Patent Description:
A multitude of signal processing applications involve the conversion of received analog signals into digital values for processing. Such approaches have been widely implemented for successfully processing signals in many different applications. For such applications, converting and otherwise processing the signals accurately can be challenging, in view of which much effort may be put forth in ensuring that the resulting signals are accurate.

One type of ADC involves sigma-delta conversion, in which an analog input signal is sampled and quantized into a digital signal. The digital signal may be processed through unary DACs, with the resulting analog signal added to the input signal to reduce errors in the quantization. However, while this approach has been useful, errors in the DACs and/or otherwise present challenges to providing an accurate analog feedback signal.

These and other matters have presented challenges to efficiencies and accuracy of various signal processing and conversion implementations, for a variety of applications.

The present invention concerns an apparatus for error compensation according to claim <NUM> and a corresponding method for error compensation according to claim <NUM>.

Various example embodiments are directed to issues such as those addressed above and/or others which may become apparent from the following disclosure concerning the processing of signals, and particularly the conversion of analog signals to digital signals.

In certain example embodiments, aspects of the present disclosure involve ascertaining mismatches between respective digital-to-analogue convertor (DAC) circuits, and compensating for the mismatches. Such an approach may, for example, involve determining mismatch values for respective DACs by correlating usage of individual DAC components with a (compensated) output signal of the ADC (e.g., a multi-bit sigma-delta ADC). In this context, each DAC circuit may be part of an overall DAC, with each DAC circuit converting a LSB unit or other portion of a digital signal converted by the overall DAC.

In accordance with one or more aspects of the disclosure, an apparatus for error compensation includes an analog-to-digital converter (ADC) circuit configured and arranged to convert an analog signal into a digital signal, a plurality of digital-to-analog converter (DAC) circuits respectively configured and arranged to convert a portion of the digital signal into an analog signal, and a compensation circuit configured and arranged to correct an output of the ADC circuit. Specifically, the compensation circuit corrects the output by generating, for each DAC circuit, a feedback signal indicative of an incompatibility between an analog output of the DAC circuit, as converted to a digital signal by the ADC circuit, and digital inputs provided to the DAC circuits. Respective gains are applied to the digital inputs from each DAC circuit based on the feedback signal for the corresponding DAC circuit, therein providing modified digital inputs. The corrected output is then generated based on a combination of the digital signal output from the ADC and the modified digital inputs to the respective DAC circuits.

Another aspect of the disclosure is directed to a method for error compensation in an analog-to-digital converter (ADC) circuit having a digital-to-analog converter (DAC) circuit that generates an analog signal used in converting an analog input signal to a digital signal. For each respective LSB unit of a digital signal converted by the DAC circuit, a feedback signal is generated and that is indicative of a mismatch between an analog output of the DAC circuit, as converted to a digital signal by the ADC circuit, and a digital signal input to the DAC circuits. A gain is applied to the unit of the digital signal converted by the DAC circuit based on the feedback signal. Errors in the DAC circuit are compensated using the respective bits of the digital signal with the gain applied thereto.

Another aspect of the disclosure is directed to an apparatus for estimating and correcting errors in an analog-to-digital converter (ADC) circuit. The apparatus includes a plurality of variable gain circuits respectively configured and arranged to apply a gain to a portion of a signal provided to a digital-to-analog converter (DAC) circuit based on feedback signals for the respective portions of the signal. A feedback circuit is configured and arranged to generate the respective feedback signals for each DAC circuit, each feedback signal being based on an output of the DAC circuit for which it is provided and an input signal provided to the DAC circuit. An output circuit is configured and arranged to correct the output of the ADC circuit using the respective outputs of the variable gain circuits.

On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the appended claims.

Aspects of the present disclosure are believed to be applicable to a variety of different types of apparatuses, systems and methods involving signal processing, as may be applicable to a multitude of disparate types of communications. In certain implementations, aspects of the present disclosure have been shown to be beneficial when used in the context of radio communications, such as those utilized in automobiles and other vehicles, and in these and other applications that may employ sigma-delta ADCs. In some embodiments, signals converted from analog to digital form are processed to provide feedback and related correction to facilitate characterization and correction of mismatch, error or other processing aspects. While not necessarily so limited, various aspects may be appreciated through the following discussion of non-limiting examples which use exemplary contexts.

