Loop Antennas
Loop Antennas
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环形天线
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
Glenn S. Smith
中科院分区：
文献类型：
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作者：
Glenn S. Smith
环形天线具有结构简单、成本低、通用性强等特点。它们可以有不同的形状：圆形、三角形、正方形、椭圆形等。它们被广泛用于直到微波频段(高达≈3 GHz)的通信链路。它们也被用作微波频段的电磁(EM)探头。电小环路被广泛用作低MHz范围(3 MHz到30 MHz，或大约10 m到100 m的波长)的紧凑型发射和接收天线。环状天线通常分为电小(Cλ)和电大(Cλ∼)两类。这里，C表示循环的周长。单圈的小环具有较小的辐射电阻(<；1Ω)，通常可与其损耗电阻相媲美。然而，他们的抗辐射能力可以通过增加更多的圈数来提高。而且，小环路是窄带的。典型的带宽不到1%。然而，巧妙的阻抗匹配可以提供从同轴电缆到环状天线的低反射过渡，调谐频率范围高达1：10。此外，在环路直径在半米到几米量级的高频和甚高频频段，环路可以由大直径的管子或同轴电缆或宽铜带制成，这可以大大降低损耗。
Loop antennas feature simplicity, low cost and versatility. They may have various shapes: circular, triangular, square, elliptical, etc. They are widely used in communication links up to the microwave bands (up to ≈ 3 GHz). They are also used as electromagnetic (EM) field probes in the microwave bands. Electrically small loops are widely used as compact transmitting and receiving antennas in the low MHz range (3 MHz to 30 MHz, or wavelengths of about 10 m to 100 m). Loop antennas are usually classified as electrically small ( / 3 C λ < ) and electrically large (C λ ∼ ). Here, C denotes the loop’s circumference. The small loops of a single turn have small radiation resistance (< 1 Ω) usually comparable to their loss resistance. Their radiation resistance, however, can be improved by adding more turns. Also, the small loops are narrowband. Typical bandwidths are less than 1%. However, clever impedance matching can provide low-reflection transition from a coaxial cable to a loop antenna with a tuning frequency range as high as 1:10. Moreover, in the HF and VHF bands where the loop diameters are on the order of a half a meter to several meters, the loop can be made of large-diameter tubing or coaxial cable, or wide copper tape, which can drastically reduce the loss.