Abstract: A filter device is provided including a substrate (302) and a plurality of horizontal gap closing actuator (GCA) devices (550) disposed on a first surface of the substrate. The plurality of GCA devices includes and one or more GCA varactors (700). Each one of the plurality of horizontal GCA devices includes at least one drive comb structure (602a, 602b, 702a, 702b), at least one input/output (I/O) comb structure (616a, 676b, 716a, 716b), and at least one truss comb structure (604, 704) interdigitating the drive comb and the I/O comb structures. The truss comb structure is configured to move along a motion axis between at least a first interdigitated position and a second interdigitated position based on a bias voltage applied between the truss comb structure and the drive comb structure.

Abstract: A method to track and control the resonance frequency of a band-pass filter provides a solution for the sensitivity limitations against temperature and process variations. A phase sensing module obtains the phase difference between the input and output and a negative feed-back control architecture can be used to tune the filter's resonance over the input RF frequency.

Abstract: A noncontact communication apparatus is disclosed which includes: an antenna resonance circuit configured to have a coil for communicating with an opposite party through electromagnetic coupling; a changing block configured to change a Q-factor of the antenna resonance circuit; and a control block configured to control the antenna resonance circuit to transmit and receive data to and from the opposite party at one of a plurality of communication speeds prepared beforehand, the control block further controlling the changing block to reduce the Q-factor the higher the communication speed in use.

Abstract: A switched capacitor includes a capacitor and a switch. The capacitor is coupled between a p-node and an n-node and includes interleaved p-fingers and n-fingers. A number of the p-fingers is greater than a number of the n-fingers. The switch is coupled between the n-node and ground.

Abstract: A variable frequency resonator includes a series resonance circuit and a parallel resonance circuit. The series resonance circuit includes a first inductor, a first capacitor and a variable capacitance diode which are connected together in series. A reverse bias voltage is applied to the variable capacitance diode. A signal source is connected to the series resonance circuit. The parallel resonance circuit includes a second inductor and a second capacitor which are connected together in parallel. One terminal of the parallel resonance circuit is connected to a connection point between the first inductor and the first capacitor, and the other terminal of the parallel resonance circuit is connected to a connection point between the variable capacitor and the one terminal of the signal source.

Abstract: Various embodiments include apparatus, systems, and methods having a conductive contact configured to couple to a resistor-capacitor (RC) network, a device unit coupled to the conductive contact, and a mode switching unit to change a characteristic of a signal at the conductive contact based at least in part on an RC time constant of the RC network. The mode switching unit may switch the device unit between a first operating mode and a second operating mode based on a signal level of the signal.

Abstract: An active filter circuit includes an inductance-capacitance (LC) circuit (110) for wireless frequency input, a bi-directional mixer (120) and a filter impedance (130) series-coupled across at least part of the LC circuit (110), and another mixer (420) coupled to at least some portion of the LC circuit. Other circuits, processes, receivers, transmitters and transceivers are disclosed.

Abstract: A filter includes a first varactor with a first end electrically connected to a signal input end, a second varactor with a first end electrically connected to a second end of the first varactor, and a second end electrically connected to ground, and an inductor with a first end electrically connected to the second end of the first varactor, and a second end electrically connected to ground. The filter is capable of adjusting its frequency response by changing capacitance of the first varactor and/or the second varactor.

Abstract: A method and apparatus is provided for avoiding pattern blockage due to scatter from an object in which an artificial surface directs the energy from the antenna prior to arriving at a blocking structure such that either the wave fronts of the energy are linear when they arrive at the blocking structure or the phase of the energy incident on the object is adjusted such that the energy reflected from the object is in phase with energy directly from the antenna radiating elsewhere in the far field pattern, or both.

Abstract: Disclosed herein is an intermediate frequency filter having a variable pass band, which is capable of varying a pass band to minimize loss at a plurality of intermediate frequencies? The intermediate frequency (IF) includes a band pass filter unit arranged between a frequency conversion IC and a demodulation unit and configured to filter an IF signal output from the frequency conversion IC and output a resulting signal. A band varying unit is connected to the band pass filter unit and is configured to vary a pass band of the band pass filter unit. A switching unit connects or disconnects the band varying unit to or from the band pass filter unit. A control unit detects the IF signal and controls the switching unit in response to the IF signal so that the band varying unit is connected to or disconnected from the band pass filter unit.

