ANALYSIS AND COMPARISON OF WAVE PROPAGATION IN MICROSTRIP LINES AND COPLANAR WAVEGUIDES

Despite their obvious advantages over microstrips, coplanar waveguides (CPWs) have not been widely used as probes for wave coupling in mixer circuits. Microstrips are still the preferred option. One major reason is because CPWs are generally believed to exhibit higher attenuation than microstrip probes. Here, we present numerical analysis between the loss of waves in normal and superconducting CPWs and microstrips. The results show that the loss in microstrips is generally higher than that found in CPWs at dimensions larger than the wavelength. At dimensions comparable and smaller than the wavelength (i.e. q < 2.2), however, the loss in a CPW appears to be significantly lower. The results suggest strongly that, with careful design, CPWs can be a better alternative for the coupling of waves in Superconductor Insulator Superconductor (SIS) mixer circuits.