Design of a printed MIMO/diversity monopole antenna for future generation handheld devices

This article presents a printed crescent‐shaped monopole MIMO diversity antenna for wireless communications. The port‐to‐port isolation is increased by introducing an I ‐shaped conductor symmetrically between the two antenna elements and shaping the ground plane. Both the computed and experimental results confirm that the antenna possesses a wide impedance bandwidth of 54.5% across 1.6–2.8 GHz, with a reflection coefficient and mutual coupling better than ?10 and ?14 dB, respectively. By further validating the simulated and the measured radiation and MIMO characteristics including far‐field, gain, envelope correlation and channel capacity loss, the results show that the antenna can offer effective MIMO/diversity operation to alleviate multipath environments. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:348–359, 2014.     

Measurement and Explanation of DC/RF Power Loci of an Active Patch Antenna

A case study of an active transmitting patch antenna revealed a characteristic loop locus of DC power versus RF output power as drive frequency was varied, with an operational bandwidth substantially smaller than the impedance bandwidth of the radiator. An approximate simulation technique, based on separation of the output capacitance of the power transistor, yielded easily visualized plots of power dependence on internal load impedance, and a simple interpretation of the experimental results in terms of a near‐resonance condition between the output capacitance and output packaging inductance.     

A novel measurement method of a single dust particle permittivity at a microwave frequency band as I/P to accurate scattering computations. Part I

In electromagnetic scattering computation the scattering properties of a single particle can be evaluated if the solid permittivity of its constituent material is known. If the material is not homogeneous (e.g. water layer on the particle surface) both the structure and the permittivity of the different parts must be known. However, it is possible (at least at microwave frequencies) to define an equivalent homogeneous permittivity $\left( {\bar \varepsilon } \right)$ which would produce the same scattering properties for a homogeneous particle of the same outer shape as the real one. In this work a novel measurement method of a single particle scattering for evaluating the dielectric properties of dust is derived. Results are compared with another work on bulk/scaled measurement (Part II) of dust permittivity at the same frequency band (X-band) gave matched results.     

Measuring the Structure of Mixed-Grain-Size Sediment Beds

A new sampling technique called wax coring is presented in this paper that enables the determination of the composition of the surface and subsurface of a sediment bed formed during flume experiments. A wax-impregnated circular core is removed from the bed and melted in a series of well-defined layers that are then sieved separately to provide data describing the variation with depth of the particle-size distribution. The volumetric equivalence of the grain-size distribution obtained for an internal layer is demonstrated theoretically and empirical data are obtained concerning the active layer concept that is often used in the modeling of mixed-grain-size sediment transport.     

Analysis of multivariable control performance assessment techniques

Control performance assessment (CPA) techniques provide an indication of how current controller performance compares with what would be considered to be ideal. The ideal performance is typically referred to as a ‘benchmark’. This paper argues that there are two fundamental requirements for any CPA algorithm. The first is that it should be able to detect any change in the performance of a control system and the second is that it should be able to identify the potential improvement that can be made to the performance of the control system if it were to be re-tuned or re-designed. The ability of current multivariable CPA techniques to address these two issues is reviewed and a novel monitoring strategy for application to multivariable control systems is proposed. The ability of this strategy to provide an improved approach to detecting changes in multivariable control performance and identifying the potential improvements that are possible through re-tuning the controller are illustrated using simulated and industrial data.     

Calibration techniques for Olympus 20 GHz switched polarizationsatellite beacon measurements

A measurement of the complete transmission matrix of a slant path using a switched polarization satellite beacon needs to be properly calibrated in both amplitude and phase to yield the best characterization of the hydrometeors which affect propagation. For accuracy, error contributions from the satellite and earth station should be separated and corrected individually. It is shown how this can be achieved by indirect methods which rely on minimal theoretical expectations of the form of the transmission matrix. Methods to calibrate the amplitude and phase offsets of the satellite and receiver, and to assess the satellite polarization purity, are demonstrated using the Olympus satellite at 20 GHz. Small amplitude imbalances in the beacon are found and corrected, but a large correction for an unexpected phase offset is required. Good polarization purity of the beacon is inferred     

A novel measurement method of bulk/scaled dust permittivity at a microwave frequency band as I/P to accurate scattering computations. Part II

In order to compute the scattering properties of individual sand/dust particles dispersed in air, as in a true sand/dust storm, we need to derive a permittivity value which is representative of sand/dust particle with its layer of water. As a first step in this, we applied Looyenga??s formula to extract the permittivity of the dry sand/dust component from the mixture which is measured. Measured results could be used to estimate electromagnetic wave propagation impairments in communication systems.