Abstract: A surface acoustic wave filter comprising; a first bidirectional ID transducer (5) of symmetrical form; a second ID transducer (1) acoustically coupled with the first transducer and comprising two parts (1A, 1B) each of which parts is in the form of one half of a respective bidirectional ID transducer (9 or 11) of symmetrical form, the two parts being positioned with respect to one another and the first transducer so that when respectively excited by corresponding signals of different phases they co-operate to produce a unidirectional acoustic signal propagating towards the first transducer from one side thereof; and a third transducer (3) acoustically coupled with the first transducer and comprising two parts (3A, 3B ), each of which parts is electrically connected in parallel with a respective one of the two parts of said second transducer, and each of which parts of the third transducer is effectively in the form of the mirror image about the center line (7) of the first transducer of the other half of the

Abstract: A dispersive transducer 100 which has non-equidistant distribution of the finger electrodes 6, 7, 16 and 17 according to band-width such that the finger electrodes 16 and 17 of the low frequency portion 11 of the transducer have a width c and spacing d1 (or d2) which are equal to the corresponding portions of the highest frequency part 13 of the transducer such that reflections are substantially reduced or eliminated.

Abstract: A surface acoustic wave device sealing method prepares a cavity-defining member and lead members for electrical connection. A surface acoustic wave element having a wave propagation surface and electrodes is bonded to the cavity member by an adhesive applied to the circumferential edge of the cavity so that the propagation surface is opposed to the interior of the cavity, and the electrodes are exposed to the exterior of the cavity member. The electrodes are connected to the lead members, and the resulting unitary body is sealed by a mass of resin.

Abstract: Each IDT (inter-digital transducer) of a SAW (surface acoustic wave) device is formed on a thin resistive doped silicon film having the same pattern as the IDT, which improves adhesion of the IDT to the substrate. The silicon film also constitutes electroacoustic absorbers between the IDTs and edges of the substrate, and can have a linearly tapered edge adjacent to each IDT to suppress reflections at the absorber boundary. The SAW device is formed by sputtering silicon onto the substrate, subsequently forming the IDTs, and then etching the silicon from areas where it is not wanted.

Abstract: A surface wave filter with an input transducer and an output transducer. The input and output transducers have finger weightings such that a finger-overlap profile of the input/output transducer repeats in multiple fashion in the output/input transducer.

Abstract: An interdigitated transducer (IDT) has parallel electrodes extending inwardly from one voltage rail and parallel electrodes extending inwardly from another voltage rail. The respective electrodes are interleaved to give a region of overlap or apodization within which the SAW is generated or received, the width of the apodized area varying along the length of the IDT. To prevent performance degradation in the event of an open circuit in a non-overlap region, the electrodes associated with a particular voltage rail are additionally linked by a thin conductor positioned near the boundaries between the apodized or overlap region and each of the non-overlap regions.

Abstract: A surface wave filter having an interdigital structure in which last active fingers of a first comb structure, which is to be connected to ground, extend as close as possible to a busbar of an opposite comb structure. Interference signals based on the discontinuity of the end of the interdigital structure are eliminated.

Abstract: A surface acoustic wave-convolver arrangement having transducers whose fingers are curved such that they correspond to a respective wave front of a wave issuing from the integration electrode.

Abstract: Each IDT (inter-digital transducer) of a SAW (surface acoustic wave) device has a linearly tapered back edge formed by reflection-suppressing fingers of successively decreasing length spaced apart with a pitch of lambda/4 behind the active region of the IDT, where lambda is the wavelength of a SAW to be propagated, whereby SAW reflections at the back edge of the IDT are substantially eliminated. A thin resistive doped silicon film between the back edge of each IDT and the adjacent edge of the substrate absorbs waves propagated via this back edge. The film underlies the IDTs to provide improved adhesion to the substrate.

Abstract: An acoustic transducer is arranged as a ladder having uprights and rungs consisting of contact pads and interdigital fingers respectively. The transducer has inter-rung spaces 17 occupied by arrays of reflector strips. Each reflector strip is offset by .lambda./8 from a respective position distant 1/2n.lambda. from a transducer finger center, .lambda. being the transducer finger center and n as integer. The .lambda./8 offset reflector strips provide constructive interference between transducer output waves travelling in one direction and destructive interference in the opposite direction. This provides a transducer with undirectional properties which can be manufactured in one metal deposition process. Unwanted reflections at fingers may be reduced by additional blooming reflector banks or by repositioning reflector strips to provide both unidirectional and blooming properties.

