6.3.1 Introduction

Distributed MEMS transmission-line (DMTL) circuits and elements are widely used in the design and development of filters, traveling-wave amplifiers, nonlinear transmission-line segments, matching circuits, and phase shifters. Deployment of periodic-loaded transmission line offers very wideband operations in microwave and mm-wave spectral regions [1]. For the DMTL configuration, transmission-line geometrical parameters and physical dimensions can be defined to achieve a periodic transmission line with a characteristic impedance of 50 ?. It is critical to mention that the DMTL is a high-impedance line with the characteristic impedance ( Z ₀) greater than 50 ? with CPW center conductor width ( W) capacitively loaded by the periodic installation of MEMS bridges [1] with specific width ( w) and spacing ( s) as illustrated in Figure 6.3a. The DMTL is connected to 50 ? feed lines and test pads needed to obtain relevant performance parameters. The transmission-line model of the DMTL along with MEMS bridge is shown in Figure 6.3b, identifying the bridge capacitance ( C _b) and the transmission-line inductance ( L _t) and capacitance ( C _t) per unit length. The periodic unloaded transmission-line elements can be easily implemented using CPW transmission-line segments. The top view of the DMTL using CPW lines is shown in Figure 6.3 identifying the bridge dimensions, namely, width ( w), and the length l equal to W + 2 G, where G