Seiko Epson Corporation

Kabushiki Kaisha Suwa Seikosha

Michiaki Takagi

Takashi Yamazaki

Eishi Momosaki

Satoru Hayashi

Masahiro Oshio

Katsuro Yoneya

Mitsuru Nagai

Keigo Iizawa

Shigeo Kanna

Yoshio Maeda

Yoshinori Ikusaka

A longitudinally coupled multi-mode SAW resonator filter includes input and output interdigital transducers (IDTs) with a control IDT therebetween to control a state of the surface acoustic wave. The input, output, and control IDTs alternatively arrange two different zones C and E having respective electrode period lengths PC and PE, being equal to a sum of the electrode finger width L and spacing S between electrode fingers, and a number of respective pairs MC and ME of electrode fingers is set to 1 in both zones C and E. Electrode fingers in zones C and E are all connected to a feeder conductor. Hence, a filter having small insertion loss, and a wide fractional bandwidth of 2000-4000 ppm is achieved by canceling and decreasing sums of reflected waves from the electrode fingers in zones C and E, and decreasing the effective reflection coefficient per the electrode finger.

Resonator SAW filter having a control interdigital transducer between input and output interdigital transducers

In a substrate in which a reflection coefficient &#x3b3; of a surface acoustic wave per electrode is small, the invention obtains a Q value or a CI value level, which is equivalent to or higher than that of a related art product, at a device size which is equivalent to the related art product which addresses the problem that the size of a surface acoustic wave resonator becomes larger. A surface acoustic wave resonator includes one interdigital transducer to excite a surface acoustic wave in a propagation direction x on a piezoelectric plate and a pair of reflectors arranged on both sides thereof in the propagation direction. The interdigital transducer is divided into three regions. The electrode fingers of the interdigital transducer of each region are formed at a fixed pitch which differs within 2%. The surface acoustic wave resonator possesses a single peak response. The form in which a vibration displacement envelope amplitude in the interdigital transducer region is normalized is a form which takes a maximum value 1 at the center position, which smoothly takes a value in a range of 0.33 to 0.53 at a position &#xbc; from both ends, and which smoothly takes a value in a range of 0.048 to 0.177 at positions at both ends.

Surface acoustic wave resonator with an interdigital transducer divided into regions having a different fixed pitch

The invention provides a longitudinal double-mode SAW filter that has a large reflection coefficient by the electrode conductors and having flat pass band characteristics. In the longitudinal double-mode SAW filter, nearly all of higher-order natural mode oscillation displacements ASand Aare made present in the first and second interdigital transducer regions. An electrode finger phase weighting is formed to correspond to a BPSK sign where a phase sign changes into 0 or &#x3c0; at a polarity-changing point on an electrode charge distribution function Q(x) that generates on the electrode due to natural modes of oscillation. A single pair of natural modes, which exist stationary in the direction X of propagation of the surface acoustic waves that are utilized, is selected. A symmetrical mode charge distribution (Q(x), &#x2212;Q(x)) and an obliquely symmetrical mode charge distribution (Q(x), Q(x)) are generated in order to correspond to the regions of IDTand IDTThe PTNG in the control IDTregion is set to be in the range of 1.02 to 1.04 so as to couple the two together.

Longitudinal double-mode saw filter utilizing electrode finger phase weighting

A transversally coupled double-mode SAW filter using a surface acoustic wave has two SAW resonators which have curtain-like electrodes and a pair of reflectors on both side thereof, respectively, and which are disposed in parallel on a piezoelectric flat plate in the propagation direction of the surface acoustic wave. The curtain-like electrodes of the SAW resonators have a first bus bar of electrically positive electrode which extends in the propagation direction of SAW and second and third bus bars of electrically negative electrode which extend in parallel on both sides of the first bus bar. The first bus bar has multiple electrode fingers of electrically positive electrode which face the second and third bus bars on both sides thereof and which extend in a direction perpendicular to the propagation direction of SAW so as to suitably have a space of &lgr;/2, &lgr; being the wavelength of the surface acoustic wave, and a width of &lgr;/4. The second and third bus bars have multiple electrode fingers of electrically negative electrode which correspond to the electrode fingers of electrically positive electrode, face the first bus bar and extend in a direction perpendicular to the propagation direction of SAW so as to similarly have a space of &lgr;/2 and a width of &lgr;/4. Thereby, the curtain-like electrodes are constituted to invert the direction of driving field by 180&deg; with the first bus bar therebetween, and to enable making the passband width sharply broader than before by use of the frequency difference between excited primary symmetric mode and primary anti-symmetric mode.

