Abstract: A bulk acoustic wave, BAW, resonator device comprising first and second metal layers (10, 20) and an intervening piezoelectric layer (30), the first metal layer (10) comprising spaced first and second portions (12, 14), wherein the first and second portions (12, 14) are each arranged as a plurality of interconnected fingers (16, 18), and wherein each of the plurality of fingers (16) of the first portion (12) is acoustically coupled to at least one of the fingers (18) of the second portion (14). In one embodiment the fingers of the first portion (12) are interlaced with the fingers (18) of the second portion (14), thereby providing direct coupling. In another embodiment the acoustic coupling between the fingers of the first and second portions is provided indirectly by further portions (15) of the first metal layer (10).

Abstract: A multi-mode radio module (22) comprises a terminal (11) for connection to an antenna (10). A transmitting branch (DCS/PCS) and a branching circuit are coupled to the terminal (11). The branching circuit comprises at least a first and a second branch for receiving signals in first and second frequency bands (DCS, PCS), respectively. Each of the first and second branches comprise, respectively, a phase shifting circuit (PS1, PS2), a BAW or SAW band pass filter (RXF2, RXF3) coupled to the phase shifting circuit, the bandwidth of the filter being selected to pass a wanted signal in one of the first and second frequency bands but reject an unwanted signal in the other of the second and first frequency bands, and a low noise amplifier (LNA2, LNA3) coupled to an output of the band pass filter. The response of each of the band pass filters (RXF2, RXF3) is phase shifted to present an open circuit at the wanted frequency in the other branch.

Abstract: The invention relates to an arrangement with two piezoelectric layers (2, 5) and to a method of operating the arrangement as a filter. One (2) of the two piezoelectric layers (2, 5) in the arrangement is situated between an electrode (3) and a middle electrode (4), and the other one (5) of the two piezoelectric layers (2, 5) is positioned between another electrode (6) and said middle electrode (4) such that a bulk acoustic wave resonator is formed. The one and the other electrode (3, 6) and the middle electrode (4) are connected to circuitry means for applying high-frequency signals to at least one of the two piezoelectric layers (2, 5) such that the bulk acoustic wave resonator has at least one resonance frequency when the circuitry means are in one switching state, and that the bulk acoustic wave resonator has at least one other resonance frequency different from the at least one resonance frequency when the circuitry means are in another switching state.

Abstract: A ladder filter comprises series and shunt resonators (2, 4). The or each shunt resonator (4) has a static capacitance which is more than four times the static capacitance of the input or output series resonators (2i, 2o). This provides increased shunt resonator capacitance which reduces the effective coupling across the a series-shunt section, thereby enabling a smaller number of series-shunt filter sections to used to achieve good stop-band rejection, while still providing good performance in the pass-band. The invention is based on the recognition that filter bandwidth can be traded for improved out-of-band rejection.

Abstract: A bulk acoustic wave device has a number of resonator elements (14) which are laterally spaced such that a signal (26) applied between to one resonator element (141) at a resonant frequency of the device is coupled to the other resonator elements (142, 143, 144) by acoustic coupling between piezoelectric layers of the resonator elements (14). There are two outer resonator elements (141, 145) and at least one inner resonator element (142, 143, 144). The terminals of the inner resonator elements are electrically connected together. This connection provides an AC short which eliminates the effect of the parasitic capacitances of the inner resonator elements, and provides electromagnetic shielding between the input and output of the device, by reducing the parasitic capacitance between the input and output upper electrodes.

Abstract: A ladder filter comprises series and shunt resonators (2,4). The or each shunt resonator (4) has a static capacitance which is more than four times the static capacitance of the input or output series resonators (2i,2o). This provides increased shunt resonator capacitance which reduces the effective coupling across the a series-shunt section, thereby enabling a smaller number of series-shunt filter sections to used to achieve good stop-band rejection, while still providing good performance in the pass-band. The invention is based on the recognition that filter bandwidth can be traded for improved out-of-band rejection.

Abstract: A bulk acoustic wave device has a number of resonator elements (14) which are laterally spaced such that a signal (26) applied between to one resonator element (141) at a resonant frequency of the device is coupled to the other resonator elements (142, 143, 144) by acoustic coupling between piezoelectric layers of the resonator elements (14). There are two outer resonator elements (141, 145) and at least one inner resonator element (142, 143, 144). The terminals of the inner resonator elements are electrically connected together. This connection provides an AC short which eliminates the effect of the parasitic capacitances of the inner resonator elements, and provides electromagnetic shielding between the input and output of the device, by reducing the parasitic capacitance between the input and output upper electrodes.

