Abstract: A single chip receiver is disclosed herein. The chip only requires an external antenna for operation. A decoder is formed on chip for performing logical operations on demodulated digital data. A baseband filter is controlled by external control signals to have one of a plurality of discrete frequency response bandwidths depending on the type of signal to be received. To compensate for process variations in the implementation of the IC, bias currents setting the operating conditions for various amplifiers and other components in the system are adjusted based on frequency control signals in a PLL circuit in the local oscillator. Since the magnitude of the control signal reflects the process variations, the bias currents are adjusted based on the control signal to offset these variations in other portions of the receiver.

Abstract: An apparatus and method for processing a digital broadcast signal are provided. The method includes cutting off a noise frequency of a received digital broadcast signal and low-noise amplifying the noise cut-off signal, limiting an amplitude of the low-noise amplified signal spectrum to an amplitude of the digital broadcast signal spectrum, and cutting off a noise frequency of the amplitude limited signal spectrum and passing only a signal corresponding to a frequency band of the digital broadcast signal.

Abstract: A receiver apparatus includes a band-pass filter having a variable frequency band coupled to a node for receiving a received signal including a plurality of channels to output at an output node thereof a limited-band signal made by limiting a frequency band of the received signal to a frequency band of a desired channel, a frequency conversion unit coupled to the output node of the band-pass filter to output at an output node thereof an intermediate frequency signal made by converting frequencies of the limited-band signal, and a control unit configured to adjust an intermediate frequency of the intermediate frequency signal by controlling the frequency conversion unit in response to at least one of a signal speed and a channel frequency interval of the received signal.

Abstract: A semiconductor device interconnecting unit configured to input/output a high-frequency signal having a millimeter wave band to/from a semiconductor device is provided. The semiconductor or device interconnecting unit includes a part of a band pass filter configured to pass therethrough the high-frequency signal having a millimeter wave band by using an LC resonance circuit, and a remainder of the band pass filter, wherein the part and the remainder are separated from each other. The part is provided inside the semiconductor device, and the remainder is provided outside the semiconductor device. The part and the remainder include capacitors having variable capacitors added thereto, respectively. A pass band for the high-frequency signal having a millimeter wave band is changed by changing capacitance values of the variable capacitors.

Abstract: The present invention receives simultaneously RF signal of different frequency band and processes the RF signal received, at this time a BPS receiver minimizes aliasing generated by RF signal. The present invention comprises a sampling process unit which samples a signal summing a first RF signal and a second RF signal of different frequency bands with time gap, a quantization process unit which generates a first stream signal and a second stream signal, a digital signal down-converted through respective time information in the signal summing the first RF signal and the second RF signal and a signal process unit which performs FIR filtering with reference to phase shift for a respect frequency band of the first stream signal and the second stream signal, separates the first RF signal and the second RF signal based on a result of the performance.

Abstract: In one embodiment, the present invention includes a method for receiving a radio frequency (RF) signal and mixing the RF signal with a master clock to obtain a mixed signal, cyclically rotating the mixed signal to each of N gain stages for at least one cycle of the master clock, and summing the outputs of the N gain stages to provide an output signal.

Abstract: An FM receiver that is suitable for reducing a transmission bandwidth WF of a bandpass filter to remove adjacent-channel interference, and increasing WF to prevent audio distortion. A detection output signal SOUT is inputted to an HPF 122 when a reception electric field strength signal SM-DC indicates an intermediate or stronger electric field. In a weak electric field, an AC component signal SM-AC, which is extracted from an intermediate signal SIF1 prior to detection and which has fewer high-pass noise components than SOUT, is inputted to the HPF 122. A control circuit 120 detects a case as an adjacent-channel interference state when a large amount of high-pass components passes through the HPF 122, and reduces WF of an IFBPF 70 in order to remove adjacent-channel interference. When a small amount of high-pass components is transmitted, WF is increased in order to minimize audio distortion.

