. Furthermore, we could obtain a new knowledge about the structural design of balanced SAW filters. The balanced SAW filter usually takes a symmetrical structure. However, in the extended optimum design problem of the balanced SAW filter, we supposed that the balanced SAW filter could take an unsymmetrical structure. Then we compared the best solution of the extended optimum design problem with the best solution of the original optimum design problem. As a result, we found that the unsymmetrical structure of the balanced SAW filter could improve the balance characteristics without losing the filter characteristics. If we increase the degree of the design freedom, or the number of design parameters, in the optimum design problem, the search space of DE is also expanded. As a result, the probability that DE finds the optimal solution decreases. On the other hand, the extended search space of DE may cover a new optimal solution that is better than the optimal solution in the original search space. In the optimum design of the balanced SAW filter, we could successfully increase the degree of the design freedom and utilize the power of DE. Future work will focus on the revision of the classic DE used in this time. Since several variants of DE have been proposed (Chakraborty, 2008), we would like to compare their performances in the optimum design problems of various balanced SAW filters.

This paper presents a robust optimum design approach to tackle the structural design of surface acoustic wave (SAW) filters. The frequency response characteristics of SAW filters are governed primarily by their geometrical structures: the configurations of inter-digital transducers (IDTs) and grating reflectors fabricated on piezoelectric substrates. For deciding an optimal structure of SAW filters based on the computer simulation, the equivalent circuit model of IDT, which includes several uncertain parameters, has to be utilized. In order to cope well with the designing imperfections caused by the inevitable dispersion of these uncertain parameters, the quality engineering technique, or the Taguchi method, is employed. First of all, according to the Taguchi method, the signal to noise ratio (SNR) of SAW filters is defined to evaluate their robustness. Then, for increasing the SNR of SAW filters as much as possible without losing their specified functions, the robust optimum design of SAW filters is formulated as a constrained optimization problem. Furthermore, a memetic algorithm combining an evolutionary algorithm based on the penalty function method with a local search is proposed. Finally, the memetic algorithm is effectively applied to the robust optimum design of a resonator type SAW filter. Computational experiments show that the proposed memetic algorithm not only can find a feasible solution of the constrained optimization problem, or a desirable structure of objective SAW filter, but also can drastically improve the robustness of the SAW filter.

Surface acoustic wave (SAW) filters are widely used as RF filters for GHz-band in mobile communication terminals. Recently high performance SAW filters are required as the frequency is higher and the frequency band is wider in mobile communication systems. Above all low insertion loss SAW filters are required, which make mobile communication terminals sensitive and low power consumption. In this paper, a new structure of a low loss high pass filter with SAW resonators, a design method, and fabricated results are reported. This filter is composed of one port SAW resonators as series elements and series resonant circuits as shunt elements. We call it an m-derived ladder high pass SAW filter. The m-derived ladder high pass SAW filter has good features of low insertion loss and high attenuation in wide frequency range although the pass band frequency is apart from the rejection band frequency. We fabricate the new structure of the filter. The resonant circuits as shunt elements consist of chip capacitors and chip inductors and the one port SAW resonators as series elements are fabricated on 128/spl deg/YX-LiNbO/sub 3/ substrates. Consequently, the insertion loss of the fabricated filter is less than 0.5 dB at the frequency of 940-958 MHz, and the rejection band attenuation is more than 33 dB at the frequency of 810-828 MHz.

Chip scale package (CSP) for surface acoustic wave (SAW) filter has been implemented on silicon with thick oxidized porous silicon (OPS) layer using the thick plated metal wall and flip-chip bonding technique and the RF performance of SAW filter was measured. The key approach of this article was that the SAW filter and semiconductor RFICs were packaged on same substrate (OPS) with same packaging method (epoxy molding) at the same time. In packaging the SAW filter, the surface should be maintained in hermetic void for the performance reliability, and this has been solved by metal wall and epoxy molding compound. The silicon with thick OPS layer had good RF performance. The transmission line loss was below 0.1 dB/mm in L-band. flip-chip bonded SAW filter on OPS layer showed the -2.6 dB passband loss and 0.95 dB maximum ripple in 865-895 MHz range and the stopband attenuation was below -50 dB. For the demonstration of CSP SAW filter, we have developed the dual mode (CDMA and AMPS) receiver module where the SAW filter was interconnected between low noise amplifier (LNA) and down mixer which was also assembled on OPS layer using multichip module technology.

