﻿ 水面无人艇搭载鞭天线最佳工作频率分析
 舰船科学技术  2023, Vol. 45 Issue (1): 90-93    DOI: 10.3404/j.issn.1672-7649.2023.01.016 PDF

Analysis of the best working frequency of whip antenna on surface unmanned vehicle
XIU Meng-lei, LI Li-hua, HOU Wen-da, WANG Long-fei
Department of Communication Engineering, Naval University of Engineering, Wuhan 430000, China
Abstract: In order to ensure that the surface unmanned vehicle and the receiving target achieve close-range communication, the whip antenna radiation and electromagnetic wave propagation characteristics are combined in the 3～50 MHz frequency band to determine the maximum field strength that can be received at different distances. The radiation efficiency of the whip antenna on the sea surface under multiple conditions is calculated and the simulation results are obtained; the ground wave propagation attenuation factor model is used for quantitative analysis and simulation experiments, and finally the best working frequency of the whip antenna at different distances under various conditions when working on the sea surface is obtained. Theoretical analysis and simulation results show that as the distance increases, the corresponding reception field strength of the whip antenna in various states decreases, with the increase of the tilt angle, the optimal operating frequency shows an increasing trend, and the reception field strength continues to decrease.
Key words: whip antenna radiation     electromagnetic wave propagation     best working frequency     receiving field strength
0 引　言

1 辐射性能分析

 $D(\theta ,\varphi ) = \frac{{S(\theta ,\varphi )}}{{{S_0}}} = \frac{{{{\left| {E(\theta ,\varphi ,r)} \right|}^2}/240{\text{π}} }}{{{P_r}/4{\text{π}} {r^2}}} 。$ (1)

 $\eta=\frac{P_{r}}{P_{i z}}=\frac{r^{2}|E(\theta, \varphi, r)|^{2}}{60 P_{i z} D(\theta, \varphi)} \times 100 {\text{%}} 。$ (2)

 $D(\theta ,\varphi ) = \frac{{4{\text{π}} {F^2}(\theta ,\varphi )}}{{\displaystyle\int_0^{2{\text{π}} } {\displaystyle\int_0^{\text{π}} {{F^2}(\theta ,\varphi ){\rm{d}}\theta {\rm{d}}\varphi } } }}。$ (3)

 图 1 鞭天线在流动海面工作状态图 Fig. 1 Working state diagram of whip antenna in the flowing sea water surface

 图 2 1 m鞭天线在3～50 MHz频段倾斜不同角度时的辐射功率对比 Fig. 2 Comparison of radiated power of 1 m whip antenna when tilted at different angles in the 3～50 MHz frequency band

1）对于在海面上工作的鞭天线，在3～50 MHz的频段下，对于1 m鞭天线，随着频率的不断增加，鞭天线辐射功率也不断增加。这是因为在该范围内，天线的辐射电阻会随着 $h/\lambda$ 的增大而增大，在物理尺寸一定的情况下，电尺寸将直接决定辐射功率。

2）天线的倾斜角度越大，天线的辐射功率不断减小，这是因为倾斜角度越大，天线与海面地损耗不断增大，此时海水会吸收更多的能量，导致天线辐射能力有所下降。

2 传播特性分析

 $\left| E \right| = \frac{{173\sqrt {{P_r}D} }}{r}A。$ (4)

 ${d_0} = 80{f^{ - 1/3}}，$ (5)

 $A = \frac{{2 + 0.3d}}{{2 + d + 0.6{d^2}}} - \sqrt {\frac{d}{2}} \exp ( - 1.44d{\rm{log}}{\varepsilon _r}) \cdot {\rm{sin}}\beta 。$ (6)

 $d \approx 1.745 \times {10^{ - 4}} \cdot \frac{{f \cdot \cos \beta }}{\sigma } \cdot \frac{{r \times {{10}^8}}}{\lambda }，$ (7)
 $\beta = - {\tan ^{ - 1}}\frac{{({\varepsilon _r} + 1) \cdot f}}{{1.8 \times {{10}^4}\sigma }} 。$ (8)

3 接收场强分析

 图 3 鞭天线在3～50 MHz频段不同倾斜角度在部分距离的接收场强 Fig. 3 Receiving field strength of whip antenna in the 3～50 MHz frequency band with different tilt angles at partial distance

4 结　语

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