Abstract: Systems for delivering a plurality of broadcast programs where the transmitter and receiver roll-off factors are mismatched. A system in accordance with the present invention comprises a transmitter comprising a modulator, and a plurality of receivers, each receiver in the plurality of receivers receiving the plurality of broadcast programs, each receiver in the plurality of receivers further comprising a demodulator; wherein the modulator has a first root-raised cosine filter having a first roll-off factor and each receiver has a second root-raised cosine filter having a second roll-off factor, the first roll-off factor being smaller than the second roll-off factor.

Abstract: An integrated circuit includes an on-chip filter component that forms a programmable bandpass filter with the at least one off-chip bandpass filter component. The programmable bandpass filter is programmable based on a control signal. An RF receiver generates inbound data in response to a received signal from the programmable bandpass filter.

Abstract: A receiving apparatus is provided. The receiving apparatus comprises a chip carrier including at least one stack of layers, wherein at least one layer in the stack supports radio frequency transmission lines, tunable bandpass filters, wherein each bandpass filter is integrated within an associated radio frequency transmission line, and at least one integrated micro-chip on the chip carrier. The at least one integrated micro-chip couples selected bandwidth regions of received broadband radio frequency signals to the tunable bandpass filters via the associated radio frequency transmission line. The at least one integrated micro-chip outputs each filtered selected bandwidth region to an associated one of a plurality of intermediate frequency modules.

Abstract: A multiple stage band pass filter of a Radio Frequency (RF) Integrated Circuit is provided with a low pass mixer output filter coupled to receive a down sampled analog information signal, a buffer coupled to an output of the low pass mixer output filter, a low pass buffer output filter coupled to an output of the buffer and a plurality of band pass filters coupled to an output of the low pass buffer output filter.

Abstract: The present invention is an RF filter that translates impedances of an IF circuit to create a filter with an RF center frequency having the high Q roll-off characteristics of an IF filter. The RF filter is self-aligned with the frequency of an RF local oscillator. The RF filter has an impedance divider, which is formed by coupling an RF impedance circuit to a translated IF impedance circuit. The translated IF impedance circuit includes an RF passive mixer and an IF impedance circuit. The mixer translates the impedance of the IF impedance circuit by mixing an RF input signal with an RF local oscillator signal, which determines the RF center frequency. Filtered RF signals may be provided by the impedance divider. Filtered IF signals may be provided by the IF impedance circuit. To effectively translate and preserve the IF impedance characteristics, the IF impedance circuit presents a high impedance at harmonics of the RF local oscillator signal.

Abstract: A system for detecting and minimizing interference in a radio receiver includes a plurality of bandpass filters having different response characteristics, a power detector configured to compare a power output of a first bandpass filter and a second bandpass filter, and logic to cascade a third bandpass filter when the difference in power output between the power output of the first bandpass filter and the power output of the second bandpass filter exceeds a threshold amount.

Abstract: An integrated circuit includes a dual-conversion tuner, firstly upconverting so as to place a signal outside the reception band, then downconverting with zero intermediate frequency. A bulk acoustic wave type filter is calibrated in such a way as to accurately determine its central frequency. This filter is positioned between the two frequency transposition stages of the tuner. After baseband filtering, the signals are digitized then processed in a digital block BNM which includes a channel decoding module.

Abstract: In the receive subsystem, the analogue-to-digital converter (40) works on the output of the low-noise amplifier (33), at a chosen rate (F), which corresponds to a bandwidth sampling. The processing stages comprise a custom circuit (5) with * an input memory (510) arranged to contain N successive digital samples, renewed at the chosen rate in blocks of M samples, * a complex digital low-pass filtering function (511, 512), of chosen cut-off frequency, operating on the input memory to supply N filtered digital samples, * an M-periodic summing function (531) on the N filtered digital samples, supplying M filtered and summed digital samples (533), * an M1M discrete Fourier transform stage (55), operating on these M filtered and summed digital samples, the digital signals on the M outputs (559) of the Fourier transform representing M separate channels, of width defined by the cut-off frequency of the abovementioned low-pass filter.