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.

Surface Acoustic Wave (SAW) filters are a key device for mobile communication systems, and the high performance and low-loss of SAW filters has been increasing rapidly. The general design procedures for practical SAW filter are a trial-and-error approach by expert designers. The researches on the design of SAW filters using some different optimization algorithms (i.e. variable neighborhood search) have been the local search method so far. In these researches, the SAW filters are IDT type. Recently, the front-end with ladder type filter has proposed. This filter is low-loss type. The research of the ladder type SAW filter design using the optimization algorithm has not been performed. So, this paper proposed the design method of a ladder type SAW filter using simulated annealing.

Modern achievements and directions of improvement of surface acoustic wave (SAW) filters for mobile communication systems are presented. SAW technology is continues to dominate in a tasks of filtration in radio frequency (RF) part of telecommunication systems. Innovative technologies of filters production and packaging allow to improve their characteristics and can reduce the size. I.H.P. SAW filter have a high Q-factor and good temperature and frequency characteristics. The main requirements to modern SAW filters are minimal losses, temperature stability, low level of nonlinear signals, high power durability, small dimensions. CSSP (Chip Sized SAW Package) technology and DSSP (die-sized SAW packaging) technology allow to produce miniature components and can integrate them into modules. The current trend of increasing the number of frequency bands and the introduction of new standards makes the problem of creating a flexible RF module with high-quality tunable SAW filters extremely actual.

We designed surface acoustic wave (SAW) filters for a multiplex transmission system of multilevel inverter circuits, and applied them to a single-phase three-level inverter. To reduce the transmission delay time of the SAW filters, a four-channel SAW filter array was fabricated and its characteristics were measured. The delay time of the SAW filters was <350 ns, and the delay time difference was reduced to ≤184 ns, less than half that previously reported. The SAW filters withstood up to 990 V, which is sufficient for the inverters used in most domestic appliances. A single-phase three-level inverter with the fabricated SAW filters worked with a total delay time shorter than our target delay time of 2.5 µs. The delay time difference of the proposed system was 0.26 µs, which is sufficient for preventing the inverter circuit from short-circuiting. The SAW filters controlled a multilevel inverter system with simple signal wiring and high dielectric withstanding voltages.

It is well known that the surface acoustic wave (SAW) filter is not well adapted to high power use. To improve its power characteristic, the use of a number of identical SAW filters to compose a parallel connection SAW filter system which has the same transmission characteristics as a single one but is durable enough for high power use is proposed. To realize this end, a matching method using the conjugate image impedances is needed to design the matching circuits of the system. In experimenting, the authors used the 800-MHz-band SAW filter to compose a two-piece, a three-piece, and a four-piece SAW filter system which can endure, respectively, 4.0 W, 6.0 W, and 8.0 W input power for more than 30 min without damage. This result also gives the possibility of designing super-high-power SAW filters using the technique described above. >

Multilevel inverter circuits with a number of power switching devices (10-100) have been reported to generate favorable output sinusoidal waveforms and high output voltage in recent research on power electric circuits. Meanwhile, next-generation switching devices based on wide-gap semiconductors can be installed in high-temperature environments such as near a motor or in an engine room to reduce energy loss and electromagnetic interference. To address these issues, we proposed a multiplex transmission system with SAW (Surface Acoustic Wave) devices to satisfy the requirements of simple signal wiring and high heat resistance. In this paper, we show that the SAW filters on SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Al/LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> structure have good electrical characteristics for the proposed system.

To cope with ubiquitous wireless connectivity and the increased and faster data delivery in 5G communication, surface acoustic wave (SAW) filters are progressively requiring wider bandwidths. Conventional bulk 15°YX-LiNbO3 substrates with a large coupling coefficient (K2) are attractive for the low-cost mass production of wideband SAW filters, but these generally suffer from spurious responses, limiting their practical application. In this work, a novel and simple SAW configuration is proposed that uses thickness-modulated interdigital transducer (IDT) structures to overcome the limitations set by spurious responses. Different from the conventional design where the thicknesses of the IDT electrodes in the series and parallel resonators generally kept the same, the proposed configuration adopts IDT electrodes of different thicknesses in the series and shunt resonators to suppress or remove unwanted spurious Rayleigh modes from the filter passband. Two different ultra-wideband SAW filter designs employing thickness-modulated IDTs were designed and fabricated to validate the effective suppression of spurious modes. The SAW filters experimentally featured spurious-free responses in the passband as well as a large 3 dB fractional bandwidth (FBW) in the 18.0% and 24.1% ranges and low insertion losses below 1 dB. This work can significantly broaden the range of applications for SAW devices and can open a pathway to commercialize ultra-wideband SAW filters in 5G communication systems.