Various embodiments are directed to improving signal processing in an ADC such as a delta-sigma ADC. An analog signal is sampled and quantized into a digital signal and delta modulated (encoding the voltage or current of the input signal). A corresponding signal (e.g., the digital signal or a corresponding thermometer code used in generating the digital signal) is passed through one or more <NUM>-bit DACs. The resulting analog feedback signal from the DACs is subtracted (delta) to the input analog signal at it is being processed (a sigma operation can be carried out in a loop filter, which may include integrators (sigma)). As part of this process, feedback is generated and provided to the signal corresponding to respective outputs of the DACs, which accounts for mismatch across the respective DACs and improves the resulting signal that is subtracted from the input analog signal.

As used herein, a DAC may involve respective units (e.g., circuits) therein, with mismatch between the units being estimated and compensated for. For example, a <NUM>-bit quantizer can be used, with the <NUM>-bit value being encoded into a <NUM>-bit code that provides an indication of how the DAC-units are configured.

In the following description, various specific details are set forth to describe specific examples presented herein. It should be apparent to one skilled in the art, however, that one or more other examples and/or variations of these examples may be practiced without all the specific details given below. In other instances, well known features have not been described in detail so as not to obscure the description of the examples herein. For ease of illustration, the same reference numerals may be used in different diagrams to refer to the same elements or additional instances of the same element. Also, although aspects and features may in some cases be described in individual figures, it will be appreciated that features from one figure or embodiment can be combined with features of another figure or embodiment even though the combination is not explicitly shown or explicitly described as a combination.

Various embodiments are directed toward circuitry and related methods involving the conversion of analog signals to digital signals. Such embodiments may, for example, involve a sigma-delta (SD) analog to digital converter (ADC). An analog loopfilter with transfer "H" may be fed with a signal obtained by subtracting the main analog input signal and a feedback signal generated by a digital to analog converter (DAC). The output of the loopfilter may be sampled and quantized at a high sampling rate. The quantizer resolution may be generally low, such as <NUM> binary bits, and the quantizer may produce a multi-bit (e.g., <NUM>-bit) thermometer coded output. The thermometer code is shuffled by a random control signal (e.g., pseudo-random signal), resulting in a scrambled thermometer code "D[<NUM>:<NUM>]. " In a more particular embodiment, the value of the summed thermometer coded bits is equal to the sum of elements at the output of the quantizer. The digital representation for Dx is <NUM>'s and <NUM>'s, in which a binary <NUM> is represented by -<NUM>, while a binary <NUM> is represented by +<NUM>. The combined output Y can be computed by: <MAT> where D<NUM>, D<NUM> and D<NUM> are respective bit outputs of the DAC. The shuffled data is converted to the analog domain by the DAC, which may include three unit elements (circuits) each having unit element value "u. " Such unit elements may, for example, be implemented as a respective DAC circuit that, together, form the bit outputs of the DAC. Each unit can be activated as +u or -u, depending on D[<NUM>:<NUM>]. The outputs of the three unit elements are combined before they are subtracted from the input signal.

Each DAC element may have a certain mismatch compared to their desired value u. The mismatches are represented by ε[<NUM>:<NUM>]. The output frequency domain representation for Y of this sigma date loop equals: <MAT> <MAT> The last term is the error caused by static DAC mismatch, which can be corrected for by adding a term with the opposite value. The transfer function, <MAT> may be constant for frequencies which are the band of interest. In that case, the error term can be compensated for when there is a way to extract the errors ε[<NUM>:<NUM>], knowing D[<NUM>:<NUM>]. Multiplying the combined output signal Y with the individual D[<NUM>:<NUM>] produces: <MAT> <MAT> <MAT>.

Since Dx is either +<NUM> or -<NUM>, Dx<NUM> = <NUM>. Assuming that probabilities P(D0,=<NUM>), P(D1=<NUM>) and P(D2=<NUM>) are equal (e.g., guaranteed by the shuffle control signal): <MAT> Then, the following holds for the first term in the Y·Dx equations: <MAT> This means the same average value can be subtracted from each error signal.