Transverse double mode saw filter

A multi-longitudinal-mode-coupled resonator type SAW filter having flat passband characteristic is provided. In the multi-longitudinal-mode-coupled resonator type SAW filter, an energy trapped type SAW resonator is formed on a frequency upward type piezoelectric substrate, and an IDT is divided into three IDTs, a first IDT arranged to a transmitter side, a second IDT arranged to a receiver side, and a third IDT arranged between the first IDT and the second IDT to control the amplitude of the vibration displacement in two modes for forming a filter. A frequency potential is optimized by changing an electrode period length of each IDT. Resonance amplitude strengths in the two modes are thus equalized and passband transmission characteristics are thus flattened. A filter having a relatively wide bandwidth of 1000 to 1500 ppm is fabricated by using a substrate having a small electromechanical coupling factor, such as a quartz crystal substrate.

Multi-longitudinal mode coupled saw filter

Two-port saw resonator

A high-precision surface acoustic wave (SAW) device improves the frequency-temperature characteristics of a conventional surface acoustic wave device several-fold. In this high-precision surface acoustic wave device, two one-port SAW resonators, or two two-port SAW resonators, alternatively, two one-port-resonator-type, two-port-resonator-type or transversal-type filters are placed in parallel with each other. Further, these resonators or filters are excited and are elastically coupled to each other in such a way as to be in an oblique symmetry mode. Moreover, the frequency-temperature characteristics of the two elements are made to differ from each other. Furthermore, a flat frequency-temperature characteristic, which cannot be realized by a single element, is realized by being synthesized from the frequency-temperature characteristics of the two elements.

Surface acoustic wave device and method for designing same using

Saw device

A quartz oscillator temperature sensor which measures temperature based on the change in resonance or oscillation frequency of a quartz oscillator with the change in temperature the oscillator can be constructed by cutting a piece of quartz from a wafer with a thickness of about 80 to 150 .mu.m by rotating the plane of the crystal defined by the electrical and mechanical axes 15.degree. to 25.degree. about the electrical axis and then forming the wafer into a quartz tuning fork. The tuning fork is housed in a case sealed with a stem and coupled to electrical leads with heat resistent solder formed with more than about 90 wt % Pb and less than 10% Sn. The area within the case should be at a substantially high vacuum.

Quartz oscillator temperature sensor

A quartz oscillator temperature sensor which measures temperature based on the change in resonance or oscillation frequency of a quartz oscillator with the change in temperature of the oscillator can be constructed by cutting a piece of quartz from a wafer with a thickness of about 80 to 150 .mu.m by rotating the plane of the crystal defined by the electrical and mechanical axes 15 to 25.degree. about the electrical axis and then forming the wafer into a quartz tuning fork. The tuning fork is housed in a case sealed with a stem and coupled to electrical leads with heat resistent solder formed with more than about 90 wt % Pb and less than 10% Sn. The area within the case should be at a substantially high vacuum.

Method of forming a quartz oscillator temperature sensor

An oscillator circuit for simultaneously outputting two frequency signals comprises a single resonator vibrating in two modes at different frequencies, an amplitude modulating circuit for modulating one of said two frequencies with a third frequency, a feedback circuit receiving the output of the amplitude modulating circuit, a detector demodulating the amplitude modulated signal, the demodulated signal being the third frequency used to modulate the output of the resonator. The two frequencies of the resonator are close together in value and the third frequency signal is the difference in frequency of the two resonator outputs. Circuit outputs are one resonator frequency and the difference frequency.

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Suwa, Japan

Michiaki Takagi