A method of arraying of receiving radio antennas involves utilization of all of the signal information available across a broad spectral band that includes any signal(s) of interest. As used here, "arraying" signifies combining the signals received by multiple antennas at different locations in such a way as to improve reception, as though one had a single larger antenna. Going beyond synthesis of a larger antenna, the present method also provides for extraction of Doppler frequency shifts and differential delays of signals, thereby enabling the generation of information on the ranges and velocities of signal sources. The method was devised to enhance spacecraft-tracking and -telemetry operations in NASA's Deep Space Network (DSN); the method could also be useful in such other applications as radio astronomy, commercial satellite communications, and radio (including television) broadcasting.

In This Implementation of Full-Spectrum Combining, as many as eight signals in a 16-MHz-wide IF band centered at 300 MHz are processed by digital and analog means to generate an enhanced IF signal, allowing for improvement of telemetry and navigation data.
In this method, the signals from the multiple antennas in an array are combined in real time by use of correlation processing, among other techniques, implemented by a combination of analog and digital electronic hardware and software. The signal received at each antenna is characterized by a delay and a Doppler shift that depend on the relative position and motion of the antenna and the spacecraft or other signal source. In order to achieve full-spectrum arraying, it is necessary to alter the signal received by each antenna to make its delay and Doppler shift equal to the delays and Doppler shifts of the similarly altered signals received by the other antennas. The altered signals are then combined coherently to obtain an improved detection of telemetry and navigation data.

In the original DSN application (see figure), the signals received by as many as eight geographically diverse antennas are processed by full-spectrum receivers (FSRs) followed by a full-spectrum combiner (FSC). The analog signal from each antenna is first down-converted to an intermediate-frequency (IF) band centered at 300 MHz. Then in an FSR, the IF signal is subjected to a combination of analog-to-digital (A/D) conversion and frequency down-conversion that yields an in-phase (I) and a quadrature-phase (Q) data stream, each consisting of 8-bit samples at a rate of 16 megasamples per second. The delay and phase of the I and Q streams from each antenna are altered by use of a delay line and a phase rotator. Adjustment is made first by using delay prediction, followed by a feedback measurement of residual delay and phase by the FSC.

In the FSC, cross-correlations of upper and lower sidebands from different antennas (e.g., of the upper sideband received by antenna 1 with the upper sideband received by antenna 2) are computed. The correlations contain information on frequency-dependent and frequency-independent phase offsets related in known ways to differential delays and Doppler shifts. The correlations are processed to generate phase and a delay offset for feedback to each FSR. The I and Q data streams from the FSRs are weighted and summed; the sum signal is then subjected to digital-to-analog (D/A) conversion and frequency up-conversion to obtain the desired enhanced IF signal.

This work was done by Andre Jongeling, Timothy Pham, and David Rogstad of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp  under the Electronics & Computers category.

NPO-20874

Topics:
Antennas Computer software and hardware Electronic equipment Electronics & Computers Radio equipment Satellite communications Spacecraft Telecommunications Telemetry Vehicles
This Brief includes a Technical Support Package (TSP).
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Full-Spectrum Arraying of Receiving Radio Antennas

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Overview

The document appears to be a technical report related to work conducted at the Jet Propulsion Laboratory (JPL) under the auspices of NASA. It discusses advancements in the field of radio antenna technology, specifically focusing on the full-spectrum arraying of receiving radio antennas. This innovative approach aims to enhance the reception of signals, which is crucial for tracking and telemetry operations within NASA's Deep Space Network.

The report emphasizes the importance of combining data from multiple antennas to improve signal reception. By utilizing this method, the system can effectively extract vital information, such as Doppler frequency shifts and differential delays, which are essential for accurate communication with spacecraft. This technology not only benefits space exploration but also has broader applications in fields like radio astronomy, satellite communications, and broadcasting.

The document includes references to specific commercial products, processes, or services, clarifying that such references do not imply endorsement by the U.S. Government or JPL. This is a standard disclaimer in technical reports to maintain objectivity and neutrality regarding commercial entities.

Overall, the report highlights the significant advancements in antenna technology that can lead to improved communication capabilities for NASA's missions. By leveraging the full-spectrum arraying technique, the agency aims to enhance its ability to receive and process data from distant spacecraft, thereby supporting ongoing and future exploration efforts in space.

In summary, the document serves as a technical overview of a specific project at JPL, detailing the methodologies and potential applications of advanced radio antenna technology in the context of NASA's mission objectives. It underscores the collaborative efforts between JPL and NASA to push the boundaries of space communication and exploration.