# Performance Analysis of Channel Imbalance Control and Azimuth Ambiguity Suppression in Azimuth Dual Receiving Antenna Mode of LT-1 Spaceborne SAR System

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## Abstract

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## 1. Introduction

## 2. LT-1 DRA Mode and Channel Error Model

#### 2.1. LT-1 Signal Model and Channel Constant Amplitude-Phase Error

#### 2.2. APC Position Error

- The X-axis direction is the satellite track direction.
- The Y-axis direction is perpendicular to the X-axis direction.
- The Z-axis faces away from the center of the Earth.
- The P point is the target point.

## 3. Influence of Channel Error on Imaging Performance

## 4. LT-1 SAR Performance Analysis

#### 4.1. Consistency Calibration Method for Channel Error

#### 4.2. Calibration Point Imaging Results

#### 4.3. Scenarios Imaging Results

#### 4.3.1. Wilderness Scenarios

#### 4.3.2. City Scenarios

#### 4.3.3. Land and Sea Interface Scenarios

#### 4.4. Discussion

## 5. Conclusions

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 3.**Phase error caused by APC position error. (

**a**) L-band phase error, (

**b**) C-band phase error, (

**c**) the phase error caused by APC position error and the different antenna beam, and (

**d**) the phase error caused by APC position error and the same antenna beam.

**Figure 4.**Azimuth profile of point-like target. (

**a**) No channel error, (

**b**) 1.3 dB amplitude error, (

**c**) 0.5 rad phase error, (

**d**) time-variant phase error caused by APC position error, and (

**e**) space-variant phase error caused by APC position error.

**Figure 5.**Effect of invariant amplitude error on point-like target imaging. (

**a**) PSLR, (

**b**) ISLR, and (

**c**) IRW.

**Figure 7.**Effect of azimuth APC position error on point imaging. (

**a**) PSLR affected by azimuth APC error, (

**b**) ISLR affected by azimuth APC error, and (

**c**) IRW affected by azimuth APC error.

**Figure 10.**The phase difference and L1 norm of dual-channel frequency domain signal. (

**a**) The phase difference of simulation results, (

**b**) the phase difference of LT-1 measured data results, (

**c**) the L1 norm of simulation results, and (

**d**) the L1 norm of LT-1 measured data results.

**Figure 11.**Location of the test sites and study area. (

**a**) optical image of the test site, (

**b**) SAR image of the test site.

**Figure 12.**Phase error estimation and reconstruction spectrum of calibration field scene. (

**a**) Azimuth time-varying phase error estimation, (

**b**) range space-varying phase error estimation, (

**c**) reconstruction spectrum without channel error calibration, and (

**d**) reconstruction spectrum with channel error calibration.

**Figure 13.**Contour of calibration points. (

**a**) Point 1, (

**b**) point 2, (

**c**) point 3, (

**d**) point 4, (

**e**) point 5, (

**f**) point 6, (

**g**) point 7, and (

**h**) point 8.

**Figure 14.**Profile of calibration points. (

**a**) Point 1, (

**b**) point 2, (

**c**) point 3, (

**d**) point 4, (

**e**) point 5, (

**f**) point 6, (

**g**) point 7, and (

**h**) point 8.

**Figure 15.**Imaging results of wilderness scenarios: (

**a**) azimuth time-varying phase error estimation results, (

**b**) range space-varying phase error estimation, (

**c**) reconstruction spectrum without channel error calibration, (

**d**) reconstruction spectrum with channel error calibration, (

**e**) focused image without channel error calibration, and (

**f**) focused image with channel error calibration.

**Figure 16.**Imaging results of city scenarios: (

**a**) azimuth time-varying phase error estimation results, (

**b**) range space-varying phase error estimation, (

**c**) reconstruction spectrum without channel error calibration, (

**d**) reconstruction spectrum with channel error calibration (

**e**) focused image without channel error calibration, and (

**f**) focused image with channel error calibration.

**Figure 17.**Imaging results of land and sea interface scenarios: (

**a**) focused image without channel error calibration, and (

**b**) focused image with channel error calibration.

Parameter | Symbol | Value | Unit |
---|---|---|---|

Platform velocity | ${V}_{s}$ | 7635 | $\mathrm{m}/\mathrm{s}$ |

Carrier frequency | ${f}_{0}$ | 1.26 | $\mathrm{GHz}$ |

Nearest slant range | ${R}_{0}$ | 817 | $\mathrm{km}$ |

Azimuth antenna length | ${L}_{az}$ | 2 × 4.9 | $\mathrm{m}$ |

Doppler bandwidth | ${B}_{a}$ | 2761 | $\mathrm{Hz}$ |

Azimuth sampling frequency | ${F}_{a}$ | 1795 | $\mathrm{Hz}$ |

Number of channels | $\mathrm{M}$ | 2 | \ |

Parameter | Symbol | Value | Unit |
---|---|---|---|

Platform velocity | ${V}_{s}$ | 7635 | $\mathrm{m}/\mathrm{s}$ |

Carrier frequency | ${f}_{0}$ | 1.26 | $\mathrm{GHz}$ |

Signal bandwidth | ${B}_{r}$ | 80 | $\mathrm{MHz}$ |

Signal pulse duration | ${T}_{p}$ | 70 | $\mathsf{\mu}\mathrm{s}$ |

Nearest slant range | ${R}_{0}$ | 817 | $\mathrm{km}$ |

Azimuth antenna length | ${L}_{az}$ | 4.9 × 2 | $\mathrm{m}$ |

Rang sampling frequency | ${F}_{r}$ | 90 | $\mathrm{MHz}$ |

Azimuth sampling frequency | ${F}_{a}$ | 1742 | $\mathrm{Hz}$ |

Number of channels | $\mathrm{M}$ | 2 | \ |

Calibration Point | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
---|---|---|---|---|---|---|---|---|

Latitude | 42.01435 | 42.01508 | 42.01464 | 42.01483 | 42.01553 | 42.01568 | 42.01648 | 42.01237 |

Longitude | 91.80460 | 91.84039 | 91.88072 | 91.92124 | 91.96425 | 92.01358 | 92.07841 | 92.14480 |

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**MDPI and ACS Style**

Xu, Z.; Lu, P.; Cai, Y.; Wu, Y.; Wang, R. Performance Analysis of Channel Imbalance Control and Azimuth Ambiguity Suppression in Azimuth Dual Receiving Antenna Mode of LT-1 Spaceborne SAR System. *Remote Sens.* **2023**, *15*, 2765.
https://doi.org/10.3390/rs15112765

**AMA Style**

Xu Z, Lu P, Cai Y, Wu Y, Wang R. Performance Analysis of Channel Imbalance Control and Azimuth Ambiguity Suppression in Azimuth Dual Receiving Antenna Mode of LT-1 Spaceborne SAR System. *Remote Sensing*. 2023; 15(11):2765.
https://doi.org/10.3390/rs15112765

**Chicago/Turabian Style**

Xu, Zongxiang, Pingping Lu, Yonghua Cai, Yirong Wu, and Robert Wang. 2023. "Performance Analysis of Channel Imbalance Control and Azimuth Ambiguity Suppression in Azimuth Dual Receiving Antenna Mode of LT-1 Spaceborne SAR System" *Remote Sensing* 15, no. 11: 2765.
https://doi.org/10.3390/rs15112765