This paper proposes a compact reconfigurable (bandstop/bandpass) and frequency-tunable structure based on S-shaped split ring resonators (S-SRRs). It is known that an S-SRR coupled to a coplanar waveguide (CPW) provides a stopband in the transmission characteristic of the line. It is shown here that this behaviour of the S-SRR can be switched between fundamental resonance and second harmonic response by introduction of a PIN diode in the center segment of the S-SRR. Alternatively, if the S-SRR is loaded with a varactor diode instead of a switch, the frequency of the stopband can be continuously tuned from the S-SRRs fundamental resonance frequency to its second harmonic. Furthermore, it is shown that if a pair of shunt PIN diodes are introduced across the slots of the host CPW, the structure can be reconfigured from a bandstop to a bandpass structure. Thus, the proposed resonator structure can be used as the building block of reconfigurable (bandstop/bandpass) filters with tunable operating frequency. Finally, in order to demonstrate a practical application of the proposed structure, an ultrawideband antenna with a tunable band-notch is designed and experimentally validated.Index Terms-Reconfigurable antennas, S-shaped split ring resonator (S-SRR), ultrawideband antenna.

This paper proposes a two-dimensional alignment and displacement sensor based on movable broadside-coupled split ring resonators (BC-SRRs). As a basis for this sensor, a one-dimensional displacement sensor based on a microstrip line loaded with BC-SRRs is presented firstly. It is shown that compared to previously published displacement sensors, based on SRR-loaded coplanar waveguides, the proposed one-dimensional sensor benefits from a much wider dynamic range. Secondly, it is shown that with modifications in the geometry of the BC-SRRs, the proposed one-dimensional sensor can be modified and extended by adding a second element to create a high-dynamic range two-dimensional displacement sensor. Since the proposed sensors operate based on a split in the resonance frequency, rather than the resonance depth, they benefit from a high immunity to environmental noise. Furthermore, since the sensors' principle of operation is based on the deviation from symmetry, they are more robust to ambient conditions such as changes in the temperature, and thus they can be used as alignment sensors as well. A prototype of the proposed two-dimensional sensor is fabricated and the concept and simulation results are validated through experiment.Keywords: metamaterials, alignment sensor, displacement sensor, two-dimensional, high dynamic range Preprint submitted to Sensors and Actuators A: Physical January 17, 2014 Pre-print of: Horestani, Ali K., et al. "Two-dimensional alignment and displacement sensor based on movable broadside-coupled split ring resonators" in Sensors and actuators (Ed. Elsevier), vol. 210

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This paper presents a step‐by‐step procedure for the design of a slot array antenna in groove gap waveguide technology. The design procedure is based on defining an effective width for groove gap waveguides. To accomplish this, a direct equivalent correspondence is assumed between the groove gap waveguide and a rectangular waveguide. It is demonstrated that once the effective width of the groove gap waveguide is found, conventional equations for the design of slot‐array rectangular waveguide antenna can be utilised to accurately design a slot array antenna in gap waveguide technology. Thus, unlike other methods available in literature, the proposed method only requires the knowledge of propagation constant in the dominant mode of the groove gap waveguide. Since analytic equations are utilised, the design of a slot array groove gap waveguide antenna with very good impedance matching and desired side‐lobe level can be accomplished in a fast optimisation process. Using the proposed method, slot array antennas with uniform and Chebyshev distribution of slots are designed. Finally, a prototype of a designed antenna is fabricated and its reflection coefficient and radiation pattern are measured to provide an experimental verification.