The Details

Schematic of the network connections in the Data System

A Closeup of the downconversion modules, showing test/inject circuits

A closeup of the IF relays

The full RF system

Motivation

In 1992, Dr. Gordon Hurford developed a technique on locating solar bursts based on spectral measurements. From there the Owens Valley Radio Observatory (OVRO) in California the Solar Astronomy group at Caltech developed a radio measurement device called the Solar Radio Burst Locator (SRBL) whose task was to detect solar radio flare activity. This project was funded by the USAF whose interests were to improve space weather forecasts through use of burst location and spectral analysis.

Using the SRBL model, Bell Labs and New Jersey Institute of Technology (NJIT) developed a device whose purpose was to study solar radio bursts in the area of wireless communications and space weather. This device was called the Solar Radio Spectropolarimeter (SRSP).

Currently, Dr. David Thomson and his team are hoping to make improvements on the SRSP model to obtain a solar radio measurement device specifically tailored to measurements in the communications bands. Queen's SRT will perform waveform capture in any of the cell-phone and wireless communications bands. We have designed an 8 channel superheterodyne receiver for this purpose. Four of the channels are for signal observations and the remaining 4 channels are for the removal of ground-based interference.


Implementation


Electrical

The RF system is comprised of 8 identical channels operating at an IF frequencies 100-150MHZ. The system is capable of downconversion anywhere in 500Mhz-2Ghz. System upgrades are planned to allow downconversion upto 18Ghz. The radio system is designed to receive signals at both solar minimum and maximum, in the range of -91dBm to -41dBm. The SRT will operate in the (radio) noisy environment of Queen's campus, Kingston. As such, it will employ a noise reduction scheme utilizing three polarized antennas in the shadow of the reflector to obtain a noise estimate that will be removed from the signal channels. The signal channels are comprised of two polarizations at two gains, one fixed at a low attenuation, the other variable at high attenuations received by antennas at the focus of the parabolic reflector.

Systems

The data system is the final stage in the superheterodyne converter. It comprises a rack of sun v20z servers. Four of which are equipped with 100MS/s A/D converters and two equipped with FC connected disk arrays. The final downconversion is accomplished using undersampling. Both the local oscillator for the first down conversion and the sample clock on the A/D converters are locked to the same rubidium reference oscillator, minimizing any frequency drifting. The four A/D converters are sampled in large window blocks, and a variety of statistical methods may be performed on all six computers in a ditributed fashion, as they are all connected via an over-connected gigabit network.

The control system is implemented on two custom-built AMD mini-ITX computers. These systems are mounted in the SRT, on the roof. The computers have no hard disk drives, and are encased in their own faraday cages. Their connections to the rest of the systems are made by two independent fibre links. The control hardware is a National Intruments DIO-96; programmed using the COMEDI interface. Motion control is accomplished by custom circuits for each axis, as is RF control for each channel.

Mechanical

The mechanical milestone occurred during the summer of 2004 when the scope of the project was finally defined well enough to start drafting and calculating dimensions. After that last summer was finished with the arrival of the Yoke, Base and RF box and gear box assemblies from the Mechanical machine shop here on campus. One summer later provided the opportunity to, for the first time, have the entire telescope assembled in the lab where the smaller components could be installed. The cover for the dish was reconstructed to enclose the new antenna design as well the antenna mount was assembled on the dish. All the panels on the structure were RF shielded and weather sealed which now prepared the telescope to be installed on the roof of the building. After a short delay with some I beams needing to be installed on the roof the telescope was finally installed on October 20, 2005.


Roadmap


Electrical

Systems

Mechanical

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