Abstract: An apparatus for capturing power supply harmonics for use in powering a load, comprising a series resonant circuit coupled between an energy source having a waveform comprising a sinusoidal fundamental frequency and a sinusoidal harmonic, and a load that is not the earth, wherein the series resonant circuit is tuned to the harmonic frequency whereby the energy of the harmonic is directed to the load.

Abstract: A method of tuning the stopband attenuation of an absorptive bandstop filter having at least a first and second resonator, where the first resonator includes a first tuning element that exhibits a first resonant frequency, the second resonator includes a second tuning element that exhibits a second resonant frequency, and the tuning elements are used to adjust the corresponding resonant frequencies, includes 1) adjusting the first resonant frequency using the first tuning element; and 2) adjusting the second resonant frequency using the second tuning element, such that both resonant frequencies are coordinated to obtain a selected stopband attenuation level and to thus realize a frequency-selective variable attenuator.

Abstract: A radio transceiver device includes circuitry for radiating electromagnetic signals at a very high radio frequency both through space, as well as through wave guides that are formed within a substrate material. In one embodiment, the substrate comprises a dielectric substrate formed within a board, for example, a printed circuit board. In another embodiment of the invention, the wave guide is formed within a die of an integrated circuit radio transceiver. A plurality of transceivers with different functionality is defined. Substrate transceivers are operable to transmit through the wave guides, while local transceivers are operable to produce very short range wireless transmissions through space. A third and final transceiver is a typical wireless transceiver for communication with remote (non-local to the device) transceivers.

Abstract: A high frequency filter includes an inductor, a serial resonance circuit including an inductor and capacitors, a serial resonance circuit including an inductor and capacitors, and a varactor diode connected between a connection point between the capacitor and the capacitor and a connection point between the capacitor and the capacitor. A controller simultaneously changes two attenuation pole frequencies of the filter device by changing a capacitance of the varactor diode.

Abstract: A noise measurement system in a power stabilization network, a variable filter applied to the power stabilization network, and a method for measuring noise in the power stabilization network are provided. A power line communication signal from the power stabilization network is attenuated relative to a particular frequency using a filter in order to allow the power line communication signal to operate within an input range of an Electromagnetic Interference (EMI) measurer. A signal from a forbidden frequency band is transmitted to the EMI measurer without any attenuation or influence on a noise floor.

Abstract: There is provided a filter circuit that includes: a flying capacitor which maintains polarity when switching from an input terminal to an output terminal, and the polarity of which is reversed when switching from the output terminal to the input terminal; a first capacitor that is provided in parallel to the flying capacitor, at the input terminal of the flying capacitor; and a second capacitor that is provided in parallel to the flying capacitor, at the output terminal of the flying capacitor. The flying capacitor includes a variable capacity element such that capacity becomes smaller when switching from the input terminal to the output terminal and capacity becomes larger when switching from the output terminal to the input terminal.

Abstract: A filter circuit device is disclosed having a printed circuit board with first and second opposed major surfaces, an input, and an output. A first signal path is disposed on the printed circuit board extending from the input toward the output. A resonant circuit element is coupled to the first signal path and configured as a filter circuit. The resonant circuit element comprises a coil-wound tunable inductor element in serial electrical communication with an etched inductor element. The coil-wound tunable inductor element and the etched inductor element are in parallel electrical communication with a capacitor. A second signal path is further disposed on the printed circuit board extending from a first node on the first signal path. A shunt element is disposed on the second signal path that comprises a conductive grounding path terminated to electrical ground. An inductor and a capacitor in series electrical communication are coupled to the grounding path.

Abstract: This invention features an absorptive tunable bandstop filter with wide tuning range including first and second branches of all-pass filter networks, an input power divider for splitting the input signal and passing approximately half of the input signal power through each said branch of said all-pass filter networks, and an output power divider for recombining the signal power from each said branch of said all-pass filter networks, at least one of said branches of said all-pass filter networks being electrically tunable to provide an approximately 180° phase difference with similar amplitudes of the split said signal power to be recombined at said output power divider for rejecting but substantially absorbing selected frequencies.

