The world's largest low-frequency (10-250MHz) radio telescope, the pan-European Low-Frequency Array (LOFAR), is undergoing an upgrade of its hardware, firmware and software to improve its unique observing capabilities. The upgrade targets a variety of scientific use cases, ranging from galaxy evolution, transients and cosmic rays to space weather and lightning research. The LOFAR2.0 upgrade will increase the sensitivity of the telescope by doubling the number of digitized antennas operating in the 10-90 MHz frequency range, and allowing simultaneous observing with the antennas between 110 and 250 MHz. We present the validation of the LOFAR2.0 system following a stepwise approach, measuring its performance according to increasing complexity. Early integration test systems has ensured a smooth transition from validating a single receiver to the full-scale station. Subsequent array releases integrate the upgraded stations, combined with an upgraded clock distribution, network, central processor and telescope manager to validate the LOFAR2.0 telescope incrementally and ensure smooth transition to operations.
KEYWORDS: Antennas, Design, Signal processing, Clocks, Phased arrays, Analog to digital converters, Digital signal processing, Electromagnetic coupling, Field programmable gate arrays
The Low-Frequency Array, or LOFAR, is the world's largest low-frequency radio telescope consisting of over 100 000 antenna elements spread across more than 50 stations throughout Europe. LOFAR2.0 is an upgrade of LOFAR which will significantly improve its sensitivity and overcome several limitations encountered during the last 10 years of operation. The digital beamformers form the core of each LOFAR station. They are called antenna processing sub-racks (APS), where all antenna signals are digitized and digitally processed to form beams on the sky. These beamformers have stringent performance requirements, such as high linearity due to strong radio-frequency interference, good timing for high beamformer efficiency, and very low common-noise and cross-talk to be sky-noise limited over long integration times. The designs of the new LOFAR2.0 beamformer are presented, showing how a balance was struck between performance and cost enabling the production of high volumes, easy installation and maintenance in the field. The antenna processing subrack consists of low-noise receiver units (RCU) which digitise about a hundred RF signals, a clock and control board (APSCT) to distribute the sampling clock and control the digitisers, a power generation board (APSPU), UniBoard2s where FPGAs perform the beamforming, and a midplane that connects all the boards together while also shielding the sensitive receivers. The APS therefore has boards ranging from high-speed, high-density digital processing devices and high-current power converters to low-noise RF electronics. It has hundreds of devices to power, cool, control and monitor and hundreds of gigabits of data which need to be transferred between boards. The first LOFAR station has been upgraded with new beamformers and the first results will be presented. This demonstrates the new capabilities LOFAR2.0 will have with the new beamformers.
The high level of expertise accumulated by Teledyne in designing ROIC for different spectral imaging sensors (from X-rays to far–infrared) enables the company to develop high performance thermal imaging sensors optimized for Size, Weight, Power and Cost (SWaP-C). The specific ROIC design discussed avoids almost any trade-off between scene dynamic range and NETD which is the main issue encountered by all other FPA suppliers. In this paper, we will show how to achieve a NETD of 50mK with a dynamic range higher than 1000°C without any FPA adjustment settings. Key characteristics of the sensitive material are described to highlight the capabilities of this technology for system operation: mainly the ease of operation due to fully digital ROIC and specific design will be demonstrated. Finally, we will see how all the previously mentioned key parameters are paving the way to affordable, powerful thermal imaging modules and cameras.
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