For the <MAT>, the average values may not be same, since Qe may depend on the DAC-element that was chosen. <MAT> contains mainly high-frequency content, since it is filtered by the NTF of the modulator. By low-pass-filtering Y such that the high frequency noise is suppressed, <MAT>, which limits the contribution of <MAT> to the error signal. The last term in the error signal contains DAC element error information, modulated by the data signals D[<NUM>:<NUM>] and filtered by the STF. There are three errors (ε[<NUM>:<NUM>]) that are estimated to correct the DAC mismatches. It is possible to linearize the <NUM>-element DAC with two variables. This simplifies the problem; one variable is eliminated by enforcing the following restriction: <MAT>.

This may result in a DAC gain error which may be corrected. From Equation <NUM>, the following can be derived: <MAT> With this simplification, the last term of Equation <NUM>, it can be simplified to <MAT> When Y is low-pass filtered, such that term (Qe· Dx)/(<NUM>+u·H) can be neglected, together with Equation <NUM> and Equation <NUM>, Equation <NUM>, Equation <NUM> and Equation <NUM> can be approximated for low frequencies as (Dx · Dy parts are averaged values): <MAT> <MAT> <MAT>.

The second term in Equation <NUM> is a measure for DAC-element error ε<NUM>, since Dx<NUM> = <NUM>, and the average of Dx · Dy is typically smaller than <NUM>. Same holds for the other equations for ε<NUM> and ε<NUM>. The remaining first term is identical for all three equations, so if we subtract the average of the three error signals, this term is eliminated.

As may be implemented in accordance with one of the above example embodiments and/or on or more other example embodiments, an apparatus and or method involves an analog-to-digital converter (ADC) circuit configured and arranged to convert an analog signal into a digital signal, and a plurality of digital-to-analog converter (DAC) circuits, each DAC circuit being configured and arranged to convert a portion of a digital signal into an analog signal. A compensation circuit is configured and arranged to generate a compensation output by, for the output of each DAC circuit, generating a feedback signal based on an indication of an incompatibility between the analog conversion of the digital signal and a signal corresponding to a combined output of an analog conversion by all of the DAC circuits. A gain is applied to a digital signal corresponding to an input to each DAC circuit, based on the feedback signal, and the compensation output is generated based on a digital signal output by the ADC circuit and the modified digital signal (with the gain applied thereto). In some embodiments, different gains are applied to different ones of the inputs to the DAC circuits, each gain being tailored to the mismatch of the output of the DAC circuit relative to the output of the other DAC circuits. In certain implementations, the ADC circuit generates quantized bits, which are also used in providing the corrected output.

The compensation circuit may be implemented in a variety of manners, using a variety of components. In some implementations, the DAC input signal is generated by combining the digital inputs to the DACs with the digital output of the ADC to produce the corrected output. For each respective component of the corrected output that correspond to a particular unit of the DACs, the respective component is multiplied with the modified digital input for the particular one of the DACs. An averaged product of the DACs is generated by combining the product of the multiplying with the product of the multiplying of the other components of the corrected outputs that correspond to other ones of the DACs to provide a combined product, and dividing the combined product by a total number of the DACs. The averaged product is then subtracted from the product of the multiplying and the feedback signal for the particular one of the DACs is generated based upon the difference. In certain implementations, the average value is subtracted from the feedback signal after integration. Further, the compensation circuit may, for example, include a variable gain amplifier and feedback circuit configured to apply a variable gain to the digital input used for generating the feedback signal for each respective digital input.

In certain embodiments, the feedback signal is generated by combining the digital inputs to the DACs with the digital output of the ADC to produce the corrected output. For each respective component of the corrected output that corresponds to a particular one of the DACs, the respective component is multiplied with the modified digital input for the particular one of the DACs. The feedback signal may also be generated by subtracting an averaged value corresponding to the digital inputs provided to all of the DACs. The result of the subtracting may further be combined with the feedback signal. The feedback signal may also be generated by setting a variable gain for the DAC circuit to compensate for analog conversion of the portion of the digital signal to which the variable gain is being applied.

