Leaky-Wave Antennas

First introduced in 1950s [86], leaky-wave antennas (LWA) are popularly known for their beam-scanning capabilities. LWAs radiate because of the leakage of the travelling wave as it propagates through a guiding structure [87], [88]. LWAs generally have an inherent property of frequency-controlled beam-scanning, which means that the radiated beam direction changes with the change in operating frequency. This is because all the radiating elements in an LWA are fed sequentially, and with change in frequency, the inherent phase shift between radiating elements changes, which directly impacts the beam direction as shown in Figure 3.