communications antenna tower
Soft Decision Analyzer
The Soft Decision Analyzers (SDA) closed-loop data detection allows it to measure real-time correlation observations with frame, codeword, and packet losses, as well as quality of service (QoS) and quality of experience (QoE) events. The SDA incorporates two techniques for identifying bit slips. The first is an examination of the received data stream's relation to the transmitted data content. The second is a direct examination of the receiver's recovered clock signals relative to a reference. Using these two techniques allow for a better understanding of receiver performance in this regard. The SDA detects receiver bit slips within a +/- 4-bit window and offers continuous four-quadrant tracking for multiple modulation schemes and signal-to-noise ratio measurements using techniques that work even in the presence of symbol-clipping. It continuously monitors correlation results to characterize slips and quadrant change and is capable of performing analysis even when the receiver being tested is subjected to high error-rate conditions (30 percent or beyond). The SDA also incorporates a watchdog trigger that permits the system to automatically recover from large receiver upsets while continuing its performance analysis.
Multi-colored Lasers
Optical Tunable-Based Transmitter for Multiple High-Frequency Bands
NASA Glenn's researchers have developed a means of transporting multiple radio frequency carriers through a common optical beam. In contrast to RF infrastructure systems alone, this type of hybrid RF/optical system can provide a very high data-capacity signal communication and significantly reduce power, volume, and complexity. Based on an optical wavelength division multiplexing (WDM) technique, in which optical wavelengths are generated by a tunable diode laser (TDL), the system enables multiple microwave bands to be combined and transmitted all in one unit. The WDM technique uses a different optical wavelength to carry each separate and independent high-frequency microwave band (e.g., L, C, X, Ku, Ka, Q, or higher bands). Since each RF carrier operates at a different optical wavelength, the tunable diode laser can, with the use of an electronic tunable laser controller unit, adjust the spacing wavelength and thereby minimize any crosstalk effect. Glenn's novel design features a tunable laser, configured to generate multiple optical wavelengths, along with an optical transmitter. The optical transmitter modulates each of the optical wavelengths with a corresponding RF band and then encodes each of the modulated optical wavelengths onto a single laser beam. In this way, the system can transmit multiple radio frequency bands using a single laser beam. Glenn's groundbreaking concept can greatly improve the system flexibility and scalability - not to mention the cost of - both ground and space communications.
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