UWB Region Research Articles

A Conformal Frequency Reconfigurable Antenna with Multiband and Wideband Characteristics.

A compact flexible multi-frequency antenna for smart portable and flexible devices is presented. The antenna consists of a coplanar waveguide-fed slotted circular patch connected to a rectangular secondary resonator (stub). A thin low-loss substrate is used for flexibility, and a rectangular stub in the feedline is deployed to attain wide operational bandwidth. A rectangular slot is etched in the middle of the circular patch, and a p-i-n diode is placed at its center. The frequency reconfigurability is achieved through switching the diode that distributes the current by changing the antenna’s electrical length. For the ON state, the antenna operates in the UWB region for −10 dB impedance bandwidth from 2.76 to 8.21 GHz. For the OFF state of the diode, the antenna operates at the ISM band (2.45/5.8 GHz), WLAN band (5.2 GHz), and lower X-band (8 GHz) with a minimum gain of 2.49 dBi and a maximum gain of 5.8 dBi at the 8 GHz band. Moreover, the antenna retains its performance in various bending conditions. The proposed antenna is suitable for modern miniaturized wireless electronic devices such as wearables, health monitoring sensors, mobile Internet devices, and laptops that operate at multiple frequency bands.

A modified microstrip line fed compact UWB antenna for WiMAX/ISM/WLAN and wireless communications

A novel design of compact UWB antenna is presented using a spanner shaped microstrip line. The proposed antenna consists of a rectangular patch with step slot at one of the lower edge and the defected ground plane embedded with a mirror imaged ‘P’ shaped slot. By using the novel spanner shaped feed line, the measured bandwidth of 153.22% (2.94–22.2 GHz) for VSWR ≤ 2 is achieved. The realised gain of the antenna is calculated and it is varying from −1.38 to 5.18 dB for the entire band of operation. The radiation patterns of the antenna are measured at 3.1, 6.85, 10.6 and 18 GHz which includes lower, middle and upper cut off frequencies of UWB region. The prototype of the design is fabricated and measurement is carried out in order to validate the proposed results. Also, the time domain analysis is performed to calculate the group delay and fidelity factor which are satisfying the UWB limits.

DESIGN OF DEFECTED GROUND BAND PASS FILTERS USING STEPPED IMPEDANCE RESONATORS

In this paper, band-pass fllters based on the microstrip conflguration and utilizing coupled defected ground structures are presented. The 50› microstrip line has a gap discontinuity in the middle and characterized by stepped impedance resonators on either half. The four fractal geometries tested for defected ground are the flrst and second iterations of the modifled Moore curve, the closed staircase curve and a dual concentric closed staircase curve. The fllters have a compact size and planar geometry. The modifled Moore flrst iteration has a measured pass band from 2.27GHz to 11.86GHz, whereas the second iteration has a measured pass band from 1.85GHz to 6.71GHz. The measured pass band of the closed staircase fllter is from 2.38GHz to 7.21GHz. The dual-concentric closed-staircase DGS fllter ofiers a dual-band response with the measured pass band being from 2.41GHz to 5.01GHz and from 5.81GHz to 8.35GHz. All the fllters can have applications in the UWB region. A parametric study showing the efiect of the various controlling parameters is also presented.

Optimum Design of Novel UWB Multilayer Microstrip Hairpin Filters with Harmonic Suppression and Impedance Matching

Optimum design of a novel ultra-wideband multilayer microstrip hairpin filter is presented, providing for harmonic suppression and impedance matching between source and load impedances. The theory of N-coupled transmission lines is employed to obtain an equivalent circuit for development of a design procedure based on the method of least squares. A prototype model of proposed two-layer filter of order 5 is fabricated for 3.1–10.6 GHz. The dimensions of designed filter are 23 mm × 7 mm. The insertion loss in the passband varies from 0.3 dB to 3 dB (in the worst case at the edge of passband) and in the stopband is about 30 dB up to 20 GHz. Its group delay in the UWB region is about 0.5 ns. Close agreement among the filter frequency responses as obtained by the proposed method, full-wave computer simulation softwares, and measurement data verify the effectiveness of the proposed filter structure and design methods.

A Double Square Loop Antenna with 45° Step Beam Steering

A novel form of Double Square Loop (DSL) antenna for beam adaptive applications is presented and analysed. The double square loop antenna consists of two identical square loops with a common centre placed at 45° to each other. The antenna is fed either at the eight external corners or at the eight mid-points of the inner track, which when excited one at a time steer the beam through 360° in steps of 45°. Also, the antenna can operate in four separate frequencies in UWB region with at least 500 MHz bandwidth, thus offering wideband multichannel operation which is useful to several communication standards.