Abstract: A notch filter (100) includes a parallel coupled delay line (104) and surface acoustic wave resonator (102) which provides a pole at a desired passband. The surface acoustic wave resonator (102) and the delay line (104) are configured to provide a zero at an undesired frequency or stopband. In this way, the notch filter (100) augments the stopband rejection of an associated cascaded surface acoustic wave ladder filter (105). The notch filter (100) also provides a pole at a desired frequency or passband such that losses due to the notch filter (100) at the desired passband are minimized, thereby improving overall insertion loss performance.

Abstract: A method (100) of providing a time delay to a signal utilizing a surface acoustic wave ladder filter includes a first step (102) of providing a piezoelectric substrate. A second step (104) includes disposing series and shunt coupled surface acoustic wave transducers in a ladder configuration on the substrate with each of the transducers having an associated aperture and an associated number of interdigital electrode elements. A third step (106) includes configuring the associated aperture and an associated number of interdigital electrode elements for each surface acoustic wave transducer for maximum phase linearity of the ladder filter and uniform group delay response from the ladder filter. A fourth step (108) includes adjusting the number of transducers in the ladder filter to provide a desired average group delay. Subsequently passing a signal through the ladder filter will delay the signal by a time equal to the group delay.

Abstract: An acoustic wave ladder filter (55) incorporating split resonators (50) in place of single, small static capacitance resonators in legs of the ladder filter (55). The split resonators (50) have approximately the same frequency but less than twice the static capacitance as the single resonator they replace. The decrease in static capacitance results in a lower capacitance ratio, r. In addition, the Q of the split resonators is higher than the single resonator they replace. Therefore, the average Q/r ratio for the filter (55) increases providing higher performance in terms of insertion loss and ultimate rejection. The basic filter configuration remains relatively unchanged and thus matched to the proper impedances.

Abstract: A method and apparatus for a ladder filter (300, 400) incorporating same. The filter (100) includes a substrate and a first series resonator (100, 305, 403) disposed on the substrate and electrically coupled in series between the first electrical port (301, 401) and a first node. The first series resonator (100, 305, 403) includes a first series acoustic reflector (303), a first series gap (112), a first series transducer (105, 304, 403), a second series gap (112) and a second series acoustic reflector (115', 306) collectively disposed in an in-line configuration along a principal axis of the substrate. The filter (300, 400) also includes a first shunt resonator (100', 310, 404) disposed on the substrate and electrically coupled in shunt between the first node and ground.

Abstract: An acoustic wave filter (200, 300) having a substrate for supporting propagation of acoustic waves, and first (220, 315), second (235, 330) and third (210, 310) acoustic wave transducers disposed on the substrate. The first acoustic wave transducer (220, 315) includes at least one bus bar (221, 316) electrically coupled to a first electrical port (205, 305) of the acoustic wave filter (200, 300). The second acoustic wave transducer (235, 330) is disposed on the substrate in line with the first acoustic wave transducer (220, 315) and is acoustically coupled thereto. The second acoustic wave transducer (235, 330) includes at least one bus bar (236', 331) electrically coupled to a second electrical port (240, 345) of the acoustic wave filter (200, 300). The third acoustic wave transducer (210, 310) includes at least one bus bar (211, 311') electrically coupled to the first electrical port (205, 305).

Abstract: A method and apparatus for an acoustic wave filter (110) with reduced bulk-wave scattering loss and a ladder filter (30, 40) incorporating same. The method includes steps of providing an acoustic wave propagating substrate (111) and disposing a first reflector (112) on a first surface thereof. The method also includes disposing a first transducer (115) to a first side of the first reflector (112). The first transducer (115) is separated from the first reflector (112) by a first gap (118) having a first width (114) exceeding one-fourth of the acoustic wavelength. The method also includes disposing a second reflector (112') to a side of the first transducer (115) opposite the first reflector (112). The first (112) and second (112') reflectors each include a group of periodically disposed reflective elements (113, 113'). The second reflector (112') is separated from the first transducer (115) by a second gap (140) having a second width (139).

