An oversampling filter oversamples a digital audio signal. A ΔΣ modulator delta-sigma modulates a signal output from the oversampling filter. A D/A converter converts a signal output from the ΔΣ modulator into an analog audio signal. The oversampling filter includes a processor configured to run firmware and a computational algorithm is configurable based on the firmware.

A signal processing structure and method are presented. A first digital filter operates on received sigma-delta modulated (SDM) input signals. A second pre-processing digital filter receives a SDM input signal, directly low pass filter the SDM input signal and provides an output SDM signal. The output sigma-delta modulated signal is provided as an input for said first digital filter. In standard digital systems operating with digital microphones, filtering of the microphones' output signal requires to first convert the signal into pulse code modulation (PCM), then filter and finally convert back to pulse density modulation (PDM). This approach increases the latency of the system because decimation and interpolation must be performed in order to pass from PDM to PCM. By using filters that operate directly on the oversampled PDM output of the digital microphones it is possible to reduce the latency of the system and minimize the hardware area.

Systems and methods are disclosed for a signal convertor comprising a resistor or current source coupled to a positive virtual ground node and a negative virtual ground node, wherein the resistor or current source is configured to switch from the positive virtual ground node (VGP) to the negative virtual ground node (VGN), wherein the switching of the resistor or current source results in a shaping of the low frequency noise from the resistor.

Systems and methods are disclosed for a signal convertor comprising a resistor or current source coupled to a positive virtual ground node and a negative virtual ground node, wherein the resistor or current source is configured to switch from the positive virtual ground node (VGP) to the negative virtual ground node (VGN), wherein the switching of the resistor or current source results in a shaping of the low frequency noise from the resistor.

A radio frequency (RF) transmitter includes a set of input ports to receive baseband samples of a signal to be transmitted on a set of disjoint frequency bands, a set of filter banks, there is one filter bank for each input port, each filter bank includes a plurality of digital polyphase interpolation filters to sample a shifted phase of the corresponding sequence of baseband samples and to interpolate the sampled phases to produce a plurality of sequences of interpolated baseband phased samples with the shifted phase, and a set of oscillators banks, each oscillator bank includes a plurality of polyphase Digital Direct Synthesizer (DDS) corresponding to the plurality of digital polyphase interpolation filters to generate a plurality of sequences of samples of digital waveform. The RF transmitter includes a set of mixer banks to mix corresponding sequences of samples of digital waveform and interpolated baseband phased samples to up convert each sequence of interpolated baseband phased samples to the effective frequency, a parallel digital combiner to combine in-phase sequences of interpolated baseband phased samples of different frequency bands to produce a plurality of sequences of multiband upconverted samples, and a pulse encoder to modulate and encode the plurality of sequences of multiband upconverted samples to produce a plurality of encoded multi-band signals. The RF transmitter converts the plurality of encoded multi-band signals into a RF bitstream and radiate the RF bitstream as an analog signal.

A high-speed digital transmitter for wireless communication systems includes a plurality of transmitter chain circuits configured to respectively receive incoming component signals having a first frequency and to produce outgoing transmission signals having a second frequency greater than the first frequency in a first domain. In some aspects, the incoming component signals are up-sampled to the second frequency using a plurality of streams processed concurrently at a predetermined sample rate over a predetermined number of interpolation filter stages in each of the plurality of transmitter chain circuits. The high-speed digital transmitter also includes a serializer configured to combine the outgoing transmission signals from the plurality of transmitter chain circuits into a serialized transmission signal having a third frequency greater than the second frequency in a second domain different from the first domain.

A radio frequency (RF) transmitter includes a set of input ports to receive baseband samples of a signal to be transmitted on a set of disjoint frequency bands, a set of filter banks, there is one filter bank for each input port, each filter bank includes a plurality of digital polyphase interpolation filters to sample a shifted phase of the corresponding sequence of baseband samples and to interpolate the sampled phases to produce a plurality of sequences of interpolated baseband phased samples with the shifted phase, and a set of oscillators banks, each oscillator bank includes a plurality of polyphase Digital Direct Synthesizer (DDS) corresponding to the plurality of digital polyphase interpolation filters to generate a plurality of sequences of samples of digital waveform. The RF transmitter includes a set of mixer banks to mix corresponding sequences of samples of digital waveform and interpolated baseband phased samples to up convert each sequence of interpolated baseband phased samples to the effective frequency, a parallel digital combiner to combine in-phase sequences of interpolated baseband phased samples of different frequency bands to produce a plurality of sequences of multiband upconverted samples, and a pulse encoder to modulate and encode the plurality of sequences of multiband upconverted samples to produce a plurality of encoded multi-band signals. The RF transmitter converts the plurality of encoded multi-band signals into a RF bitstream and radiate the RF bitstream as an analog signal.

Systems and methods provide architectures for various applications, for example, for software defined radios and other high frequency (HF) application. Embodiments can provide novel multi path ?? architectures that form the basis for novel N path Sigma Delta (N??) modulators, N?? digital to analog converters (N?? DAC) and N?? analog to digital converters (N?? ADC).

A digital-to-analog converter (DAC) circuit includes a first DAC that produces a first analog output signal based upon a received multi-bit digital signal and upon a received clock. A second DAC that produces a second analog output signal based upon the received multi-bit digital signal and upon the received clock, wherein the first and second DACs are connected in parallel and process the same multi-bit digital signal. In one embodiment, the DACs produce differential signals. A low pass filter connected to receive the first and second analog outputs is configured to sum the first and second analog outputs and to filter the summed first and second analog outputs to produce an ingoing analog signal. An amplifier is connected to receive the ingoing analog signal to produce an amplified ingoing analog signal.

The present invention discloses an implementation method and a device of a multi-bit - modulation-based digital speaker system. The method comprises, 1) digital format converting; 2) oversampling interpolation filtering; 3) multi-bit - modulating; 4) thermometer coding; 5) multi-channel mismatch shaping; 6) coding format converting; 7) multi-channel digital power-amplifying; 8) driving a speaker array or a multiple voice coil speaker to sound. The device comprises: a digital input interface, an oversampling interpolation filter, a multi-bit - modulator, a thermometer coder, a multi-channel mismatch shaper, a coding format converter, a multi-channel digital power-amplifier, and a speaker array or a multiple voice coil speaker; each portion being connected in proper order. The present invention can achieve a high-power output under a low-voltage power supply, save power consumption, implement a single-chip integration of a multi-channel reproducing system, reduce the volume and weight of the system and the implementing cost, and improve the quality of the reproduced sound.