Abstract: A surface acoustic wave device disclosed herein has input and output electrodes (21, 22) one of which (21) comprises a first interdigital electrode (23) defining even components of a frequency response and a second interdigital electrode (24) defining odd components thereof, the second interdigital electrode (24) being disposed outside the envelope of the first interdigital electrode (23). A portion of the second interdigital electrode (24) is disposed within a non-overlapping region of the first interdigital electrode (23), that is a region outside the envelope of the first interdigital electrode (23) and especially a region environed with a straight line running through the top of the envelope in a direction parallel with the propagating direction of the surface waves.

Abstract: The frequency response of an intermediate frequency filter for an intercarrier sound television receiver is modified to provide a substantially constant gain response portion over a predetermined range of frequencies centered about the 45.75 MHz intermediate frequency picture carrier. Picture carrier phase modulation induced by the Nyquist slope of the conventional intermediate frequency response is thereby eliminated over the predetermined frequency range reducing audio "buzz" by decreasing the phase modulation transferred to the 4.5 MHz intercarrier sound signal by the intermediate frequency picture carrier. In a preferred embodiment, the modified intermediate frequency response is established by a surface acoustic wave filter.

Abstract: A surface acoustic wave (SAW) filter consists of two acoustically coupled transducers built on the same piezoelectric film or substrate. The transducers are constructed by depositing a conducting comb structure having interdigitated fingers on the substrate. Spacer elements are placed between gaps of the same polarity within the comb structure. The addition of the spacer elements permit non-zero gap weights of the same sign to follow one another, in contrast to the standard structure which forces these sources to alternate in sign. This added flexibility results in new withdrawal weighted structures that significantly increase the bandwidth over which the rejection band performance is good and also reduces passband ripple. The increase in the accuracy of the withdrawal weighting permissible with these new structures improves filter performance.

Abstract: A surface acoustic wave transducer comprises a piezoelectric substrate, a first comb-shaped electrode with strips having the same width of .lambda./8 (.lambda. is the wavelength of a surface acoustic wave), and a second comb-shaped electrode with strips having the same width of .lambda./8. The strips of these comb-shaped electrodes are spaced apart from each other for a distance of .lambda./8. The strips of either electrode form pairs. Of each pair of strips, one strip has a narrow portion having a width of .lambda./16 and the other strip has a broad portion having a width of 3.lambda./16, which extends along the narrow portion. The narrow and broad portions of the strips of either comb-shaped electrode both acoustically and electrically reflect surface acoustic waves, whereas the other portions of the strips only electrically reflect the waves.

Abstract: An acoustic wave filter device with low loss and low passband ripple characteristics. The filter comprises three bidirectional electroacoustical transducers disposed along a common axis on the surface of a substrate of piezoelectric material. The two outer transducers of the three function as input transducers and the center transducer functions as an output transducer. One of the input transducers is of the antisymmetric type and has a transfer characteristic that differs in phase angle by ninety degrees with respect to the other input transducer, which is of the symmetric type. This ninety-degree difference applies at all frequencies, so that any energy reflected from the output transducer and again reflected by an input transducer will be subject to a phase shift of 180 degrees in the case of energy reflected from the antisymmetric input transducer, and no phase shift in the case of the symmetric input transducer.

Abstract: An acoustic surface wave device using an interdigital electrode array 2, 3 to launch and receive surface waves overcomes problems of diffraction by making the arrays approximately 3.lambda..sub.c wide between the outer boundaries of the bus bars. As a result, the arrays can each only propagate and transduce a single acoustic surface waveguide mode which is symmetrical about the axis of the array.

Abstract: An acoustic surface wave device uses an in-line arrangement of two apodized interdigital electrode arrays 2, 3 to launch and receive surface waves to overcome problems of short overlap sources and of diffraction by making the arrays approximately 3.lambda..sub.c wide between the outer boundaries of the bus bars so that the arrays can each only propagate and transduce a single acoustic surface waveguide mode which is symmetrical about the axis of the array. Because the acoustic surface wave energy is propagated in a guided mode, energy launched by pairs of electrodes with a short overlap rapidly spreads to fill the entire transducer aperture and a similar situation in reverse applies at the receiver.

Abstract: Compound surface acoustic wave matched filters comprise chirp-biphase and biphase code multiplex transducer pairs on piezoelectric substrates. Both alternatives offer significantly improved processing gain when compared with conventional biphase filters. The advantage is realized by convolving the correlation peak of the chirp or biphase input transducer on the response of the conventional biphase output transducer, thus achieving a large processing gain with a minimum number of transducer electrodes.

