A Compact CPW-Fed UWB Antenna with Dual Band-Notched Characteristics

A compact CPW-fed planar UWB antenna with dual band-notched property is presented. The dual band rejection is achieved by etching a C-shaped slot on the radiation patch and two L-shaped parasitic strips in the ground plane. The experimental and measured results show that the proposed antenna exhibits an impedance bandwidth over an ultrawideband frequency range from 2.4 to 12.5 GHz with VSWR less than 2, except for two stopbands at 3.3 to 3.75 GHz and 5.07 to 5.83 GHz for filtering the WiMAX and WLAN signals, respectively. It also demonstrates a nearly omnidirectional radiation pattern. The fabricated antenna has a tiny size, only 32 mm × 32 mm × 0.508 mm. The simulated results are compared with the measured performance and show good agreement. The simple structure, compact size, and good characteristics make the proposed antenna an excellent candidate for UWB applications

Wideband Printed Antenna Design Using a Shape Blending Algorithm

The shape of the tuning stub of the wide slot printed antenna is an important factor which affects the antenna’s performances. In this paper, a new design and optimization method of wideband printed slot antenna using a shape blending algorithm is presented. The proposed antenna consists of a wide rectangular slot and a tuning stub, whose profile is formed by the shape blending outcome from a pie and a diamond shape. The method is used to design an ultra-wideband antenna. The impact on the impedance bandwidth through the antenna geometry change with the different shape blending results has been investigated and analyzed. To verify the proposed design, the antenna prototype was designed, fabricated, and measured. The measured results are compared with the simulation and show good agreement

Achievement of Various Widebands: A Design of Wide-Slot Antennas Using Shape Blending

When designing printed wide-slot antennas, the shape or profile of the tuning stub is a key geometric structure that affects the impedance bandwidth of the antenna. This article introduces a new process for designing tuning stub shapes, which are the blended results of a diamond and a circle. By using different geometry shapes, the design could generate a series of bandwidths with a regular trend. Detailed investigations and analysis were conducted on some key geometry parameters to explore their impact on the impedance bandwidth of the antenna. To certify the new design method, several prototypes were simulated, developed, and measured. The experimental and simulated results showed good agreement with each other. The results indicate that by properly selecting various blended shapes, a BW range from 80.1 to 117.3% for a VSWR of less than 2 could be obtained, which provides a convenient model for a wideband antenna design

A Tunable Constant-Absolute-Bandwidth Bandpass Filter with Switchable Ability

This paper presents a tunable bandpass filter (BPF) with constant absolute bandwidth (CABW) and switchable properties. The BPF is performed by using a tri-mode cross-shape resonator (CSR) loaded with varactors. The CABW and switchable ability are achieved by adjusting the resonant frequencies. Meanwhile, the two transmission zeros (TZs) produced by center-loaded stubs strengthen the skirt selectivity in the on-state and the isolation in the off-state. For demonstration, a tri-pole switchable BPF with three control voltages is implemented and verified, and the control mechanism is simple. In the on-state, it exhibits a 120 MHz, 3 dB CABW with the measured insertion loss (IL) of 2.2–2.5 dB in the tuning range of 0.816–1.188 GHz. In the off-state, the measured isolation is better than 27 dB

A Tunable Constant-Absolute-Bandwidth Bandpass Filter with Switchable Ability

This paper presents a tunable bandpass filter (BPF) with constant absolute bandwidth (CABW) and switchable properties. The BPF is performed by using a tri-mode cross-shape resonator (CSR) loaded with varactors. The CABW and switchable ability are achieved by adjusting the resonant frequencies. Meanwhile, the two transmission zeros (TZs) produced by center-loaded stubs strengthen the skirt selectivity in the on-state and the isolation in the off-state. For demonstration, a tri-pole switchable BPF with three control voltages is implemented and verified, and the control mechanism is simple. In the on-state, it exhibits a 120 MHz, 3 dB CABW with the measured insertion loss (IL) of 2.2–2.5 dB in the tuning range of 0.816–1.188 GHz. In the off-state, the measured isolation is better than 27 dB

Morphologies, classification and genesis of pockmarks, mud volcanoes and associated fluid escape features in the northern Zhongjiannan Basin, South China Sea

Based on new high-resolution multi-beam bathymetry and multichannel seismic reflection data, two new groups of numerous pockmarks and mud volcanoes were discovered in the northern Zhongjiannan Basin at water depths between 600 and 1400 m. Individual pockmarks are circular, elliptical, crescent-shaped or elongated, with diameters ranging from several hundreds to thousands of meters and tens or hundreds of meters in depth, and they often form groups or strings. Crescent pockmarks, approximately 500–1500 m wide in cross-section and 50–150 m deep, occur widely in the southern study area, both as individual features and in groups or curvilinear chains, and they are more widespread and unique in this area than anywhere else in the world. Conical mud volcanoes, mostly with kilometer-wide diameters and ca. 100 m high, mainly develop in the northern study area as individual features or in groups. Seismic data show that the observed pockmarks are associated with different kinds of fluid escape structures and conduits, such as gas chimneys, diapirs, zones of acoustic blanking, acoustic turbidity and enhanced reflections, inclined faults, small fractures and polygonal faults. The mapped mud volcanoes appear to be fed from deep diapirs along two main conduit types: the conventional conduits with downward tapering cones and another other conduit type with a narrow conduit in the lower half and emanative leakage passages in the upper half. Various types of pockmarks are found and a comprehensive pockmark classification scheme is proposed, according to: (a) their shape in plan view, which includes circular, elliptical, crescent, comet-shape, elongated and irregular; (b) their magnitude, which includes small, normal, giant and mega-pockmarks; and (c) their composite pattern, which includes composite pockmarks, pockmark strings and pockmark groups. For the genesis of the crescent pockmark (strings), a 5-stage speculative formation model is proposed, implying possible controlling factors of gravity sliding/slumping, fluid escape activity and sandbodies intrusion. Seismic data suggest that the mud volcanoes have likely undergone two episodes of evolution, which include a widespread drastic formation of mud volcanoes with dome-like structures, a wide range of seepage occurrences and the formation of complex sediments in the first stage, and the appearance of pockmarks, conical mud volcanoes (groups), and the formation of deformed, filled or broken buried complex sediments by continuous fluid flow processes during stage 2, in the Pliocene and the Quaternary. Pockmark gullies are extensively found along the slope, due to the interaction of slope failure and fluid escape processes. The Cenozoic sedimentary cover is thin in the Northern Zhongjiannan basin, which evolved from a Late Cretaceous or Palaeogene–Oligocene rift to the Neogene–Quaternary post-rift thermal subsidence, and therefore intense deep thermogenic fluid flow can easily affect the soft Cenozoic sediments, produce complex sediment deformation, and form numerous fluid flow structures at the seafloor, in particular pockmarks and mud volcanoes that dominantly emerged during the period of post-rift thermal subsidence and neotectonic movement since ca. 5.5 Ma