TABLE OF CONTENTS The manufacturing cost of a microstrip circuit is mainly determined by the material cost of the substrate. Therefore, it is important to consider efficient use of the substrate area in addition to the fulfillment of the electrical requirements. This makes it necessary that the circuit elements on a substrate often cannot be interconnected in a straight line. Circuit elements are commonly placed together with a high package density that requires the inclusion of bends in the interconnecting transmission lines.
A right-angled or 90 bend is shown in Figure 6.68. Figure 6.69 shows the quasi-static equivalent circuit. In the vicinity of the corner of the bend, the electromagnetic field and current flux lines are disturbed. Near the inner corner edge, current flux line density is increased. At the outer corner, excess charge is accumulated and additional electrical fringe field occurs. The series inductance L b of the equivalent circuit represents the current flux distortion, and the parallel capacitance C b represents the distortion of the electrical field. T 1 and T 2 denote the reference planes of the microstrip discontinuity.
Closed-form expressions for the right-angled bend capacitance and inductance have been published by Gupta et al. [26]:
| (6.105) |  |
| (6.106) |  |
Regarding the following geometry and material data, an accuracy of 5%, and 3% respectively, is quoted:
| (6.107) |  |
| (6.108) |  |
Assume a...
