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ATNF Interference Mitigation Projects - Possibilities for Collaboration
with NRAO in MRI Proposal



P. Hall, J. Bell, R. Ekers

21 January, 1999





(a) Characterization of Undesired Signals


1. Design of manipulation and visualization software for accessing licenced
transmitter databases supplied by spectrum management agencies or, in
the case of satellites, compiled by the ATNF and related agencies.

STATUS: Funded ($A20k); basic systems in place for ATNF operational use;
continuing development at 0.25 man-year level.

2. Construction of a portable RFI characterization test set, including a
high-resolution correlation spectrometer, allowing the measurement
equipment to attain the sensitivity levels needed in tracking
interference to radio astronomy services.

STATUS: Funded ($A50k); completion target for end 1999; 1.5 m-yr
commitment.





(b) Front-end or IF Mitigation of Undesired Signals


1. Topologies and devices for high dynamic range LNAs.

STATUS: no present funding or other commitment; contingent on SKA study
or other funding. Proposed commitment would be of order 1 engineer for 1
yr ($A75k + 1 m-yr).

2. High-temperature superconducting band-stop filters (high-order, very low
insertion loss, devices).

STATUS: Funded at demonstrator level; underway; collaboration with James
Cook University, CSIRO Telecommunications and Industrial Physics and
industry; approx. 0.1 m-yr from ATNF. Probable extension to ATNF/CTIP
collaboration with JCU. Extended project would be of order 1 engineer for
1 yr ($A75k + 1 m-yr). Assessed as priority area, noting ability of
collaborators to design and fabricate quality devices with fast turn-
around.

3. Tunable (possibly adaptive) IF filter for unwanted satellite signals
(to be demonstrated on Iridium signals).

STATUS: underway; student project to end shortly.

4. Photonic IF notch filters (Q>1000, high dynamic range, filters based on
fibre optic gratings; possibly extendable to adaptive techniques).

STATUS: no present funding or commitment; contingent on SKA study or
other funding. Assessed as priority area with a commitment of order
$A150k + 2 m-yr envisaged.



(c) Mitigation of Undesired Signals in Multi-aperture and Multi-receiver
Arrays


1. Post-correlation cancellation (exploiting closure phase properties of
interferers in either focal or aperture planes). Application to
synthesis (ATCA, VLA, .) and single-dish instruments.

STATUS: underway; first results demonstrated; presently about 0.5 m-yr
total commitment. Priority area, relatively straightforward to extend
using additional astronomy/system personnel; ideal area for NRAO
collaboration. Note that the flexible nature of AT electronics and
software systems makes our instruments well-suited as test-beds for new
techniques.

2. S2 VLBI tape recording of data streams, with subsequent software
cancellation, possibly invoking techniques such as null steering. As
well as the obvious direct benefits, this work has potential value in the
testing and evaluation of algorithms prior to any hardware
implementation.

STATUS: underway (in collaboration with the SETI Institute); initial
results encouraging; presently about 1 m-yr committment. As for (1);
ideal area for NRAO collaboration.



(d) Key Australian Links


1. CSIRO Telecommunications and Industrial Physics (CTIP);
telecommunications systems and device fabrication experts.

2. Photonics Co-operative Research Centre (CRC); RF and optical signal
processing expertise.

3. Swinburne University of Technology, School of Biophysical Sciences and
Electrical Engineering; real-time computing and signal processing
expertise.



General note


ATNF involvement is mainly manpower limited at this early strategic phase
of interference mitigation work. In general, laboratory facilities and
supervision are readily available; most projects can be expanded by adding
graduate engineer or astronomy postdocs at an approximate annual cost of
$A75k (salary + indirect).
















































Rev 3, PJH, 21 Jan 1999