An Ultrawideband (UWB) high gain compact Vivaldi antenna with end fire radiation patterns is presented for radar and microwave imaging applications. The antenna is operating for 2.9GHz to more than 11GHz with -10dB impedance bandwidth and is designed on low cost FR4 substrate of thickness 0.8mm. While designing the proposed antenna, initially a compact exponential tapered slot Vivaldi antenna i...

A Network Coordinate (NC) system is an efficient mechanism to predict Internet distance with scalable measurements. In this paper, we focus on the node churn problem – the continuous process of nodes arrival and departure – in distributed applications. Studies on Vivaldi, a representative distributed NC system, show that under node churn the prediction accuracy of the NC system will be seriousl...

Internet coordinate systems have emerged as an efficient method to estimate the latency between pairs of nodes without any communication between them. They avoid the cost of explicit measurements by placing each node in a finite coordinate space and estimating the latency between two nodes as the distance between their positions in the space. In this paper, we adapt the Vivaldi algorithm to use...

Network coordinates (NC) system is an efficient mechanism to predict Internet distance with scalable measurements. In this paper, we focus on the node churn problem the continuous process of nodes arrival and departure in distributed applications. Studies on Vivaldi, a representative distributed NC system, shows that under node churn the prediction accuracy of the NC system will be seriously im...

In this paper, the conformal finite-difference time-domain (CFDTD) method using PSO optimization is applied to design a compact directive balanced antipodal Vivaldi antenna for ultrawideband (UWB) applications. This paper demonstrates miniaturized antipodal Vivaldi antenna (32 × 35 × 1.6mm3), having low-cross polarization levels and reasonable gain from 3.1 to 10.6 GHz. The antenna peak gain is...

Phased-array feeds are possibly the best option for the 240 to 1200 MHz band on VLA antennas due to their wide bandwidth and relatively small size. One of the greatest assets of these antennas is the ability to produce a shaped beam by appropriately phasing the elements allowing in some cases nearly uniform aperture illumination with minimal ground-directed spillover. The beam-forming propertie...

In this letter, a tapered slot ultrawide band (UWB) Vivaldi antenna with enhanced gain having band notch characteristics in the WLAN/WiMAX band is presented. In this framework, a reference tapered slot Vivaldi antenna is first designed for UWB operation that is, 3.1–10.6 GHz using the standard procedure. The band-notch operation at 4.8 GHz is achieved with the help of especially designed comple...

In [2] it was conjectured that all integer sequences (ak)k∈Z satisfying 0 ≤ ak−1 + λak + ak+1 < 1 (k ∈ Z) for real λ with |λ| < 2 are periodic. This question arose in the study of shift radix systems. The conjecture is trivially true for λ = −1, 0, 1. A computer assisted proof for λ = 1− √ 5 2 was given by Lowenstein, Hatjispyros and Vivaldi [5], where also the solution for λ = 1+ √ 5 2 is ment...

Radar operation from the CReSIS Meridian UAV requires a broadband antenna array composed of lightweight, thin, end-fire antenna elements. Toward this goal four Vivaldi antenna designs were simulated, fabricated, and characterized. The final design, dubbed the CReSIS Aerial Vivaldi – Revision A (CAV-A) provides operation over a band extending from 162 MHz to 1.121 GHz. The CAV-A measures 40 cm l...

Network Coordinate System (NCS) is an efficient and scalable mechanism to predict latency between any two network hosts based on historical measurements. Most NCS models, such as metric space embedding based, like Vivaldi, and matrix factorization based, like DMF and Phoenix, use squared error measure in training which suffers from the erroneous records, i.e. the records with large noise. To ov...