An apparatus and method for a frequency based integrated circuit that selectively filters out unwanted bands or regions of interfering frequencies utilizing one or more tunable notch or bandpass filters or tunable low or high pass filters capable of operating across multiple frequencies and multiple bands in noisy RF environments. The tunable filters are fabricated within the same integrated circuit package as the associated frequency based circuitry, thus minimizing R, L, and C parasitic values, and also allowing residual and other parasitic impedance in the associated circuitry and IC package to be absorbed and compensated.

A method of constructing an RF filter comprises designing an RF filter that includes a plurality of resonant elements disposed, a plurality 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 a sub-band between the transmission zeroes. The non-resonant elements comprise a variable non-resonant element for selectively introducing a reflection zero within the stop band to create a pass band in the sub-band. The method further comprises changing the order in which the resonant elements are disposed along the signal transmission path to create a plurality of filter solutions, computing a performance parameter for each of the filter solutions, comparing the performance parameters to each other, selecting one of the filter solutions based on the comparison of the computed performance parameters, and constructing the RF filter using the selected filter solution.

A filter circuit comprises in a signal line a band filter (BF) allowing to let pass a useful frequency band and a notch filter (NF) circuited in series to the band filter for filtering out a stop band frequency. The notch filter comprises a series circuit of a number of parallel shunt elements (SE1 . . . SE6) wherein each shunt element is shifted infrequency against the other shunt elements that the frequencies thereof are distributed (f1 . . . F6) over a notch band. All shunt elements may be realized as a SAW one-port resonator (TR.sub.NF) including regions with different pitches.

According to one embodiment, a drive circuit includes a first circuit part. The first circuit part includes a first detecting part, a second detecting part, a first circuit, and a second circuit. The first detecting part is configured to detect a first piezoelectric element current flowing in a first piezoelectric element, and output a first detection signal corresponding to the first piezoelectric element current. The second detecting part is configured to detect a first capacitance element current flowing in a first capacitance element, and output a second detection signal corresponding to the first capacitance element current. The first circuit includes a first input terminal and a second input terminal. The first circuit is configured to apply a first drive signal to the first piezoelectric element and the first capacitance element. The second circuit is configured to supply a first differential signal to the second input terminal.

A wavetrap includes a housing having a base including a base plate. The housing has a wire channel, an inductor pocket and a terminal pocket. The housing has a capacitor pocket that receives a capacitor. The wavetrap includes a defroster wire having a wire end received in the wire channel. The defroster wire extends from the housing for connection to a vehicle defroster circuit. The wavetrap includes an inductor supported by the base plate. The inductor is received in the inductor pocket. The inductor has a coil extending between a first end and a second end. The first end is coupled to the wire end of the defroster wire. The wavetrap includes a ground terminal supported by the base plate. The ground terminal is received in the terminal pocket. The ground terminal is electrically connected to a ground circuit.

Systems and methods for tuning multiplexer filters are disclosed. In one aspect, a multiplexer includes a first filter coupled to a common node, the first filter configured to pass a first band, a second filter coupled to the common node, the second filter configured to pass a second band, and at least one electrical component configured to generate a notch at a frequency between the first band and the second band.

Radio frequency (RF) systems with tunable filters are provided herein. In certain embodiments, an RF system includes a first RF processing circuit configured to process a first frequency band of a first communication standard and a second frequency band of a second communication standard. The first frequency band and the second frequency band are close in frequency and/or partially overlapping in frequency. The first RF processing circuit includes a tunable filter for changing the bandwidth of the first RF processing circuit to enhance the robustness of the first RF processing circuit to blocker or jammer signals of a third frequency band.

A power noise filter and a supply modulator including the same, and a wireless communication device including the power noise filter are provided. The power noise filter includes a band stop filter and a low pass filter. The band stop filter includes an inductor and a first capacitor, which are connected in parallel between first and second nodes. The first node receives a first voltage, which is filtered by the band pass filter to thereby generate a second voltage at the second node. The first low pass filter includes the inductor and a second capacitor, which has one end connected to the second node and an opposite end connected to a ground source.

A filter circuit (1) includes a first transmission line (11), a second transmission line (12) which has an electrical length set to ½ of an electrical length of the first transmission line, a first capacitor (21), a second capacitor (22), and a third capacitor (23). Capacitances of the first capacitor, the second capacitor, and the third capacitor are set in such a manner that a circuit including the first transmission line, the second transmission line, and the first capacitor resonates in series at a predetermined fundamental frequency, a circuit including the first transmission line, the first capacitor, and the second capacitor resonates in parallel at a third harmonic frequency being a tripled frequency of the fundamental frequency, and a circuit including the second transmission line and the third capacitor resonates in series at the third harmonic frequency.

A high-power, frequency-tunable, harmonic filtering system for multiple operating frequencies includes a first SPMT switch circuitry, a second SPMT switch circuitry, and high-power, frequency-tunable harmonic filters (HFHFs). The first SPMT single-pole terminal is configured to receive a high-power RF input signal. The second SPMT single-pole terminal is configured to output a high-power RF output signal. Each of the HFHFs is connected to a respective one of the first SPMT multi-throw terminals and a respective one of the second SPMT multi-throw terminals. Each of the HFHFs is interposed between the respective first and second multi-throw terminals along a respective RF signal pathway between them. Each operating frequency is associated with one of the HFHFs. The respective operating frequency is associated with one of multiple cutoff frequencies of the respective HFHF. A frequency response of each of the HFHF is tunable to multiple cutoff frequencies in accordance with selection of respective shunt capacitances selectable under control of a controller.