A New Impedance Matching Approach For Microstrip Rotman Lens Based On Analyzing The Standing Wave Pattern Of An Electric Field

This article proposes a new impedance matching method to provide an energy transformer between 50 omega beam ports and the cavity of a Rotman lens. The model is derived from a quarter length transition line impedance transformer. The suggested matching technique is based on determining and analyzing standing wave patterns of electric field signals underneath feeding lines of the beam ports when they are excited with a designed frequency of 2.45 GHz. The proposed approach demonstrates the ability of the model to achieve an acceptable return loss compared to traditional taper line model matching methods, even though it increases the operating bandwidth frequency based on the measured results. Moreover, it solves the optimization iteration time consuming that is required to determine the tapering line length used in the conventional impedance matching techniques. The predicted results of the return loss are validated by measurements of the fabricated prototype microstrip lens printed on an FR-4 substrate that is designed to work in the industrial, scientific, and medical (ISM) band in order to form five beams in the directions -26 degrees, -13 degrees, 0 degrees, 13 degrees, and 26 degrees.