Abstract: A piezoelectric composite material including an organic matrix, and 72-78 % by volume of a piezoelectric ceramic powder dispersed in the matrix and consisting of 25-41.6 % by weight of a first group of lead titanate particles having a first average particle size, 25-41.6 % by weight of a second group of lead titanate particles having a second average particle size and 25-41.6 % by weight of a third group of lead titanate particles having a third average particle size. The first, second and third average particle sizes are different from each other and generally 2.5-4.5 .mu.m, 5-10 .mu.m and 20-40 .mu.m, respectively. At least a portion of the lead titanate particles of one of the first to third groups may be substituted with lead titanate zirconate having a similar particle size.

Abstract: In radio communication equipment, a ladder-type piezo-electric filter is provided which operates in a high-frequency region of approximately 1.7 MHz-2 MHz. The filter is smaller than conventional ladder-type electric filters, less costly, and more easily handled and produced. In accordance with the present invention, rectangular piezo-resonators that longitudinally generate harmonic oscillation are used in the series and parallel branches of a ladder-type circuit. In each resonator, piezo-electric regions are formed by dividing surface electrodes with isolating slits. The slits are formed at the positions corresponding to the node points of the harmonic oscillation waveforms. For the piezo-resonators placed in the series branches of the ladder-type circuit, the piezo-electric regions are polarized in the same transverse direction. In each piezo-resonator used in a parallel branch, the piezo-electric regions are polarized in alternately opposite transverse directions.

Abstract: A high unidirectivity piezoelectric element whose d.sub.31, d.sub.33 or d.sub.h is substantially zero. The element may be in the form of a sheet or a cable and includes a pair of electrodes, and a piezoelectric layer interposed between the pair of electrodes and containing two, first and second inorganic piezoelectric materials which have different coercive forces from each other and which are polarized in opposite directions. The element may be obtained by first applying a direct current voltage to a layer containing the first and second piezoelectric materials to polarize the both piezoelectric materials in one direction, and then applying a reverse direct current voltage thereto so that one of the piezoelectric materials having a smaller coercive force is selectively polarized in the other direction.

Abstract: A high d.sub.h piezoelectric composite material useful for utilization for hydrophones is disclosed which includes a matrix of an organic polymeric material and two different inorganic piezoelectric powders dispersed in the matrix. One of the piezoelectric powders has a large .vertline.d.sub.31 /d.sub.33 .vertline. value, such as lead titanate zirconate, and the other piezoelecctric powder has a low .vertline.d.sub.31 /d.sub.33 .vertline. value, such as lead titanate. The average particle size of one of the two piezoelectric powders is at least two times that of the other. The total amount of the two piezoelectric powders is 65-75% by volume based on the total volume of the matrix and the two piezoelectric powder. The volume ratio of the high .vertline.d.sub.31 /d.sub.33 .vertline. piezoelectric powder to the low .vertline.d.sub.31 /d.sub.33 .vertline. piezoelectric powder is in the range of 3:2 to 9:1.

Abstract: The present invention is to overcome a problem of a variation in a resonant frequency of a microwave stripline filter which may occur at a change of temperature during when the microwave stripline filter is operated. The microwave stripline filter has resonator electrodes (3 and 4) with a predetermined pattern provided between a pair of dielectric substrates (1 and 2), one of the dielectric substrates is formed by ceramic material whose temperature coefficient of resonant frequency is negative, and the other substrate is formed by a ceramic material whose temperature coefficient of resonant frequency is positive, which results in that the mutual temperature dependency to the resonant frquency in the paired dielectric substrates can be cancelled, and thus it is possible to feasibly hold the temperature coefficient of the filter device to zero. The stripline filter according to the present invention can conveniently utilized as a band-pass filter for miniature electronic circuits.

Abstract: A ladder type piezo-electric filter comprising series piezo-electric resonators and parallel piezo-electric resonators having improved second harmonic mode, high resonance response and anti-resonance impedance near 1-7 MHz, for use in communication applications requiring filter shaving resonator dimensions less than 5 mm and operating frequencies in excess of 455 kHz.

Abstract: Underwater piezoelectric arrangement in which it comprises two piezoelectric elements made of piezoelectric ceramic-polymer composites and juxtaposed to form a single layer structure, one of the element(s) having larger hydrophone constant than that of the other element(s), and by noise cancelling of the piezoelectric assembly there can be selectively detected only charges or voltages generated by acoustic waves which acts on each element.

Abstract: Underwater piezoelectric arrangement in which it comprises two piezoelectric layers made of piezoelectric ceramic-polymer composites, one of the layers has larger hydrophone constant than that of the other layer, and by noise cancelling based on the specific construction of the piezoelectric layers only charges or voltages generated by acoustic waves which act on each layer can be selectively detected. The piezoelectric arrangement may be utilized to provide a piezoelectric cable for use in a submarine earthquake searching or fish finding hydrophone, or an acoustic measuring element under water.