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While achieving broadband angular selectivity for p-polarized wave has been well studied, it is still challenging for s-polarized wave. The reason is that at high frequencies such as terahertz spectrum, the permeability of materials has always approached unity. Here, we propose a solution to implement broadband angular selectivity for s-polarized incidences by combining an effective anisotropic diamagnetic medium and a staggered photonic structure. The diamagnetic medium is constructed with periodically arranged metallic rings, exhibiting negligible frequency dispersion in an ultra-wide terahertz band. By incorporating temperature-dependent dielectric into staggered structure, a thermally tunable broadband angular selectivity system is presented, with an adjustable selective angle ranging from 0° to 40°. Full-wave simulations verify the effectiveness of the proposed approach, breaking through the polarization limitation of the existing angular selectivity technology. The proposed approach is simple, robust, and scalable from microwave to terahertz frequencies. [ABSTRACT FROM AUTHOR]

Chaotic Colpitts circuits with fundamental frequency f * beyond 1GHz are studied by both circuit simulation and experiment using Philips’ broadband transistor with threshold frequency of 25GHz. For the basic configuration of Colpitts circuit with f * of about 1.6GHz, broadband continuous power spectra could be obtained from both circuit simulations and experiments. The harmonics of the observed signal from Agilent PSA/ESA spectrum analyzer are as noticeable as far as 12GHz. A modified Colpitts circuit structure employing the parasitic inductance of BJT (Bipolar Junction Transistor) is also proposed and investigated. By circuit simulation, chaotic attractor and broadband continuous power spectra could be obtained from the modified Colpitts circuit with f * of about 3.5GHz. Because the parasitic effects of the prototype board, the experiment result of the modified Colpitts circuit does not agree well with the simulation result. The gap between the simulation and experimental result could be bridged by replacing the lumped circuit elements with distributed ones. [ABSTRACT FROM AUTHOR]

In this paper, a random sequence generator based on chaotic circuits is presented. Fundamental principle and experimental circuit have been carried out in case of Chua’s circuit. The statistical results are in good agreement with probability characteristics of random sequence. [ABSTRACT FROM AUTHOR]

Based on the α-β bifurcation curves and the special characteristics of chaotic spectrum of chua’s circuit, this paper presents here a method for designing a Chua’s circuit which approximately satisfy specified spectrum distribution range. [ABSTRACT FROM AUTHOR]

Reports on the fabrication of a left-handed metamaterial with negative permittivity and permeability simultaneously in a specific small frequency band. Performance of refraction and beam-shifting experiments using triangular-shaped and parallelogram-shaped sample; Description of the refraction experiment.

In Physics, causality is a fundamental postulation arising from the second law of thermodynamics. It states that, the cause of an event precedes its effect. In the context of Electromagnetics, the relativistic causality limits the upper bound of the velocity of information, which is carried by electromagnetic wave packets, to the speed of light in free space (c). In anomalously dispersive media (ADM), it has been shown that, wave packets appear to propagate with a superluminal or even negative group velocity. However, Sommerfeld and Brillouin pointed out that the 'front' of such wave packets, known as the initial point of the Sommerfeld precursor, always travels at c. In this work, we investigate the negative-group-velocity transmission of half-sine wave packets. We experimentally observe the wave front and the distortion of modulated wave packets propagating with a negative group velocity in a passive artificial ADM in microwave regime. Different from previous literature on the propagation of superluminal Gaussian packets, strongly distorted sinusoidal packets with non-superluminal wave fronts were observed. This result agrees with Brillouin's assertion, i.e., the severe distortion of seemingly superluminal wave packets makes the definition of group velocity physically meaningless in the anomalously dispersive region. [ABSTRACT FROM AUTHOR]