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MeerKAT Digitiser

The South African Radio Astronomy Observatory (SARAO) continues to innovate in the field of radio astronomy with its cutting-edge Digitizer technology, a critical component of the MeerKAT telescope. This technology plays a pivotal role in converting signals received from outer space into a digital format that can be processed and analysed, driving forward our understanding of the universe.

The Digitiser is the sub-system of the MeerKAT telescope which is responsible for converting signals received from outer space into a digital format that can be manipulated by digital processing platforms such as computers and Field Programmable Gate Arrays (FPGAs). Direct sampling of the signals at the feed is performed since there is no downconversion of the signals to Intermediate Frequencies (IF).

The Digitisers are physically located on the indexer of the antenna which results in the Digitiser being exposed to all of the environmental conditions on the Karoo site. It also demands extreme radio frequency interference (RFI) requirements since the Digitiser is located within one metre of
the sensitive radio frequency (RF) receivers.

Detail design

The Digitiser consists of four main modules:

Radio Frequency Conditioning Unit (RFCU).

This module receives the RF signal from the Receiver and amplifies it to the correct levels as required by the ADC (Analogue to Digital Converter). Performs antialiasing filtering of the incoming signal based on requirements for second Nyquist band sampling.

Sampler module.

Performs analogue to digital conversion using a 10 bit monolithic ADC at a rate of 1712Msps for L-band while sampling the second Nyquist zone.

D-engine module.

This module packetises the raw ADC data on four 10 gigabit fibre optic Ethernet interfaces. The output data rate of the Digitiser is approximately 34.2 gigabits per second.

Sample Clock Generator (SCG) module.

This module is responsible for generating the sample clock required by the ADCs as well as a highly accurate precision synchronisation pulse.

Benefits

High Precision: The direct sampling and high-speed ADC conversion ensure the highest precision in capturing astronomical data.
Efficient Data Handling: The packetized data allows for efficient transmission and processing, facilitating real-time analysis.
RFI Mitigation: The design meets stringent RFI requirements, ensuring minimal interference and maximum signal integrity.
In-House Production: SARAO’s capability to produce the Digitizer in-house ensures quality control and rapid iteration of designs.

Opportunities

The Digitizer technology opens numerous opportunities for collaboration and innovation:

Partnerships with Academic Institutions: Facilitates joint research projects and the development of new astronomical theories.
Industry Collaboration: Engages with tech companies to advance digital processing platforms and data analysis tools.
Global Scientific Community: Contributes to international efforts in radio astronomy, enhancing global understanding of the cosmos.

Applications

Astronomical Research: Enhances the ability to study celestial objects with greater clarity and detail.
Real-Time Data Analysis: Facilitates immediate processing of data, crucial for observing dynamic astronomical events.
Broad Frequency Range: Supports a wide range of frequencies, expanding the scope of observable phenomena.