{
  "course": "高频电子线路",
  "title": "复杂电磁环境下的应急通信与定位保障",
  "background": "一支应急分队进入山地峡谷，北斗终端、无人机中继、单兵电台与前沿雷达同时工作，四个设备各出了一个现场难题。本学期的任务，就是把它们逐个解决。",
  "scope_note": "四个难题合起来盖住本课程的核心章节：你真正动手的是谐振、匹配、调幅检波这三块，其余工程指标只用来看结果，不反复追究。为了让四台设备能放在一起谈，全站把它们折到同一条中频通道上：中心频率 10.7 MHz、通频带 240 kHz（甚高频电台前端的典型值）。北斗终端的真实射频在 1.5 GHz 量级，这里是简化过的，参数不代表某一台真实接收机。",
  "primer": {
    "title": "这门课在解决什么",
    "lines": [
      "无线接收的核心难题不在发射，在于同一频段挤满信号的环境里，把有用信号从邻近的强干扰中选出来。",
      "完成这件事的基本单元是 LC 谐振回路：电容与电感交换储能，在 f₀ = 1/(2π√LC) 处响应最大，偏离越远响应越小——这就是选频。",
      "四台设备的故障，落点都在这一级选频与匹配上；北斗终端作主案例走完十三步，其余三个是同一套方法的迁移。"
    ],
    "source": "tasks/15-讲解稿·评委版.md 开场"
  },
  "pending_note": "表中所有要求为教学取值，待教师审定。",
  "source": "tasks/00-总体方案.md 第三节",
  "problems": [
    {
      "id": "p1",
      "ordinal": "难题一",
      "title": "北斗终端失锁",
      "device": "北斗定位终端",
      "symptom": "峡谷内强邻频干扰与多径下终端频繁失锁。",
      "consequence": "定位误差从 5 m 恶化到几十米，无法引导直升机悬停。",
      "plain_goal": "压住频差 1 MHz 的强邻频电台，同时保住 240 kHz 的通频带。",
      "requirements": [
        "中频通道邻道抑制不低于 60 dB（整机；单级选频回路按 35 dB 计）",
        "天线端驻波比不大于 1.5",
        "本振频率稳定度优于百万分之一",
        "恢复连续定位"
      ],
      "chapters": [
        "中频选频回路：LC 谐振、品质因数 Q 与带宽、邻道抑制、双调谐",
        "天线到前端的阻抗匹配"
      ],
      "display_indicators": [
        "驻波比",
        "本振频率稳定度（三点式振荡器作次要练习）",
        "定位误差热图"
      ],
      "scene": "定位误差热图",
      "accent": "blue"
    },
    {
      "id": "p2",
      "ordinal": "难题二",
      "title": "无人机图传中断",
      "device": "中继无人机",
      "symptom": "机动转弯时天线阻抗随姿态变化，功放失配进入压缩。",
      "consequence": "画面卡顿、每分钟断链数次，续航缩短三成。",
      "plain_goal": "天线阻抗随姿态变化时仍保持匹配，功放不进压缩。",
      "requirements": [
        "全姿态驻波比不大于 2",
        "功放集电极效率不低于 40%",
        "自动增益控制在 10 ms 内恢复"
      ],
      "chapters": [
        "阻抗匹配网络：L 型与 π 型，Q 值与带宽的取舍"
      ],
      "display_indicators": [
        "集电极效率（丙类功放作次要练习）",
        "自动增益控制响应时间",
        "图传覆盖热图"
      ],
      "scene": "图传覆盖热图",
      "accent": "gold"
    },
    {
      "id": "p3",
      "ordinal": "难题三",
      "title": "单兵电台被压制",
      "device": "单兵电台",
      "symptom": "强干扰把话音盖住、时断时续；检波 RC 又取得偏大，出了惰性失真。",
      "consequence": "有效通话距离缩短一半。",
      "plain_goal": "检波 RC 满足调幅度条件，包络不失真、话音不断续。",
      "requirements": [
        "包络检波不失真：RC 时间常数满足调幅度条件",
        "镜像抑制不低于 50 dB（整机；由前置选频回路多级级联形成）"
      ],
      "chapters": [
        "调幅与包络检波：惰性失真、负峰切割",
        "调频与鉴频（次要）"
      ],
      "display_indicators": [
        "自动增益控制的攻击与释放时间",
        "镜像抑制",
        "通信稳定分布图"
      ],
      "scene": "通信稳定分布图",
      "accent": "mint"
    },
    {
      "id": "p4",
      "ordinal": "难题四",
      "title": "相控阵通道不一致",
      "device": "前沿雷达",
      "symptom": "各通道幅相不一致，主瓣展宽、旁瓣抬高 8 dB。",
      "consequence": "探测距离下降。",
      "plain_goal": "各通道幅相一致，主瓣不展宽、旁瓣不抬高。",
      "requirements": [
        "各通道幅度一致性 ≤ 2 dB、相位一致性 ≤ 5°（教学取值，待教师审定）"
      ],
      "chapters": [
        "谐振回路的幅频与相频特性：Q 值对相频斜率的影响"
      ],
      "display_indicators": [
        "群时延一致性",
        "方向图旁瓣"
      ],
      "scene": "相控阵方向图",
      "accent": "red",
      "workload_note": "展示型难题，学生工作量最小。"
    }
  ],
  "plain_goal_note": "plain_goal 是卡面第一眼那句「要做到」：专业口径的一句话，带数字的要求原文收进卡上的角标，选中这张卡时在右栏整段列出。数字一条没删。"
}