Amplitude-only measurements of a dual open ended coaxial sensor system for determination of complex permittivity of materials

This paper describes a novel permittivity measurement technique using dual open ended coaxial sensors. The magnitudes of the reflection coefficient from two open ended coaxial sensors were used to determine complex reflection coefficients and permittivity of a sample under test

Jerantinine A induces tumor-specific cell death through modulation of splicing factor 3b subunit 1 (SF3B1)

Precursor mRNA (pre-mRNA) splicing is catalyzed by a large ribonucleoprotein complex known as the spliceosome. Numerous studies have indicated that aberrant splicing patterns or mutations in spliceosome components, including the splicing factor 3b subunit 1 (SF3B1), are associated with hallmark cancer phenotypes. This has led to the identification and development of small molecules with spliceosome-modulating activity as potential anticancer agents. Jerantinine A (JA) is a novel indole alkaloid which displays potent anti-proliferative activities against human cancer cell lines by inhibiting tubulin polymerization and inducing G2/M cell cycle arrest. Using a combined pooled-genome wide shRNA library screen and global proteomic profiling, we showed that JA targets the spliceosome by up-regulating SF3B1 and SF3B3 protein in breast cancer cells. Notably, JA induced significant tumor-specific cell death and a significant increase in unspliced pre-mRNAs. In contrast, depletion of endogenous SF3B1 abrogated the apoptotic effects, but not the G2/M cell cycle arrest induced by JA. Further analyses showed that JA stabilizes endogenous SF3B1 protein in breast cancer cells and induced dissociation of the protein from the nucleosome complex. Together, these results demonstrate that JA exerts its antitumor activity by targeting SF3B1 and SF3B3 in addition to its reported targeting of tubulin polymerization

Modelling, Design and Construction Of A Multipurpose Anechoic Chamber

A multipurpose anechoic chamber that operates over a very wide frequency range from 30 MHz through 18 GHz has been designed and constructed at the Faculty of Engineering of Multimedia University. An innovative design technique has been developed, giving rise to the construction of an asymmetrical-shaped anechoic chamber which fulfils the different requirements for various measurement needs using lower cost materials. The facility can be used for EMC tests, antenna measurements, monostatic and bistatic RCS measurements, RF transceiver testing, calibration of scatterometer, and other electromagnetic research experiments. It is suitable for both industrial use and basic research. Abeam-tracing technique has been used to develop a model for calculation of wave propagation in the anechoic chamber. The major advantage of beam-tracing over ray-tracing is the path loss information for multiple receiver locations can be determined simultaneously as opposed to running a ray tracing simulation for each receiver location one at a time. As a result, the computing time is greatly reduced. The computer program simulates an impulse transmitted from a dipole antenna and propagating in all directions in the form of polygon-shaped beams. The possible paths for the beams to reach the receivers are recorded. Instead of calculating the field strengths for a large number of discrete frequency points, the received impulses resulting from various multipath propagation are combined to give a time-domain impulse response. A Fast Fourier Transform (FFT) is performed to obtain the desired electric field in frequency domain for frequency range 30-1000 MHz. The asymmetrical chamber geometry has been optimised, taking into account the limited physical space, to achieve the extremely wide operating frequency range with low cost absorbing material. Combination of pyramid and wedge-shaped RF absorbers is used for lining of the chamber walls and ceiling to exploit the advantages of the different absorber shapes. The modelling method has been used to predict the site attenuation prior to the chamber construction. Ease of construction and ease of lining the absorber material on the chamber surfaces are preserved in the design. Constructability of the design allows for all seams to be properly welded. Reasonably high shielding effectiveness has been achieved. Space efficiency of the design allows for two additional screened rooms to be constructed next to the anechoic chamber: one is used as the control room to house the test and measurement equipment; and other is used for conducting certain RF measurements. The low-frequency applications of the anechoic chamber are for EMC test. The required site validation criterion of EN50147-2 and ANSI c63.4 for radiated emission measurements is met for frequencies 30-1000 MHz. The field uniformity requirements of EN61000-4-3 standard are also achieved. Thus the anechoic chamber can be used to perform radiated RF immunity test on electronic products. The quietness of the anechoic chamber is adequate for antenna measurements. Field probe measurements have been made across the quiet zone in the vertical and horizontal transverse directions, for both vertical and horizontal polarisations. The peak-to-peak interference amplitudes are less than 0.3 dB for frequencies from 3 GHz to 18 GHz. Reflectivity level as low as 53 dB has been achieved at 6GHz. The measurement facility is also suitable for accurate polarimetric measurements of both monostatic and bistatic RCS. The smallest RCS that can be reliably measured is as low as -70 dBsm for monostatic case and -80 dBsm for bistatic case. Time-gating technique is applied to improve the measurement accuracy. The scattering from 3-inch and 6-inch spheres can be accurately measured in both magnitude and phase for all four polarisation combinations. The project involves securing the financial resources, determining the required specifications, designing the chamber structure, procuring various components and instrumentation, planning the logistical arrangements(contract,shipping, insurance, haulage, time to delivery, storage space), supervising the construction process, and evaluating the anechoic chamber according to the specific performance criteria. The necessary features such as access doors, ventilation , lighting, electrical power supply, power -line filters, connection panels, cables, pneumatic air supply, turntable, and motorised antenna mast are included in the design. In this project , to reduce cost, several components of the facility have been designed and fabricated which include the knife-edge shield doors, waveguide lighting units, connection panels, low-profile non-metallic turntable, adaptive antenna elevation mechanism , and horizontal scanning mechanism. The experience gained throughout the project has given the author a through understanding of the theories, design considerations and construction of a microwave anechoic chamber