Abstract: In one embodiment, the present invention includes a mixer circuit to receive and generate a mixed signal from a radio frequency (RF) signal and a master clock signal, a switch stage coupled to an output of the mixer circuit to rotatingly switch the mixed signal to multiple gain stages coupled to the switch stage, and a combiner to combine an output of the gain stages.

Abstract: An integrated front-end filter for a tuner provides an array of from several to a multitude of passbands, each for passing at least one but less than all channels designated in a band of frequencies. Each passband is exclusively selectable. The integrated front end filter includes at least one active filter unit with an active reactance element in either of fixed and variable filter configurations and a decoder coupled to said at least one active filter unit and being responsive to a control signal for selecting a one of the passbands. In one example a multitude of active filter units of fixed filter configuration provide the multitude of passbands. Each data is stored at a predetermined location and reproduced in response to a corresponding control data signal from a tuner controller. Each data characterizes one of the plurality of passbands. The filter element is switchable from one passband to another in response to the control data signal.

Abstract: A radio-frequency (RF) apparatus, which may reside in a receiver or transceiver, includes receive-path circuitry. The receive-path circuitry includes a poly-phase filter and a harmonic filter. The poly-phase filter accepts an input signal and generates two output signals. One output signal of the poly-phase filter constitutes an in-phase (I) signal. The other output signal of the poly-phase filter constitutes a quadrature (Q) signal. The a harmonic filter couples to the poly-phase filter. The harmonic filter accepts as input signals the in-phase and quadrature output signals of the poly-phase filter.

Abstract: A direct conversion satellite tuner is fully integrated on a common substrate. The integrated tuner receives an RF signal having a plurality of channels and down-converts a selected channel directly to baseband for further processing. The integrated tuner includes on-chip local oscillator generation, tunable baseband filters, and DC Offset cancellation. The integrated tuner can be implemented in a completely differential I/Q configuration for improved electrical performance. The entire direct conversion satellite tuner can be fabricated on a single semiconductor substrate using standard CMOS processing, with minimal off-chip components. The tuner configuration described herein is not limited to processing TV signals, and can be utilized to down-convert other RF signals to an IF frequency or baseband.

Abstract: The frequency of an RF signal to be transmitted is modulated at the transmitting unit, and the modulation information is used by the receiving unit to filter out any unwanted noise. The modulation information may be used to retrieve associated filter coefficients that are used by the receiver to filter out the noise. Accordingly, for each transmit frequency, a multitude of filter coefficients stored in a memory are applied by the receiver to filter out the noise. The filtering operation may be performed after the received signal is downconverted from an RF to an audio signal.

Abstract: A system and method are presented for transceiving Time Division Multiple Access (TDMA) telephone communications through a common filter. The system includes a tunable ferro-electric bandpass filter (FE BPF), a controller, a low noise amplifier (LNA), and a power amplifier (PA). The FE BPF has a control input to accept tuning voltage signals from the controller and two signal ports. In response to the tuning voltage signals, the FE BPF selects a transmit or receive frequency passband between the signal ports. The FE BPF first signal port is connected to the LNA and the PA and the FE BPF second signal port is connected to an antenna in a wireless device. The LNA and PA are activated and deactivated in response to control signals from the controller.

Abstract: An apparatus includes a filter module, an amplification module, and an adjustment signal source. The filter module generates a filtered signal based on a received signal. This filtered signal has a level shift corresponding to a difference between a direct current (DC) level of the filtered signal and a DC level of the received signal. From the filtered signal and an adjustment signal, the amplification module generates an amplified signal. The adjustment signal, which is provided by the adjustment signal source, may control (e.g., diminish) an effect of the level shift on a DC level of the amplified signal.

