Composite Sinusoidal-Modulated HMSIW Leaky-Wave Antenna Array With Flat-Topped Scanning Beams for Millimeter-Wave Applications

This letter proposes a leaky-wave antenna (LWA) array featuring flat-topped scanning beams based on the half-mode substrate integrated waveguide (HMSIW) structure. The array consists of two HMSIW LWA elements placed back-to-back, sharing a single row of composite sinusoidal-modulated vias. These vias are mapped from single-period sinusoidal-modulated structures with different periods, whose radiation beams are superposed in a weighting way according to the desired flat-topped radiation pattern. By etching some edge slots on the two sides of the array, the flat-topped beams can be scanned from backward to forward, including the broadside direction, without encountering the open stopband (OSB) phenomenon. Two antenna prototypes with three- and five-beam superpositions are fabricated and measured to validate the proposed design. The impedance bandwidth (|<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub>|<−10 dB) is across 30 GHz to 40 GHz with the beam scanning range from −34° to 30°, the 3 dB beamwidth at the center frequency is 46.4°, and the peak gain can go up to 7.4 dBi. Moreover, a three-dimensional cylindrical array composed of six proposed LWAs is designed and simulated to provide a multibeam full coverage in the azimuth plane when fed from different ports and a flat-topped beam-scanning in the elevation plane as the frequency varies, which is preferred for the applications of millimeter-wave (MMW) communication and radar systems.