A. Elsherbini

Development of a Novel UWB Vivaldi Antenna Array Using SIW Technology

A compact Vivaldi antenna array printed on thick substrate and fed by a Substrate Integrated Waveguides (SIW) structure has been developed. The antenna array utilizes a compact SIW binary divider to significantly minimize the feed structure insertion losses. The low-loss SIW binary divider has a common novel Grounded Coplanar Waveguide (GCPW) feed to provide a wideband transition to the SIW and to sustain a good input match while preventing higher order modes excitation. The antenna array was designed, fabricated, and thoroughly investigated. Detailed simulations of the antenna and its feed, in addition to its relevant measurements, will be presented in this paper.

UWB antipodal vivaldi antennas with protruded dielectric rods for higher gain, symmetric patterns and minimal phase center variations

In this paper, the authors proposed a technique to improve the gain, narrow the H-plane beamwidth, and minimize the phase center variations with frequency by utilizing Vivaldi antenna with a protruded dielectric rod. A sample antenna was fabricated and measured, and preliminary measured results are very promising, and in good agreement with the simulation results.

A highly efficient Vivaldi antenna array design on thick substrate and fed by SIW structure with integrated GCPW feed

A compact Vivaldi antenna array printed on thick substrate and fed by a substrate integrated waveguide (SIW) structure is presented here. The array utilizes an SIW binary splitter to significantly minimize the feed structure insertion losses. Meanwhile, the splitter is fed with an integrated CPW to sustain a good input match and prevent higher order modes excitation over wide band operation. Extensive simulation and measurements were carried out and was presented here with a comparison to previously developed arrays.

A Compact Microstrip Multi-Layer Lowpass Filter Using Triangle Slots Etched in the Ground Plane

In this paper we present a new concept for implementing cascaded lowpass filters and multi-layer LPF by employing Pi-arrowhead resonators as a defected ground structure (DGS) and as a resonator cell in the upper layer. The effect of the arrowhead area of a DGS on the performance of the conventional LPF is examined. The LPF is designed easily by extracting the equivalent circuit elements of a uniform arrowhead DGS slot and compensating for the capacitance of the transmission line (Boutejdar et al., 2005). The proposed multi-layer LPF is 50% shorter than the conventional LPF. Only two cells of the new structure are necessary to obtain better performance by suppressing ripples and enlarging stopband. The measured results show excellent agreement with simulated and equivalent circuit results

A new cross-head defected ground structure (CDGS) for a compact low-pass filter with a wide stop-band

A novel technique has been investigated to achieve better S-parameters performance than previously reported, in which, a new crosshead DGS on planar transmission lines was used. The proposed DGS behaves as a resonant element, which allows for size compactness and high harmonic suppressions in the reject-band. These characteristics make the new DGS advantageous as compared to the arrow-square-head ones. Simulated and measured results of the proposed filter are presented and show good agreements.

Experimental development of a circularly polarized antipodal tapered slot antenna using SIW feed printed on thick substrate

In this paper, we propose a SIW fed circularly polarized (CP) tapered slot antenna which have a good return loss and a wide band axial-ratio. The performance of the antenna has been extensively optimized based on both CST Microwave Studio and Ansoft-HFSS simulation to obtain wide band CP operation. In the following sections, we introduce the theory of operation, the details of the design and the measured results.

A novel lowpass filter with ultra-wide stopband and improved q-factor performance using H-Defected Ground Structure (DGS)

In this paper, a novel compact wideband high-rejection LPF using H-defected ground structure(DGS) is presented The effect of the DGS H-slot on the Q factor characteristics is examined. Comparison between the new DGS LPF and conventional filters shows that the proposed filter with its simple geometric structure including only two H-cells guarantees a suppressed ripples passband and a very large section of a stopband From 2.5 to 16 GHz, the investigated DGS-LPF has a rejection level better than 20 dB. Measured results show good consistency with calculations.

Notch bandwidth and filter order trade-offs in band-notched monopole antennas for UWB applications

In this paper, we have optimized the performance of both the slot notched and compact coplanar waveguide (CRW) cell (CRCC) notched monopoles to eliminate the local oscillator (LO) leakage, but their presence could impact the overall UWB performance. The added slot in the patch and the CRCC in the feed-line of the planar monopole antenna act as 1st order and 2nd order band-stop filters respectively. Their rejection bandwidth and associated filter order number would affect the time domain UWB signal performance. It has been demonstrated that when narrowing the notch bandwidth and increasing the filter order, the first pulse amplitude (FPA) is higher, which could benefit the UWB positioning system, however, it renders longer power delay spread (PDS), which is undesirable for UWB communication system. The trade-off between FPA and PDS has been investigated and utilized to optimize the band-notched planar monopole design.

A new compact tunable bandpass filter using defected ground structure with active devices

A new tunable bandpass filter using Hairpin-DGS and varactor as active device has been presented. Both, the simulated and the measured results have demonstrate that the proposed passive one pole DGS BPF may be easily transformed to a tunable BPF by adding a simple variable capacitor on the DGS-element. The measured results have shown a good one pole bandpass response with a high quality factor and with a good sharpness in transition range. Additional the proposed BPF is very compact in comparison with the conventional tunable filters. The introduced BPF has been designed to meet the requirements of modern wireless communication systems.

A simple method to control the reject band of microstrip low pass filter using a new multi-ring defected ground structures (DGS)

A new double close-loop DGS lowpass filter cell is proposed. The cutoff and resonance frequencies bounding the stopband were shown to be easily controllable by the length of microstrip capacitor. Using the obtained characterization curves, a new multi-ring DGS Lowpass filter with very wide reject band and superior characteristics could be realized. Moreover, this filter can also provide a 20dB wide upper stopband up to 4 times the cutoff frequency. The measurement results have shown good agreement with the simulated results. Finally, this newly proposed compact and high-performance LPF can be used in a wide range of applications of microwave components and antenna arrays.