Coplanar transmission line

Planar resonators and microstrip and coplanar transmission lines represent the passive elements in almost any integrated circuit technology at first, on chip integration in socalled mmics (monolithic microwave integrated circuits) with SiGe or m/v semiconducting active... 

It was apparent that voids were created in the top/bottom of the dielectric seal during processing of the samples that contained the microstrip transmission line. For this reason, a majority of the testing was performed on samples containing the coplanar transmission line. 

Microwave in Microfiuidics, Fig. 7 (a) Top view of the coplanar transmission line heater for droplet heating [3], (b) Cross-sectional view of the system with microchannel and the coplanar transmission line. The E field distribution is calculated using numerical... 

Both thin- and thick-film technology allow planar microstrip or coplanar transmission lines. However, requirements on line and coupling-gap accuracy do not always permit traditional screen printing. Etching techniques or photosensitive paste systems offer a potential solution. LTCC provides more design freedom. Impedance-matched line transitions (e.g., from microstrip to stripline or to an embedded waveguide) are possible. 

The variation in the impedance of the microstrip transmission line samples was approximately 150% greater than that of the samples that employed the coplanar type transmission line. Figure 4-7 shows a composite of the coplanar waveforms while Figure 4-8 shows a composite of the microstrip waveforms. 

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. 

Issadore et al. [3] extended the microwave heating cmicept to two phase systems. A coplanar transmissimi line stracture is used to heat water droplets suspended in fluorocarbrni oil in a microcharniel. The system operates at 3 GHz and the conductive lines of the transmission line are obtained by using indium alloy wires which has a skin depth of6.625 pm at the operating frequency. Twochannels with a cross section of 100 x 50 pm... 

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... 

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

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]. 

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