Printed leaky-wave antenna with aperture control using width-modulated microstrip lines and TM surface-wave feeding by SIW technology

This letter presents a width-modulated microstrip line leaky-wave antenna (LWA) with substrate-integrated waveguide and microstrip feeding. In particular, the planar antenna system consists of an integrated surface-wave launcher and three identical rows of quasi-periodic width-modulated microstrip lines for TM leaky-wave excitation, which produces a tailored binomial-like aperture distribution on the guiding surface. The behavior of the antenna when changing the width-modulated lines for different aperture distributions is also analyzed and presented. The measured LWA demonstrates a fan beam pattern in the far field with realized gain values greater than 10 dBi and with a beam direction of about -20° from broadside at 23 GHz. Also, far-field measurements and near-field data indicate that the half-power beamwidth is below 10°, and the position of the main beam maximum is relatively stable, i.e., ranging from about -23° to -15° between 23 and 24 GHz. The measured prototype is also well matched over these frequencies and |S₁₁| < -20 dB at 23.5 GHz.