针对S波段通信系统中的无源互调(PIM)干扰问题,提出了一种基于热致振动的无源互调新机理.在双频微波输入条件下,从拍现象中温度波动出发,通过热致振动中的阻抗变化关系,建立了统一的传输线非线性方程,然后以波导为对象进行了多物理场仿真分析和实验验证.设计并加工了3种不同窄边厚度的BJ-22型波导,利用大功率无源互调测量系统,在47～53 dBm功率范围内测试波导9阶PIM功率.结果表明,相同大功率输入条件下,波导壁越薄,波导PIM越强,显示热致振动会引起PIM并受振动程度的影响.%A new mechanism of passive intermodulation (PIM) based on thermally induced vibration is proposed to deal with the problem caused by PIM in communication systems at S-band. In the dual-frequency microwave signals input conditions, starting with the temperature fluctuation of beat phenomenon, a unified nonlinear equation of transmission line was established by using the impedance changing equation in thermally induced vibration, then waveguide was selected as the object to do multi-physics simulation analysis and experimental verification. Three BJ-22 microwave waveguides with different narrow wall thicknesses were designed and fabricated. The waveguides' 9th order PIM with power ranging from 47 dBm to 53 dBm was tested by using the high power PIM measurement system. The results show that the waveguide with thinner narrow wall produced higher PIM power compared to that with thicker narrow wall under the same conditions. It indicates that the thermal induced vibration of the transmission line will lead to PIM effects and it is affected by the degree of vibration.
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