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A new N-way partially-filled radial combiner design is proposed. The design integrates the advantages of printed circuit board (PCB) technology and those of air cavities into a single reactive power combiner. Minimal transmission losses are achieved using an air cavity, and the PCB allows flexibility with regard to port terminations. Importantly, simple and accurate PCB etching is exploited to achieve a wide-band central port match, without resorting to the typical high accuracy machining of the central feed pin. A 16-way prototype was manufactured and tested. When symmetrically excited, the measured input reflection coefficient is less than –15 dB over 20 % fractional bandwidth at 4 GHz. Peripheral port signal amplitude and phase imbalances are within ± 0.3 dB and 2.5 degrees, respectively. The prototype incurs less than 0.45± dB transmission loss, yielding a combining efficiency better than 90% in the operating band. Additionally, the cavity housing as tested was made without the use of CNC machines.

This paper presents a general coaxial-conical-coaxial transmission line transition with a built-in impedance taper that can explicitly be chosen or optimized. The presented transition has a smooth profile, which is advantageous for peak power handling, and provides more degrees of freedom and greater flexibility to optimize devices compared with other transitions between conical and coaxial lines or coaxial lines of different sizes. The method is validated by designing and fabricating an eight-way coaxial line combiner, 0.55 $\lambda $ long and $0.26~\lambda $ in diameter, with a measured reflection coefficient of better than −22 dB over a 115% bandwidth (BW), and better than −12 dB over a 130% BW.

Background. ST-segment elevation myocardial infarction (STEMI) is one of the main contributors to morbidity and mortality in South Africa (SA). Timeous intervention by means of percutaneous coronary intervention (PCI) or fibrinolysis can significantly improve the outcome of STEMI. Objectives. To determine the median time interval between diagnosis and fibrinolysis in patients presenting to centres within the drainage area of Tygerberg Hospital, Cape Town, SA, and compare it with the European Society of Cardiology (ESC) recommendation of 10 minutes. Methods. A retrospective medical record review of patients presenting to the abovementioned centres between 1 March 2017 and 28 February 2018 was performed. The primary presenting centre, time between diagnosis and fibrinolysis and discharge medication were recorded, in addition to other relevant demographic information. Results. A total of 492 patients were identified, of whom 447 were included in the study. Three hundred and eighteen patients received fibrinolysis, of whom 18 (5.7%) were treated within 10 minutes of diagnosis. The median time interval between diagnosis and fibrinolysis was 67 (interquartile range (IQR) 32.5 -122.5) minutes. Conclusions. Most patients received fibrinolysis >10 minutes after diagnosis, which indicates suboptimal therapy when compared with the ESC guidelines. Future studies should investigate the factors prolonging this therapeutic delay.

This work investigates the effects of the number of array feed elements on the overall system $G/T_{sys}$ for phased array feed systems, in the context of scanning along a single angular plane. It is shown that the negative impact of receiver noise caused by larger feeds on overall system sensitivity can outweigh the contribution to system gain in noisy systems. A numerical study is conducted which shows how a linear array can achieve superior performance to planar arrays with realistic receiver noise parameters.

A method for the design of a conical to coaxial transmission line transition with an arbitrary smooth impedance profile is presented. This type of transition is often used in conical line combiners, and has previously either had a constant impedance or an impedance profile that could not be explicitly designed. The method presented herein provides the designer with more design freedom by allowing an arbitrary impedance profile to be chosen or optimized, with the geometry following from the designed impedance profile. A conical combiner with significantly improved bandwidth performance is designed using the presented method. The performance predicted by the circuit model is in good agreement with full-wave simulations and measurements.

A conical transmission line power combiner is designed using a surrogate optimization method which achieves a significant speed-up factor over previous design methods as well as improved design flexibility.

In the paper, “Compact conical-line power combiner design using circuit models,” (Beyers, R.D. and de Villiers, D.I.L., IEEE Trans. Microw. Theory Techn., vol. 62, no. 11, pp. 2650–2658, Nov. 2014) corrections were made to several equations.