# Sunder S. Kidambi, Austin US

## Sunder S. Kidambi, Austin, TX US

Patent application number | Description | Published |
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20100164763 | ERROR ESTIMATION AND CORRECTION IN A TWO-CHANNEL TIME-INTERLEAVED ANALOG-TO-DIGITAL CONVERTER - A two-channel time-interleaved analog-to-digital converter (TIADC) system that provides for estimation and correction of offset, gain, and sample-time errors. Error in the offsets of the two ADCs that form the TIADC produces a spurious signal at the Nyquist frequency that can be used to minimize the difference of offsets of the ADCs. The difference in gain between the two ADCs produces spurious signals reflected around the Nyquist frequency whose magnitudes can be reduced by minimizing the difference in signal power between the two ADCs. An Automatic Gain Control loop corrects the scaling of the input signal due to the average of the gains of the ADCs. Phase error produces spurious signals reflected around the Nyquist frequency that are π/2 out of phase with those due to the gain error. Minimizing the difference between the correlation of consecutive signals from the ADCs reduces the magnitude of these image tones. | 07-01-2010 |

20100253557 | CALIBRATION OF OFFSET, GAIN AND PHASE ERRORS IN M-CHANNEL TIME-INTERLEAVED ANALOG-TO-DIGITAL CONVERTERS - Techniques for correcting component mismatches in an M-channel time-interleaved Analog to Digital Converter (ADC). In order to obtain an error measure for offset, gain or phase, errors, outputs from each ADC are either summed or averaged over N | 10-07-2010 |

20110063149 | CALIBRATION OF OFFSET, GAIN AND PHASE ERRORS IN M-CHANNEL TIME-INTERLEAVED ANALOG-TO-DIGITAL CONVERTERS - Techniques for correcting component mismatches in an M-channel time-interleaved Analog to Digital Converter (ADC). In order to obtain an error measure for offset, gain or phase, errors, outputs from each ADC are either summed or averaged over N | 03-17-2011 |

20110128175 | Sampling Method For Time-Interleaved Data Converters In Frequency-Multiplexed Communications Systems - A wide band analog-to-digital converter used in a frequency multiplexed communication system. The converter includes a plurality, M, of time-interleaved analog-to-digital converter subunits (ADC subunits). The sampling rate, FS | 06-02-2011 |

20110199096 | CORRECTION OF NON-LINEARITIES IN ADCS - Techniques for calibrating non-linearities of ADCs are described, which can be applied whether or not the non-linearities change with frequency. When the non-linearities do not change (are static), the frequency of a calibrating signal is first estimated coarsely in a calibration mode, then a fine estimate is determined using the coarse estimate. These estimates are then used to predict the sinusoidal signal using a linear predictor. A Look Up Table (LUT) containing corrections to the ADC is derived from this result. The LUT is then used in a normal operating mode to correct the output of the ADC. In a case where the characteristics of the non-linearities of the input signal are dynamic and thus change with frequency, a frequency spectrum of interest is broken into several regions. In each of these regions, a frequency is identified and used as a calibrating signal to generate the corresponding LUT. During normal operation of the ADC, in a first method, the bin corresponding to dominant frequency of the signal is identified using a short-length FFT. This bin is used to select the appropriate LUT for operating on the output of the ADC to provide the calibrated output. In a second method used when dynamic input is expected, a single LUT is developed using the averages values from the LUTs determined from the various regions. | 08-18-2011 |

20120075129 | CALIBRATION OF IMPAIRMENTS IN A MULTICHANNEL TIME-INTERLEAVED ADC - Techniques for correcting component mismatches in an M-channel time-interleaved Analog to Digital Converter (ADC). A number, M, of clock signals drive a corresponding number of main ADC elements with a selected plurality of different clock phases. Each of the ADCs has at least one of an offset correction input, a gain correction input, or a phase correction input. The M digital values output by the ADCs are interleaved to form a digital representation of the input signal. Also provided is a reference ADC that outputs reference digital values in response to at least one of the M clock signals at a time. The output of the reference ADC is compared and/or combined with the output from a selected one of the main ADCs to provide an estimate of offset, gain or phase. The error is accumulated to determine a corresponding correction of offset, gain or phase which is then fed back to the respective input of the corresponding main ADC. | 03-29-2012 |

20120268299 | ROBUST GAIN AND PHASE CALIBRATION METHOD FOR A TIME-INTERLEAVED ANALOG-TO-DIGITAL CONVERTER - A time-interleaved analog to digital converter (TIADC) that uses a digital filter to remove sampling-frequency symmetries that might otherwise degrade error correction. In an embodiment, two Analog to Digital Converter (ADC) cores provide a set of two ADC outputs. Interleaving the digital signals output by the ADC cores forms a digital representation of the input signal. The ADC cores have an offset correction input, a gain correction input, or a sample time correction input. Prior to estimating one or more of these errors, the ADC core output signals are filtered, with the filtering depending upon expected aliasing characteristics of the input signal. | 10-25-2012 |

20120274490 | MULTIPLIER-FREE ALGORITHMS FOR SAMPLE-TIME AND GAIN MISMATCH ERROR ESTIMATION IN A TWO-CHANNEL TIME-INTERLEAVED ANALOG-TO-DIGITAL CONVERTER - Techniques for the estimation of sample-time and gain mismatch errors in a two-channel time interleaved analog to digital converter that are devoid of any multiplication operation. In a sample-time mismatch error evaluation, the signs and the absolute values from the two ADCs are used to provide an estimate of the sample-time mismatch error. In a gain error estimation algorithm, the absolute values of the outputs from the two ADCs are subtracted and accumulated. The errors can then be corrected, in a preferred embodiment, using suitable adaptive sample time and gain correction techniques. | 11-01-2012 |

20120274491 | GRADIENT-BASED APPROACH TO SAMPLE-TIME MISMATCH ERROR CALIBRATION IN A TWO-CHANNEL TIME-INTERLEAVED ANALOG-TO-DIGITAL CONVERTER - Correcting phase error in a two-channel TIADC system in a manner that is independent of the Nyquist zone(s) occupied by the input signal. In the preferred approach this is done using the gradient of a phase error estimate. The gradient may be determined from a simplified expression of linear regression; the direction of the adaptation is then controlled by the sign of the gradient. The adaptive algorithm converges to the optimal value regardless of the Nyquist zone occupied by the input signal. | 11-01-2012 |