Abstract: A surface acoustic wave device includes apodized interdigital electrode arrays 2,3 coupled by a multistrip coupler 5. In a device in which the apodization 8 comprises a main lobe flanked by a succession of minor lobes, the effects of diffraction relating to short electrode pair overlaps are reduced by dividing at least the far end of the array into two or more series connected array portions 21, 22. Difficulties arising from unbalanced electrode edge overlaps at transitions 20 between different members of electrode pairs connected in series are reduced by locating such transitions in the region of nulls in the apodization pattern.

Abstract: A surface wave device (10) having substrate with at least a surface layer of piezoelectric material (12) and at least one pair of opposing electrically conducting pads (14 and 16) is disclosed. A first group of at least three electrodes (18, 20 and 22) in a distance (24) of one half wavelength of a preselected operating frequency is disposed on the piezoelectric surface between the opposing pads. At least one of the electrodes is electrically connected to one of the opposing pads and the remaining electrodes are electrically connected to the other opposing pad. The sequence of the three electrodes is unevenly distributed with respect to which of the pads the electrodes are connected to. At least two additional groups of at least three electrodes similar to the first group have sequences of electrodes within each group that is distinct from the other groups.

Abstract: A surface wave device includes a substrate (12 in FIG. 7) having a surface layer of piezoelectric material (14), at least one pair of opposing electrically conducting pads (16 and 18) and at least two electrodes (20 and 22) which generate surface waves that vary significantly in strength in a direction transverse to the opposing pads. An ungrounded pad (16) forms an electrode array of parallel segmented electrodes (24), joined by electrically conducting connecting bars (26), having more segmented electrodes near the center of the transverse distance than near the pads. A grounded electrode (22) forms a segmented electrode array having segmented electrodes (44) joined by electrically conducting connecting bars (46) having fewer segmented electrodes near the center of the transverse distance than near the pads.

Abstract: An echo-compensating surface acoustic wave interdigital transducer in which the entire length of the end finger of the transducer at each end is connected directly or indirectly to at least one of the bus bars, the end finger extends only partially across the aperture of the transducer, and the space which is colinear with the end finger across the remaining portion of the aperture is not occupied by any surface-acoustic-wave-reflective structure. The end finger is substantially a quarter of an acoustic wavelength out of phase with the nearest interior finger with respect to an incident wave at the operating frequency of the transducer, so that the acoustic reflections of the end finger and the nearest interior finger are in phase-opposition to each other.

Abstract: An electrical device package comprising an open ended container and an enclosure defining a cavity in which an electrical device is contained. The enclosure is positioned in the container and is sealed therein by a filling of moulding material.The package is particularly suitable for containing surface acoustic wave devices e.g. filters where contact with the moulding material during and after packaging must be avoided.

Abstract: An acoustic surface wave filter device having an input transducer of interleaved overlapping electrode structure. Acoustic surface wave absorbing material is disposed on a region of the electrodes within the overlap envelope and back of the electrodes having the maximum amount of overlap. The absorbing material suppresses waves traveling backward in the transducer thus greatly reducing the problem of spurious signals caused by acoustic reflections from the edges of the electrodes within the overlap envelope.

Abstract: A surface acoustic wave device comprises on a piezoelectric substrate a first interdigital electrode array for converting electric signals into surface acoustic waves and a second interdigital electrode array for receiving the surface acoustic waves propagating from the first interdigital electrode array along the surface portion of the piezoelectric substrate to convert them into electric signals again. The lengths of overlapping of the pairs of adjacent interdigital electrode or finger portions in each of the first and second electrode arrays are not the same. The distribution of the overlapping finger lengths in one of the first and second electrode arrays along the direction of propagation of the surface acoustic waves or the transverse direction of the piezoelectric substrate is such that the overlapping finger length has the minimum value at a central portion of the one electrode array and gradually increases toward both sides of the one electrode array.

Abstract: A withdrawal transducer structure is employed in a narrow-band surface acoustic wave device requiring many pairs of interdigital transducer fingers or in a high-frequency surface acoustic wave device in which the thickness of interdigital transducer fingers is large relative to the wavelength of the surface acoustic wave, so that the interdigital transducer fingers may not severely adversely affect the characteristics of the device. The interdigital transducer fingers in the input and output piezoelectric transducers are suitably partly omitted leaving some of them or dummy fingers are additionally provided to eliminate the adverse effect of the interdigital transducer fingers on the characteristics of the device, so that the narrow-band or high-frequency surface acoustic wave device can operate with improved performance without having any unnecessary frequency response.

