点聚焦透镜天线焦斑附近波长延长

Elongation of the wavelength in a focused beam of spot-focusing lens antenna

利用简易装置搭建“测量线”系统,采用驻波法测量了点聚焦透镜天线焦斑附近轴线上不同位置处的波长λF,与自由空间中的波长λ0 相比,找出λF 随轴向距离变化而变化的关系,并对该变化进行定性分析.通过对2 种点聚焦透镜天线的测量,发现焦斑附近的波长λF 较之自由空间中的波长λ0 有0-5%的延长,且延长量随离焦点距离的增大而减小.最后对测试系统的精确度和误差源进行了分析.

A slotted line system is constructed with simple devices. The wavelengthsλ F of differentpositions at the axis of spot-focusing lens antenna are measured based on the method of standing wave. Bycomparing with wavelength λ0 of free space, the relation that λF changes with the axial length is found, andqualitatively analyzed. Through the actual measurement on two kinds of spot-focusing lens antennas,it canbe confirmed that the wavelength λF near the focal spot has a elongation of 0 to 5 percent in comparison toλ0 in free space, and this elongation will reduce with the increase of the distance to the focus. Finally,precision and error analysis of the test system is given.