A pop sound suppression method, an audio output circuit, and a terminal suppress a pop sound that is generated when an audio output circuit is in an alternating current (AC) coupling structure. The output circuit includes an output power amplifier, a common-mode voltage buffer, a reference voltage generation circuit, a powered-on pop sound suppression switch, and a common-mode switch. The powered-on pop sound suppression switch is configured to control, in a power-on process of the audio output circuit, a voltage level of an output node to be zero. The common-mode switch is configured to control, when a reference voltage level of the reference voltage generation circuit is zero, the voltage level of the output node to be equal to the reference level.

A pop sound suppression method, an audio output circuit, and a terminal suppress a pop sound that is generated when an audio output circuit is in an alternating current (AC) coupling structure. The output circuit includes an output power amplifier, a common-mode voltage buffer, a reference voltage generation circuit, a powered-on pop sound suppression switch, and a common-mode switch. The powered-on pop sound suppression switch is configured to control, in a power-on process of the audio output circuit, a voltage level of an output node to be zero. The common-mode switch is configured to control, when a reference voltage level of the reference voltage generation circuit is zero, the voltage level of the output node to be equal to the reference level.

Systems and methods for suppressing transient outputs from an amplifier system are provided. An amplifier having a plurality of bias levels may be controlled to initiate a change in the level of a bias signal provided to the amplifier. The level of the bias signal is ramped from an initial bias level to a final bias level over numerous steps. The steps include at least one step in which the level of the bias signal is between the initial bias level and the final bias level. An amplifier system having multiple stages may be controlled to enable each stage and selectively couple each stage in a sequence that couples an output stage to an output terminal at the completion of the sequence.

Systems and methods for suppressing transient outputs from an amplifier system are provided. An amplifier having a plurality of bias levels may be controlled to initiate a change in the level of a bias signal provided to the amplifier. The level of the bias signal is ramped from an initial bias level to a final bias level over numerous steps. The steps include at least one step in which the level of the bias signal is between the initial bias level and the final bias level. An amplifier system having multiple stages may be controlled to enable each stage and selectively couple each stage in a sequence that couples an output stage to an output terminal at the completion of the sequence.

One example includes a digital communications converter. The converter includes at least one analog signal port configured to couple to at least one radiating element associated with an antenna structure coupled to an exterior surface of a vehicle. The at least one analog signal port can be configured to at least one of transmit and receive analog radio frequency (RF) signals respectively to and from the at least one radiating element. The converter also includes a digital interface configured to at least one of receive the analog RF signals or transmit the analog RF signals via the respective at least one analog signal port. The converter is also configured to convert between the analog RF signals and digital communication signals on a digital transmission medium that are at least one of transmitted to the digital communications converter via a digital communications cable and transmitted from the digital communications converter via the digital communications cable.

One example includes a digital communications converter. The converter includes at least one analog signal port configured to couple to at least one radiating element associated with an antenna structure coupled to an exterior surface of a vehicle. The at least one analog signal port can be configured to at least one of transmit and receive analog radio frequency (RF) signals respectively to and from the at least one radiating element. The converter also includes a digital interface configured to at least one of receive the analog RF signals or transmit the analog RF signals via the respective at least one analog signal port. The converter is also configured to convert between the analog RF signals and digital communication signals on a digital transmission medium that are at least one of transmitted to the digital communications converter via a digital communications cable and transmitted from the digital communications converter via the digital communications cable.

A transceiver system compensates for baseline wandering in an analog signal in the analog stage before sampling the analog signal and processing the analog signal in the digital stage. The transceiver system includes an analog to digital converter that samples the analog signal after baseline wandering compensation, a digital equalizer to condition the digital samples, and the slicer to determine transmitted symbols from the digital samples. The transceiver system includes a subtraction block that determines the difference between an input and an output of the slicer, a digital to analog converter that converts a difference between the input and the output of the slicer, a low pass filter that filters out high frequency components of the difference between the input and the output of the slicer thereby to extract out the baseline wandering, and a signal summation circuit that subtracts the baseline wandering from the analog signal.

The present invention proposes an audio signal muting apparatus setting and adjusting a time for removing pop noise and muting an audio signal based on the set and adjusted timing. Further, the present invention proposes a digital signal converting apparatus for muting an analog audio signal based on a timing for removing pop noise when converting a digital audio signal into an analog audio signal in connection with an audio signal reproducing apparatus.

Due to strong needs to reduce the dimensions and the cost of the RF filters and to reduce the number of filters required in an mobile handsets and wireless system covering numbers of operation bands, tunable RF filters which can cover as many bands or frequency ranges as possible are needed so that the number of filters can be reduced in the mobile handsets and wireless systems. The present invention provides tunable surface acoustic wave (SAW) IDT structures with the resonant frequency of the acoustic wave to be excited and to be transmitted tuned by digital to analog converters (DACs). The DAC converts an input digital signal to an output DC voltage and provide DC bias voltages to the SAW IDTs through integrated thin film biasing resistors. The polarity and the value of the output DC voltage are controlled by the input digital signal to achieve selection and tuning of the resonant frequency of the SAW IDTs.

Due to strong needs to reduce the dimensions and the cost of the RF filters and to reduce the number of filters required in an mobile handsets and wireless system covering numbers of operation bands, tunable RF filters which can cover as many bands or frequency ranges as possible are needed so that the number of filters can be reduced in the mobile handsets and wireless systems. The present invention provides tunable surface acoustic wave (SAW) IDT structures with the resonant frequency of the acoustic wave to be excited and to be transmitted tuned by digital to analog converters (DACs). The DAC converts an input digital signal to an output DC voltage and provide DC bias voltages to the SAW IDTs through integrated thin film biasing resistors. The polarity and the value of the output DC voltage are controlled by the input digital signal to achieve selection and tuning of the resonant frequency of the SAW IDTs.