Analysis of the polarization properties of dual polarized inverted vee dipole antennas over a ground plane

This paper presents the derivation of an explicit closed-form expression of dual-polarized inverted-vee dipole antenna behavior based upon electromagnetic theory and physical explanations. The expression is used to determine the intrinsic cross-polarization ratio (IXR) as function of the droop angle, position of the sky-vector, the height above a ground plane and frequency. The expression is verified using full-wave simulations with a Method-of-Moments solver, and shows excellent agreement with simulations. It explains the increase observed in IXR if an infinite perfect electric conductor ground plane is deployed

Closed-form Jones matrix of dual-polarized inverted-vee dipole antennas over lossy ground

This paper presents a closed-form expression for the Jones matrix of a dual-polarized inverted-vee dipole antenna based on the Lorentz reciprocity theorem and the basic rules of electromagnetic refraction. The expression is used to determine the intrinsic cross-polarization ratio (IXR) as a function of droop angle, position of the source in the sky, antenna height, frequency, and reflection coefficient of the underlying ground. The expression is verified using full-wave simulations with a method-of-moments solver, showing very good agreement. It explains the increase in the IXR when the antenna is placed over a perfect electric ground plane. This result is used to explain the polarization properties of the Square Kilometre Array Log-periodic Antenna. Through the LOw-Frequency ARray Low-Band Antenna (LOFAR-LBA), the importance of the size of the ground plane is explained. Finally, design consideration for high polarization purity antennas is discussed

Ship autopilot and rudder roll damping using L1 adaptive control

The aim of this traineeship is to design an L1 adaptive controller for a ship autopilot in combination with rudder roll damping. Rudder roll damping means that the rudder of the ship is used to reduce wave induced roll motions of the ship. L1 adaptive control theory is a new adaptive control architecture which decouples estimation (adaptation) from control (robustness), and with that allows for arbitrary fast adaptation. L1 adaptive control is first used to control the heading of a ship. A simple one degree of freedom model is used with a non-linear steering characteristic. The adaptive controller is used to estimate this nonlinearity. The designed adaptive autopilot is then used on a more complex four degree of freedom model.This used benchmark ship model is a 360 ton naval vessel. The L1 adaptive control theory is also used to design a controller which uses the rudder to dampout roll motion of the ship. A model which only contains the equations of motion in roll was used for this. Finally the autopilot is combined with roll damping to get a controller which combines rollreduction with low heading interference

Correction to ”Closed-Form Jones Matrix of Dual-Polarized Inverted-Vee Dipole Antennas over Lossy Ground”

In the Appendix of the paper [1, p. 33], the authors would like to make the following correction. In (11), it should have read (Formula Presented) Consequently, in (13), it should have read (Formula Presented) It should be mentioned that the error is typographical and did not influence the results as presented in the paper

Analysis of Surface Waves Modes in Planar Connected Arrays for Radio Astronomy

© 2018 IEEE. A planar array of closely spaced capacitively coupled antennas over a ground plane can be designed to have a broadband and smooth response, making it an interesting candidate for a low-frequency radio-astronomy instrument. However, surface wave modes propagating over the array plane can seriously degrade the response. We will show the derivation of a necessary condition for which surface wave modes will propagate along a planar array of closely spaced capacitively connected antennas. The derivation will be based upon the transverse resonance method [2] applied to the equivalent circuit of a unit cell of an infinite capacitively connected array. From the necessary condition a simple design consideration can be derived which would prevent the excitation of unwanted surface waves on the structure. Finally, we will show how adding resistive loading in the form of the low-noise amplifiers can dampen the unwanted surface wave effects

Recent Progress on the Design of Aperture Arrays for Radio Astronomy

© 2018 Radio Society. Design considerations and contemporary methods for analyzing and designing aperture arrays for radio astronomy are reviewed, with reference to the SKA. The use of computational electromagnetic tools to evaluate array performance, including embedded element patterns is addressed, as well as an approximation which includes some effects of mutual coupling. The subsequent inclusion of network models of the RF front-ends and including the beamformer are also considered. The analysis of receiving systems is specifically discussed

Effects of Survivorship Care Plans on patient reported outcomes in ovarian cancer during 2-year follow-up - The ROGY care trial

Item does not contain fulltextOBJECTIVE: The aim of this study was to assess the long-term impact of an automatically generated Survivorship Care Plan (SCP) on patient reported outcomes in ovarian cancer in routine clinical practice. Outcome measures included satisfaction with information provision and care, illness perceptions and health care utilization. METHODS: In this pragmatic cluster randomized trial, twelve hospitals in the South of the Netherlands were randomized to 'SCP care' or 'usual care'. All newly diagnosed ovarian cancer patients in the 'SCP care' arm received an SCP that was automatically generated by the oncology provider, by clicking a button in the web-based Registrationsystem Oncological GYnecology (ROGY). Ovarian cancer patients (N=174, mean age 63.3, SD=11.4; all stages) completed questionnaires directly after initial treatment and after 6, 12 and 24months. RESULTS: First questionnaires were returned from 61 (67%) ovarian cancer patients in the 'SCP care' arm and 113 (72%) patients in the 'usual care' arm. In the 'SCP care' arm, 66% (N=41) of the patients reported receipt of an SCP. No overall differences were observed between the trial arms on satisfaction with information provision, satisfaction with care or health care utilization. Regarding illness perceptions, patients in the 'SCP care' arm had lower beliefs that the treatment would help to cure their disease (overall, 6.7 vs. 7.5, P<0.01). CONCLUSIONS: SCPs did not increase satisfaction with information provision or care in ovarian cancer patients. Our trial results suggest that ovarian cancer patients may not benefit from an SCP. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT01185626