Abstract: An integrated circuit includes an on-chip antenna interface, coupled to an off-chip antenna interface having at least one off-chip filter component that forms a programmable filter with the at least one off-chip filter component. The programmable filter is programmable based on a control signal. An RF receiver generates inbound data in response to a received signal from the programmable filter.

Abstract: Disclosed herein are systems and methods for recovering a sub-carrier signal from a multiplexed signal having an embedded pilot tone signal. The recovery system includes circuitry for recovering a pilot signal from the received multiplexed signal, for generating a frequency-doubled signal from the recovered pilot signal, and for phase-shifting the frequency-doubled signal by a pre-determined phase difference from the embedded pilot tone signal. Another recovery system includes circuitry for recovering a pilot signal from the received multiplexed signal, for phase-shifting the pilot signal by a pre-determined phase difference from the embedded pilot tone signal, and for generating a frequency-doubled signal from the phase-shifted signal.

Abstract: Various embodiments are directed to removing interfering signals in a broadband radio frequency (RF) receiver by implementing a silicon tuner arranged to replicate high quality factor (Q) performance without the advantages of using high Q components available for module tuners. In one or more embodiments, tuned filter elements within a broadband silicon tuner are reused to maximize the attenuation of unwanted signals while minimizing induced undesirable channel ripple. In various implementations, a number of tuned passive inductor/capacitor filter elements are combined as required such that filter elements for an unused frequency band are reconfigured to provide attenuation of and enhanced immunity to unwanted signals. Other embodiments are described and claimed.

Abstract: A high frequency signal selected via a pre-filter is inputted to first and second frequency conversion circuits together with a local oscillation signal. The first and second frequency conversion circuits each output a difference frequency component between both input signals. An output signal of the first frequency conversion circuit is inputted to an intermediate frequency filter while an output of the intermediate frequency filter is inputted to an amplifier. An output signal of the first frequency conversion circuit is inputted to an amplifier. The amplifier selects and amplifies any one of an intermediate frequency signal outputted from the intermediate frequency signal and an output signal of the second frequency conversion circuit, and thereafter, output it.

Abstract: Embodiments of an active bandpass filter are described. Such a filter includes a transistor; a series-tuned inductive-capacitive (LC) network (STLCN) in a common source circuit associated with the transistor to produce a tuned degenerative filtering of at least one interfering signal; and a first, variable resistance associated with the STLCN to provide a first control of a resonance quality factor (Q) associated with the filter. Other embodiments may be described and claimed.

Abstract: The present invention provides systems and methods for pre-filter in a VHF receiver using Micro-Electro-Mechanical Systems (MEMS) filters. The system includes an antenna, and first and second Micro-Electro-Mechanical Systems (MEMS) filters. The first MEMS filter filters a signal received by the antenna based on a first pre-defined bandwidth, and the second MEMS filter filters the signal filtered by the first MEMS filter based on a second bandwidth. The system also includes an analog to digital converter that converts the signal filtered by the second MEMS filter into a digital signal, a down converter that down converts the digital signal produced by the A to D converter, and a digital signal processor that processes the down converted digital signal produced by the down converter. The first and second MEMS filters or the down converter are adjustable based on a received tuning signal.

Abstract: A band pass filter includes a first micro-strip port for receiving a radio-frequency signal, a second micro-strip port for outputting a filtered radio-frequency signal and comprising at least one resonating cavity formed for enhancing rejecting effect of image frequency corresponding to the filtered radio-frequency signal, and a plurality of resonators arranged between the first micro-strip port and the second micro-strip port for performing band pass filtering on the radio-frequency signal to generate the filtered radio-frequency signal.