Abstract: A compositionally stratified multi-layer Ba1-xSrxTiO3 (BST) heterostructure material is described which includes a lower layer of crystallized Ba1-xSrxTiO3 perovskite oxide where x is in the range of 0.36-0.44, inclusive, deposited on a substrate; an intermediate layer of crystallized Ba1-xSrxTiO3 perovskite oxide where x is in the range of 0.23-0.27, inclusive, in contact with the lower layer; and an upper layer of crystallized Ba1-xSrxTiO3 perovskite oxide where x in the range of 0.08-0.13, inclusive, in contact with the intermediate layer. A phase shifter and/or preselector tunable device including a compositionally stratified multi-layer BST hererostructure material is described according to the present invention. Temperature sensitivity of an inventive phase shifter is reduced by at least 70% in the temperature interval of 20 to 90° C., inclusive, and by at least 14% in the temperature interval of ?10 to 20° C., inclusive, compared to a compositionally homogeneous 60/40 BST material.

Abstract: Methods and systems for filters embedded in an integrated circuit package are disclosed and may include controlling filtering of signals within an integrated circuit via one or more filter components embedded within a multi-layer package bonded to the integrated circuit. The one or more filter components may be electrically coupled to one or more switchable capacitors within the integrated circuit. The filter components may include transmission line devices, microstrip filters, transformers, surface mount devices, inductors, and/or coplanar waveguide filters. The filter components may be fabricated utilizing metal conductive layers and/or ferromagnetic layers deposited on and/or embedded within the multi-layer package. The integrated circuit may be electrically coupled to the multi-layer package utilizing a flip-chip bonding technique.

Abstract: A tunable inductor includes a main wiring and at least one tuning module. The main wiring is arranged to encircle an inductor area of the tunable inductor. In addition, the tuning module is arranged to couple associated nodes of the main wiring. For example, each tuning module of the at least one tuning module includes a first switch positioned within the inductor area, and further includes at least one auxiliary wiring. When the first switch is turned on, the tuning module couples two nodes of the main wiring, where the at least one auxiliary wiring is arranged to couple the two nodes when the first switch is turned on. In particular, a patterned ground plane is arranged to decrease the energy loss of the tunable inductor, and more particularly, to prevent the tunable inductor from suffering energy loss. The patterned ground plane includes some conductive sections forming a W-like shape.

Abstract: The invention relates to a variable capacitance circuit which achieves reduction in both of distortion and current consumption and furthermore achieves requirements of high power handling capability, cost reduction, and downsizing of the circuit.

Abstract: A tunable filter and a tunable duplexer are provided, both of which comprise an input terminal, an output terminal, four fixed capacitors, three variable capacitors and three fixed coils; wherein the variable capacitors are grounded at one end and, at the other end, connected to the fixed coils to form three sets of series-connected LC circuit; wherein the connecting points of the three sets of series-connected LC circuit, the input terminal and the output terminal are connected with the fixed capacitors, respectively.

Abstract: To provide a capacitative device capable of accurately securing a capacitance value, a variable capacitative device capable of sufficiently securing a capacity variability rate, and a resonance circuit that uses the capacitative devices. A capacitative device according to the present invention includes a capacitative device body constituted of a dielectric layer and at least a pair of capacitative device electrodes that sandwich the dielectric layer and cause a desired electric field in the dielectric layer; and stress adjustment portions to adjust a stress caused in the dielectric layer of the capacitative device body.

Abstract: An adaptive cable equalizer includes a data signal input unit, a clock signal input unit, a variable equalizer that inputs a data signal input from the data signal input unit, and a transition time measuring portion that measures a transition time of a data signal output from the variable equalizer, with an equalizer control loop being configured that controls characteristics of the variable equalizer based on the output signal of the transition time measuring portion. The adaptive cable equalizer further includes a control circuit that controls response characteristics of the control loop according to the frequency of a clock signal input from the clock signal input unit. This enables a quick response at fast transfer rates by making the relationship between the response time of the control loop and the number of data bits substantially constant even when the transfer rate changes from a slow transfer rate to a fast transfer rate.

Abstract: On-chip integrated variable inductors, methods of making and tuning an on-chip integrated variable inductor, and design structures embodying a circuit containing the on-chip integrated variable inductor. The inductor generally includes a signal line configured to carry an electrical signal, a ground line positioned in proximity to the signal line, and at least one control unit electrically coupled with the ground line. The at least one control unit is configured to open and close switch a current path connecting the ground line with a ground potential so as to change an inductance of the signal line.

