ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada / At ITC 2009, we described the real-world complications of fielding an airborne Synthetic beamforming Telemetry System, which simultaneously supports 20 individual beams (10 at each of 2 polarizations). We described how our layered Open-Source software approach helped us to modify the system rapidly after delivery without disrupting mission operations. Since then, we have further extended the software toolset that we developed to dissect the System behavior via post-mission replay and analysis, and to compare high-resolution in-flight measurements with our detailed physics simulations. This analysis has shown that the most significant factor affecting operational performance of the System was variation in the relative phase of the elements from day to day. These variations were traced to a variety of hardware issues, none of which could be resolved without major cost and effort. As an alternative approach, we developed a dynamic auto-tuning capability that optimizes the phase calibration of the System using each actual signal source as it is being tracked. This results in improved signal-to-noise performance while reducing the need for dedicated in-air calibration flights that we had previously created. We believe that the flexibility of digital beamforming, allied with a modular and easily-extensible software architecture, have again proven capable of quickly and cheaply mitigating real-world operational issues, without (so far) requiring any hardware modification of the delivered System.

Acoustic Receiving Line Arrays are critical tools for measuring the acoustic properties of any oceanographic region. Vertical, horizontal, and combinations of the two array configurations allow us to measure acoustic propagation, bottom characteristics through inversion, and ambient noise. These properties are vitally important for effective implementation of any passive or active detection system in both shallow and deep water environments. Measurement systems must be designed with flexibility since the exact array design that yields the best signal processing results is not known prior to a survey. Flexibility, in this case, refers to large numbers of hydrophones, higher sample rates for greater bandwidth, and longer recording time to facilitate experimentation at each survey site. Repeated deployment and recovery of such a system demands a battery powered autonomous design that can be deployed and recovered from available research vessels at sea. Conventional deep ocean analog array cable designs, while power efficient, become physically challenging in size and weight when the sensor count exceeds 100 and array lengths remain in the 100s of meters. The purpose of this thesis is to detail the design, development, and testing of a pressure tolerant full ocean depth rated prototype acoustic line array with digital telemetry of all hydrophone data from the sensors to the recording system. The design is to support up to 300 hydrophones each with a maximum sample rate of 4 kHz and a per sensor power requirement of ¾ of a watt. Lower sensor counts will allow higher sample rates to be used based on available telemetry bandwidth. A single element of a line array was built and tested at the University of Texas at Austin Applied Research Laboratories and it was used to demonstrate real-time telemetry and recording of acoustic hydrophone data. / text

ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada / A conventionally designed radio frequency amplifier operated in its linear region exhibits low DC to RF conversion efficiency. Typically, for a power amplifier designed for digital modulation applications, the amplifier is operated “backed-off” from its P1dB point by a factor of 10 or -10 dB. The typical linear amplifier is biased for either Class A or Class A/B operation depending on the acceptable design trade-offs between efficiency and linearity between these two methods. A novel design approach to increasing the efficiency of a linear RF power amplifier using a modified Odd-Way Doherty technique is presented in this paper. The design was simulated, built and then tested. The design yields improvements in efficiency and linearity.