Analysis and Implementation of Self-Packaged Multi-Layer Suspended Coplanar Waveguide and its Applications in Filtering Circuits

In this paper, ideal suspended coplanar waveguide model is analyzed by using conformal mapping method, and the characteristic impedance is formulated and verified. A self-packaged suspended coplanar waveguide (SCPW) using multi-layer PCB technique is proposed and implemented with a experimental insertion loss of no more than 0.5dB, and return loss of better than 15.8dB from DC to 10GHz, which eliminates the drawbacks of the traditional suspended circuits such as bulky size, heavy weight and difficult to be integration because of their indispensable metal cavity and mechanical assemble. Both self-packaging and inside/outside end connection are used to reduce the wave leakage. Based on the self-packaged multi-layer suspended coplanar waveguide, a high frequency selective and high isolated multi-resonator coupled diplexer with measured isolation of no less than 42.5dB, and out-of-band suppression of more than 37dB as well as multiple transmission zeros have been implemented. A reflectionless bandstop filter with a measured S
₁₁
attenuation of more than 13.8dB is also implemented for demonstrating the availability of the self-packaged multi-layer SCPW.