Abstract: Methods and systems for filters embedded in an integrated circuit package are disclosed and may include controlling filtering of signals within an integrated circuit via one or more filter components embedded within a multi-layer package bonded to the integrated circuit. The one or more filter components may be electrically coupled to one or more switchable capacitors within the integrated circuit. The filter components may include transmission line devices, microstrip filters, transformers, surface mount devices, inductors, and/or coplanar waveguide filters. The filter components may be fabricated utilizing metal conductive layers and/or ferromagnetic layers deposited on and/or embedded within the multi-layer package. The integrated circuit may be electrically coupled to the multi-layer package utilizing a flip-chip bonding technique.

Abstract: A tuning method and circuit for an LC tank resonant circuit, including an inductor and a variable capacitor, are described. In a tuning mode, an RF input signal is applied to an input port of the circuit, and the RF output signal is monitored as a variable capacitor control input is varied. A peak output is detected, and the corresponding variable capacitor control input is stored, and applied to the variable capacitor in an operating mode. In one embodiment, the variable capacitor control input is adjusted for delay in the peak detection process. In one embodiment, the variable capacitor comprises a coarse capacitor and a fine capacitor; the tuning procedure is repeated for each capacitor; and both coarse and fine variable capacitor control inputs are stored and applied to the respective capacitors in operating mode.

Abstract: Tunable matching network topologies are disclosed. A network in accordance with the present invention comprises at least one inductor, and at least one tunable capacitor, in parallel with the inductor, wherein the at least one tunable capacitor tunes the at least one inductor self-resonant frequency.

Abstract: A method and apparatus for dynamically varying the impedance of a tank circuit whereby, over time, the response of the circuit to a received signal is maximized.

Abstract: A controllable filter arrangement with a voltage controlled device that subjects a signal to a predetermined impedance as part of the filtering process when the voltage controlled device is in an active state. In an inactive state, the voltage controlled device may subject the signal to an impedance that prevents all frequencies of the signal from passing. This configuration may advantageously increase frequency selectivity and reduce insertion loss, size, cost, and tuning complexity when compared with conventional filter designs.

Abstract: A tunable RF filter comprises a signal transmission path having an input and output, a plurality of resonant elements disposed along the signal transmission path between the input and output, and a set of non-resonant elements coupling the resonant elements together to form a stop band having a plurality of transmission zeroes corresponding to respective frequencies of the resonant elements, and at least one sub-band between the transmission zeroes. The set of non-resonant elements comprises a first plurality of non-resonant elements respectively coupled in parallel with the resonant elements, and a second plurality of non-resonant elements respectively coupled in series with the resonant elements. The first plurality of non-resonant elements comprises at least one variable non-resonant element for selectively introducing at least one reflection zero within the stop band to create a pass band in one of the one sub-band(s) without varying any of the second plurality of non-resonant elements.

Abstract: Various embodiments include apparatus, systems, and methods having a conductive contact configured to couple to a resistor-capacitor (RC) network, a device unit coupled to the conductive contact, and a mode switching unit to change a characteristic of a signal at the conductive contact based at least in part on an RC time constant of the RC network. The mode switching unit may switch the device unit between a first operating mode and a second operating mode based on a signal level of the signal.

Abstract: A radio-frequency (RF) front-end circuit includes a tunable filter, a negative transconductance circuit coupled with the tunable filter to produce a tuning oscillation signal, and a counter arranged to determine a frequency of the tuning oscillation signal. The RF front-end circuit also includes a control circuit arranged to shift the frequency of the tuning oscillation signal by adjusting the tunable filter until the frequency of the tuning oscillation signal falls within an acceptable frequency range corresponding to a desired channel frequency band.

Abstract: A radio transceiver device includes circuitry for radiating electromagnetic signals at a very high radio frequency both through space, as well as through wave guides that are formed within a substrate material. In one embodiment, the substrate comprises a dielectric substrate formed within a board, for example, a printed circuit board. In another embodiment of the invention, the wave guide is formed within a die of an integrated circuit radio transceiver. A plurality of transceivers with different functionality is defined. Substrate transceivers are operable to transmit through the wave guides, while local transceivers are operable to produce very short range wireless transmissions through space. A third and final transceiver is a typical wireless transceiver for communication with remote (non-local to the device) transceivers.