In some embodiments, the ADC circuit converts the analog signal into the digital <NUM> signal with quantized bits. The DAC circuits convert, for each quantized bit, a corresponding quantized bit into an analog value. The compensation circuit generates the feedback signal based on an indication of an incompatibility between the analog conversion of the quantized bit and a combination of quantized bits provided as inputs to the DAC circuits, and applies the gain to each quantized bit provided as inputs to the DAC circuits, based on the feedback signal. The corrected output is generated based on the quantized bits that are modified with the respective gains applied thereto. In this context, the feedback signal may be generated by subtracting, for respective values corresponding to each DAC circuit, an averaged value corresponding to the digital outputs of all of the DACs. The feedback signal may also be generated by combining the result of the subtracting with the feedback signal. Further, different gain values may be applied to different ones of the quantized bits provided to the respective DAC circuits, each gain value being tailored to the mismatch of an output of the ADC circuit relative to a corresponding input to the DAC circuits.

In connection with one or more embodiments, the input signal to the DACs as characterized herein may be generated using a variety of approaches. In some instances, quantized bits provided are generated and randomized as inputs to the plurality of DAC circuits. In other embodiments, the input signal is generated from and/or based on the output of the ADC.

Various methods may be implemented in accordance with the apparatuses characterized herein above. Further, such methods may be implemented with the apparatuses shown in the figures and characterized below.

Turning now to the figures, <FIG> shows an apparatus <NUM> as may be implemented in accordance with one or more embodiments. The apparatus <NUM> includes a plurality of DAC units (<NUM>-N), with two DACs <NUM> and <NUM> shown for simplicity. Each DAC receives a digital input, as may correspond to an analog signal being processed by an ADC <NUM>. The outputs of the respective DACs are combined at ADC <NUM> and used with an analog input signal to generate a digital output that is used for feedback. Specifically, the digital input to DAC <NUM> is combined with the output of the ADC at block <NUM>, the digital input to DAC <NUM> is combined with the output of the ADC at block <NUM>, and the respective outputs of the combining at blocks <NUM> and <NUM> are averaged at block <NUM> and utilized to generate a feedback signal at each of blocks <NUM> and <NUM>. The respective feedback signals are provided to a combining circuit <NUM>, which applies a gain to the respective digital inputs and combines the inputs with the gain applied thereto with the output of the ADC to provide a corrected output.

<FIG> shows an apparatus <NUM>, which may be utilized for DAC error estimation and compensation, in accordance with one or more embodiments. The apparatus includes a DAC block <NUM>, which generates respective output bits that are processed with an applied feedback gain at <NUM> to provide a corrected output. Blocks <NUM> and <NUM> are utilized to generate the respective feedback gain signals provided for each DAC output. Referring to the upper DAC output for DAC1, the output is passed to filter <NUM> and low-pass filtered (e.g., to attenuate the <MAT> terms). Each DAC element is filtered individually, so the DAC correction can be done after filtering. A variable gain circuit <NUM> operates to apply a gain factor to the filtered output, which may correct for DAC errors. The gain values may be <NUM>+ estimated DAC errors. The gain-corrected outputs of the DACs are added together at <NUM> to compose a corrected output signal.

The DAC output signals are delayed "(z-?)" as shown at block <NUM>, to compensate for delay in the low-pass filter. Multipliers (including <NUM>) multiply the compensated output (low-pass filtered, corrected Y) with the individual DAC outputs. This leads to the error indicator values from Equation <NUM>, Equation <NUM> and Equation <NUM> (Y· Dx) as noted above. These error indicators contain part of the input signal times STF (transfer function), and on average may be the same for all three indicators. The average of the three error signals is generated at <NUM> and <NUM> (e.g., added and divided by three), and then subtracted from each error indicator as shown at <NUM>. What is left is (on average) the last term of Equation <NUM>, Equation <NUM> and Equation <NUM>, which are indicators of the error values. Three individual first order control loops with integrator circuitry (<NUM>, <NUM>, <NUM>) minimize these error values by adapting the error correction actuators, and provide an output that is fed back to the variable gain circuits, such as at <NUM>, and used to provide the corrected output from adder <NUM> (e.g., as an ADC input).

