本文为南非开普敦大学（作者：Darren Grant Coetzer）的硕士论文，共98页。

尽管存在恶劣的天气条件或阴影黑暗，合成孔径雷达（SAR）可以提供一个针对地球表面广阔区域的高分辨率图像远程观测平台。通过成立一个本地的专业组织以展示南非的SAR能力，向南非和国际社会提供高质量图像。本论文是该项目的一部分。它的目的是描述用于SASAR II（X波段SAR）设计和实施的发射机和相关频率分配单元（FDU）。虽然发射机和FDU是两个独立的单元，但它们最终是相互连接的。发射机的任务是通过接收低功率基带啁啾波形，并通过一系列混频器、滤波器和放大器将其转换为高功率微波信号。FDU本质上是收发器的心脏，提供所有混频器本地振荡器（LO）的驱动输入。它还对DAC和ADC进行计时，这使得基本上类似的收发信机能够与数字电路通信。结果表明，所产生的啁啾信号具有良好的保真度。然而，LO馈通在啁啾的中心频率处叠加。作为先前阶段的结果，杂散信号存在于啁啾中心频率和9142 MHz处的16 MHz偏移处。系统传递函数表明啁啾信号的外频率存在2dB衰减，其原因在于发射机滤波器和放大器中的群延迟。

Synthetic aperture radar (SAR) can providehigh-resolution images of extensive areas of the earth′s surface from aplatform operating at long ranges, despite adverse weather conditions ordarkness. A local consortium was established to demonstrate a consolidatedSouth African SAR ability to demonstrate to the local and internationalcommunities, by generating high quality images with a South African X-banddemonstrator. This dissertation forms part of the project. It aims to describethe design and implementation of the transmitter and associated frequencydistribution unit (FDU) for the SASAR II, X-band SAR. Although the transmitterand FDU are two separate units, they are ultimately linked. The transmitter hasthe task of taking a low-power, baseband, chirp waveform and, through a seriesof mixers, filters and amplifiers, converting it to a high-power, microwavesignal. The FDU is essentially the heart of the transceiver and provides driveto all the mixer local oscillator (LO) inputs. It also clocks the DAC and ADCwhich allow the essentially analogue transceiver to communicate with thedigital circuitry. It is found that the chirp signal produced is ofsatisfactory fidelity. LO feedthrough, however, is superimposed at the chirps′centre frequency. As a result of previous stages, spurious signals exist at 16MHz offset from the chirps′ centre frequency and at 9142 MHz. The systemtransfer function reveals that 2 dB roll-off is present at the outerfrequencies of the chirp signal. Group delay in the transmitter filters andamplifiers is held responsible for this.

1 引言

1.1 职权范围

1.2 发展规划

2 项目背景

2.1 背景信息

2.2 基本SAR理论

2.3 系统概述

2.4 发射机

2.5 频率分配单元

3 发射机设计与实现

3.1 Chirp理论与仿真

3.2 混频器与滤波器

3.3 BIT

3.4 所提出发射机的功率需求

3.5 小结

4 频率分配单元的设计与实现

4.1 频率合成器

4.2 功率问题

4.3 电路板设计

4.4 放大器

4.5 微波外壳设计

4.6 相位噪声与抖动

4.7 小结

5 测试

5.1 引言

5.2 放大器测试

5.3 合成器测试

5.4 FDU的功率电平

5.5 发射机功率电平

5.6 Chirp完整性

5.7 杂散信号

5.8 系统传输函数

5.9 讨论与分析

6 结论与建议

6.1 结论

6.2 未来工作建议

附录A Chirp的MATLAB仿真代码

附录B 合成器绘图

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