Non-Diffracting All-Metal Leaky-Wave Antenna

All-metal corrugated leaky-wave antennas lend themselves to applications requiring low loss, high gain, focused near field, as well as compact and robust structures. This work investigates the near-field focusing abilities of radially periodic, azimuthally symmetric leaky-wave antennas, studied through dispersive analyses of the leaky mode supported by the linearized period of the annular structure, which allows for flexible optimization of the radiation performance in terms of non-diffracting range and bandwidth at different frequencies. It is, in fact, possible to easily change the working frequency by uniformly scaling the dimensions of the structure, whose behavior can be described by the same dispersive analysis in the corresponding frequency band. Numerical analyses of an all-metal leaky-wave launcher operating beyond 100 GHz are reported, achieved by suitably scaling a K-band design originally developed for far-field applications. The open stopband is suppressed, offering therefore enhanced focusing capability. Zeroth-order Bessel beams are presented, operating around 160 GHz. This opens new opportunities for realizing compact, non-diffracting, and low-loss radiating structures, as well as feeding systems for near-field coupled transmit-arrays. Future investigations will also consider more compact implementations.