A Novel Dielectric-Loaded Dual-Mode Cavity for Cellular Base Station Applications

A new class of dual mode dielectric resonator filter for mobile communication systems is presented. The proposed resonator exhibits high unloaded quality factor and reasonably wide spurious operating window. Based on this cavity, a 4-pole dual-mode Generalised Chebyshev filter is developed and fabricated in the stacked configuration. An unexpected spurious mode is appeared at 2.3 GHz due to improper coupling. A coupling technique for eliminating the unexpected spurious resonance is proposed. The obtained experimental and measured results with an asymmetric transmission zeros confirm the validity of the proposed resonator for releasing filters for cellular-radio base stations

A TE11 Dual-Mode Monoblock Dielectric Resonator Filter

A novel TE11 monoblock dual-mode dielectric resonator filter is presented in this paper. The proposed filter is made of a single piece of ceramic with silver plated external surfaces and metallic lids for hosting tuning elements. The dominant TE11 dual-mode is supported by H-shape dielectric resonator having r =45. The resonator is ultra-compact in size and offers a maximized space utilization since no metallic housing is required. In addition, the proposed resonator offers a high unloaded quality factor, reasonably wide spurious window and lend itself to implement tunability. One prototype filter operating at 1.96 GHz with 50-MHz bandwidth is designed

Compact Triple-Mode Microwave Dielectric Resonator Filters

This paper presents a novel and compact triple-mode dielectric resonator (DR) band- pass filter (BPF) based on a single waveguide cavity. A triple-mode resonator can be achieved by pairing the degenerate EH₁₁ modes with a TM01δ mode. The DR structure is composed of two slitted pieces of dielectric pucks that are placed in the middle of a cylindrical metallic cavity. The resonator offers a size reduction ratio of about 15.6% compared with equivalent air-filled coaxial filters. A coaxial probe is used to excite the degenerate EH₁₁ modes while the TM01 mode is excited using a vertical hole etched in the ceramic pucks. Finally, a 3rd order generalised Chebyshev BPF is simulated using HFSS software. The filter has finite transmission zeros(TZ) on the high or low side of the passband

Design and Characterisation of HE11 Dual-Mode Dielectric-Loaded Filter for Cellular Base Station Applications

This paper presents a HE11 dual-mode dielectric-loaded bandpass filter for cellular base station applications. The filter consists of a ceramic puck that is placed centrally on the base of a metallic housing. The resonator offers a size reduction ratio of approximately 7:1 compared with equivalent air-filled coaxial filters. The filter is designed at a resonant frequency of 2.05 GHz and bandwidth of 50 MHz. The spurious-free window (SFW) was 500 MHz from the fundamental frequency. A fourth order dual-mode bandpass filter is designed, fabricated, and tested to validate the proposed approach. A good agreement between the measurement and simulation results is demonstrated

Broadband Dual-Mode Dielectric Resonator Filters

This paper presents a broadband dual-mode microwave filter suitable for mobile communications. The Conductor loaded dielectric resonator filter reported in [5] is used as the basic building block for these devices. A simple input coupling configuration is introduced to improve the filter bandwidth significantly with less than half of the physical volume of TEM filters and good electrical performance. The basic properties of this resonator have been studied using a finite element method electromagnetic software (HFSS). Fundamental design rules for broadband bandpass filters have been presented. A two-pole bandpass filter was designed, fabricated and measured to verify the proposed approach

Miniature Triple-Mode Dielectric Resonator Filters

In this paper, a new class of triple-mode microwave filters is presented. These devices use the degenerate pair of the HE11δ mode and the single TM01δ mode in dielectric-loaded cavities with an unloaded Q-factor of 3000-5000 and reasonable spurious-free window. The proposed structure is obtainable in less than one-quarter of the physical volume of equivalent TEM filters. A finite-element method solver for electromagnetic structures (HFSS) is used to study the main properties of this resonator. Fundamental design rules for triple-mode bandpass filters with controllable finite transmission zeros are presented. Design examples of bandpass filters with finite transmission zeros on the high or low or both sides of the passband are demonstrated. Measured results demonstrate excellent performance

Investigation of Stored Energy Distribution in Filters Using K-Means Clustering Algorithm

The k-means clustering algorithm has been implemented to find patterns in the time-averaged stored energy distribution in various filter networks. A large data set comprising of numerous topologies for 50 different single band specifications has been investigated. By finding key characteristics within this data set, general guidelines for predicting the optimum topology for power handling have been established

Compact broadband frequency selective microstrip antenna and its application to indoor positioning systems for wireless networks