<FIG> is a flow diagram for an approach to converting analog signals to digital signals and related error compensation, as may be implemented in accordance with one or more embodiments. At block <NUM>, a digital signal is converted to an analog signal at multiple DACs. An input analog signal is converted signal in an ADC at block <NUM>, using the analog output from the multiple DACs. At block <NUM>, a feedback signal is generated based on input signals provided to the DACs and mismatches indicated in the output of the ADC, which correspond to an analog mismatch in an output of the DACs. A gain is applied to signals corresponding to those provided as inputs to the DACs at block <NUM>. This thus provides a modified signal corresponding to the actual input to the DACs as modified to account for errors in the operation of the DACs to convert the actual input into an analog signal. At block <NUM>, the output of the ADC is corrected using the modified signal. This output may, for example, be provided for use at block <NUM>, as shown via the arrow in the figure.

<FIG> shows another apparatus <NUM>, for compensating for errors in an ADC. The apparatus <NUM> includes a <NUM>-bit (<NUM>-level) DAC <NUM> that is steered with a <NUM>-bits thermometer code D[<NUM>:<NUM>] provided to a random selector circuit <NUM>, such as by using a pseudorandom binary sequence (PRBS). Static DAC element errors are indicated by εp/n0[<NUM>:<NUM>]. The D[<NUM>:<NUM>] thermometer code may be generated internally or provided as an input from an external source. The following <NUM>-bits codes in Table <NUM> can be generated with the associated DAC output levels:.

The levels -<NUM>*e and +<NUM>*e can be made in three ways, based on random selection, resulting in D*[<NUM>:<NUM>]. The output of the DAC is combined with an analog input signal and provided to an analog transfer function circuit <NUM>, which may be partly linear or non-linear, and includes an ADC circuit. The digital output of the analog transfer function circuit is provided along with the D*[<NUM>:<NUM>] output of the random selector circuit <NUM> as inputs for a DAC element estimation and correction circuit <NUM>, which may operate as noted above to provide correction relative to respective values generated in the DAC <NUM>.

<FIG> shows a DAC element estimation and correction circuit <NUM>, in accordance with another example embodiment. Individual bits D*[<NUM>:<NUM>] are multiplied with <NUM> +/- a correction factor, where the correction factors may compensate for εp/n0[<NUM>:<NUM>] errors. The corrected values are combined with an input <NUM> generated by an analog to digital conversion circuit, using a digital combining function/circuit <NUM>. In this context, the circuit <NUM> may be implemented for circuit <NUM> in <FIG>, with the input D*[<NUM>:<NUM>] provided by random selection circuit <NUM> and the input <NUM> provided by the analog transfer function circuit <NUM>. The output of the combining function Ycor is the corrected output and may be used for further processing.

In some implementations, a filter circuit <NUM> filters the output Ycor using a pass-band range tuned such that DAC-errors are deteriorating the performance in the pass-band frequency range. The output of this filter is correlated (using multipliers <NUM>, <NUM> and <NUM>) with the individual D*[<NUM>:<NUM>] bits (which may be delayed via delay circuit <NUM> to accommodate for delay in the optional filter and HA(s)). The filter circuit <NUM> and delay circuit <NUM> may be swapped.

The outputs of the correlators <NUM>, <NUM> and <NUM> provide a measure of how one single DAC element influences a combined output signal. There may be a strong correlation, since the corrected output Ycor is (partly) constructed from D*[<NUM>:<NUM>]. This correlation may be (on average) common for each correlator output, since the DAC element selection is pseudo random. This common correlation can be removed by subtracting the average output value from each correlator output, with the average output value being generated at <NUM> and <NUM> and subtraction respectively carried out for correlations <NUM>, <NUM> and <NUM> at <NUM>, <NUM> and <NUM>. The output of the correlators <NUM>, <NUM> and <NUM> (with common correlation subtracted) are fed to integrators with a small integrator gain. The integrator outputs are used to steer the correction factors which multiply with D*[<NUM>:<NUM>]. When the integrators have settled, the correction values should be such that all correlator outputs are 'balanced' on average, so there is on average no difference between the correlator outputs.