Abstract: An RF signal filter/resonator includes a core of dielectric material having top, bottom, and side surfaces. At least one through-hole extends through the core. In one embodiment, the core defines first and second alignment/coupling elements formed on the core for aligning and coupling the filter on and to another coupling element or structure such as a printed circuit board. In one embodiment, the alignment/coupling elements are first and second spaced-apart tabs of different configuration which protrude outwardly from one of the side surfaces, are adapted to be fitted in complementarily configured slots in the printed circuit board, and define respective RF signal input/output pads. In another embodiment, the tabs protrude outwardly from the top surface of the core.

Abstract: An embodiment of a baseband filter in a transmitter subsystem of a wireless device comprises an operational amplifier (op-amp), a pole circuit, a feedback capacitor, and an active device. The op-amp is adapted to produce an amplified signal that includes noise gain produced by the op-amp. The pole circuit is electrically coupled with an output terminal of the op-amp, and is adapted to receive the amplified signal and to attenuate the noise gain to produce a filtered, amplified signal. The feedback capacitor is electrically coupled between the first pole circuit and an input terminal of the op-amp, and is adapted to compensate for a phase shift produced by the pole circuit. The active device is electrically coupled with the pole circuit, and is adapted to amplify the filtered, amplified signal and to produce a baseband filtered output signal.

Abstract: A surface acoustic wave (SAW) expander based transmitter and correlator based receiver comprises SAW devices that perform expander or correlator functions based on the types of signals inputted to the SAW devices. The SAW devices incorporate chirp with adaptive interference and programmable coding capabilities. The SAW devices and method of operating the devices allow the implementation of very low power radios that overcome problems with temperature drift, lithography constraints and interference and jamming suffered by prior art implementations.

Abstract: A switched capacitor narrow band pass filter includes a first switch including a first pole movable between two first switch terminals, a second switch including a second pole moveable between second switch terminals, and a third switch including additional poles movable between third switch terminals. The filter further includes an effective capacitor coupled to the first pole and a plurality of matchinq capacitors coupled respectively to the second and third switch terminals. The additional poles are coupled to the third switch terminals according to a first predetermined sequence and to the third switch terminals at a predetermined frequency. A differential amplifier assembly includes two positive and two negative terminals coupled to the additional poles in a second predetermined sequence wherein two of the additional poles are coupled to the positive terminals and two others of the additional poles are coupled to the negative terminals for signal summation.

Abstract: A downconverter and upconverter are provided which can obtain a sufficient image rejection ratio in a low-Intermediate Frequency (IF) scheme while reducing power consumption and can suppress Error Vector Magnitude (EVM)-related degradation in a zero-IF scheme. A complex-coefficient transversal filter rejects one side of a positive or negative frequency, and converts a Radio Frequency (RF) signal to a complex RF signal configured by real and imaginary parts. A local oscillator outputs a real local signal with a set frequency. A half-complex mixer, connected to the complex-coefficient transversal filter and the local oscillator, performs a frequency conversion process by multiplying the complex RF signal output from the complex-coefficient transversal filter and the real local signal output from the local oscillator, and outputs a complex signal of a frequency separated by the set frequency from a frequency of the RF signal.

Abstract: A heterodyne receiving circuit for a digital communication system including a first band pass filter receiving a signal from an antenna, an amplifying circuit and a second narrow band pass filter for selecting one particular channel within a band of frequencies. The two filters are carried out with integrated BAW-type tunable resonators which can be adjusted, respectively, by a first electrical signal and a second electrical signal generated by two PLL-type frequency control loops. The second frequency control loop has a variable division factor for the purpose of selecting one particular channel within said band of frequencies. In addition, the receiving circuit includes a mixer for mixing the signal generated at the output of said second filter with a local oscillation frequency in order to produce an intermediate frequency. The division factor is controlled by a digital processing of the intermediate frequency.

Abstract: A radio frequency tuner comprises one or more tracking filters ahead of at least one frequency changer. A controller has a filter alignment mode and a reception mode. Each filter has one or more resonant networks comprising an inductance and a switched capacitor network which is digitally controlled for selecting the network resonant frequency. In the alignment mode, the controller determines the difference between the nominal and actual capacitances of the network for achieving a known resonant frequency in order to determine a correction factor for the capacitor network. The correction factor is then used during normal reception by the tuner.