Abstract: A bandpass filter and a method for making a bandpass ladder filter having a center frequency, a first port and a second port. The method has steps of providing a first L network having a first connection, a second connection and an inductive impedance at the center frequency and providing a second L network having a first connection, a second connection and a capacitive impedance at the center frequency. The method further has steps of coupling the first connection of the first L network to the first port, coupling the first connection of the second L network to the second connection of the first L network and coupling the second connection of the second L network to the second port.

Abstract: An acoustic wave filter with reduced bulk-wave scattering loss has a center frequency and an associated acoustic wavelength. The filter includes a substrate and a first reflector having a first group of periodically disposed reflective elements. The filter includes a first transducer on a first side of the first reflector. The filter also includes a first gap having a first width, located between the first reflector and the first transducer. The first width exceeds one-fourth of the acoustic wavelength. The filter includes a second reflector and a second gap disposed between the first transducer and the second reflector. The second gap has a second breadth exceeding one-fourth of the acoustic wavelength. A first waveguiding element is positioned within the first gap and having a first breadth. The first width exceeds the first breadth.

Abstract: A reflector arrangement for an acoustic wave device comprises an acoustic wave propagating substrate, reflection elements having at least two different widths separated by at least one gap breadth disposed on the acoustic wave propagating substrate. The at least two different widths enhance reflected waves produced by the propagating acoustic wave in such a fashion as to achieve a total acoustic reflectivity which is independent of variations in width of the reflection elements.

Abstract: A low-loss acoustic wave filter includes a piezoelectric substrate, a first strongly unidirectional acoustic wave transducer and a second strongly unidirectional acoustic wave transducer. Each of the first and second strongly unidirectional acoustic wave transducers are acoustically coupled to one another. Each of the first and second strongly unidirectional acoustic wave transducers further comprises an acoustic wave reflector and a weakly unidirectional acoustic wave transducer. The acoustic wave reflector and the weakly unidirectional acoustic wave transducer are coupled to the piezoelectric substrate.

Abstract: An acoustic wave filtering apparatus includes an acoustic wave propagating substrate for supporting propagation of acoustic waves and a plurality of acoustic wave filters for filtering an electrical signal. Each of said plurality further comprises an input for supplying electrical input signals, an input unidirectional acoustic wave transducer for converting electrical signal energy into acoustic energy, an output unidirectional acoustic wave transducer for converting acoustic signals to electrical signals, and an output for combining and delivering electrical output signals to external electrical apparatus.

Abstract: A reflector arrangement for an acoustic wave device comprises an acoustic wave propagating substrate, reflection elements having at least two different widths separated by at least one gap breadth disposed on the acoustic wave propagating substrate. The at least two different widths enhance reflected waves produced by the propagating acoustic wave in such a fashion to as to achieve a total acoustic reflectivity which is independent of variations in width of the reflection elements.

Abstract: An acoustic wave device comprises an acoustic wave transducer coupled to an acoustic wave propagating substrate. The acoustic wave transducer converts signal energy between electrical and acoustical forms. Acoustic reflectors are placed one on either side of the acoustic wave transducer. The acoustic reflectors are composed of acoustic reflection elements spaced approximately one wavelength apart, and provide enhanced acoustic acoustic reflections together with relaxed fabrication constraints.

Abstract: An acoustic transducer for an acoustic wave device which includes an acoustic wave propagating substrate, the transducer adapted to couple to an electrical load and/or source. The transducer includes at least a pair of comb electrodes formed on the substrate. It includes apparatus for applying an electrical load and/or source across the pair of comb electrodes. The first of the combs has a plurality of electrode fingers. The second comb has at least one electrode finger. The widths of the electrode fingers are the same. Gaps of at least two different widths are disposed between the electrodes.