A filter including a piezoelectric substrate; a surface acoustic wave (SAW) device on the piezoelectric substrate and including unequally spaced interdigitated input and output transducer electrodes of unequal widths, wherein the input transducer electrodes are to convert an incoming radio frequency (RF) electrical signal into surface acoustic waves; a SAW propagation path between the input and output transducer electrodes; and a magnetostrictive film in the SAW propagation path to filter the surface acoustic waves that are at a ferromagnetic resonance frequency of the magnetostrictive film, wherein the output transducer electrodes are to convert the filtered surface acoustic waves into an outgoing electrical RF signal. The SAW device may operate in a wide-band pass configuration. The wide-band pass configuration result in a transmission of frequencies up to 60 dB. The magnetostrictive film may include a ferromagnetic material. The interdigitated input and output transducer electrodes may include unequal widths between adjacent electrodes.

Embodiments of resonator circuits and modulating resonators and are described generally herein. One or more acoustic wave resonators may be coupled in series or parallel to generate tunable filters. One or more acoustic wave resonances may be modulated by one or more capacitors or tunable capacitors. One or more acoustic wave modules may also be switchable in a filter. Other embodiments may be described and claimed.

In one aspect, a time division interleaving band-pass filter can be used in voice activity detection, which operates at different central frequencies in respective intervals of a predetermined period of time. The band-pass filter circuitry includes multiple band-pass filtering channels sharing a common transistor circuit, bias circuit and current mirror circuit. The multiple band-pass filtering channels operate in a time division interleaving manner, which enables the sharing of the common set of band-pass filter circuitry components. Thus, the present invention allows a reduced chip area as the area does not increase proportionally with the number of filtering channels. The invention also mitigates the influence of transistor fabrication variations on the filter's central frequencies. Moreover, pulse durations t.sub.i are additionally introduced to the determination of the central frequencies, dispensing with the need for matching of current mirror circuits and transistors and resulting in higher accuracy of the band-pass filter's central frequencies.

An apparatus and method of removing common mode noise in the case of measuring a biosignal using a capacitive coupling active electrode (CCE) is provided. A frequency band of a common mode signal may interact with a shield voltage and thus, a frequency band of a biosignal may be compensated for.

Embodiments of resonator circuits and modulating resonators and are described generally herein. One or more acoustic wave resonators may be coupled in series or parallel to generate tunable filters. One or more acoustic wave resonances may be modulated by one or more capacitors or tunable capacitors. One or more acoustic wave modules may also be switchable in a filter. Other embodiments may be described and claimed.

A novel and useful high-order discrete-time charge rotating (CR) infinite impulse response (IIR) low pass filter is presented. The filter utilizes history capacitor arrays incorporating banks of capacitors. A linear interpolation technique is used in the IIR filter with second order antialiasing filtering, whose transfer function is sinc(x).sup.2 per stage. It also uses a g.sub.m cell, rather than operational amplifiers, and is thus compatible with digital nanoscale technology. A 7.sup.th-order charge-sampling discrete time filter is disclosed. The order of the filter is easily extendable to higher orders. The charge rotating filter is process scalable with Moore's law and amenable to digital nanoscale CMOS technology. Bandwidth of the filter is precise and robust to PVT variation. The filter exhibits very low power consumption per filter pole, low input-referred noise, wide tuning range, excellent linearity and low area per minimum bandwidth and filter pole.

In a system comprising a plurality of gain elements configured in parallel to one another, a harmonically tuned filter provides an isolation circuit to prevent odd-mode differential oscillations. A harmonically tuned filter comprises resistors, inductors, and capacitors (RLC) to selectively allow one or more specific harmonics to pass through the isolation circuit to suppress the odd-mode oscillation. Direct current (DC) and other non-harmonically-related frequencies do not pass through the isolation circuit. Since the resistor is used to dissipate specifically the energy of the harmonic frequencies causing the odd-mode oscillation, the current density through the resistor is much lower than the current density of a typical odd-mode resistor without a harmonically tuned filter.

Embodiments of resonator circuits and modulating resonators and are described generally herein. One or more acoustic wave resonators may be coupled in series or parallel to generate tunable filters. One or more acoustic wave resonances may be modulated by one or more capacitors or tunable capacitors. One or more acoustic wave modules may also be switchable in a filter. Other embodiments may be described and claimed.

The trans-filter compresses in band AWGN, demodulates input signals and has no threshold due to applied noise. Two frequency selective networks with opposite amplitude vs frequency slopes are designed to remain 180 degrees out of phase over the signal band. Output amplitudes are equal at band center and are summed producing a monotonic amplitude vs frequency characteristic going thru zero at center frequency with abrupt phase reversal. This produces the parabolic output noise density and differentiates applied signals. Absence of nonlinear circuit components and product devices prevents generation of noisenoise products, avoiding the threshold phenomenon. Exponentially modulated digital signals produce output impulses due to the slope and abrupt phase reversal. The impulses have strong fundamental frequency components and may be recovered at baseband without frequency conversion. Cascading trans-filters increases noise reduction and impulse amplitude. The trans-filter algorithm may be used separately or in conjunction with one or more hardware trans-filters.

An apparatus is disclosed that includes a frequency multiplexer circuit coupled to an input node and configured to receive an input signal via the input node. The frequency multiplexer circuit comprises a first filter circuit, a second filter circuit, and a third filter circuit. The apparatus also includes a switching circuit that is configurable to couple at least two of a first output of the first filter circuit, a second output of the second filter circuit, or a third output of the third filter circuit to a single output port.