Conceptual-based design of an ultrabroadband microwave metamaterial absorber

By introducing metallic ring structural dipole resonances in the microwave regime, we have designed and realized a metamaterial absorber with hierarchical structures that can display an averaged −19.4 dB reflection loss (∼99% absorption) from 3 to 40 GHz. The measured performance is independent of the polarizations of the incident wave at normal incidence, while absorption at oblique incidence remains considerably effective up to 45°. We provide a conceptual basis for our absorber design based on the capacitive-coupled electrical dipole resonances in the lateral plane, coupled to the standing wave along the incident wave direction. To realize broadband impedance matching, resistive dissipation of the metallic ring is optimally tuned by using the approach of dispersion engineering. To further extend the absorption spectrum to an ultrabroadband range, we employ a double-layer self-similar structure in conjunction with the absorption of the diffracted waves at the higher end of the frequency spectrum. The overall thickness of the final sample is 14.2 mm, only 5% over the theoretical minimum thickness dictated by the causality limit.

Numerical Study of Extremely Wideband-Modified Biconical Radiation Structures for Electronic Support Measures Application

Using the finite difference time domain (FD-TD) method, this paper studies radiation structures that can have multiple tunable frequency bands between 0.4 GHz and 4 GHz, a fixed band in [3.97, 5.36] GHz and an extremely wideband from 6.14 GHz to 68.27 GHz, where a frequency band is defined by the voltage standing wave ratio (VSWR) less than or equal to two. The base radiation structure has a modified-biconical antenna configuration, called base MBA, and is fed by a square-coaxial line with characteristic impedance close to 50 ohms. A dielectric ring and an outer dielectric cover are used between the two modified cones to enlarge the frequency band and strengthen the structure. An equal number of metallic-rings can be stacked at both circular-ends of cones in the base MBA to tune the positions of the frequency bands that are lower than 4 GHz and to alter their vertical polarization (V-pol) patterns. However, compared with those of the base MBA, these stacked metallic rings do not make significant changes to the VSWR in the [3.97, 5.36] GHz and [6.14, 28.27] GHz bands and the radiation patterns in the [6.14, 28.27] GHz band. The simulation results show that the base MBA and its metallic-ring-loaded versions all have V-pol radiation characteristics at all frequency bands and have donut-shaped omnidirectional patterns only when the wavelength is bigger than the length of the structure. When the wavelength is less than the size of the radiation structure, the donut shape is modified with ripples on the V-pol radiation pattern. Sometimes deep notches could be observed when MBAs operated at the higher end of the extremely wideband. A 0.2 mm cube was used to construct the antenna structures with the consideration of using the 3D metal/dielectric printer technology to build the antennas in the future.

A metallic ring penile foreign body causing penile strangulation: a rare case report

Strangulation of penis is a rare clinical entity, which requires urgent urological management to prevent its devastating outcomes. The treatment of penile strangulation is immediate decompression of the constricted penis to facilitate free blood flow. Many different techniques have been described in literature to remove the constricting penile foreign bodies, but there is no universally accepted technique. Each case needs individualized handling in removing the foreign body. The procedure should be done with as little discomfort to the patient as possible and under anesthesia. Here we present to you a case report on a rare case of a metallic ring penile foreign body causing penile strangulation.

Bandwidth improvement of planar antennas using a single-layer metamaterial substrate for X-band application

To prevent far-field radiation characteristics degradation while increasing bandwidth, an attempt has been made to design and fabricate a microstrip antenna. An electromagnetic band gap (EBG) structure, including a layer of a metallic ring on a layer of Rogers 4003C substrate, is used. For a better design, a patch antenna with and without the EBG substrate has been simulated. The results show that the bandwidth can be improved up to 1.6 GHz in X-band by adding the EBG substrate. Furthermore, using this structure, a dual-band antenna was obtained as well. Finally, to validate the simulation results, a comparison has been done between simulation data and experimental results which demonstrate good agreement.

Penile Rings: No Innovation without Evaluation

Penile strangulation is a rare clinical entity which if left untreated can cause serious urogenital problems. We present the case of 45-year-old male patient who presented with penile strangulation after applying a metallic ring. Strangulation of the external male genitalia is a serious problem that requires urgent intervention in order to avoid serious complications. If left untreated, it can result in gangrene and penile amputation. Management of penile strangulation is a real challenge for the treating surgeon and should be treated as an emergency in order to avoid vascular compromise.