Citation
Abstract
A set of small, separately steerable reflector antennas has been used as a transmitting phased array for the purpose of demonstrating techniques that can be used in a larger array to serve the future uplink transmission needs of NASA’s Deep Space Network. We envision an operational array with 100 or more antennas that could generate the order of 1 TW of effective isotropic radiated power (EIRP). The demonstration is a small-scale version of this with five antennas and about 1 MW of EIRP. Each antenna has a 1.2-m-diameter aperture and a 2-W power amplifier, and the array operates in the 14.0- to 14.5-GHz communication satellite band. The main technical challenge for an uplink array is to ensure that the carrier phases of the signals from all antenna elements are aligned when the signals arrive at the receiver on a distant spacecraft. This requires a method of phase calibration. In the demonstration, we have shown that active receivers attached to the Earth near the array can be used as calibration targets. Measurements made at these receivers have been successfully used to calculate the phase adjustment needed at each antenna to achieve the desired alignment, even though the destination spacecraft is in a direction and at a distance very different from that of the calibrator. When the calculated adjustments are applied at the antennas, the combined power at a spacecraft has been shown to be within 1 dB of that expected for perfect alignment. Commercial satellites in geostationary Earth orbit were used for these tests. Other objectives of the demonstration, all successfully accomplished, include: (1) Show that a new and simple electronics architecture, specifically designed for phase and delay stability, can implement all functions of NASA deep space uplinks at low cost, supporting mass production for large arrays. (2) Show that phase alignment can be maintained for at least a few hours without recalibration. In fact, stability over several days has been demonstrated. (3) Show that data can be transmitted on the aligned carriers at substantial speeds with no degradation in bit error rate compared with single-antenna transmission at the same EIRP. Note — Because of the length of this article, a list of contents with page numbers is provided to aid the reader.
Keywords
Details
- Volume
- 42-176
- Published
- February 15, 2009
- Pages
- 1–69
- File Size
- 5.3 MB