Abstract: A piezoelectric device includes a stacked crystal filter, a supporting substrate and an acoustic reflector between the filter and substrate for suppressing undesired resonant frequencies. The acoustic reflector includes a set of quarter wavelength layers of alternating higher and lower impedances. The reflector provides a large reflection coefficient for a bandwidth that encompasses only desired frequencies generated by the stacked crystal filter. By changing the nature of the material and the number of layers, the bandwidth and center frequency of the acoustic reflector may be varied to encompass a desired range of frequencies. To reduce the magnitude of side lobes at undesired frequencies, the impedance differences between layers of the reflector are reduced with depth into the reflector. The side lobes may also be reduced by serially connecting two stacked crystal filters having acoustic reflectors of the same material but with a different number of quarter wavelength layers.

Abstract: A microstrip patch filter in which a dielectric has a ground plane printed on one of its faces and a conductive arrangement printed on the other of said faces, the conductive arrangement includes a flat patch, input and output leads electromagnetically coupled to the flat patch, the flat patch or the dielectric substrate has a reactance-enhancing metallic constriction located along a portion of the patch. When the constriction is in the patch it forms a current-concentrating inductive constriction. When the constriction is in the dielectric substrate, it enhances the capacitance. In an embodiment, the patch has two mutually-transverse constrictions that divide the patch into four sub-patches cross-connected by current-concentrating inductive constriction.

Abstract: A free edge reflective-type surface wave resonator for reflecting SH-type surface waves between two confronting free edges of a piezoelectric substrate includes a piezoelectric substrate having two confronting free edges and an interdigital transducer having a plurality of electrode fingers which are weighted by a cross width weighting method or an electrode thinning method. The weighting of the electrode fingers is performed so that an attenuation pole of a main lobe of the weighted IDT is located outside of a frequency of an attenuation pole of a normal non-weighted IDT which has the same number of electrode finger pairs as the weighted IDT. The weighting of the electrodes is such that the main lobe of the weighted IDT and a plurality of resonance characteristics determined by the attenuation poles of the normal unweighted IDT are obtained.

Abstract: The invention relates to a resonator coupling and a radio frequency filter, which comprise a transmission line resonator (106), preferably a helix resonator, having an upper and lower end, a transmission line (108, SL3) for coupling to the resonator, and a tap point (121), at which the transmission line (108, SL3) and the transmission line resonator (106) are in direct contact with each other, whereby the transmission line (106) is divided at the tap point (121) into a lower and upper part, the lower part comprising a first part (SL1) and the upper part comprising a second part (SL2). A coupling element (SL4) is placed at the tap point (121) in parallel with the transmission line resonator (106), coupled (M1) electromagnetically to the transmission line resonator (106), thus improving the stop/pass ratio of the filter.

Abstract: The invention relates to a resonator structure and radio frequency filter in which the resonating frequency of a transmission line resonator can be switched in a stepwise manner between at least three values. The switching is implemented as follows: a regulating element including a switch that has at least three states is arranged in connection with the resonator. The three states of the switch correspond to different values of the specific impedance and, hence, the resonating frequency of the transmission line resonator. The regulating element is in accordance with a known arrangement: it may be e.g. a coupling element formed of a strip line on the surface of a low-loss substrate or ceramic, or a side circuit including a capacitive and inductive element, coupled to the resonator.

Abstract: The invention relates to a radiofrequency filter in which the coupling between the transmission line resonators is effected by using both a slot coupling and a link coupling. The coupling slot and the coupling link are designed so that changes of the coupling intensity in the link coupling caused by shifting of the resonator element is of the same size and of the opposite sign as a corresponding change in the slot coupling, whereby the changes compensate one another. The design is based on the fact that the distance of the coupling link from the resonator is longer close to the coupling slot than far away from the coupling slot.

Abstract: The present invention provides surface acoustic wave devices which do not require a balanced-to-unbalanced transformer circuit regardless of the type of the peripheral circuits of the balanced type surface acoustic wave filter, i.e. a balanced type device or an unbalanced type. A transmitting interdigital transducer and a receiving interdigital transducer are formed on a substrate comprising 41.degree. Y cut-X propagation lithium niobate. A balanced type surface acoustic wave filter is formed on a substrate comprising 36.degree. Y cut-X propagation lithium tantalate. The balanced type surface acoustic wave filter comprises two series-arm surface acoustic wave resonators and two crossed-arm surface acoustic wave resonators connected in a lattice. The substrate on which the transmitting interdigital transducer and the receiving interdigital transducer are formed and the substrate on which the balanced type surface acoustic wave filter is formed are located in a ceramic package.

Abstract: A SAW filter is disclosed which includes two reflectors and a group of interdigital transducers (IDTs) located therebetween on a piezoelectric substrate, wherein the IDTs comprises at least four input IDTs and output IDTs alternatively aligned on the substrate in a SAW propagation direction to increase an transducer efficiency between an electronic signal and SAWs. Further, a distance between the center lines of the end electrode fingers of the adjacent input and output IDTs are set to be in a range from 0.625 .lambda. to 1.25 .lambda. (.lambda.: wave length of SAW) to establish input and output impedances of the SAW filter.

Abstract: A radio frequency filter comprising several resonator circuits, such as duplex filter, is provides with a given passband. Signal frequencies generating spurious response, mirror frequencies, etc. can be effectively attenuated so that the filter comprises one more resonator circuit connected as a bandstop circuit. That comprises a transmission line resonator (Res), a series connection of an inductive element (MLIN2) and a capacitance diode (D), one end of the series connection being couples to a coupling point in the transmission line resonator, dividing it into two parts (TLIN1, TLIN2), and the other end being couples to the output connector (1) of the radio frequency filter. In addition, means are provided for carrying the direct voltage (V+) to the cathode of the capacitance diode, whereby the series resonance frequency changes according to the control voltage.

