Discover a modern approach to the analysis, modeling and design of high sensitivity phased arrays. Network theory, numerical methods and computational electromagnetic simulation techniques are uniquely combined to enable full system analysis and design optimization. Beamforming and array signal processing theory are integrated into the treatment from the start. Digital signal processing methods such as polyphase filtering and RFI mitigation are described, along with technologies for real-time hardware implementation. Key concepts from interferometric imaging used in radio telescopes are also considered. A basic development of theory and modeling techniques is accompanied by problem sets that guide readers in developing modeling codes that retain the simplicity of the classical array factor method while incorporating mutual coupling effects and interactions between elements. Combining current research trends with pedagogical material suitable for a first-year graduate course, this is an invaluable resource for students, teachers, researchers, and practicing RF/microwave and antenna design engineers.

Phased Arrays for Radio Astronomy, Remote Sensing, and Satellite Communications

Phased arrays have a long history in radio astronomy. Large, sparse synthesis arrays have been in use for decades to capture high-resolution images of deep space objects. More recent work has extended the range of applications to other types of arrays, including aperture arrays (AAs) and phased array feeds (PAFs) for multibeam reflector antennas. The extreme sensitivity required for astronomical instrumentation is driving advances in numerical electromagnetic modeling, design optimization of large arrays, low noise amplifiers, minimization of receiver noise, cryogenic PAFs, array calibration, optimal beamforming, interferometric imaging, and array signal processing algorithms for radio-frequency interference mitigation. We give an overview of research progress, current and planned array-based instruments, and open challenges in these areas related to the new generation of sparse arrays, PAFs, and AAs that are in development for astronomical observatories around the world.

High-Sensitivity Phased Array Receivers for Radio Astronomy

Self-adapting conformal antennas for changing spherical surfaces are investigated in this work. More specifically, the theory on the relationship between the radius of the spherical surface, element spacing of the conformal array and required phase compensation is developed. Initially, for theoretical validation, a 4 × 4 phased array antenna is assembled with individual microstrip antennas used as the radiators at 2.47 GHz. Each antenna is connected to a commercially available voltage controlled phase shifter with identical SMA cables and then each phase shifter is connected to a port on a sixteen-way power divider. This phased-array antenna allows for convenient placement of individual patches on the spherical surface and precise phase control. For further validation, a second 4 × 4 phased-array antenna with embedded phase shifters and a sensing circuit is manufactured. The sensing circuit is used to measure the radius of curvature of the spherical surface and use this information to autonomously apply the appropriate phase compensation, based on the previous theoretical developments, to recover the radiation pattern of the array for different spherical surfaces at 2.47 GHz. Overall, good agreement between theory, simulation and experimental data is shown and that it is possible to recover the radiation pattern autonomously.

Phase-Compensated Conformal Antennas for Changing Spherical Surfaces

Various challenges have arisen in the measurement of phased array feeds for radiotelescopes. We focus here on measuring the equivalent noise temperature and the sensitivity of these feeds. We outline the differences between characterizing phased array feeds compared with traditional single horn feeds and provide results from our experience in developing phased array feeds for the Australian Square Kilometre Array Pathfinder.

Measuring radiotelescope phased array feed noise and sensitivity

Phase compensation techniques based on projection method and convex optimization (phase correction only) for comparing the maximum gain of a phase-compensated conformal antenna array have been discussed. In particular, these techniques are validated with conformal phased array antenna attached to a cylindrical-shaped surface with various radii of curvatures. These phase compensation techniques are used to correct the broadside radiation pattern. It is shown that the maximum broadside gain compensated is still less than the gain of a linear flat array for any surface deformation. This fundamental maximum compensated gain limitations of the phase compensation techniques can be used by a designer to predict the maximum broadside obtainable theoretical gain on a conformal antenna array for a particular deformed surface.

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Broadside Pattern Correction Techniques for Conformal Antenna Arrays

Phased array feeds (PAFs) for large diameter single dish radio telescopes offer the capability for multiple simultaneous beam formation and wide field-of-view surveys An L-band PAF front end design is presented for the Five-hundred-meter Aperture Spherical Telescope (FAST), which is currently under construction and when complete will be the largest single dish radio telescope in the world A broadband PAF element at L-band was designed in conjunction with the FAST optics and focal plane field distribution, fabricated, and tested The simulated performance of the array meets the FAST PAF performance requirements for field of view, efficiency, sensitivity, and other key parameters A unique aspect of the FAST PAF is the need for feed cabin vibration compensation A study of the use of adaptive beamforming to compensate for lateral movement is given

Design Study of an L-Band Phased Array Feed for Wide-Field Surveys and Vibration Compensation on FAST

Phased array feeds (PAFs) for large telescopes are currently moving from the research stage to prototype instruments with the capability for scientific observations. We report on progress towards an L-band array element design optimized for the Green Bank Telescope, imaging algorithms and real time digital signal processing, and a preliminary PAF front end design for the China Five Hundred Meter Aperture Spherical Telescope (FAST).

Chengjin Jin

Papers

Design Study of an L-Band Phased Array Feed for Wide-Field Surveys and Vibration Compensation on FAST

Progress in high sensitivity phased array feeds for large single-dish radio telescopes