Characterization of radiated sparking noise in the SKA environment Philip Kibet Prof HC Reader Stellenbosch University SKA Postgraduate Bursary and Postdoctoral Fellowship Programme 2009Philip Kibet

Introduction To investigate and mitigate RFI from sparking noise on the SKA’s system environment To study and characterize sparking noise from power lines To examine antenna characteristics of a scale- modelled power line To simulate radiation characteristics of power lines SKA Postgraduate Bursary and Postdoctoral Fellowship Programme 2009 Philip Kibet

Spark-gap noise characteristics – Identify profile of sparking noise spectrum – Locate and correct noise source – Propagation distance direct from source & along line – Antenna characteristics of line – Variation of gap size and line voltage effect SKA Postgraduate Bursary and Postdoctoral Fellowship Programme 2009 Philip Kibet

Sparking noise measurement Sparking noise on 22kV grid test power line at Karoo support-base; Carnarvon Spectral and temporal characteristics Lateral, and longitudinal profiles SKA Postgraduate Bursary and Postdoctoral Fellowship Programme 2009Philip Kibet

Measurements Contd. SKA Postgraduate Bursary and Postdoctoral Fellowship Programme 2009Philip Kibet Longitudinal profile - sparking noise decay along line length. Points P4, P56, P78, P910 & PT13; 10m away from line. Points H3, H4, H5 & H6; 100m away from line & 50m apart

Sparking noise Contd. SKA Postgraduate Bursary and Postdoctoral Fellowship Programme 2009 Philip Kibet Lateral profile Points H1, H2 & H3; 50m apart H1 10m from, & perpendicular to, SG2 Noise levels decreases with distance away from the source

Frequency & time domain characteristics SKA Postgraduate Bursary and Postdoctoral Fellowship Programme 2009 Philip Kibet

Simulated radiation characteristics of power lines PEC finite ground plane & up to 300m line length Electrically large model requires enormous computing resources Line length, impedance & point of pulse injection varied Pattern shape does not change with termination impedance variation Horizontal radiation patterns in end-fire mode whose shape, level & orientation vary with source frequency SKA Postgraduate Bursary and Postdoctoral Fellowship Programme 2009Philip Kibet

Scale-modelled power line 200 th scale-modelled power line on metallic ground plane Radiation patterns measured in an anechoic chamber Pulse from VNA input to model & rotated on turn-table S21 measurement taken for azimuthal angles for frequency range 2 – 10GHz representing scaled frequency band for 20 – 50 MHz SKA Postgraduate Bursary and Postdoctoral Fellowship Programme 2009 Philip Kibet

Scale-modelled line contd. 120 th scale-modelled line on dissipative ground medium Radiation patterns also measured at anechoic chamber. Measured horizontal pattern compared with FEKO simulations SKA Postgraduate Bursary and Postdoctoral Fellowship Programme 2009 Philip Kibet

Further Work…. Further sparking-gap measurements on the new wooden pole power line in Karoo site. Refining both simulation and physical scale- model results for clear correlation purposes. Single pulse analysis in both time and frequency domains SKA Postgraduate Bursary and Postdoctoral Fellowship Programme 2009 Philip Kibet