Abstract: A tunable bandpass filter (10) is provided. An RF signal is provided at an input of the tunable bandpass filter, and a level shifted control signal (V1, V2) inputted to the tunable bandpass filter (10) switches a first arrangement and a second arrangement of one or more tuning portions (15, 17-1, 17-2, 17-3) in or out of the tunable bandpass filter using a GaAs FET switch. The first arrangement is coupled to the second arrangement using an inductor (13). An RF signal having a desired predetermined frequency at an output of the tunable bandpass filter (10) is produced by the switching. The tuning portions include the GaAs FET switch (15), a first capacitor (17-1) connected at a first signal terminal of the GaAs FET switch and a second capacitor (17-2) connected between a second signal terminal of the GaAs FET switch and ground. Each of the tuning portions can be arranged in parallel with one another.

Abstract: A double conversion tuner system is disclosed that avoids the problem of degraded performance as a result of radiated interferers. Several selection criteria are described for specifying the parameters of the tuner, including the nominal first or high intermediate frequency, a first local oscillator signal for each desired channel, a nominal second local oscillator signal, and a bandwidth of the first intermediate frequency.

Abstract: An integrated circuit chip include a transmitter configured for transmitting an electromagnetic signal, a receiver configured for receiving an electromagnetic signal, and an amplifier operatively coupled to the receiver. The amplifier includes a plurality of variable-gain Gm-C filter stages connected in series and configured for selectively amplifying frequency components within a frequency bandwidth of the received electromagnetic signal.

Abstract: A multimode communication device with a shared signal path programmable filter and a method for utilizing a shared signal path programmable filter in a multimode communication device. Various aspects of the present invention comprise a first module adapted to receive a first communication signal (e.g., corresponding to a first communication protocol) and a second module adapted to receive a second communication signal (e.g., corresponding to a second communication protocol). A shared filter, communicatively coupled to the first and second modules, may be adapted to filter the first and/or second communication signals in accordance with a plurality of selectable sets of filter response characteristics (e.g., associated with the first and second communication protocols). A filter control module may be adapted to select a set of filter response characteristics from a plurality of such sets and program the shared filter to filter a communication signal in accordance with the selected set.

Abstract: According to various exemplary embodiments, apparatus, systems, and methods are disclosed for use with antenna systems operable for receiving first and second signals having respective first and second frequencies. In one exemplary embodiment, a controller selectively controls whether an amplifier is electrically powered via a first receiver associated with the first frequency or a second receiver associated with the second frequency depending on whether the first receiver, second receiver, or both are present and activated.

Abstract: A multiple stage band pass filter of a Radio Frequency (RF) Integrated Circuit is provided with a low pass mixer output filter coupled to receive a down sampled analog information signal, a buffer coupled to an output of the low pass mixer output filter, a low pass buffer output filter coupled to an output of the buffer and a plurality of band pass filters coupled to an output of the low pass buffer output filter.

Abstract: A tunable bandpass filter (10) is provided. An RF signal is provided at an input of the tunable bandpass filter, and a level shifted control signal (V1, V2) inputted to the tunable bandpass filter (10) switches a first arrangement and a second arrangement of one or more tuning portions (15, 17-1, 17-2, 17-3) in or out of the tunable bandpass filter using a GaAs FET switch. The first arrangement is coupled to the second arrangement using an inductor (13). An RF signal having a desired predetermined frequency at an output of the tunable bandpass filter (10) is produced by the switching. The tuning portions include the GaAs FET switch (15), a first capacitor (17-1) connected at a first signal terminal of the GaAs FET switch and a second capacitor (17-2) connected between a second signal terminal of the GaAs FET switch and ground. Each of the tuning portions can be arranged in parallel with one another.

