M. A. Zakariya

Performance analysis of reactive connectivity restoration algorithms for wireless sensor and actor networks

Preserving inter-actor connectivity is essential in most wireless sensor and actor network (WSAN) applications as nodes have to collaborate and coordinate their actions against the events reported by the sensors. However, failure of a critical (i.e., cut-vertex) node partitions inter-actor network into disjoint segments and thus hinder network operation. The prime objective of this paper is to analyze the performance of reactive connectivity restoration algorithms for delay-tolerant WSAN applications. First, we provide insights to the state-of-the-art reactive connectivity restoration algorithms. Then, we present a Nearest Non-critical Neighbor (NNN) algorithm; a localized and distributed reactive approach for reconnecting network partitions. In NNN, each actor periodically determine its criticality (i.e., cut-vertex or not) based on 2-hop information and exchange with its neighbors. In case of a critical actor failure, the neighbors detect and trigger a connectivity restoration procedure that involves controlled and coordinated node relocation. NNN prefer to displace non-critical nodes during relocation in order to minimize recovery overhead in terms of distance movement and message coordination. We analyze the performance of reactive schemes through theoretical analysis and simulations.

Analysis and realization of defected ground structure (DGS) on bandpass filter

An end-coupled line bandpass filter (BPF) is proposed and designed by placing defected ground structure (DGS) in the ground plane. DGS is used for its property of miniaturizing the size of microwave filter and also improving the mutual coupling between the resonators. The proposed dumbbell shaped DGS is used to tune the bandpass filter to 2.4 GHz with dimension of 44 mm × 18 mm. A wide tuning range of 0.64 GHz is achieved by tuning the height, length and width dimension of DGS unit cell. This filter gives an insertion loss of -0.42 dB, a return loss of -12.31 dB and -3 dB bandwidth of 0.92 GHz. The effect of DGS structure parameters on the frequency of bandpass filter is discussed here. The discussion is concerned over the change in R, L and C parameters of the bandpass filter when defected ground structure is etched in its ground plane. The results conclude that the DGS brings a change in effective inductance and capacitance of a transmission line.

Parametric effect of defected ground structure (DGS) on frequency of a bandpass filter

A stepped impedance resonator bandpass filter (SIR BPF) is proposed and designed by placing defected ground structure (DGS) in the ground plane. DGS is used for its property of miniaturizing the size of microwave filter and also improving the mutual coupling between the resonators. The proposed dumbbell shaped DGS is used to tune the bandpass filter to 2.4 GHz with dimension of 28 mm × 30 mm. A wide tuning range of 0.64 GHz is achieved by tuning the height, length and width dimension of DGS unit cell. This filter gives an insertion loss of -0.23 dB, a return loss of -38.03 dB and -3 dB bandwidth of 0.56 GHz. The tuning of SIR bandpass filter, using DGS structure parameters is discussed here. Moreover, the effect of different parameters of DGS on center frequency is shown and discussed with results.

Tuning of end-coupled line bandpass filter for 2.4 GHz using defected ground structure (DGS) parameters

Defected ground structures (DGS) have known to be serving for the improvement in characteristics of many microwave circuits. Not only DGS has various advantages in the area of microwave power amplifier, Wilkinson power divider, microwave antennas, couplers etc, it is also used in the design of microwave filter to achieve stopband effects, slow-wave effects, frequency adjustment etc. A bandpass filter based on Dumbbell-shaped DGS unit is presented here. This unit provides two transmission zeros near the passband edges. The center frequency has been tuned to 2.4 GHz using different dimensions of DGS. This filter gives an insertion loss of -0.42 dB, a return loss of -12.31 dB and -3 dB bandwidth of 0.92 GHz. The tuning of end-coupled line bandpass filter, using dumbbell DGS structure parameters is discussed here. The measurements show a close agreement with simulation results.

An improved design of microwave biosensor for measurement of tissues moisture

In this contribution, a simple but highly sensitive biosensor based on microstrip ring-resonator is presented for tissues moisture evaluation. By incorporating high impedance ring, tight and enhanced coupling mechanism the proposed 1 GHz ring-resonator demonstrates significant change in the resonance frequency than normal resonator. Simulated and measured results are in good agreement. The proposed resonator gives 37% better performance than the conventional resonator.

Microwave bandpass filter using QMSIW

A planar bandpass filter based on a technique that utilizes quarter mode of substrate integrated waveguide (SIW) is presented. This concept reduces the circuit foot print of SIW to a quarter of its size, along with miniaturization good performance and high quality factor is maintained by the structure. The design concept for single-pole resonator structure is presented; and by coupling the resonators a two-pole substrate integrated waveguide bandpass filter is achieved for the frequency of 5.9 GHz. The results show that the filter insertion losses are better than 2 dB and return losses are less than 20 dB. The measured frequency response is in good agreement with the simulated response in the region of interest.

Recent advances in miniaturization of Substrate integrated waveguide bandpass filters and its applications in tunable filters

The concept of Substrate integrated waveguide (SIW) has emerged to be a good replacement of rectangular waveguides in low-cost and high-volume microwave and millimeter wave band applications. A number of bandpass filters have been developed since the advent of the SIW technology. However, its various forms have also been introduced in order to bring about further reduction in the footprint of these filters. This paper presents a review on the technological implementation of Substrate integrated waveguide bandpass filters and its variant miniaturization techniques developed so far. It also covers the SIW technology applied in tunable filters.

Parabolic reflector fed by Cylindrical Dielectric Resonator Antenna with high gain

A single element circular slot aperture coupled Cylindrical Dielectric Resonator Antenna (CDRA) with a parabolic reflector is simulated and presented. The measured bandwidth of the single element CDRA is about 1.8 % (5.32 - 5.52) while the simulated bandwidth is 1.11% (5.32 - 5.44 GHz). A comprehensive parametric study has been conducted to realize the effects of reflector parameters to increase the directivity of the designed antenna. The simulation of the antenna with parabolic reflector shows that it can enhance the gain about 240% as compared to the single element CDRA without reflector. The experimental results show that the antenna covers 5 GHz band, which satisfies the basic requirement of the WLAN application IEEE 802.11a.

Aperture coupled Cylindrical Dielectric Resonator Antenna design with box shaped reflector

A single element circular slot aperture coupled Cylindrical Dielectric Resonator Antenna (CDRA) with a box shaped reflector is designed and presented. The simulated bandwidth achieved for the designed antenna is about 1.11% (5.32 GHz-5.44 GHz) while the measured bandwidth is about 1.8% (5.32 GHz-5.52 GHz). This method enhances the directivity of the CDRA upto 53% i.e from 5 dBi to 7.5 dBi. The analysis of the effects of changing the slot size, slot position and different parameters of the reflector to increase the directivity and to reduce the backlobe level has been carried out. The experimental results illustrate that the designed antenna works over 5 GHz band, therefore it can be used in WLAN application IEEE 802.11a.

2.45 GHz cylindrical dielectric resonator antenna fed by dielectric image line

In this paper, the experimental study on cylindrical dielectric resonator antenna (CDRA) with an aperture coupled dielectric image line (DIL) is presented using a CCTO material. The CDRA is fed by a 50Ω dielectric image line at a frequency around 2.45 GHz. High permittivity (εr = 55) DIL samples with different heights are employed. The CST microwave studio is used to analyze the different results in term of return loss, bandwidth and radiation pattern. The DIL feeding technique has shown a better directivity for CDRA as compared to microstrip line coupling.