Abstract: A tuning arrangement for a resonant circuit, the tuning arrangement having an output reactance dependent upon a plurality of input applied signals one of which is an input tuning signal, and including: an array of tuning circuits connected in a network whose output reactance is used to control the resonance frequency of the resonant circuit, each tuning circuit having a control input and having a reactance which varies in dependence upon the value of a control signal applied to the control input; elements for generating a plurality of different control signals for application to the control inputs of the tuning circuits; and each such control signal varying substantially linearly with the input tuning signal throughout a predetermined range specific to that control signal, so that the frequency response of the resonant circuit to the input tuning signal is substantially linear throughout a desired range of the input tuning signal.

Abstract: Exemplary embodiments of the present disclosure provide a method and controller for damping multimode electromagnetic oscillations in electric power systems which interconnect a plurality of generators and consumers. The controller for damping such oscillations includes a phasor measurement unit (PMU) and a power oscillation damper (POD) controller. Each oscillating mode signal is damped and then superposed to derive a control signal. A feedback controller is used to feedback the control signal to a power flow control device in the power system.

Abstract: An electronically tuned, absorptive, low-loss notch filter with high RF power handling capability is obtained using a four-port quadrature hybrid coupler connected to a matched pair of band pass resonator devices and resistive terminations. The notch filter design uses series-only tuning elements for the band pass resonator devices to raise the RF power handling of the band pass resonators far above conventional techniques while also being tunable at high speeds. The notch filter architecture and method can be used for interference cancellation in a wide range of wireless technologies, such as cellular phone, wireless routers, hand-held radios, satellite communications, and any other environments where there are a number of wireless technologies in close signal proximity.

Abstract: A compositionally stratified multi-layer Ba1-xSrxTiO3 (BST) heterostructure material is described which includes a lower layer of crystallized Ba1-xSrxTiO3 perovskite oxide where x is in the range of 0.36-0.44, inclusive, deposited on a substrate; an intermediate layer of crystallized Ba1-xSrxTiO3 perovskite oxide where x is in the range of 0.23-0.27, inclusive, in contact with the lower layer; and an upper layer of crystallized Ba1-xSrxTiO3 perovskite oxide where x in the range of 0.08-0.13, inclusive, in contact with the intermediate layer. A phase shifter and/or preselector tunable device including a compositionally stratified multi-layer BST hererostructure material is described according to the present invention. Temperature sensitivity of an inventive phase shifter is reduced by at least 70% in the temperature interval of 20 to 90° C., inclusive, and by at least 14% in the temperature interval of ?10 to 20° C., inclusive, compared to a compositionally homogeneous 60/40 BST material.

Abstract: An active filter circuit includes an inductance-capacitance (LC) circuit (110) for wireless frequency input, a bi-directional mixer (120) and a filter impedance (130) series-coupled across at least part of the LC circuit (110), and another mixer (420) coupled to at least some portion of the LC circuit. Other circuits, processes, receivers, transmitters and transceivers are disclosed.

Abstract: A low pass filter includes an RF input terminal, an RF output terminal, a plurality of inductors coupled in series between the RF input and output terminals, at least one electrically tunable capacitor coupled between ground and a node of one of the inductors. At least one of the inductors includes a winding, and a resistance and a capacitance coupled in series across a portion of the winding to enhance the out of band rejection of the low pass filter.

Abstract: A signal processing arrangement (REC) comprises a filter (PPF) with variable filter elements (FE). A switching circuit (SWCT) switches a filter element (FE1) and, subsequently, another filter element (FE3) from a filter state to an adjustment state and back again to the filter state. A filter element that is in the filter state contributes to a suppression of unwanted signals. A filter element that is in the adjustment state affects a characteristic of a measurement signal (Sm). An adjustment circuit (ADCT) adjusts the filter element that is in the adjustment state so that the characteristic of the measurement signal is substantially equal to a target value (TV).

Abstract: Tuning a programmable power line filter, the power line filter including a live line, a neutral line, and a ground line connected to input terminals of the filter on an input side of the filter, the live line and the neutral line connected through inductors in the filter to output terminals on an output side of the filter, X-capacitors selectably connected through tuning switches between the live line and the neutral line, Y-capacitors selectably connected through tuning switches between the live line and ground and/or between the neutral line and ground, and a tuning control circuit connected to the tuning switches and selectably connected through one or more programming switches to the load, including measuring by the tuning control circuit the input impedance of the load and programming by the tuning control circuit the tuning switches in dependence upon the input impedance of the load.

