This is an arbitrary distinction. Propagation Main article: Radio propagation Microwaves travel solely by line-of-sight paths; unlike lower frequency radio waves, they do not travel as ground waves which follow the contour of the Earth, or reflect off the ionosphere skywaves. Microwaves are absorbed by moisture in the atmosphere, and the attenuation increases with frequency, becoming a significant factor rain fade at the high end of the band. A spectral band structure causes absorption peaks at specific frequencies see graph at right. Troposcatter Main article: Tropospheric scatter In a microwave beam directed at an angle into the sky, a small amount of the power will be randomly scattered as the beam passes through the troposphere.

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E82—C, NO. A theoretical analysis is given by a combination of the conformal mapping technique and the variational principle. Numerical results demonstrate signi? Introduction In monolithic microwave integrated circuits MMICs , microwave passive circuits usually dominate the chip size than the active devices. To reduce their size, miniaturization of the microstrip line and coplanar waveguide CPW , which are two fundamental transmission lines widely used in MMICs, is necessary.

In this paper, we present a technique for the miniaturization of such two lines by using airbridge technology. Airbridge technology is widely used in the MMICs such as a shell of the microwave transmission lines or circuit elements [1]—[3], [16]. In case of the transmission lines with airbridge, the existing of airbridge may greatly a? Comparing with the conventional microstrip line, in which the width of the strip is determined by the thickness of the substrate for a required characteristic impedance, the ABMSL can have a smaller size strip primarily depending on the dimensions of the airbridge.

Obviously, the airbridge can also protect the lines physically and electrically, and prevent the radiation loss and crosstalk from Manuscript received December 26, Manuscript revised March 19, This concept of using airbridge is originally from the design consideration of the traveling-wave optical modulator using LiNbO3 , in which a conductor cover over the microwave deriving electrodes was introduced to speed up the propagation of the microwave in order to match the optical velocity [4], [5].

In this paper, we present an analysis of the proposed airbridged lines to show the e? With the consideration of including the multilayered structures which are widely introduced in MMICs in recent years [6], [7], the substrate of the proposed lines are taken as a three-layered one for a more general case. The fundamental substrate used in analysis is GaAs its dielectric constant: Since several widely used methods of analysis, such as confor- Fig. The method of analysis in this paper employes a combination of the conformal mapping technique and the variational principle under quasi-TEM wave approximation [4], [12].

After a description of the analysis method for airbridged microstrip line as a sample, we present a series of numerical results to demonstrate the characteristics of the proposed lines. Theory of Analysis 2. First, we transform the upper region including the airbridge and the strip conductor into an upper semi-in?

In contrast, the electric energy in the lower multilayered dielectric region is derived directly by Fourier series expansion or Fourier transform in the horizontal layer direction, i. This derivation for the multilayered region is fairly complicated but the? Expanding the potential into Fourier series yields an expression of the Fourier coe? Finding their solution on a computer and back them to Eq.

From above relations, the total electric energy in the whole region in per unit length then becomes M? From this table, we can? This means that we can design a much smaller size ABMSL for a required characteristic impedance by using airbridged structure.

Table 1 clearly shows the miniaturization e? To give an example of comparison, we roughly de? According to above de? Figure 6 shows the numerical results of the characteristic impedance and e?

Changing of a small hb gives a sharp change of the characteristics. Figure 7 shows the numerical results of the characteristic impedance and e? As can be seen from the results in Figs. Numerical Results and Discussions Numerical results are presented to demonstrate the characteristics of the proposed lines shown in Fig. The conductors in the lines are assumed perfectly conducting. Width of the lower multilayered region a is taken as more than times of the width of the central electrode in order to simulate the open structure, which is an enough value to eliminate the e?

To con? As shown in Fig. An adaptive non-uniform discretization of the boundary has been made in calculation by taking the sharp variation of the potential into account.

This can be easily understood by considering the fact that very small size airbridge makes the electric? Figure 8 shows the e? Both the characteristic impedance and e? The thickness of the strip conductor gives more in? Figure 9 shows the e? It is should be noticed that the presented data are based on TEM wave approximation, as mentioned previously, so there is a limitation to use the data for high frequency operation due to the dispersion of those microstrip lines under consideration. From the experimental data given in [15] for a 50 ohm microstrip line on a ?

This indicates a criterion to using the quasi-TEM data, though the dispersion characteristics strongly depends on the relative dimensions to operating wavelength and the dielectric constant of the substrate. In addition to the dispersion property, this paper does not give an analysis result for leaky-wave, which is another important phenomenon occurring in printed circuits such as microstrip lines and CPWs.

The cuto? This frequency is far beyond the frequency range under consideration of the present MMICs. Conclusion Acknowledgement The author is very much thankful for the helpful discussions with Professor K.

Atsuki, the University of Electro-Communications, and Dr. References [1] E. Wasige, G. Kompa, F. Rangelow, W. Scholz, F. Shi, R. Kassing, R. Meyer, and M. Watson and K. Weller, K. Herrick, and P.

Noguchi, O. Mitomi, H. Miyazawa, and S. Lightwave Technology, vol. Davies and D. MTT, pp. Tokumitsu, T. Hiraoka, H. Nakamoto, and M. EC, no.

Kitazawa, D. Polifko, and H. Itoh, ed. Li and K. Li, K. Atsuki, and T. MTT, no. An analysis of the two lines was presented to show the e? The method of analysis is a combination of the conformal mapping technique and the variational principle, which will provide a very powerful and e? The numerical results demonstrated that the proposed lines: ABMSL and ABCPW have advantages of much smaller size and wider range of characteristic impedance as well as the preventing of radiation loss on principle.

Using airbridge has also an advantage that the dielectric substrate for the lines can be many materials, comparing the micromachining technique where the substrate is usually Si. The airbridge technique can be considered as an e?

Finlay, R. Jansen, J. Jenkins, and I. Bessemoulin, C. Algani, G. Alquie, and V. He received the B. His research interests include electromagnetic analysis, microwave circuit analysis and design, optical waveguides, and optical devices such as optical modulators and photodetectors in high speed optical communications, and the interactions between microwaves and optical waves.


Microwave integrated circuits,



0470336404 - Microwave Integrated Circuits, by Gupta, K C



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