Coplanar waveguide

J. Papapolymerou, G. E. Ponchak, E. Dalton, A. Bacon, and M. M. Tentzeris, Crosstalk between finite ground coplanar waveguides over polyimide layers for 3-D MMICs on Si substrates, IEEE Trans. Microw. Theory Tech., vol. 52, no. 4, pp. 1292—1301, Apr. 2004. doi 10.1109/TMTT.2004.825714... 

The test results suggest that the fuel cell seal variant which contains the coplanar waveguide structure is probably a better candidate than the microstrip variant for the goal of designing a seal that might be indicative of defects or precursors to seal failure, as the sample-to-sample variability is much greater in the microstrip variant. 

Mkrowave in Mkrofluidks, Fig. 5 Cross-sectional and top view of the coplanar waveguide heater presented in Ref. [4]. The ehannel is aligned with the coplanar waveguide so that the fluid interacts with the microwave power. The mimtfluidic chip is made of PDMS, and the electrodes of the coplanar waveguide are made of Cr/Au (Figure from Ref. [4], Reproduced by permission of lOP PubUshing, http //dx.doi.Org/10.1088/0960-1317/17/l 1/ 008)... 

One of the most important parameters in the heater design is the thickness of the conductive lines employed in the coplanar waveguide [4]. Using a thin conductor increases the conductive losses within the transmission line. Shah et al. use cmiductors with a thickness of 0.5 pm, which is smaller than or close to the skin depth of gold in the frequency band of 300 MHz—40 GHz. As shown in Fig. 6,45-75 % of the total power is dissipated by conductive losses. 

Coplanar waveguide structures are used for transmission line-based sensing methods. Booth et al. used the coplanar waveguide structure between the microfluidic channel and the quartz substrate. The microfluidic channel and the transmission line are aligned so that the microwave power propagation and the fluid flow directirui are orthogruial as shown in Fig. 8. As a result, the microwave power experiences three types of transmissirui fines ... 

Microwave in Microfiuidics, Fig. 8 The coplanar waveguide used for characterization of liquids in microchannels [6]. The channel is bonded on top of the coplanar waveguide and fluid flow is perpendicular to the microwave power flow. As a result the transmission line parameters are different in regions covered by PDMS and the channel. The same structure is simulated and the complex permittivity that gives the same results as the measurement is found... 

Itotia IK, Drayton RF (2002) Porosity effects on coplanar waveguide porous silicon interconnects. 

Table 1 RF electrical characteristics of various coplanar waveguides (CPW) on p-type OPS or mesoporous silicon. All the CPW are made of gold, except for (Contopanagos et al. 2008a) aluminum. F is the loss measurement frequency and tps is the PS thickness ...

Coplanar waveguides (CPW) 2-3 Metal-insulator-metal (MIM) capacitor 4 Planar inductors 3 RF electrical isolation 1... 

Coplanar waveguide has an advantage over microstrip because of the fact that CPW line width is independent of the line impedance. The CPW probe is a microwave transition from coaxial to coplanar wave probe pad [37]. Care must be taken to design transitions that have minimum loss. 

Ghione, G. and Goano, M., The influence of ground-plane width on the ohmic losses of coplanar waveguides with finite lateral ground planes, IEEE Transactions on MTT, Vol. 45, No. 9,1997, pp. 1640-1642. 

Fig. 3.7 Sketch of two configuration for contact poling. Left coplanar waveguide geometry (CPW), right sandwich configuration (parallel plate electrodes)...

Recently poling and modulation of a polymeric Mach-Zehnder modulator with conductivity dependency free, overcoming the latter poling issues, has been accomplished by using an in-plane coplanar waveguide (CPW) stmcture.[48] Furthermore, the use of buried electrode can improve overlap factor to enhance poling efficiency. A MZ modulators using the buried CPW showed the Vn s of 6.7 V [53]. 

Keywords Flexible electronics, polydimethylsiloxane (PDMS), microfabrication, transmission line, coplanar waveguide (CPW), pneumatic switching, metamaterials, negative index, terahertz, fishnet... 

Flexible electronic devices are increasingly capturing the attention of researchers in radio frequency (RF) technologies and metamaterials physics, and are not limited to electronics applications such as light emitting diodes (7). These devices are driven by the pliable, conformal, and stretchable characteristics of elastomeric substrates [7-13], Examples of RF and terahertz devices demonstrated on flexible device platforms include curved antennas [12], millimeter-wave patch flexible antennas and coupled line filters [13], coplanar waveguide antenna [14], stretchable microfluidic RF antenna [15], frequency selective surfaces and metamaterials [8], microwave frequency switches [16], tunable metamaterials [17, 18], and tunable dielectric and magnetic properties [10]. 

Figure 14.3 Schematic of a coplanar waveguide showing its geometry and RF testing arrangement.

Figure 14.4 Fabricated elastomeric coplanar waveguides utilizing 3- am-thick gold layers (a) Electron micrograph of microcracked morphology, (b) atomic force microscope scan showing surface microcracks, and (c) 40-mm-long gold CPW electrodes (with dimensions as shown in Figure 14.3) remain conductive when flexed as shown.

Coplanar waveguides with four different lengths (10, 20, 30, and 40 mm) were measured and the transmission coefficient (Sj,) was recorded. The transmission properties for these four measurements are presented in Figure 14.5. From... 

Figure 14.5 Measured transmission properties of coplanar waveguides on PDMS for four different lengths.

Figure 14.6 Simulated microwave effective index of the coplanar waveguide as a function of substrate dielectric constant. The intersection of the simulated and measimed indices occiu s at 2.72 and corresponds to the dielectric constant of PDMS.

In this section, we report on the combination of PDMS-based RF electronic devices and pneumatic valves to achieve a pneumatically-switched RF coplanar waveguide. PDMS has stable high frequency dielectric constant and low loss [21], while pneumatic valve technology offers a non-electronic form of control of RF devices eliminating electromagnetic interference and parasitic effects caused by bias lines. The outcomes present opportunities for pneumatically-switched addressable RF devices and elements. These can be utilized to control RF transmission in order to potentially activate or disable RF devices such as antenna and metamaterials [28]. 

Figure 14.14 Return loss of the pneumatically-switched coplanar waveguide device.

R.N. Simons, Coplanar Waveguide Circuits and Components and Systerms, Wiley-IEEE Press, 2001. 

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