Abstract: This Surface Acoustic Wave (SAW) filter has a tilted, interdigital transducer and a normal interdigital transducer separated from each other on a piezoelectric substrate. An input signal with a large bandwidth is applied to the tilted transducer, while an output signal is obtained from the normal transducer. Guaranteed attenuation can be greatly improved, and ripple in the pass band markedly reduced, by grounding one of the electrodes of the tilted transducer. This electrode is the one containing the longer of the two electrode fingers closest to the normal transducer.

Abstract: A high-performance surface acoustic wave filter is provided having a relative band width greater than 0.2, a shape factor less than 1.5, and a flat group delay time characteristic. The filter has input and output transducers, each with overlapped interdigital electrode fingers, spaced on the surface of a piezoelectric substrate, including an apodized transducer and a second transducer. The envelope of the overlapped portions of the electrode fingers in the apodized transducer includes a main lobe and a plurality of side lobes. The height of side lobes of the apodized transducer which are located farther from the second transducer is greater than the height of side lobes nearer the second transducer. The heights of corresponding side lobes on opposite sides of the main lobe are mathematically related.

Abstract: A surface acoustic wave convolver (10) with parabolic horns (16, 18), a typical horn (16) having a compensating stub (16a) at the horn input end (16b) disposed centrally on the horn longitudinal axis (19) to maintain the phase coherence at the horn output end Z(16c) of a wave traversing said horn (16).

Abstract: Stripes of a transducer or a reflector in a surface acoustic wave device are arranged such that the distribution of effective lengths of interdigital electrodes follows a function of impulse response in the direction of propagation of an acoustic wave and a total number of stripes in the direction of propagation is equal for each section in the direction normal to the direction of propagation, in order to attain a desired frequency response without sacrificing a transfer efficiency.

Abstract: A surface acoustic wave transducer having a piezoelectric thin film, interdigital electrodes disposed on one side surface of said piezoelectric thin film and an apodized counter electrode disposed on the opposite-side surface of said piezoelectric thin film. The outline of the apodized counter electrode is composed of parallel edges parallel to fingers of the interdigital electrode and perpendicular edges perpendicular to the fingers. The parallel edges are positioned in gaps between the fingers, so as not to lie over the fingers. Such structure remarkably reduces the deviation of characteristics of the transducer due to the incomplete alignment of the counter electrode with the interdigital electrode.

Abstract: A surface acoustic wave device includes a piezoelectric substrate, transmitting and receiving transducers provided on the surface of the substrate for propagating acoustic waves between the transducers, and absorbers provided between an end of the substrate and respective transducers for absorbing unwanted acoustic waves. The shape of the absorber is in relation to the energy distribution of the acoustic waves.

Abstract: An elastic surface wave device comprises an input transducer and an output transducer, these transducers being provided on one surface of a piezoelectric substrate and spaced apart a predetermined distance from each other. The input transducer is provided on its side facing the output transducer with at least one separate comb electrode which is electrically insulated from the rest of the input transducer.

Abstract: An elastic surface wave device having an input electrode, a pump electrode and an output electrode provided on a body of the device. The output electrode is juxtaposed with the input electrode on the body of the device on the same side with reference to the pump electrode and a multistrip coupler is provided between the pump electrode and the input and output electrodes so as to output, through the output electrode, a backward wave signal from the pump electrode.

Abstract: In order to reduce the reflectivity of an apodized surface acoustic wave transducer, one portion of the dummy area thereof is bare and another portion is 100% metallized, and the boundary between these two regions is shaped to equalize total acoustic transit times across the transducer aperture. This avoids any net refraction, and thus permits any acoustic wavefronts which traverse the two regions to remain flat.

Abstract: An acoustic surface wave device comprises transducers including interdigital electrodes formed on the surface of a piezoelectric material substrate of ceramic such as PZT, or a single crystal of such as LiNbO.sub.3 or a piezoelectric thin film of such as ZnO, wherein an electrical signal is converted into an acoustic surface wave and vice versa. The interdigital electrodes have been changed of the overlapping lengths of the adjacent electrode fingers that are overlapped with each other in accordance with a weighting function determined by a desired pass characteristic. A portion of the transducer region where an undesired acoustic surface wave is propagated, i.e. the portion outside of the envelope of the interdigital electrodes determined by the weighting function, is provided with an acoustic surface wave absorbing material such as silicon rubber. In a certain example, dummy electrodes may be provided between the electrode fingers of the interdigital electrodes.