Abstract: A method of, and apparatus for, obtaining a representation of an electrical circuit (400) suitable for time-domain simulation. The electrical circuit comprises a physical structure (102), which is modelled using electromagnetic field analysis, and also comprises a remainder circuit (104) of circuit components which are interconnected with the physical structure. The electromagnetic field analysis is capable of generating at least a high-frequency equivalent circuit which is representative of the physical structure (102) and is valid at the operating frequency of the circuit but not at DC. The method comprises including a set of DC sources (E1 to Ek) to ensure that, in a time-domain simulation, improved DC bias conditions are provided for any non-linear components in the remainder circuit. The DC sources may be voltage sources in each interconnection, current sources between each interconnection and a zero voltage reference interconnection, or a combination of the two.

Abstract: A method of, and apparatus for, obtaining a representation of an electrical circuit (400) suitable for time-domain simulation. The electrical circuit comprises a physical structure (102), which is modelled using electromagnetic field analysis, and also comprises a remainder circuit (104) of circuit components which are interconnected with the physical structure. The electromagnetic field analysis is capable of generating at least a high-frequency equivalent circuit which is representative of the physical structure (102) and is valid at the operating frequency of the circuit but not at DC. The method comprises including a set of DC sources ( E1 to Ek) to ensure that, in a time-domain simulation, improved DC bias conditions are provided for any non-linear components in the remainder circuit. The DC sources may be voltage sources in each interconnection, current sources between each interconnection and a zero voltage reference interconnection, or a combination of the two.

Abstract: A simulator and its operation, for simulating electromagnetic behaviour of an IC (integrated circuit) of thin-film passive circuit components, uses a simple equivalent circuit model to minimise computer processing time while retaining good model accuracy in spite of the energy losses and different film thicknesses, conductivities and dielectric properties which occur in a passive integration IC.

Abstract: A method of controlling a circuit simulator for examining the electromagnetic behaviour of an electrical conductor pattern is based on reducing the equivalent circuit model of the pattern. The pattern is first represented by a collection of geometrical elements, whose size is determined by the scale of the geometrical details that is well below the minimum wavelength contemplated. Selection of a set of those elements that lie approximately at a distance of one wavelength from one another and expressing the field values of the non-selected elements in terms of the field values for the selected elements permits correlating a low rank admittance matrix and the matrices of the Maxwell equations. Typically, an effective reduction of four orders of magnitude in the number of equivalent circuit components is obtained without losing model accuracy.

Abstract: A method of, and apparatus for, simulating an electronic system which comprises a sequence of interconnected functional blocks. The method comprises providing a high level macro model of each of the functional blocks, providing a low level description of each of the functional blocks in terms of a detailed circuit and/or physical layout and extracting parameters of each high level macro model from the low level description of the corresponding block by processing operations prior to simulation. The simulation comprises applying inputs signals to the system, computing the behavior of each functional block in the sequence, including the interaction with its neighbors, using the extracted parameters of the high level macro models, and monitoring the signals at the output of the system to determine if the system behaves as anticipated.

Abstract: A surface acoustic wave device in which the two ports of an input transducer (2) provided on a piezoelectric substrate (1) are coupled to the two ports of an output transducer (3) via respective reflective multi-strip couplers (12, 13). In order to avoid the necessity of providing external tuned matching components to attain the low potential insertion loss of such a device, the number of electrodes and center-to-center distances of the electrodes of at least one of the transducers are chosen so that the impedance of that transducer is substantially real for a range of frequencies which contains the center-frequency of the device response characteristic as determined by the couplers.

Abstract: A resonator or filter which comprises a bar (1) of piezoelectric material provided with electrodes (2,3) which are spaced from the two ends of the bar. In operation, thickness shear vibrations occur between the electrodes and the bar width to thickness ratio is such that said vibrations in turn produce Nth harmonic flexure vibrations which propagate across the bar width, N being an even number. In order to accelerate the rate of decay of the vibrations towards the (supported and hence energy-absorbant) ends of the bar, and thus to reduce the distance between the electrodes and the ends of the bar for a given quality factor, (N/2-1) slots (4), some of which may be omitted, are provided in each of these ends so that each end is divided into N/2 prongs (5) of equal width.

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: Surface acoustic wave bandpass transversal filters, e.g. television intermediate frequency filters, comprising a +.theta..degree. rotated Y-cut X-propagating lithium niobate substrate with .theta. in the range from 121.degree. to 127.degree., preferably 123.degree. to 125.degree.. For a suitable range of filter bandwidths (35 db bandwidth between 0.05 and 0.5) these substrates provide reduced degradation of the filter upper stopband predominantly due to indirect bulk shear waves in the frequency range from the passband up to the frequency where direct bulk longitudinal wave degradation becomes significant. This frequency range is 41.5 MHz to approximately 55 MHz for a U.K. system t.v. i.f. filter and is 60.25 MHz to approximately 90 MHz for a Japanese system t.v. i.f. filter.