STRIPS

Abstract: The process starts with a primary mask, which may be characterized as a pattern of parallel, photoresist strips having substantially vertical edges, each having a minimum feature width F, and being separated from neighboring strips by a minimum space width which is also approximately equal to F. From this primary mask, a set of expendable mandrel strips is created either directly or indirectly. The set of mandrel strips may be characterized as a pattern of parallel strips, each having a feature width of F/2, and with neighboring strips being spaced from one another by a space width equal to 3/2F. A conformal stringer layer is then deposited. The stringer layer material is selected such that it may be etched with a high degree of selectivity with regard to both the mandrel strips and an underlying layer which will ultimately be patterned using a resultant, reduced-pitch mask. The stringer layer is then anisotropically etched to the point where the top of each mandrel strip is exposed. The mandrel strips are then removed with an appropriate etch. A pattern of stringer strips remains which can then be used as a half-pitch mask to pattern the underlying layer. This process may also be repeated, starting with the half-pitch mask and creating a quarter-pitch mask, etc. As can be seen, this technique permits a reduction in the minimum pitch of the primary mask by a factor of 2-N (where N is an integer 1, 2, 3, . . . ).

Abstract: A simple procedure for designing a sinusoidally-modulated reactance surface (SMRS) that radiates at an arbitrary off-broadside angle is outlined. The procedure allows for nearly independent control of the leakage and phase constants along the surface. Printing an array of metallic strips over a grounded dielectric substrate is discussed as a way to practically implement the theoretical SMRS. A method of mapping the gaps between metallic strips to a desired surface impedance is presented as an efficient alternative to mapping methods used in the past. A printed leaky-wave antenna with a sinusoidally-modulated surface reactance is designed using the procedure mentioned above. The TM-polarized antenna radiates at 30° from broadside at 10 GHz, and exhibits an experimental gain of 18.4 dB. Theoretical, simulated, and experimental results are presented.

Abstract: A frequency-dependent hybrid-mode analysis of single and coupled slots and coplanar strips is presented. The dispersion characteristic and characteristic impedance of the structures are obtained by applying a Fourier transform technique and evaluating the resulting expressions numerically using the method of moments. Numerical results are presented and compared with results published by other investigators. The experimental performance of a slot-line coupler is compared with predicted performance based upon the results presented here for coupled slots. Excellent agreement has been obtained in all cases.

Abstract: An analysis is made of the odd and even TEM modes on a pair of parallel co-planar strips midway between ground planes. Rigorous formulas are presented for the case of zero-thickness strips, while approximate formulas are given for strips of finite thickness and for strips printed on opposite sides of a thin dielectric sheet supported in air between ground planes (AIL construction). The characteristic impedances and the phase velocities of the two modes are necessary and sufficient information for the design of directional couplers, coupled-line filters, and other components utilizing the coupling between parallel-strip lines. In order to facilitate design work, nomograms are included in the paper which give the dimensions of the coupled-strip cross section in terms of the odd- and even-mode characteristic impedances. The characteristic-impedance scales of these nomograms may be read to an accuracy of better than one per cent over a wide range of values that is sufficient for most purposes.