Abstract: A centrifugal blower is described herein. The centrifugal blower may be a belt-driven geared centrifugal blower. The centrifugal blower may comprise an impeller, an inlet, and an outlet. The impeller pulls air in through the inlet, compresses and speeds up the air, and directs the air out the outlet. A motor may power a pulley system coupled to the belt that, in turn, drives a gear set. The gear set then drives the impeller. A mounting frame for the centrifugal blower may comprise a plurality of mounting holes for increasing the airflow to the gear set for cooling there. A belt tensioner may be coupled to the pulley system for setting a preload in the pulley system. An adjustment system for adjusting the tension provided by the belt tensioner is disclosed.

Abstract: A centrifugal blower is described herein. The centrifugal blower may be a belt-driven geared centrifugal blower. The centrifugal blower may comprise an impeller, an inlet, and an outlet. The impeller pulls air in through the inlet, compresses and speeds up the air, and directs the air out the outlet. A motor may power a pulley system coupled to the belt that, in turn, drives a gear set. The gear set then drives the impeller. A mounting frame for the centrifugal blower may comprise a plurality of mounting holes for increasing the airflow to the gear set for cooling there. A belt tensioner may be coupled to the pulley system for setting a preload in the pulley system. An adjustment system for adjusting the tension provided by the belt tensioner is disclosed.

Abstract: In accordance with some embodiments of the present disclosure, a circuit comprises an input node configured to receive a current-mode input signal and an input stage that includes an input device communicatively coupled to the input node. The input device is configured to receive the input signal at the input node. The circuit additionally comprises bias circuitry communicatively coupled to the input stage and configured to provide a bias current for the input device. The bias circuitry is also configured to remove at least a portion of the bias current from the input signal through a feedback loop associated with the input node such that the input signal is received by the input device with at least a portion of the bias current removed. The circuit further comprises an output stage communicatively coupled to the input stage and configured to output a current-mode output signal based on the input signal.

Abstract: In accordance with some embodiments of the present disclosure, a circuit comprises an input node configured to receive a current-mode input signal and an input stage that includes an input device communicatively coupled to the input node. The input device is configured to receive the input signal at the input node. The circuit additionally comprises bias circuitry communicatively coupled to the input stage and configured to provide a bias current for the input device. The bias circuitry is also configured to remove at least a portion of the bias current from the input signal through a feedback loop associated with the input node such that the input signal is received by the input device with at least a portion of the bias current removed. The circuit further comprises an output stage communicatively coupled to the input stage and configured to output a current-mode output signal based on the input signal.

Abstract: In accordance with some embodiments of the present disclosure, a method for tuning a semi-digital finite impulse response (sFIR) filter comprises coupling a switch between an output of a shift register element associated with an input of the sFIR filter and a resistor coupled to an output of the sFIR filter. The shift register element and the resistor are associated with a tap of the sFIR filter. The method further comprising at least one of closing the switch according to a control signal to couple the resistor with the output of the shift register element such that a tap is added to the sFIR filter and opening the switch according to the control signal to decouple the resistor from the output of the shift register element such that a tap is subtracted from the sFIR filter to tune the corner frequency of the sFIR filter.

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: 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: Methods and corresponding systems for calibrating a digital-to-analog converter include selecting first and second code regions in the digital-to-analog converter, wherein the first and second code regions are separated by a boundary. Thereafter a waveform sequence is input into the digital-to-analog converter, wherein the waveform sequence has a zero offset at the boundary. Then a relative compensation value between the first and second code regions is adjusted to reduce a distortion in an output of the digital-to-analog converter. A magnitude of a third harmonic distortion of the waveform sequence can be used to measure distortion in the output. Adjusting the relative compensation can include converting the output of the digital-to-analog converter to a digital sequence, filtering the digital sequence, and measuring a harmonic distortion in the digital sequence.

Abstract: Methods and corresponding systems for calibrating a digital-to-analog converter include selecting first and second code regions in the digital-to-analog converter, wherein the first and second code regions are separated by a boundary. Thereafter a waveform sequence is input into the digital-to-analog converter, wherein the waveform sequence has a zero offset at the boundary. Then a relative compensation value between the first and second code regions is adjusted to reduce a distortion in an output of the digital-to-analog converter. A magnitude of a third harmonic distortion of the waveform sequence can be used to measure distortion in the output. Adjusting the relative compensation can include converting the output of the digital-to-analog converter to a digital sequence, filtering the digital sequence, and measuring a harmonic distortion in the digital sequence.

Abstract: A cordless telephone has receive (12) and transmit (14) signal paths for passing voice signals. Sidetones normally appear in the receive signal path from the near party's voice. A signal strength comparator (34) monitors the transmit signal path and the receive signal path and asserts a gain control signal when the transmit path signal strength exceeds a threshold set to a predetermined value below the receive path signal strength. The gain control signal decreases the gain (42) in the receive signal path to reduce undesirably loud sidetones in the speaker earpiece. When the transmit path signal strength is less than the predetermined threshold, the gain control signal is not asserted allowing maximum amplification in the receive signal path as the sidetone is sufficiently small as to not interfere with the main received voice signal, or otherwise become noticeably loud in the speaker earpiece.

Abstract: A variable gain control circuit (10) provides an output signal having a gain dependent on first (34) and second (52) reference current sources. An amplifier circuit (14, 20) generates first and second dynamic control voltages that control current flow through an input stage (30) referenced to the first reference current source. The dynamic control voltages produce similar currents in an output stage (32) referenced to the second reference current source. The dynamic control voltages to the input and output stage allow the variable gain amplifier circuit to operate with low power supply potentials which is especially useful in battery applications.