Miniaturization is one of the driving design goals for large number of wireless applications, especially mobile phones. These market trends call for more thin and small size components with high reliability performance. In this paper, we describes the wafer level surface acoustic wave (SAW) filter package, 1.0 times 0.8 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , which is applicable for radio frequency (RF) stage in mobile phones. The SAW filter is reduced in size and thickness by using a 4" wafer level package process technique. The technique uses interconnection via and LiTaO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (LT)-LiTaO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (LT) wafer bonding structure. The interconnection via is formed through LT wafer by using sand blasting or laser drilling method. The AuSn eutectic bonding enables the connection of the signal pad on the SAW chip, with gold metallized LT wafer package. This eutectic bonding ensures that the SAW chip is protected mechanically and connected electrically, with the package. In order to simulate and optimize the structure and characteristics of wafer level SAW filter package, we used HFSS and ADS software. Frequency responses of measurement and simulation are compared with wafer level SAW filter package. The results of reliability tests for wafer level SAW filter package was discussed.

In this paper, we describes the wafer level surface acoustic wave (SAW) filter package, 1.0times0.8 mm2, which is applicable for radio frequency (RF) stage in mobile phones. The SAW filter is reduced in size and thickness by using a 4 wafer level package process technique. The technique uses interconnection via and LiTaO3 (LT)-LiTaO3 (LT) wafer bonding structure. The interconnection via is formed through LT wafer by using sand blasting or laser drilling method. The AuSn eutectic bonding enables the connection of the signal pad on the SAW chip, with gold metallized LT wafer package. This eutectic bonding ensures that the SAW chip is protected mechanically and connected electrically, with the package. In order to simulate and optimize the structure and characteristics of wafer level SAW filter package, we used HFSS and ADS software. Frequency responses of measurement and simulation are compared with wafer level SAW filter package. The results of reliability tests for wafer level SAW filter package will be discussed.

Surface acoustic wave (SAW) filters play a critical role as radio frequency components in the front-end module of electronic equipment. The conventional design methods of SAW filters heavily rely on researchers’ experiences and extensive software simulations, thus requiring substantial computational expenses. To overcome these limitations, this work explores the machine learning techniques to speed up the design of ladder-type SAW filters. A novel approach is proposed by combining the convolutional neural network (CNN) and cuckoo search (CS) optimization method. The method utilizes neural networks as surrogate models, replacing simulation software to predict the performance of SAW filters. This substitution aims to reduce the time needed for the entire filter optimization process. The incorporation of CS optimization method avoids the reliance of the optimization process on the designer’s experiences. Numerical examples are provided to demonstrate that the proposed method is efficient to design SAW filters with different frequency bands. Additionally, the method is adaptable to designing filters with diverse topologies, design standards, and varying numbers of resonators.

During the manufacture of ZnO/glass surface acoustic wave (SAW) filters, two kinds of problems sometimes arise. One is that the average frequency of the SAW filters changes greatly depending on the production lot of glass sheets. The other is that SAW filters made from the same production lot of glass sheets have largely separated double peaks in the frequency distribution. Previously, it had been considered that the frequency variation of ZnO/glass SAW filters depended on such factors as the ZnO film thickness and its elastic quality. The authors focused on the glass substrates as the cause of this variation and measured the leaky SAW (LSAW) velocity on the glass substrates using an ultrasonic microscope to clarify the mechanism. As a result, it was clarified that the LSAW velocities on the glass substrates showed a large variation within and between production lots of glass sheets, and the frequency of ZnO/glass SAW filters largely depended on the LSAW velocity on glass substrates. Moreover, the authors clarified the cause of the difference in the LSAW velocity between glass substrates and were able to reduce the variation of the LSAW velocity.