A Survey of Flat Profile Microwave Antennas.
Abstract
Microstrip is a form of strip transmission line and its geometry is shown in cross section. It was conceived in 1952, but development of its uses at microwave frequencies was slow due to lack of low dielectric constant materials and processing difficulties. The parameters required for design of microstrip devices are line impedance, Z sub m, and effective dielectric constant, epilson sub eff, which is used to determine the wavelength in the line, lamba sub m. Wheeler has derived expressions for these, using a conformal transformation technique. He presents expressions for synthesis, that is, determination of w/h and episilon sub eff given Z sub m and episilon sub d, the substrate dielectric constant, and for analysis, that is determination of Z sub m and episilon sub eff given w/h and episilon sub d. Wheeler's analysis produces two sets of expressions each valid below and above a certain value of w/h. Wheeler chooses this crossover value as 2. Hammerstad has compared the results of Wheelers expressions to those given by an accurate but quite complex method involving Greens functions. By adjusting some of the constants he has reduced the errors from about 4% to less than 1%. Owens has adopted the same approach but reduced both the discontinuity and absolute errors by altering the crossover point. For high dielectric constant materials (episilon sub d = 10) dispersion has been noticed at 1GHz and differences of 10% in Z sub m and episilon sub eff from electrostatic values occur at 10 GHz Schmitt and Sarges have described a dynamic solution to microstrip propagation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1977
- Accession Number
- ADA116834
Entities
People
- Jaylen James
- P. S. Hall