# High-Precision ADC Spectrum Testing under Non-Coherent Sampling Conditions

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## Abstract

**:**

## 1. Introduction

## 2. ADC Spectrum Testing

## 3. Fundamental Waveform Estimation and Reconstruction Algorithm

#### 3.1. Fitting of Sine Test Signals

#### 3.1.1. Three-Parameter Sine-Fitting Method

#### 3.1.2. Four-Parameter Combination Estimation Algorithm

#### 3.2. Reconstructing Coherent Sine Signals

## 4. Numerical Simulation

#### 4.1. Functionality

#### 4.2. Robustness

#### 4.3. Computation Time

## 5. Experimental Verification

#### 5.1. AD976 Test

- Connect the AD976 board to be tested to the DC power supply and the evaluation board in the specified environment; input a high-precision sine wave ${f}_{in}=\mathrm{44,055.15234375}$ Hz with the sampling frequency set to ${f}_{samp}=200$ kHz.
- Power up the device and mode control, and connect the device’s digital output to the digital acquisition terminal through the high-speed interface.
- Provide a frequency-specific analog input signal through a high-performance RF signal source, and connect a fixed-frequency filter to the AD976 analog input.
- Use the logic analyzer/evaluation board to set the AD976 for dynamic conversion and acquisition of the digital output signals of the device.
- DFT to the obtained data to obtain the frequency domain information.

#### 5.2. AD9230 Test

- Apply a 1.8 V power supply.
- Apply a voltage of −1 dBFS amplitude to the ADC under test, then a sine wave source at ${f}_{in}=\mathrm{10,002,700}$ Hz, and filter the sine wave input to remove distortion and random noise from the input signal.
- Apply a sample clock with the specified sampling frequency ${f}_{samp}=\mathrm{75,366,400}$ Hz to the ADC under test.
- After the ADC has stabilized, collect 32,768 output conversion data points.
- Use the proposed algorithm and DFT to obtain the spectrum.

## 6. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

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**Figure 5.**The simulated spectrum of a 16-bit ADC under three sets of conditions (original, coherently sampled, and after processing with the proposed algorithm).

**Figure 9.**Spectrum tests using different test methods: (

**a**) full spectrum; and (

**b**) amplified fundamental spectrum [13].

Method | Time (ms) | Functionality |
---|---|---|

Direct DFT | 39 | Inaccurate |

Hanning | 40 | Inaccurate |

Blackman-Nuttall (4-term) | 42 | Inaccurate |

Window in [13] | 87 | Accurate |

FIRE | 80 | Accurate |

Proposed Method | 72 | Accurate |

Date Set | Method | SNR (dB) | SINAD (dB) | THD (dB) | SFDR (dB) |
---|---|---|---|---|---|

Test 1 | Coherent | 75.065 | 75.145 | −90.248 | 81.142 |

Non-coherent + Algorithm | 74.112 | 73.373 | −88.566 | 79.523 | |

Non-coherent + Window in [13] | 73.553 | 72.469 | −87.935 | 77.946 | |

Test 2 | Coherent | 75.213 | 75.314 | −90.568 | 80.997 |

Non-coherent + Algorithm | 74.248 | 73.674 | −89.023 | 79.653 | |

Non-coherent + Window in [13] | 73.973 | 71.466 | −88.575 | 78.795 | |

Test 3 | Coherent | 74.965 | 75.665 | −89.844 | 81.616 |

Non-coherent + Algorithm | 73.568 | 74.472 | −88.265 | 79.945 | |

Non-coherent + Window in [13] | 72.761 | 72.429 | −86.963 | 78.149 |

Dynamic Indicators | Standard Values in Datasheet | Test Results |
---|---|---|

SNR | 63.8 dB (Min); 64.6 dB (Typ); | 62.329 dB |

SINAD | 63.7 dB (Min); 64.5 dB (Typ); | 63.097 dB |

ENOB | 10.6 bits (Typ) | 9.198 bits |

WORST HARMONIC (Second OR Third) | −82 dB (Typ); −78 dB (Max); | −78.280 dB |

WORST OTHER (SFDR Excluding Second and Third) | −89 dB (Typ); −84 dB (Max); | −85.247 dB |

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**MDPI and ACS Style**

Peng, X.; Li, J.; Zhang, D.; Hu, C.; Sun, N.; Jiang, J.
High-Precision ADC Spectrum Testing under Non-Coherent Sampling Conditions. *Sensors* **2022**, *22*, 8170.
https://doi.org/10.3390/s22218170

**AMA Style**

Peng X, Li J, Zhang D, Hu C, Sun N, Jiang J.
High-Precision ADC Spectrum Testing under Non-Coherent Sampling Conditions. *Sensors*. 2022; 22(21):8170.
https://doi.org/10.3390/s22218170

**Chicago/Turabian Style**

Peng, Xiaofei, Jie Li, Debiao Zhang, Chenjun Hu, Ning Sun, and Jie Jiang.
2022. "High-Precision ADC Spectrum Testing under Non-Coherent Sampling Conditions" *Sensors* 22, no. 21: 8170.
https://doi.org/10.3390/s22218170