Abstract: A piezoelectric resonator adapted for use in the band from several hundreds of kilohertz to 2 MHz utilizes a newly discovered width vibration mode and permits use of a simplified support structure which reduces stress on the resonator and reduces the overall size of the resonator. The resonator has a substantially rectangular cross-sectional shape having a pair of shorter sides and a pair of longer sides. To achieve the newly discovered vibration mode, the ratio of the length b of the longer sides to the length a of the shorter sides is set to be within +10% of a value given byb/a=n(-2.70.sigma.+2.86)where n is an integer and .sigma. is the Poisson's ratio of the ymaterial used to form the resonator.

Abstract: A ladder-type electric filter device having rubber plates each provided on one or both sides of each of the piezoelectric resonators so as to be brought into resilient contact with the surface of the associated piezoelectric resonator. The rubber plates are shaped so as to not be brought into contact with the respective corner edges of the respective piezoelectric resonators which generate extensive contour vibrations. Thus, the contour vibrations are not suppressed, the insertion loss can be reduced, and a mechanical quality factor Q can be substantially decreased, thereby improving group delay frequency characteristics.

Abstract: A surface acoustic wave device includes a substrate having piezoelectricity, at least two input electrodes, provided on the substrate, for exciting first and second surface acoustic waves, and an output electrode for taking a convolution signal of the two surface acoustic waves out. The substrate has a roughness configuration on a back face thereof and a maximum depth of the roughness configuration is not less than a wavelength of bulk waves of convolution output taken out of the output electrode.

Abstract: A SAW resonator for forming a frequency trap has a surface wave substrate and at least one interdigital transducer located on the surface wave substrate. The interdigital transducer includes a pair of comb-shaped electrodes each having a plurality of electrode fingers arranged so that the pair of comb-shaped electrodes interdigitates with each other. An overlapping width of the electrode fingers of the interdigital transducer is set such that in an impedance-frequency characteristic a transverse mode ripple occurring between a resonance point and an antiresonance point is located at the antiresonance point.

Abstract: Cavity filter with comb-line structure having a steep-flanked flanked pass-band. To obtain this steep flank, rejectors are positioned in the vicinity of the access bars of the filter, orthogonally to the teeth of the comb-line structure. The best results are obtained for the flanks corresponding to the high frequencies of the pass-band, namely with rejectors tuned to frequencies higher than the center frequency of the pass-band.

Abstract: A novel LC-type network consisting of distributed inductors and capacitors realized by means of printed patterns on a printed circuit board is disclosed. The LC-type network is based on a dielectric strip line two terminal resonance circuit consisting of a capacitance and inductance in parallel which forms a high Q resonator suitable for application in the construction of high frequency filters and oscillators. Constructing the resonator on a printed circuit board provides for high accuracy and repeatability. In addition, the need for trimming and/or tuning is eliminated thus lowering production costs.

Abstract: A strip dual mode loop resonator includes a loop-shaped strip line having a pair of straight strip lines arranged in parallel, an electric length of the loop-shaped strip line being equivalent to a wavelength of a microwave circulated in the loop-shaped strip line in two different directions according to a characteristic impedance of the loop-shaped strip line, and the straight strip lines being coupled to each other in electromagnetic coupling to change the characteristic impedance of the loop-shaped strip line. The microwave is transferred from an input strip line to the loop-shaped strip line through electromagnetic field induced by the microwave. Thereafter, the microwave is reflected in the straight strip lines of the loop-shaped strip line to produce reflected microwaves circulated in opposite directions. Thereafter, the reflected waves are resonated and filtered in dual mode in the loop-shaped strip line.

Abstract: Dual-mode cavity of waveguide bandpass filters, which allow the realization of narrow-band filters with very limited transition band and extremely low losses, without tuning or coupling screws or smooth edges. The dual mode cavity is composed of three coaxial sections of waveguide arranged in cascade and provided with irises, of which the two end sections are suited to support two modes with orthogonal polarizations and the intermediate section, consisting of a rectangular waveguide, has its side tilted with respect to the plane on which the irises lie. The whole filter composed of these cavities can be entirely designed by means of a computer and requires no tuning operation.

Abstract: A phase shifter, which can switch between a phase delay circuit and a phase leading circuit consisting of inductors and capacitors, is constituted by disposing FETs having inductors or capacitors arranged in parallel with the source and drain electrodes of each FET connected and controlling a bias voltage to be applied to the gate electrodes of the FETs to switch between the on and off conditions of the FETs. Thus, a phase shifter obtained has a small frequency characteristic.

Abstract: An interdigital converter of a surface acoustic wave filter is internally protected against electrostatic discharges. The protection is provided by a resistor which is connected in parallel to the interdigital converter.

Abstract: A surface acoustic wave device including a dielectric substrate having an input electrode and an output electrode and a grounding electrode on a first surface of the dielectric substrate, and an outer electrode on a second surface of the dielectric substrate; and a surface acoustic wave element having an electrode pad and a comb-shaped electrode disposed on a first surface of the surface acoustic wave element. The surface acoustic wave element is bonded to the dielectric substrate via a metal bump and a conductive resin formed on the electrode pad. The surface acoustic wave device further includes an insulating resin deposited on the periphery of the metal bump, and a guard layer shorter in height than the surface acoustic wave element formed adjacent the surface acoustic wave element on the first surface of the dielectric substrate.