The present subject matter relates to systems, devices, and methods for adaptively tuning antenna elements and/or associated filter elements to support multiple frequency bands. For example, a tunable filter having an input node and an output node can be selectively tunable to define one or more pass bands associated with one or more first signal bands and one or more reject bands associated with one or more second signal bands. The tunable filter can be configured to pass signals having frequencies within the first signal bands between the input node and the output node and to block signals having frequencies within the second signal bands. Furthermore, the tunable filter can be configured to selectively tune the pass bands to have a minimum pass band insertion loss at any of a variety of frequencies, including frequencies that are greater than and less than frequencies within the reject bands.

Systems, devices, and methods for tunable filters that are configured to support multiple frequency bands, such as within the field of cellular radio communication, can include a first resonator and a second resonator configured to block signals within one or more frequency ranges, and one or more coupling element connected to both the first resonator and the second resonator. The one or more coupling element can be configured to provide low insertion loss within a pass band.

Apparatus and methods for tunable filters are provided. In certain configurations, a tunable filter includes a semiconductor die attached to a laminated substrate, such as a substrate of a multi-chip module (MCM). The tunable filter includes a vector inductor implemented using two or more conductors arranged on different conductive layers of the laminated substrate. The vector inductor's conductors are inductively coupled to one another and electrically connected in parallel to provide the vector inductor with high quality factor (Q-factor). The semiconductor die includes a variable capacitor that is electrically connected with the vector inductor to operate as a tunable resonator. Additionally, a frequency characteristic of the tunable filter, such as a passband, can be controlled by selecting a capacitance value of the variable capacitor, thereby tuning a resonance of the resonator.

Examples are disclosed herein that relate to driving a resonant scanning mirror system using a linear LC resonant driving scheme. In one example, a resonant scanning mirror system includes a scanning mirror, first and second mirror drive elements, and a drive circuit to drive the scanning mirror at a resonant frequency. The drive circuit includes one or more signal sources configured to create a first source signal and a second source signal that is 180 degrees out of phase with the first source signal. The drive circuit further includes a buffer stage configured to receive the first and second source signals and output first and second drive signals, a first resonant LC stage configured to amplify the first drive signal for provision to the first mirror drive element, and a second resonant LC stage configured to amplify the second drive signal for provision to the second mirror drive element.

The present disclosure provides a radio frequency duplexer circuit and a radio frequency substrate. The radio frequency duplexer circuit includes a first terminal, a second terminal, a third terminal, a low-pass filter, and a high-pass filter. The low-pass filter includes N first filter sub-circuits coupled in series and a first tuning sub-circuit. Among the N first filter sub-circuits coupled in series, a first end of a 1.sup.st first filter sub-circuit is coupled to the first terminal, and a second end of a N.sup.th first filter sub-circuit is coupled to the second terminal. The high-pass filter includes M second filter sub-circuits coupled in series and a second tuning sub-circuit. Among the M second filter sub-circuits coupled in series, a first end of a 1.sup.st second filter sub-circuit is coupled to the first terminal, and a second end of a M.sup.th second filter sub-circuit is coupled to the third terminal.

A band antenna EMP filter apparatus having HEMP protection capability is disclosed. The apparatus includes a discharging part, a band pass filtering part, and a residual current eliminating part. The discharging part primarily discharges a transient voltage due to a high altitude electromagnetic pulse (HEMP) when the HEMP is inputted through an input part receiving a radio frequency (RF) signal of an antenna. The band pass filtering part secondarily blocks a residual current primarily discharged by the discharging part and passes only a signal of a preset frequency band to output it through an output part. The residual current eliminating part limits a transient voltage of the HEMP by eliminating a residual current passing through the band pass filtering part.

A filter circuit for reducing feedback of a consumer on an energy supply is disclosed. This filter circuit includes a multipolar input, a line choke, and a multipolar output, wherein the input is configured to receive an AC voltage from the energy supply, wherein the output is configured to be connected to the consumer, wherein the line choke includes one coil for each pole of the input, and wherein the coils of the line choke are each connected between one pole of the input and one pole of the output and energy is transferred from the input to the output and/or vice versa. A resonant current suppression (RCS) group is connected in parallel to a coil of the line choke to transmit resonant currents arising at the line choke such that voltage increases generated by the resonant currents are reduced or suppressed by the at least one RCS circuit.

A filter assembly is disclosed that includes a monolithic filter having a surface and a heat sink coupled to the surface of the monolithic filter. The heat sink includes a layer of thermally conductive material that can have a thickness greater than about 0.02 mm. The heat sink may provide electrical shielding for the monolithic filter. In some embodiments, the filter assembly may include an organic dielectric material, such as liquid crystalline polymer or polyphenyl ether. In some embodiments, the filter assembly may include an additional monolithic filter.

A wide-bandwidth resonant circuit is provided. In an embodiment disclosed herein, the wide-bandwidth resonant circuit includes a positive resonant circuit coupled in parallel to a negative resonant circuit. The positive resonant circuit and the negative resonant circuit can be configured to collectively exhibit certain impedance characteristics across a wide bandwidth. As a result, it is possible to utilize the wide-bandwidth resonant circuit to support a variety of wide-bandwidth applications, such as in a wide-bandwidth signal filter circuit.

A multilayer filter may include a plurality of dielectric layers stacked in a Z-direction. A first conductive layer may overlie one of the dielectric layers, and a second conductive layer may overlie another of the dielectric layers and be spaced apart from the first conductive layer in the Z-direction. A first via may be connected with the second conductive layer at a first location. A second via may be connected with the second conductive layer at a second location that is spaced apart in a first direction from the first location. The first conductive layer may overlap the second conductive layer at an overlapping area to form a capacitor. At least a portion of the overlapping area may be located between the first location and the second location in the first direction. The second conductive layer may be free of via connections that intersect the overlapping area.