The medium of RF signal transfer adopted for 2PAD was twisted pair differential signal cabling.While intended to demonstrate a low cost solution, the technique has brought with it several challenges, not least in terms of the losses and phase skew introduced.Some interesting engineering challenges have been faced along the way to delivering usable signals to the DSP Engineers.Faced with an aggressive RFI environment, with strong TV and GSM broadcast signals, a small, reasonably quiet band was exploited.A review of the RFI shielding policy has been required to maintain stability in the gain stages of the analogue system.An effective cabinet RFI barrier has been successfully demonstrated.Future work through PrepSKA will explore alternative cabling solutions, such as coaxial and optical fibre, with the intention of evaluating the main contenders against the cost, power, and performance requirements for SKA.

Data-cable systems are essential for an evolving Square Kilometre Array (SKA) phasedarray demonstrator project. Loss, dispersion and channel coupling are the characteristics of interest. We evaluate a Category 7 (CAT-7) cable system, which incorporates a 20 m CAT-7 cable, balun transformers, and ARJ45 connectors. Measurements from 30 MHz -1.5 GHz are made using a calibrated Vector Network Analyzer (VNA). Through, Reflect, Line (TRL) as well as Short, Open, matched Load, Through (SOLT) calibration techniques were performed, which separately test the cables and the entire system performance respectively. A further measurement isolates the baluns. The connectors and baluns are mounted on customised printed circuit boards. We investigated phase dispersion, return loss, attenuation, near-end crosstalk (NEXT) and far-end crosstalk (FEXT). The best system was found to have a linear phase response in the 30 MHz to 1.4 GHz band, with NEXT and FEXT levels below -50 dB and -63 dB respectively. Such performance makes this cable class a candidate for high-volume data streams anticipated for the SKA.

The SKADS Benchmark Scenario is an overall SKA concept which aims to meet as many as possible of the SKA requirements presented in the SKA reference design. The key element of the system design is the use of aperture array technology on all baselines below a frequency of 1 GHz which gives a field of view of 250 square degrees in the key mid-frequency band. At higher frequencies comparatively low-cost, small (6.1 m) antennas are proposed each equipped with a single wide-band feed. The detailed design of high frequency dishes and wide-band, single pixel feeds is likely under a highly complementary US TDP programme and elsewhere. This Scenario is presented in detail, concentrating in particular on the design of the key mid-frequency aperture array and drawing on the work of other projects for elements of the system outside of the expertise and scope of the SKADS project. Detailed costing of the design suggests strongly that the Benchmark Scenario is a practical and achievable implementation which delivers the scientific performance for the SKA. The “worst case” cost is estimated to be€ 1.91 Billion with an uncertainty of 9% costed for 2011. Further development of the Benchmark Scenario will include detailed scientific and astronomical evaluation and simulation together with cost optimisation and cost/performance tradeoffs.