<FIG> shows another apparatus <NUM> for correcting ADC errors, in accordance with another example embodiment. The apparatus <NUM> is similar to apparatus <NUM> of <FIG>, with a DAC <NUM>, random selector circuit <NUM>, an analog transfer function circuit <NUM>, and a DAC element estimation and correction circuit <NUM>. The analog transfer function circuit <NUM> includes summations node, where the DAC signal is subtracted from the input signal, followed by an analog loop filter, the output of which is quantized. Typically, the quantizer has a relatively low resolution. The resolution for a certain frequency band can be increased by an oversampled quantizer clock and a filter transfer of the loop filter. Any error in the feedback will result in a <NUM>-on-<NUM> error on the digital output. In this sigma-delta case, D*[<NUM>:<NUM>] can be used as the actual digital output signal (uncompensated).

<FIG> shows a DAC element estimation and correction circuit <NUM>, in accordance with another example embodiment. The circuit <NUM> may, for example, be implemented for a sigma-delta case such as via circuit <NUM> in <FIG>, and in a manner similar to that shown and described with <FIG> (with similarly numbered componentry). Corrected values are combined with an input <NUM> generated by an analog to digital conversion circuit, using a digital combining function/circuit <NUM>. The circuit <NUM> further includes optional filter circuit <NUM> and delay circuit <NUM>, with the filter circuit filtering the output Ycor which is correlated with the individual D*[<NUM>:<NUM>] bits using multipliers <NUM>, <NUM> and <NUM>. The average output value from each correlator output is generated at <NUM>/<NUM> and subtracted respectively from the output of correlators <NUM>, <NUM> and <NUM> at <NUM>, <NUM> and <NUM>, and provided to integrators <NUM>. The integrator outputs are used to steer the correction factors which multiply with D*[<NUM>:<NUM>].

In some embodiments involving a sigma-delta application, both inputs to the digital combining function/circuit <NUM> are D*[<NUM>:<NUM>], utilizing the compensated output and ignoring input <NUM>. The compensated signal is filtered in such an instance, due to quantization noise. The Band-pass or low-pass filter filters the quantization noise out. In certain implementations, strong signals are filtered, mitigating reductions in convergence accuracy of the error estimation system that may occur due to strong signals. This approach may improve estimation accuracy, and with that the convergence speed.

<FIG> shows another apparatus <NUM> for correcting ADC errors, in accordance with another example embodiment. The apparatus <NUM> is also similar to apparatus <NUM> of <FIG>, with a DAC <NUM>, random selector circuit <NUM>, analog transfer function circuit (with an ADC) <NUM>, and a DAC element estimation and correction circuit <NUM>. An analog input signal is quantized to the digital domain in two steps, first via coarse digitization at block <NUM> (e.g., into <NUM> levels), and via fine digitization at analog transfer function circuit <NUM>. A resulting digital code is subtracted from the input signal via DAC <NUM> and a subtractor <NUM>, and is quantized further with a fine ADC <NUM>. An output code is constructed by adding the coarse ADC code and fine ADC code, within the DAC element estimation and correction circuit <NUM>. In some implementations, the linearity of the fine ADC is relaxed, since the input signal is small (despite being visible in the resulting output code).

<FIG> shows another DAC element estimation and correction circuit <NUM>, in accordance with another example embodiment. The circuit <NUM> may, for example, be implemented as circuit <NUM> in <FIG>, and in a manner similar to that shown and described with <FIG> and with similarly numbered componentry. Digital combining function/circuit <NUM> combines input <NUM> with corrected input D[<NUM>:<NUM>], multipliers <NUM>, <NUM> and <NUM> correlate the output Ycor with the inputs. The correlated outputs are averaged via averaging circuitry <NUM>/<NUM>, with the average being subtracted from the correlated outputs by subtracting circuitry <NUM>, <NUM> and <NUM>, the output of which is provided to integrators <NUM> to provide respective feedback signals for compensating each respective input component as shown. When implemented with <FIG>, the coarse codes can be calibrated with variable gains before adding the coarse code with the fine code.

Terms to exemplify orientation, such as upper/lower, left/right, top/bottom and above/below, may be used herein to refer to relative positions of elements as shown in the figures. It should be understood that the terminology is used for notational convenience only and that in actual use the disclosed structures may be oriented different from the orientation shown in the figures. Thus, the terms should not be construed in a limiting manner.

