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Electromagnetic (EM) wave propagation in periodic structure is an interesting research topic in electronic, optical and laser systems. Conventionally, wave propagation in periodic media can be characterized by the Bragg's law where the resonance frequency can be determined by the periodicity of the media and a wave incident angle. However, there is also a kind of non-Bragg resonance which cannot be characterized by the traditional Bragg's law. A non-Bragg resonance has been observed in a rectangular waveguide with corrugated walls by the Cheng et al. [1]. The resonance frequency depends on the waveguide height (or thickness), the periods and amplitudes of the corrugations, and a phase shift between the corrugated walls. Since non-Bragg resonance only occurs under specific geometric conditions, it is also known as geometric resonance [1].

An electromechanically steerable directional antenna with a floating pillar array has been demonstrated for 2.4 GHz in-plane communication. A linear array of three floating pillars with a space of 0.06λ each other, a height of 0.38λ, a gap of 0.01λ from ground, and a distance of 0.06λ from the monopole is held in a piece of Styrofoam with a permanent magnet attached. The Styrofoam is rotatable in 360° in-plane scanning range around the monopole with the monopole as a rotating axis, where a permanent magnet integrated motor underneath the substrate is used to move pillars. The antenna shows a 10 dB-bandwidth of 10% and an average gain of 7 dBi with VSWR

Among short-range wireless communication systems, Ultra-wideband (UWB) technology, with a frequency allocation of 3.1–10.6 GHz, has gained a lot of popularity from researchers and the wireless industry alike due to the high data transfer rate (110–200 Mb/s) and low power consumption. However, since UWB covers the frequency spectrum of Wireless Local Area Network (WLAN) operating at 5.2 GHz (5150–5350 MHz) and 5.8 GHz (5725–5825MHz), a frequency notched function in the UWB antenna design is greatly desirable to avoid interferences from WLAN. Since 2002, various antenna structures [1, 2] and methods to notch a specific frequency band [1, 3, 4] have been introduced. Moreover, a planar integrated antenna working on both Bluetooth and UWB has been recently introduced for systems operating in those two communication systems [5, 6].