Abstract: A variable frequency resonator includes a series resonance circuit and a parallel resonance circuit. The series resonance circuit includes a first inductor, a first capacitor and a variable capacitance diode which are connected together in series. A reverse bias voltage is applied to the variable capacitance diode. A signal source is connected to the series resonance circuit. The parallel resonance circuit includes a second inductor and a second capacitor which are connected together in parallel. One terminal of the parallel resonance circuit is connected to a connection point between the first inductor and the first capacitor, and the other terminal of the parallel resonance circuit is connected to a connection point between the variable capacitor and the one terminal of the signal source.

Abstract: The present invention relates to a tunable circuit, or admittance, arrangement comprising at least one capacitive branch with at least a tunable first capacitor, and tuning application means. It further comprises at least one resonant branch comprising at least a second capacitor and an inductor, said second capacitor and said inductor being connected in series. Said at least one capacitive branch and said at least one resonant branch are connected in parallel, and said tuning application means are adapted for application of a DC tuning voltage. The capacitance of said first and/or second capacitor and/or the inductance of said inductor are selected such that the frequency dependency of the tunability of a varactor arrangement forming the equivalent varactor arrangement of the admittance arrangement can be controlled at least in a selected frequency range.

Abstract: A switched capacitor includes a capacitor and a switch. The capacitor is coupled between a p-node and an n-node and includes interleaved p-fingers and n-fingers. A number of the p-fingers is greater than a number of the n-fingers. The switch is coupled between the n-node and ground.

Abstract: Disclosed herein is an intermediate frequency filter having a variable pass band, which is capable of varying a pass band to minimize loss at a plurality of intermediate frequencies. The intermediate frequency (IF) includes a band pass filter unit arranged between a frequency conversion IC and a demodulation unit and configured to filter an IF signal output from the frequency conversion IC and output a resulting signal. A band varying unit is connected to the band pass filter unit and is configured to vary a pass band of the band pass filter unit. A switching unit connects or disconnects the band varying unit to or from the band pass filter unit. A control unit detects the IF signal and controls the switching unit in response to the IF signal so that the band varying unit is connected to or disconnected from the band pass filter unit.

Abstract: A series resonance circuit defined by a series circuit including an inductor and a capacitor and a series resonance circuit defined by a series circuit including an inductor and a capacitor are connected in shunt to a signal line. A diode is disposed between the grounding end of the series resonance circuit and the ground, and a diode is disposed between the grounding end of the series resonance circuit and the ground. The connection point between the grounding end of the series resonance circuit and the diode is connected to the ground via a frequency shifting inductor in a conductive state at high frequency, and the connection point between the grounding end of the series resonance circuit and the diode is connected to the ground via a frequency shifting inductor in a conductive state at high frequency. A matching circuit defined by a multistage T-shape LCL circuit is disposed between the series resonance circuits.

Abstract: Embodiments described a semiconductor integrated circuit includes: a first coil and a second coil which have a mutual coupling and are connected in parallel to each other; a third coil connected in series to the first coil and the second coil; a first capacitor connected in parallel to the first coil; a second capacitor connected in parallel to the second coil; a first input terminal connected to an end of the first coil and an end of the first capacitor; a second input terminal connected to an end of the second coil and an end of the second capacitor; and an input-signal supplying portion configured to supply input signals of opposite phases to the first input terminal and the second input terminal, respectively.

Abstract: An integrated variable voltage diode capacitor topology applied to a circuit providing a variable voltage load for controlling variable capacitance. The topology includes a first pair of anti-series varactor diodes, wherein the diode power-law exponent n for the first pair of anti-series varactor diodes in the circuit is equal or greater than 0.5, and the first pair of anti-series varactor diodes have an unequal size ratio that is set to control third-order distortion. The topology also includes a center tap between the first pair anti-series varactor diodes for application of the variable voltage load. In preferred embodiments, a second pair of anti-series varactor diodes is arranged anti-parallel to the first pair of anti-series varactor diodes so the combination of the first pair of anti-series varactor diodes and the second pair of anti-series varactor diodes control second-order distortion as well.