..标题：RF菲涅耳区计算器
.. slug：射频菲涅耳区
.. 日期: 2025-12-26 15:00:00 世界标准时间
..标签：网络、计算器、工具、RF、无线
..类别：计算器
..链接：
..描述：计算无线射频链路的菲涅耳区半径，以确保正确的信号传播
..类型：文本
<style>
    .calc-container {
        max-width: 900px;
        margin: 20px auto;
        padding: 20px;
    }

    .calc-header {
        margin-bottom: 30px;
        padding: 25px;
        background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
        border-radius: 12px;
        box-shadow: 0 4px 6px rgba(0,0,0,0.1);
        color: white;
    }

    .calc-header h2 {
        margin-top: 0;
        color: white;
        font-size: 28px;
        margin-bottom: 10px;
    }

    .calc-header p {
        margin: 10px 0;
        opacity: 0.95;
        font-size: 15px;
    }

    .input-grid {
        display: grid;
        grid-template-columns: 1fr 1fr;
        gap: 20px;
        margin-top: 20px;
    }

    .input-group {
        display: flex;
        flex-direction: column;
        gap: 8px;
    }

    .input-group label {
        font-weight: bold;
        font-size: 14px;
        color: rgba(255,255,255,0.95);
    }

    .input-row {
        display: flex;
        gap: 10px;
    }

    .input-group input,
    .input-group select {
        padding: 12px;
        font-size: 16px;
        border: 2px solid rgba(255,255,255,0.3);
        border-radius: 6px;
        background: rgba(255,255,255,0.95);
        transition: all 0.3s ease;
        font-family: 'Courier New', monospace;
    }

    .input-group input {
        flex: 1;
    }

    .input-group select {
        min-width: 150px;
    }

    .input-group input:focus,
    .input-group select:focus {
        outline: none;
        border-color: #4CAF50;
        background: white;
        box-shadow: 0 0 0 3px rgba(76, 175, 80, 0.1);
    }

    .calc-button {
        margin-top: 20px;
        padding: 14px 35px;
        font-size: 16px;
        background: #4CAF50;
        color: white;
        border: none;
        border-radius: 6px;
        cursor: pointer;
        font-weight: bold;
        transition: all 0.3s ease;
        box-shadow: 0 2px 4px rgba(0,0,0,0.2);
        width: 100%;
    }

    .calc-button:hover {
        background: #45a049;
        transform: translateY(-1px);
        box-shadow: 0 4px 8px rgba(0,0,0,0.3);
    }

    .calc-button:active {
        background: #3d8b40;
        transform: translateY(0);
    }

    .result-section {
        background: white;
        border: 1px solid #e0e0e0;
        border-radius: 8px;
        margin-top: 30px;
        overflow: hidden;
        box-shadow: 0 2px 4px rgba(0,0,0,0.05);
        display: none;
    }

    .result-section.show {
        display: block;
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    .section-header {
        background: linear-gradient(135deg, #4CAF50 0%, #45a049 100%);
        color: white;
        padding: 15px 20px;
        font-size: 18px;
        font-weight: bold;
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    .section-content {
        padding: 20px;
        background: #fafafa;
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    .data-row {
        display: flex;
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        padding: 10px;
        background: white;
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        border-left: 3px solid #4CAF50;
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    .data-label {
        font-weight: bold;
        color: #555;
        min-width: 220px;
        flex-shrink: 0;
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    .data-value {
        color: #333;
        font-family: 'Courier New', monospace;
        word-break: break-word;
    }

    .data-value.highlight {
        color: #4CAF50;
        font-weight: bold;
        font-size: 18px;
    }

    .info-box {
        margin-top: 30px;
        padding: 20px;
        background: white;
        border-radius: 8px;
        box-shadow: 0 2px 4px rgba(0,0,0,0.05);
        border-top: 3px solid #4CAF50;
    }

    .info-box h3 {
        margin-top: 0;
        color: #4CAF50;
        font-size: 20px;
    }

    .info-box p {
        line-height: 1.6;
        color: #555;
        margin: 10px 0;
    }

    /* Responsive design */
    @media (max-width: 768px) {
        .input-grid {
            grid-template-columns: 1fr;
        }

