Some aids in the design of microstrip components II: Nomograms

Nomograms have been developed for coupled microstrips. With the help of these, it is possible to design various microstrip components. The design of a multiplexer using the directional filter is described and experimental results are given. Nomograms relating the even and odd mode impedances of coupled microstrip lines to the width to height rate and spacing to height ratio have been developed using the relations formulated by Schwarzmann. A multiplexer using directional filters is designed to operate with three channels at frequencies of 3÷3, 3÷4 and 3÷5 GHz and bandwidths of 10 MHz in each channel. Experimental results are given. The design specifications are satisfied reasonably well.

Aids in the design of microstrip components I: Getsinger's chart

Charts relating the capacitance to the width, spacing, thickness and height above the ground plane of coupled microstrips have been obtained. These are used to design hairpin line and hybrid hairpin line filters as well as multiplexers using microstrip comb line filters. The experimental results agree reasonably well with the design specifications. Getsinger's original charts for parallel coupled bars between parallel plates have been formulated for the microstrip case. Corresponding charts relating the capacitances to the width, spacing, thickness and height above the ground plane of coupled microstrips have been obtained. Examples of the use of these charts are shown in the design of hairpin lines and hybrid hairpin line filters as well as multiplexers using comb line filters. The hairpin line/hybrid hairpin line filters were designed to operate at a central frequency of 9÷5 GHz with 11 per cent bandwidth and 0÷5 dB ripple. The three filters constituting the comb line filters have center frequencies of 2÷4, 3÷0 and 3÷6 GHz. The components so designed were fabricated and tested. The dielectric used for the microstrip was teflon. Experimental curves for the attenuation (insertion loss) and VSWR are given. The design specifications arc satisfied quite well.