The processors can be used to combine signals in interferometry and telecommunications.
A recently developed breadboard version of an advanced signal processor for arraying many antennas in NASA’s Deep Space Network (DSN) can accept inputs in a 500-MHz-wide frequency band from six antennas. The next breadboard version is expected to accept inputs from 16 antennas, and a following developed version is expected to be designed according to an architecture that will be scalable to accept inputs from as many as 400 antennas. These and similar signal processors could also be used for combining multiple wide-band signals in non-DSN applications, including very-long-baseline interferometry and telecommunications.
The inputs from the antennas are preprocessed signals in an intermediate- frequency (IF) band from 700 to 1,200 MHz. High-speed commercial offthe- shelf analog-to-digital-converter (ADC) integrated circuits sample the inputs to 8 bits at a rate of 1,280 MHz. The sample data are transmitted via fiber-optic links to signal-processing boards in a commercial high-performance, modular, digital chassis that conforms to an industry standard known as the Advanced Telecommunications Architecture (ATCA). The physical and electrical characteristics of an ATCA chassis are governed by a specification known as PICMG 3.0 (wherein “PICMG” signifies the PCI Industrial Computer Manufacturers Group and “PCI” signifies peripheral component interface).
Mounted on each signal-processing board are four field-programmable gate array (FPGA) integrated-circuit chips that are interconnected both on the board and through the ATCA back plane by serial links capable of operating at speeds up to 2.5 Gb/s. Each FPGA chip can be programmed, independently of the other FPGA chips, to perform such specific functions as implementing filter banks to convert time-domain data to frequencydomain data in frequency channels, wideand narrow-band cross-correlation, combining of the individual frequency channels, and implementing synthesizing filter banks for converting frequencydomain data back to the time domain.
This work was done by Andre Jongeling, Elliott Sigman, Kumar Chandra, Joseph Trinh, Melissa Soriano, Robert Navarro, Stephen Rogstad, Charles Goodhart, Robert Proctor, Michael Jourdan, and Benno Rayhrer of Caltech for NASA’s Jet Propulsion Laboratory.
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