Analog-to-digital converters (ADCs) can be used inside ADC architectures, such as delta-sigma ADCs. The error in such internal ADCs can degrade performance. To calibrate the errors in an internal ADC, comparator offsets of the internal ADC can be estimated by computing a mean of each comparator of the internal ADC. Relative differences in the computed means serves as estimates for comparator offsets. If signal paths in the internal ADC are shuffled, the estimation of comparator offsets can be performed in the background without interrupting normal operation. Shuffling of signal paths may introduce systematic measurement errors, which can be measured and reversed to improve the estimation of comparator offsets.

To convert a first stage input to a digital output, a delta-sigma modulator, an analog-to-digital converter and an associated signal conversion method based on an MASH structure are provided. The analog-to-digital converter includes the delta-sigma modulator and a sample and hold circuit. The delta-sigma modulator includes a first signal converter, a second signal converter and a digital cancellation logic. The first signal converter converts the first stage input to a first converted output. The first signal converter shapes a first stage quantization error to generate a second stage input. The first stage input and the second stage input are analog signals. The second signal converter converts the second stage input to a second converted output. The digital cancellation logic generates a digital output according to the first converted output and the second converted output.

Provided, among other things, is an apparatus for digitally processing a discrete-time signal that includes: an input line for accepting an input signal, processing branches coupled to the input line, and an adder coupled to outputs of the processing branches. First and second lowpass filters, each having a frequency response with a magnitude that varies approximately with frequency according to a product of raised functions, are included within baseband processors in such processing branches.

Systems and methods are provided for analog-to-digital conversion (ADC). A first quantization stage may be configured to receive an analog input signal and sample the analog input signal to generate a first digital signal, the first quantization stage may be further configured to filter the first digital signal with a first noise-shaping transfer function to generate a first noise-shaped digital output and to generate a quantization error signal based on a comparison of the analog input signal and the first noise-shaped digital output. A voltage controlled oscillator (VCO)-based second quantization stage may be configured to receive the quantization error signal and sample the quantization error signal to generate a second digital signal, the VCO-based second quantization stage may be further configured to filter the second digital signal with a second noise-shaping transfer function to generate a second noise-shaped digital output. A first digital filter may be configured to filter the first noise-shaped digital output with an equivalent signal transfer function of the VCO-based second quantization stage to generate a first stage digital output. A second digital filter may be configured to filter the second noise-shaped digital output with the first noise-shaping transfer function to generate a second stage digital output with second order noise-shaping characteristics A combination circuit may combine the first stage digital output and the second stage digital output to generate a digital ADC output signal with second order noise shaping characteristics.

A time-to-digital converter includes: an input for receiving a time-domain input signal; an output for providing a digital output signal; a time register coupled to the input and to a first node; a time quantizer coupled to the time register for providing the digital output signal at the output; and a digital-to-time converter coupled to the output for providing a feed-back signal at the first node.

A built-in self-test (BIST) circuit is provided for testing an analog-to-digital converter (ADC). A multi-order sigma-delta (ΣΔ) modulator has an input that receives an input signal, a first output generating analog test signal derived from the input signal and applied to an input of the ADC and a second output generating a binary data stream. A digital recombination and filtering circuit has a first input that receives the binary data stream and a second input that receives a digital test signal output from the ADC in response to the analog test signal. The digital recombination and filtering circuit combines and filters the binary data stream and digital test signal to generate a digital result signal including a signal component derived from an error introduced by operation of the ADC. A correlation circuit is used to isolate that error signal component.

An analog/digital converter (ADC) includes an analog stage with at least one first sigma-delta modulator and includes a digital stage with at least one second sigma-delta modulator. The analog stage is configured for outputting a digital signal to the digital stage that is indicative of a noise contribution of the at least one first sigma-delta modulator. The analog stage and the digital stage may be arranged in a multi-stage noise shaping architecture (MASH) architecture.

The present invention provides a fractional-N frequency synthesizer comprising a divider controller comprising a multistage noise Shaping (MASH) digital delta-sigma modulator comprising L stages, wherein the jth stage is configured to receive as an input the sum of the error of the preceding stage and a high amplitude dither signal derived from the error of the kth stage, where 1≤j≤k≤L.

Provided is an AD converter, including: an analog signal input circuit, configured to be input with an analog input signal, and output a first analog output signal based on the analog input signal and a second analog output signal based on the analog input signal at different timing; an integral circuit, configured to integrate the first analog output signal and the second analog output signal and output the first integral signal and the second integral signal; a predictive circuit, configured to predict an integral signal output after the output by the integral circuit based on the first integral signal and the second integral signal output by the integral circuit, and output a predictive integral signal; and a quantization circuit, configured to generate a digital signal with the predictive integral signal quantized.

An instrument configured to process signal data is disclosed. The instrument is operable to control and or change the sampling rate of the signal data from a first sample rate to a second sample rate different than the first sample rate.