The design and development process for the Square Kilometre Array (SKA) radio telescope’s Low Frequency Aperture Array component was progressed during the SKA pre-construction phase by an international consortium, with the goal of meeting requirements for a critical design review. As part of the development process a full-sized prototype SKA Low ‘station’ was deployed – the Aperture Array Verification System 1 (AAVS1). We provide a system overview and describe the commissioning results of AAVS1, which is a low frequency radio telescope with 256 dual-polarisation log-periodic dipole antennas working as a phased array. A detailed system description is provided, including an in-depth overview of relevant sub-systems, ranging from hardware, firmware, software, calibration, and control sub-systems. Early commissioning results cover initial bootstrapping, array calibration, stability testing, beam-forming, and on-sky sensitivity validation. Lessons learned are presented, along with future developments.

Medical devices making use of radio frequency (RF) and microwave (MW) fields have been studied as alternatives to existing diagnostic and therapeutic modalities since they offer several advantages. However, the lack of accurate knowledge of the complex permittivity of different biological tissues continues to hinder progress in of these technologies. The most convenient and popular measurement method used to determine the complex permittivity of biological tissues is the open-ended coaxial line, in combination with a vector network analyser (VNA) to measure the reflection coefficient (S11) which is then converted to the corresponding tissue permittivity using either full-wave analysis or through the use of equivalent circuit models. This paper proposes an innovative method of using artificial neural networks (ANN) to convert measured S11 to tissue permittivity, circumventing the requirement of extending the VNA measurement plane to the coaxial line open end. The conventional three-step calibration technique used with coaxial open-ended probes lacks repeatability, unless applied with extreme care by experienced persons, and is not adaptable to alternative sensor antenna configurations necessitated by many potential diagnostic and monitoring applications. The method being proposed does not require calibration at the tip of the probe, thus simplifying the measurement procedure while allowing arbitrary sensor design, and was experimentally validated using S11 measurements and the corresponding complex permittivity of 60 standard liquid and 42 porcine tissue samples. Following ANN training, validation and testing, we obtained a prediction accuracy of 5% for the complex permittivity.

The next generation of radio instruments will generate an unprecedented amount of data, with the Square Kilometre Array (SKA) predicted to generate approximately 160 TB of raw data per second. The computational resources required to process this data are considerable, and alongside this challenge there is an associated one: How is this data going to be transported efficiently? Compute servers composing the processing backends of these instruments must be capable of receiving a high data throughput, with enough leftover resources to perform the required computations. In this paper we present a high-performance and flexible library for packet acquisition. This library was developed as part of the effort to prototype a single Low Frequency Aperture Array (LFAA) station, the low frequency component of the SKA. This resulting LFAA demonstrator, the Aperture Array Verification System (AAVS), generates several types of data streams which must be received and processed. The data acquisition (DAQ) library was designed to be capable of receiving and processing multiple data stream types simultaneously whilst minimizing system load. We present the philosophy behind the design and implementation of this library, as well as provide some benchmarking results.