The Research On Principle And Applciation Of Micro-wave Interdigital Structure

Miniaturization of microwave devices is one of the vital technology fields of mini-mizing modern communication system and electronics equipment. Currently, there are some methods to realize the miniaturization of planar microwave devices, such as adopting periodic structures with slow-wave characteristics, low temperature Co-fired Ceramic (LTCC) technology and so on. And the periodic structures are widely accepted by re-searchers due to their easy fabrication and low cost. In this paper, a kind of periodic struc-ture, the horizontal interdigital structure which has slow-wave characteristics will be stud-ied. The paper includes the following work: analysis on characteristics, derivation of ex-pression, and the application in miniaturization.The paper contains 6 chapters. Firstly, research background and used softwares are introduced, and then the basic principle of microstrip transmission line is stated, laying the ground work of the study.After that, theoretical study is carried out. Various models of interdigital structure are listed in the paper. After simulate and compare them, the paper gives the theoretical analy-sis of their simulation results, drawing a conclusion that the horizontal interdigital structure is suitable to be used in the miniaturization design.And then, the slow-wave characteristic of horizontal interdigital structure is studied. A fact is found by simulation that the horizontal interdigital structure has a larger electrical length than the same sized conventional microstrip line. It's the very reason why the hori-zontal interdigital structure is useful for miniaturization. Afterwards, the paper gives the simulation results of a series of horizontal interdigital structures with different sizes, and an expression to calculate the phase of horizontal interdigital structure is derived. What's more, the expression is proved to be accurate and reliable by simulation.Finally, two microstrip devices based on horizontal interdigital structure are designed one of which is square loop resonator band pass filter and the other is 3dB double branch directional coupler. The result shows that slow-wave characteristic of horizontal interdigi-tal structure can reduce device's area efficiently while its performance stays the same. What's more, the expression shortens design period. The miniaturized devices are also fab-ricated, and the measurements agree with simulation proving the expression's accuracy. It shows that the expression provides a novel technique way of quickly designing microstrip deviceses based on horizontal interdigital structure.