The skilled artisan would recognize that various terminology as used in the specification (including claims) connote a plain meaning in the art unless otherwise indicated. As examples, the specification describes and/or illustrates aspects useful for implementing the claimed disclosure by way of various circuits or circuitry which may be illustrated as or using terms such as blocks, modules, device, system, unit, controller, converter, integrator, and/or other circuit-type depictions (e.g., reference numerals <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> of <FIG>, depict a block/module as described herein). Such circuits or circuitry are used together with other elements to exemplify how certain embodiments may be carried out in the form or structures, steps, functions, operations, activities, etc. For example, in certain of the above-discussed embodiments, one or more modules are discrete logic circuits or programmable logic circuits configured and arranged for implementing these operations/activities, as may be carried out in the approaches shown in <FIG>. In certain embodiments, such a programmable circuit is one or more computer circuits, including memory circuitry for storing and accessing a program to be executed as a set (or sets) of instructions (and/or to be used as configuration data to define how the programmable circuit is to perform), and an algorithm or process as described in connection with error estimation herein, such as shown in and described in connection with <FIG>, is used by the programmable circuit to perform the related steps, functions, operations, activities, etc. Depending on the application, the instructions (and/or configuration data) can be configured for implementation in logic circuitry, with the instructions (whether characterized in the form of object code, firmware or software) stored in and accessible from a memory (circuit). As another example, where the specification may make reference to a "first [type of structure]", a "second [type of structure]", etc., where the [type of structure] might be replaced with terms such as ["circuit", "circuitry" and others], the adjectives "first" and "second" are not used to connote any description of the structure or to provide any substantive meaning; rather, such adjectives are merely used for English-language antecedence to differentiate one such similarly-named structure from another similarly-named structure (e.g., "first circuit configured to combine. " is interpreted as "circuit configured to combine.

Claim 1:
An apparatus (<NUM>) for error compensation, the apparatus (<NUM>) comprising:
an analog-to-digital converter circuit, ADC, (<NUM>) configured and arranged to convert an analog signal applied at the input of the ADC into a digital signal (<NUM>; <NUM>; <NUM>) at the output of the ADC;
a plurality of digital-to-analog converter circuits, DACs, (<NUM>, <NUM>), each DAC (<NUM>, <NUM>) being configured and arranged to convert a respective portion of a scrambled thermometer code (D*[<NUM>:<NUM>]) that is generated as a result of shuffling a thermometer code corresponding to the signal (<NUM>, <NUM>, <NUM>) at the output of the ADC (<NUM>) and which is applied at the digital input of the DAC (<NUM>, <NUM>) into a respective analog signal at the output of the DAC (<NUM>, <NUM>); and
a compensation circuit (<NUM>; <NUM>; <NUM>; <NUM>) configured and arranged to correct the digital signal (<NUM>; <NUM>; <NUM>) at the output of the ADC (<NUM>) by:
for each DAC (<NUM>, <NUM>), generating a respective feedback signal indicative of a mismatch between the respective analog signal at the output of the DAC (<NUM>, <NUM>), as converted to a corresponding digital signal by the ADC (<NUM>), and the respective portion of the scrambled thermometer code (D*[<NUM>:<NUM>]) provided to the DAC (<NUM>, <NUM>);
for each DAC (<NUM>, <NUM>), applying a respective gain to the digital input to the DAC (<NUM>, <NUM>) based on the respective feedback signal for the DAC (<NUM>, <NUM>), therein providing a respective modified digital signal; and
generating a corrected output (Ycor) based on a combination of the digital signal (<NUM>; <NUM>; <NUM>) at the output of the ADC (<NUM>) and the respective modified digital signals of each DAC (<NUM>, <NUM>); (<NUM>, <NUM>);
wherein the generation of the respective feedback signal includes:
for each DAC (<NUM>, <NUM>) generating a respective correlation of the respective portion of the scrambled thermometer code (D*[<NUM>:<NUM>]) provided to the DAC (<NUM>, <NUM>) with the corrected output (Ycor),
for each DAC (<NUM>, <NUM>) subtracting an averaged value corresponding to the average of the respective correlations of all DACs (<NUM>, <NUM>) from the respective correlation of the DAC (<NUM>, <NUM>) to obtain a respective correlation with the common correlation subtracted,
for each DAC (<NUM>, <NUM>) generating the respective feedback signal based on the respective correlation with the common correlation subtracted.