Abstract: A bulk acoustic wave (BAW) device comprises a piezoelectric layer disposed between a first electrode layer and a sandwich electrode. The sandwich electrode includes a first layer of a first material having a first acoustic impedance and a second layer of a second material having a second acoustic impedance that is less than the first acoustic impedance of the first layer. The second layer of the sandwich electrode having the lower acoustic impedance is disposed between the first layer and the piezoelectric layer. The sandwich electrode combined with the piezoelectric layer and first electrode can cause the BAW device to resonate at a frequency whose wavelength corresponds to an acoustic cavity length of the BAW device, depending on an acoustic mirror included on one side of the BAW device. In one example, the acoustic cavity length is about 1.5 times of the resonant frequency wavelength.

Abstract: An apparatus is disclosed for bridge filters. In example aspects, the apparatus includes a filter circuit with a current balun and a filter core. The current balun includes a first terminal coupled to a first port of the filter circuit, a second terminal, a third terminal, and a fourth terminal. The current balun also includes a first inductor galvanically coupled between the first terminal and the second terminal. The current balun further includes a second inductor galvanically coupled between the third terminal and the fourth terminal. The filter core is coupled between the current balun and a second port of the filter circuit. The filter core is galvanically coupled to the second terminal of the current balun and to the fourth terminal of the current balun.

Abstract: An apparatus is disclosed for a bridge-type filter. In example aspects, the apparatus includes a filter circuit having a first port, a second port, and a filter core. The filter core is coupled between the first port and the second port. The filter core includes at least one transformer, a first resonator arrangement, and a second resonator arrangement. The first resonator arrangement is coupled to the at least one transformer and includes multiple acoustic resonators. The second resonator arrangement is coupled to the at least one transformer and includes multiple acoustic resonators.

Abstract: An apparatus is disclosed for a lattice-type filter. In example aspects, the apparatus includes a filter circuit having a first port that is single-ended and a second port that is single-ended. The filter circuit also includes a transformer, a first resonator, a second resonator, a third resonator, and a fourth resonator. The transformer includes a first terminal, a second terminal, and a third terminal, with the third terminal coupled to the second port. The first resonator is coupled between the first port and the first terminal of the transformer. The second resonator is coupled between the first port and the second terminal of the transformer. The third resonator is coupled between the first terminal of the transformer and a ground. The fourth resonator is coupled between the second terminal of the transformer and the ground.

Abstract: An apparatus is disclosed for harmonic reduction with filtering. In example aspects, the apparatus includes a filter circuit with first and second filter ports, first and second lattice filters, and first and second signal manipulator circuits. The first signal manipulator circuit includes a first port, a second port, and a third port coupled to the first filter port. The first signal manipulator circuit splits an input signal into multiple split signals, shifts a phase thereof to produce at least one phase-shifted split signal, and provides the phase-shifted split signal to the first and second ports. The first lattice filter is coupled to the first port, and the second lattice filter is coupled to the second port. The second signal manipulator circuit includes a first port coupled to the first lattice filter, a second port coupled to the second lattice filter, and a third port coupled to the second filter port.

Abstract: The present disclosure provides an apparatus that includes a plurality of filter circuits configured to filter one or more signals. The plurality of filter circuits includes a first filter component configured to have a first passband that spans adjacent transmission frequency ranges of a first communication band and a second communication band. The plurality of filter circuits further includes a second filter component having a second passband that spans a reception frequency range of a third communication band. The plurality of filter circuits further includes a third filter component having a third passband that spans adjacent reception frequency ranges of the first communication band and the third communication band. The plurality of filter circuits further includes a fourth filter component having a fourth passband that spans the second reception frequency range of the second communication band.

Abstract: The present disclosure provides an apparatus that includes a plurality of filter circuits configured to filter one or more signals. The plurality of filter circuits includes a first filter component configured to have a first passband that spans adjacent transmission frequency ranges of a first communication band and a second communication band. The plurality of filter circuits further includes a second filter component having a second passband that spans a reception frequency range of a third communication band. The plurality of filter circuits further includes a third filter component having a third passband that spans adjacent reception frequency ranges of the first communication band and the third communication band. The plurality of filter circuits further includes a fourth filter component having a fourth passband that spans the second reception frequency range of the second communication band.

Abstract: An antenna arrangement including a first antenna element connected to a first feed point and having a first electrical length; a second antenna element connected to a second feed point, different to the first feed point, and including: a first portion which extends from the second feed point and has a second electrical length, similar to the first electrical length, which enables the first portion to electromagnetically couple with the first antenna element, and a second portion which extends from the second feed point and has a third electrical length, different to the first electrical length of the first antenna element and to the second electrical length of the first portion.

Abstract: An antenna arrangement including a first antenna element connected to a first feed point and having a first electrical length; a second antenna element connected to a second feed point, different to the first feed point, and including: a first portion which extends from the second feed point and has a second electrical length, similar to the first electrical length, which enables the first portion to electromagnetically couple with the first antenna element, and a second portion which extends from the second feed point and has a third electrical length, different to the first electrical length of the first antenna element and to the second electrical length of the first portion.

Abstract: A filter device and a method for fabricating filter devices can package filters, especially acoustic wave filters, by bonding a carrier (substrate) wafer carrying manufactured filters to another wafer referred to as a capping wafer. A capping wafer/substrate eliminates the need for a conventional package to protect the sensitive filters, which reduces both product size and product costs significantly. Even though additional packaging is possible (i.e. in plastic molded packages, or in glob-top packages), it is not required for the reliability of the filters.

Abstract: A filter device comprises a substrate having a top surface and a bottom surface, and at least one acoustic wave situated on the top surface of the substrate, wherein the bottom surface of the substrate is roughened to reduce the reflection of an acoustic wave back to the acoustic wave filter. The effect achieved by the roughening of the bottom surface of the substrate that an acoustic wave which is generated by the acoustic wave filter and reaches the bottom surface of the substrate, is basically scattered so the acoustic wave that is actually reflected back to the acoustic wave device is reduced which, in turn, improves the performance characteristics of the acoustic wave filter.

Abstract: A filter device comprises a substrate having a top surface and a bottom surface, and at least one acoustic wave situated on the top surface of the substrate, wherein the bottom surface of the substrate is roughened to reduce the reflection of an acoustic wave back to the acoustic wave filter. The effect achieved by the roughening of the bottom surface of the substrate that an acoustic wave which is generated by the acoustic wave filter and reaches the bottom surface of the substrate, is basically scat acoustic wave that is actually reflected back to the acoustic wave device is reduced which, in turn, improves the performance characteristics of the acoustic wave filter.

Abstract: A filter device and a method for fabricating filter devices can package filters, especially acoustic wave filters, by bonding a carrier (substrate) wafer carrying manufactured filters to another wafer referred to as a capping wafer. A capping wafer/substrate eliminates the need for a conventional package to protect the sensitive filters, which reduces both product size and product costs significantly. Even though additional packaging is possible (i.e. in plastic molded packages, or in glob-top packages), it is not required for the reliability of the filters.