        .input-row {
            flex-direction: column;
        }

        .input-group select {
            width: 100%;
        }

        .data-row {
            flex-direction: column;
        }

        .data-label {
            margin-bottom: 5px;
            min-width: auto;
        }
    }
</style>
<div class="calc-container">
<div class="calc-header">
<h2>射频菲涅耳区计算器</h2>
<p>计算无线 RF 链路的菲涅耳区半径。菲涅耳区是无线电波离开天线后传播到的视线路径周围的椭圆形区域。</p>
<div class="input-grid">
<div class="input-group">
<label for="frequency">频率：</label>
<div class="input-row">
<input id="frequency" placeholder="Enter frequency" type="text" value="2.4"/>
<select id="freunit">
<option value="ghz">兆赫</option>
<option value="mhz">兆赫兹</option>
<option value="khz">千赫</option>
<option value="hz">赫兹</option>
</select>
</div>
</div>
<div class="input-group">
<label for="distance">距离：</label>
<div class="input-row">
<input id="distance" placeholder="Enter distance" type="text" value="1"/>
<select id="unit">
<option value="feet">英里</option>
<option value="meters">公里</option>
</select>
</div>
</div>
</div>
<button class="calc-button" onclick="fresnelZone()">计算菲涅尔区</button>
</div>
<div class="result-section" id="results">
<div class="section-header">计算结果</div>
<div class="section-content">
<div class="data-row">
<div class="data-label">菲涅耳区半径：</div>
<div class="data-value highlight" id="fnr">-</div>
</div>
<div class="data-row">
<div class="data-label">中心点位置：</div>
<div class="data-value" id="center">-</div>
</div>
</div>
</div>
<div class="info-box">
<h3>关于菲涅尔区</h3>
<p>
<strong>什么是菲涅尔区？</strong>菲涅尔区是两个天线之间的视线路径周围的椭圆形区域。无线电波在传播时会扩散，该区域代表这些波可以产生建设性或破坏性干扰的区域。</p>
<p>
<strong>为什么它很重要？</strong>为了获得最佳的射频链路性能，第一菲涅尔区至少 60% 的区域应没有障碍物（建筑物、树木、地形）。该计算器可帮助您确定无线链路中点所需的间隙半径。</p>
<p>
<strong>使用方法：</strong>输入您的工作频率和天线之间的总距离。计算器将显示菲涅尔区最宽点（链接中心）的半径。</p>
</div>
</div>
<script>
function fresnelZone() {
    // Set variables from input
    var frequency = Number(document.getElementById("frequency").value);
    var freunit = document.getElementById("freunit").value;
    var distance = Number(document.getElementById("distance").value);
    var unit = document.getElementById("unit").value;

    if (freunit == "ghz") {
        var sf = frequency;
    } else if (freunit == "mhz") {
        var sf = frequency/1000;
    } else if (freunit == "khz") {
        var sf = frequency/1000000;
    } else {
        var sf = frequency/1000000000;
    }


    var d1 = distance / 2;
    var d2 = d1;
    if (unit == "feet") {
        //var radius = Math.round(72.05 * Math.sqrt((d1*d2/(sf))));
        var radius = Math.round(36.03 * Math.sqrt((distance/sf)))
        var distunit = "Miles"
    } else {
        //var radius = Math.round(17.32 * Math.sqrt((d1*d2/(sf))));
        var radius = Math.round(8.657 * Math.sqrt((distance/sf)))
        var distunit = "Kilometers"
    }

    document.getElementById("fnr").textContent = radius + " feet";
    document.getElementById("center").textContent = "Located " + d1 + " " + distunit + " from the first antenna";

    // Show results section
    document.getElementById("results").classList.add("show");

    // Scroll to results
    document.getElementById("results").scrollIntoView({ behavior: 'smooth', block: 'start' });
}

// Add enter key support
document.addEventListener('DOMContentLoaded', function() {
    document.getElementById("frequency").addEventListener('keypress', function(e) {
        if (e.key === 'Enter') {
            fresnelZone();
        }
    });

    document.getElementById("distance").addEventListener('keypress', function(e) {
        if (e.key === 'Enter') {
            fresnelZone();
        }
    });
});
</script>