Reliability Analysis And Research On Electrical Performance Of Coaxial Step Attenuator

With the rapid development of wireless communications,the low-end frequencies of the electromagnetic wave spectrum have become saturated,and the rise of the millimeter wave technology has become inevitable.Because of the higher frequency of millimeter-wave,the skin effect is more severe during transmission,resulting in new signal integrity issues.Therefore,in the era of high-frequency and high-speed signals,the reliability of traditional attenuators will face new challenges.Theoretical analysis and calculation,numerical simulation analysis and other methods are used to study the transmission performance of the coaxial step attenuator.First,the transmission performance of the coaxial step attenuator under low-frequency DC working conditions is analyzed.Holm's a-spot theory is used to calculate the contact resistance of the contacts in the attenuator,and the correlation of the cantilever beam in material mechanics is used.The calculation formula analyzes the deformation of the reeds that make up the contact pair.A test bench for measuring the contact resistance of the reeds and the through-pieces in the attenuator is designed,and the contact resistance and contact in the attenuator are measured using this test bench.From the analysis of the results,it can be seen from the analysis of the relationship curve of times that an appropriate increase in the size of the contact force helps to improve the ability of the contact to resist external interference and improve the reliability of the contact.Then,the electromagnetic simulation software HFSS is used to analyze the signal integrity of the coaxial step attenuator at high frequencies.The analysis results show that the attenuator has low loss in the direct working state,and has the characteristics of low loss.Its voltage standing wave ratio shows that the attenuator has a large resonance at two frequency points,reducing the reliability of the attenuator.Therefore,in view of the resonance problem of the attenuator,ferrite is used as the microwave absorbing material for optimization,which effectively reduces the voltage standing wave ratio at the resonance point.This paper also introduces the influence of contact resistance in the simulation analysis,and analyzes the influence of contact resistance on the signal integrity of the attenuator through simulation.Finally,the dismantled reeds and the coatings of the attenuating sheets on the failed batches of samples are analyzed by scanning electron microscope,and analyzes the influence of temperature and elastic modulus on the contact force through theoretical calculations and simulation calculations.The coaxial step attenuator has the following reliability risks:(1)The size margin is too small when installed and matched,and the reed may collide with the working circuit of the attenuator when it is in contact with the attenuator plate;(2)the reed and severe friction in the contact area of the thimble leads to serious wear of the thimble.A large amount of wear products accumulated on the reed and even accumulate on the contact area between the reed and the attenuator of the through-piece as the reed moves,which affects the signal integrity;(3)The contact force of the attenuator itself is designed to be 6g,and the ability to resist external interference is weak.Once the reed is fatigued or working in an extreme temperature environment,there is a risk of insufficient contact force and unreliable contact.