This study presents a low-profile broadband microstrip patch antenna with filtering response. The proposed antenna consists of a rectangular patch and four parasitic gap-coupled elements, two L- and two rectangular-shaped patches. A broadband quasi-elliptic boresight gain response is obtained without using any extra filtering circuits. The input impedance of each radiating element, i.e., driven patch and parasitic elements, is matched to its radiating quality factor and the couplings between patches are optimised for broadband impedance bandwidth with filtering response. Prototype hardware is designed and fabricated on Kappa 438 substrate with a relative permittivity of 4.4 and thickness of 3.2 mm. The antenna exhibits a total size of 25 × 23 × 3.2 mm 3 with relative impedance bandwidth (voltage standing wave ratio<;2) of 60% ranging from 4.4 to 7.8 GHz. The experimental results demonstrate good performance with nearly flat gain and good filtering response. The proposed filtering antenna exhibits low pulse distortion in time domain which makes it a good candidate for location-aware Internet-of-things applications employing the IEEE 802.15.4 ultra-wideband standard. Switchable sector base-station antenna system is studied to demonstrate the capability of this design to enhance the localisation and communication performance of the wireless network

HCV Infection among Saudi Population: High Prevalence of Genotype 4 and Increased Viral Clearance Rate

HCV is a major etiological agent of liver disease with a high rate of chronic evolution. The virus possesses 6 genotypes with many subtypes. The rate of spontaneous clearance among HCV infected individuals denotes a genetic determinant factor. The current study was designed in order to estimate the rate of HCV infection and ratio of virus clearance among a group of infected patients in Saudi Arabia from 2008 to 2011. It was additionally designed to determine the genotypes of the HCV in persistently infected patients. HCV seroprevalence was conducted on a total of 15,323 individuals. Seropositive individuals were tested by Cobas AmpliPrep/Cobas TaqMan HCV assay to determine the ratio of persistently infected patients to those who showed spontaneous viral clearance. HCV genotyping on random samples from persistently infected patients were conducted based on the differences in the 5′untranslated region (5′UTR). Anti-HCV antibodies were detected in 7.3% of the totally examined sera. A high percentage of the HCV infected individuals experienced virus clearance (48.4%). HCV genotyping revealed the presence of genotypes 1 and 4, the latter represented 97.6% of the tested strains. Evidences of the widespread of the HCV genotype 4 and a high rate of HCV virus clearance were found in Saudi Arabia

Connexin-43 upregulation in micrometastases and tumor vasculature and its role in tumor cell attachment to pulmonary endothelium

<p>Abstract</p> <p>Background</p> <p>The modulation of gap junctional communication between tumor cells and between tumor and vascular endothelial cells during tumorigenesis and metastasis is complex. The notion of a role for loss of gap junctional intercellular communication in tumorigenesis and metastasis has been controversial. While some of the stages of tumorigenesis and metastasis, such as uncontrolled cell division and cellular detachment, would necessitate the loss of intercellular junctions, other stages, such as intravasation, endothelial attachment, and vascularization, likely require increased cell-cell contact. We hypothesized that, in this multi-stage scheme, connexin-43 is centrally involved as a cell adhesion molecule mediating metastatic tumor attachment to the pulmonary endothelium.</p> <p>Methods</p> <p>Tumor cell attachment to pulmonary vasculature, tumor growth, and connexin-43 expression was studied in metastatic lung tumor sections obtained after tail-vein injection into nude mice of syngeneic breast cancer cell lines, overexpressing wild type connexin-43 or dominant-negatively mutated connexin-43 proteins. High-resolution immunofluorescence microscopy and Western blot analysis was performed using a connexin-43 monoclonal antibody. Calcein Orange Red AM dye transfer by fluorescence imaging was used to evaluate the gap junction function.</p> <p>Results</p> <p>Adhesion of breast cancer cells to the pulmonary endothelium increased with cancer cells overexpressing connexin-43 and markedly decreased with cells expressing dominant-negative connexin-43. Upregulation of connexin-43 was observed in tumor cell-endothelial cell contact areas <it>in vitro </it>and <it>in vivo</it>, and in areas of intratumor blood vessels and in micrometastatic foci.</p> <p>Conclusion</p> <p>Connexin-43 facilitates metastatic 'homing' by increasing adhesion of cancer cells to the lung endothelial cells. The marked upregulation of connexin-43 in tumor cell-endothelial cell contact areas, whether in preexisting 'homing' vessels or in newly formed tumor vessels, suggests that connexin-43 can serve as a potential marker of micrometastases and tumor vasculature and that it may play a role in the early incorporation of endothelial cells into small tumors as seeds for vasculogenesis.</p