| The measurement of contact stress in extreme environments such as metal slit has important engineering application value. SAW(Surface Acoustic Wave) sensor has been selected to measure the contact stress in the early study. In this paper, SAW signal transmission in the slit related to the subject background will be researched. The main problems are as follows. Firstly, the interconnect and packaging of transmission line and the chip must be small and thin enough to transmission RF signal in the slit. Secondly, the performance of transmission line will become bad in the metallic slit, while working in microwave frequency band. Thirdly, the impedance between SAW chip and transmission line should be matched to improve signal transmission efficiency.In this paper, the effort is grouped around the problems mentioned above. First of all, the structure of interconnection should be chosen and optimized. Next, the effect of the metal slit on micro-strip line transmission performance should be researched. Then, the impedance matching circuit between SAW chip and transmission line will be designed, processed, and tested. The specific contents are listed as follows:1. Several interconnection methods of micro connection have been discussed, and wire bonding was chosen to connect the chip and transmission line. In addition, the parameters of wire bonding(the arch height, length, diameter and the number of bond-wires) have been optimized in order to reduce the reflection in the process of signal transmission and improve the transmission efficiency.2. The approximation method based on quasi-static formula is used to analyze the changes of transmission performance indexes(characteristic impedance and the equivalent relative dielectric constant) with various widths of metal slits. Then, a kind of micro-strip line in metal slit has been simulated by HFSS, whose simulation results were quite precise and accordant with the computations. Moreover, the effect of metal slit on the electrical length of micro-strip line has been discussed.3. Considered integration of micro-strip line and transition in metal slit, the both-branch stub matching circuit has been chosen. The smith chart tool in ADS(Advanced Design System) has been used to design the match circuit, while the parameters of match circuit were optimized in HFSS. In addition, the bonding pad used for wire bonding has been designed.4. The micro-strip matching circuit has been produced and connected with SAW chip. The static performance and dynamic load performance of SAW chips were tested by the experiment, and the test result would be analyzed.In this paper, high-frequency signal transmission in metallic slit was investigated. The signal transmission part was designed and tested by fully considered the effect of metal slit, the connection of chip and micro-strip line, the impedance matching and the dimensional limit, which has the practically applied value in measuring contact pressure in metal slit. |
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