Abstract: A method and circuit for amplifying and demodulating amplitude-modulated signals is disclosed that amplifies a primary signal into an amplified signal, bandpass filters the amplified signal into a filtered signal, compares the filtered signal with a regulation threshold and regulates the gain of the primary signal such that peak values of the filtered signal approach the regulation threshold, compares the filtered signal with a signal threshold, and demodulates the result of the comparison. Whereby a value of the signal threshold is smaller than a value of the regulation threshold.

Abstract: An electrical circuit has at least two parallel signal paths connected to one another on the antenna side and for which a band reject filter corresponding to the transmission range is implemented in a second signal path for frequency-selective improvement of insertion loss in the transmission range of a first signal path. With a band reject filter, the signal is reflected to the junction of the parallel signal paths arising from the second signal path and thus is rerouted to the first signal path.

Abstract: A surface acoustic wave filter element has a piezoelectric substrate; and a plurality of inter-digital transducer (IDT) electrodes formed on the piezoelectric substrate, wherein at least one of the plurality of IDT electrodes is connected to a balanced type terminal and other IDT electrodes are connected to balanced type terminals or unbalanced type terminals, and first wiring electrode means which is connected or to be connected to the at least one IDT electrode and second wiring electrode means which is connected or to be connected to the other IDT electrodes are disposed on planes different from each other.

Abstract: According to a disclosed method, a calibration signal is provided at a first frequency corresponding to a low frequency edge of a desired passband to an input of a filter (240). A first value is measured at an output of the filter (240). The calibration signal is provided at a second frequency corresponding to a high frequency edge of the desired passband to the input of the filter (240). A second value is measured at the output of the filter (240). The first value is compared to the second value. A characteristic of the filter (240) is changed in response to the comparing. In one form, the filter is an IF filter (240) and a receiver (200) includes both the IF filter (240) and a calibration circuit (250) for forming the calibration signal and providing the calibration signal to the IF filter to change the characteristic in response to a calibration operation.

Abstract: A tunable bandpass filter (10) is provided. An RF signal is provided at an input of the tunable bandpass filter, and a level shifted control signal (V1, V2) inputted to the tunable bandpass filter (10) switches a first arrangement and a second arrangement of one or more tuning portions (15, 17-1, 17-2, 17-3) in or out of the tunable bandpass filter using a GaAs FET switch. The first arrangement is coupled to the second arrangement using an inductor (13). An RF signal having a desired predetermined frequency at an output of the tunable bandpass filter (10) is produced by the switching. The tuning portions include the GaAs FET switch (15), a first capacitor (17-1) connected at a first signal terminal of the GaAs FET switch and a second capacitor (17-2) connected between a second signal terminal of the GaAs FET switch and ground. Each of the tuning portions can be arranged in parallel with one another.

Abstract: Comfort noise is derived from a white noise signal by filtering the white noise signal in a QMF bank to produce comfort noise signal that is selectively coupled to at least one channel in a telephone. Preferably, a plurality of QMF banks are used and the magnitude of the white noise into each filter is controlled in accordance with the magnitude of the signal in a corresponding analysis sub-band in a channel. In accordance with another aspect of the invention, the signals from higher frequency analysis sub-bands are combined and control a single input to a QMF bank, thereby increasing the low frequency resolution of the comfort noise. In accordance with another aspect of the invention, the QMF banks are cascaded upwardly (the output of one bank is coupled to the low pass input of the next bank), which also enhances the low frequency resolution of the comfort noise.

Abstract: An unconditionally stable on-chip filter includes a filtering section and at least one negative resistance module. The filtering section is operably coupled to filter a signal and includes realizable integrated circuit passive components. The at least one negative resistance module is operably coupled to compensate for integrated circuit losses of the filtering section. The realizable integrated circuit passive components have values that are robust, in comparison to parasitic values, have minimal integrated circuit real estate, and provide realizable values for various integrated circuit manufacturing processes including CMOS technology.