DIELECTRIC CONSTANT MEASUREMENT FOR THIN MATERIAL AT MICROWAVE FREQUENCIES

A practical problem in the reflection method for dielectric constant measurement is the difficulty to ensure the sample is placed exactly at the waveguide flange. A small position offset of the dielectric sample will give rise to some errors in calculating the dielectric constant, especially when a thin sample is used. To circumvent this problem, a method to determine the dielectric constant by measuring the transmission coefficient of the thin slab placed in a waveguide has been developed. Slab position offset from the measurement reference plane has no effect on the measurement accuracy. An explicit expression for the dielectric constant is obtained in terms of the transmission coefficient by simplifying the exact solution for transmission through a thin dielectric slab. The method is verified with measurement on Teflon of 0.5-mm thickness. The measured dielectric constant of Teflon shows excellent agreement of both epsilon ' and epsilon '' with published data. Subsequently, the dielectric constant of a vegetation leaf was measured

A WIDEBAND E-SHAPED MICROSTRIP PATCH ANTENNA FOR 5 - 6 GHZ WIRELESS COMMUNICATIONS

A wideband E-shaped microstrip patch antenna has been designed for high-speed wireless local area networks (IEEE 802.11a standard) and other wireless communication systems covering the 5.15-5.825 GHz frequency band. Two parallel slots are incorporated to perturb the surface current path, introducing local inductive effect that is responsible for the excitation of the second resonant mode. The length of the center arm can be trimmed to tune the frequency of the second resonant mode without affecting the fundamental resonant mode. A comprehensive parametric study has been carried out to understand the effects of various dimensional parameters and to optimize the performance of the antenna. A substrate of low dielectric constant is selected to obtain a compact radiating structure that meets the demanding bandwidth specification. The reflection coefficient at the input of the optimized E-shaped microstrip patch antenna is below -10 dB over the entire frequency band. The measurement results are in excellent agreement with the HFSS simulation results

A semi-elliptical wideband phase shifter

A new microstrip structure for realization of wideband phase shifter has been designed and fabricated. The proposed design uses edge-coupled semi-elliptical structure and an elliptical defected ground plane to increase the coupling coefficient and operating bandwidth. Simulation performed using CST Microwave Studio and measured results confirm the good performance of the proposed design. The phase deviation is better than ±4º, insertion loss less than 0.6dB and return loss better than 10dB over a wide frequency range. The achievable bandwidth is more than 2.3 : 1

Combined Feed Network for a Shared-Aperture Dual-Band Dual-Polarized Array

A new combined feed network is proposed for a shared-aperture dual-band dual-polarized array operating in the L/C band. The array comprises square, aperture-coupled patches in the C-band and a square perforated, aperture-coupled L-band patch. The feed networks of a single polarization for both the bands are combined into a single network on a single layer. Good return loss and radiation characteristics are obtained for L- and C-band frequencies

Design and development of a scatterometer system for environmental monitoring

A ground-based C-band Scatterometer System has been constructed at the Universiti Multimedia Telekom, Malaysia. The system is a full polarimetric FM-CW radar which has the capability to determine the complete backscattering matrix of a natural target. The system is to be used to conduct in situ backscatter measurement on Earth terrain such as vegetation fields, forest and soil surfaces. In this paper, a summarized report on the design and development of the system is presented

An Accurate and Efficient 3-D Shooting-and-Bouncing-Polygon Ray Tracer for Radio Propagation Modeling

This paper describes two important improvements to a 3-D shooting-and-bouncing-polygon (SBP) ray tracer for radio propagation modeling. It introduces a way to trace diffracted-reflected (D-R) rays in the SBP framework and improves SBP accuracy when the D-R rays play an important role. It also introduces a better space partitioning scheme for the use with SBP and improves the SBP's computation efficiency by more than 10× in some applications. The numerical results are compared against published measurements and 3-D full-wave solutions. They show that the improved SBP ray tracer is a good multipurpose 3-D ray tracer which can be used to simulate urban street canyon (without double over-rooftop diffraction), indoor, and tunnel propagation environments

Calibration and field experiment of a C-band polarimetric scatterometer

Presents the evaluation results of a full polarimetric C-band scatterometer system that has been designed and constructed at the Multimedia University, Malaysia. The system was tested at a football field. A metal sphere was used as the calibration target. Backscattering matrices of an 8" trihedral corner reflector and a 4"×8" dihedral corner reflector were measured. The dihedral was rotated at different angles to provide different sets of polarimetric data. The results were compared with the theoretical values to verify the effectiveness of the calibration technique. The external calibration and internal calibration procedures as well as the approach used in measuring the relative phase response are discussed