| Programmable step attenuator has broad band and good precision. Because its attenuation can be controlled by program, it has been widely used in all kinds of automatic test systems. As to the programmable step attenuator up to 40GHz, there is no mature product or design in China now. This paper gives a detailed introduction and analytic expression, parameter-characteristic curve or optimal parameter on edge-line, suspended coplanar waveguide (SCPW) characteristic impedance, distributed parameter attenuator card AC attenuation and 2.4 mm coaxial connector isolator's coplanar compensation through using conformal transformation, equation for transmission line and HFSS. Besides, the paper uses HFSS within DC-40GHz to do simulation design for match of edge-line to coaxial line, SCPW , achieving perfect match of different transmission lines under mixed transmission condition. The final actual specification and simulation result have nearly same trend and reach perfect technical specification. The design and matched compensation methods the paper introduced have important instructive meaning to design and production of programmable step attenuator. |
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