Electromagnetic Wave Theory and Applications

Contains reports on eleven research projects.Joint Services Electronics Program (Contract DAAG29-83-K-0003)Joint Services Electronics Program (Contract DAAL03-86-K-0002)National Science Foundation (Grant ECS82-03390)National Science Foundation (Grant ECS85-04381)Schlumberger-Doll Research CenterNational Aeronautics and Space Administration (Contract NAG 5-141)National Aeronautics and Space Administration (Contract NAS 5-26861)National Aeronautics and Space Administration (Contract NAG 5-270)U.S. Navy - Office of Naval Research (Contract N00014-83-K-0258)National Aeronautics and Space Administration (Contract NAG 5-725)International Business Machines, Inc.Lincoln Laborator

Low frequency VLBI in space using GAS-Can satellites: Report on the May 1987 JPL Workshop

Summarized are the results of a workshop held at JPL on May 28 and 29, 1987, to study the feasibility of using small, very inexpensive spacecraft for a low-frequency radio interferometer array. Many technical aspects of a mission to produce high angular resolution images of the entire sky at frequencies from 2 to 20 MHz were discussed. The workshop conclusion was that such a mission was scientifically valuable and technically practical. A useful array could be based on six or more satellites no larger than those launched from Get-Away-Special canisters. The cost of each satellite could be $1-2M, and the mass less than 90 kg. Many details require further study, but as this report shows, there is good reason to proceed. No fundamental problems have been discovered involving the use of untraditional, very inexpensive spacecraft for this type of mission

Optical Yagi-Uda nanoantennas

Conventional antennas, which are widely employed to transmit radio and TV signals, can be used at optical frequencies as long as they are shrunk to nanometer-size dimensions. Optical nanoantennas made of metallic or high-permittivity dielectric nanoparticles allow for enhancing and manipulating light on the scale much smaller than wavelength of light. Based on this ability, optical nanoantennas offer unique opportunities regarding key applications such as optical communications, photovoltaics, non-classical light emission, and sensing. From a multitude of suggested nanoantenna concepts the Yagi-Uda nanoantenna, an optical analogue of the well-established radio-frequency Yagi-Uda antenna, stands out by its efficient unidirectional light emission and enhancement. Following a brief introduction to the emerging field of optical nanoantennas, here we review recent theoretical and experimental activities on optical Yagi-Uda nanoantennas, including their design, fabrication, and applications. We also discuss several extensions of the conventional Yagi-Uda antenna design for broadband and tunable operation, for applications in nanophotonic circuits and photovoltaic devices

Design and development of dual-Polarised photovoltaic solar antennae for Ku-band SatComsp.

The aim of this thesis is to review the state-of-the-art of transparent patch antennae and to develop design techniques for the experimental development of dual-band, dual-polarised compact transparent patch antennae integrated with solar cells for Ku-band satellite applications. It can be specifically used for Fixed-Satellite-Services (FSS) operating over the frequency range from 11.7 GHz to 12.22 GHz (downlink) and 14.0 GHz to 14.5 GHz (uplink) bands. The research reported in this thesis demonstrated a suspended meshed patch antennae serves as a basic building-block element for a Ku-band dual-polarised transparent array antennae for long distance communications. The results are shown that the use of a suspended patch above a printed radiating patch and ground plane (all transparent) provides dual-band operation for the uplink and downlink. In this work, firstly, a compact low-profile linearly polarised meshed element has been designed, and simulated in CST Microwave Studio electromagnetic simulation software. The photovoltaic antennae element was then fabricated and measured. The comparison between the experimental results and simulation by CST demonstrates good agreement between predicted and practical measurements. The developed antennae element achieved the overall broad bandwidth of more than 1GHz (500 MHz in each of the uplink and downlink bands), and the nominal element gain is 6.055 dBi (downlink) and 7.61 dBi (uplink). A good compromise between the RF performance and the transparency is also obtained with optical transparency of 84% and negligible degradation of the RF performance. The design is then extended to develop a Ku-band photovoltaic antennae element for dualpolarised operation This element could be used for frequency re-use in Ku-band satellite downlink and uplink communicationsin order to double capacity. In addition, the simulation of a 2 x2 sub-array of dual polarised transparent antennae elements (using the experimentally measured performance of the single dual-polarised element) is presented. It has yielded a narrow beam with increased gain of 13 dBi and a cross-polar discrimination of greater than 30 dB is demonstrated, which is a requirement for frequency re-use operation. Hence, the dual-polarised 4-element sub-array described herein could be utilised as the primary building block for a 2D SatCom phased array antennae. In order to meet the full requirements of Kuband SatCom communications employing frequency re-use which essentially doubles the achievable capacity, i.e. two data channels can use the same frequency bands simultaneously using the two orthogonal polarisations with high cross-polar isolation. Using these new designs providing new knowledge in the field of photovoltaic communication antennae at high frequencies, and bridge the associated drawbacks with the current PV antennae

Submarine Communications .

Submarines operating in deep water are virtually cut off from the outer world. It becomes very important and essential to convey survivable and critical information to the submarine during the time it operates under water. Conventional means of radio communication do not serve any useful purpose as the higher frequencies get attenuated very sharply in sea water. At VLF band, which is presently being used by most of the world Navies, signal can penetrate only upto 8-10 m of depth. This depth is not sufficient under hostile environment. ELF is another band where listening depth is around 100 m but data rate is very low. This paper summarizes the various means of communication used to send messages to submarine while cruising at various depths. It seems that in the near future blue-green laser is going to be the vital means of sending large information to a submarine operating much deeper (500-700 m) with unrestricted speed

The Study of the Pioneer Anomaly: New Data and Objectives for New Investigation

Radiometric tracking data from Pioneer 10 and 11 spacecraft has consistently indicated the presence of a small, anomalous, Doppler frequency drift, uniformly changing with a rate of ~6 x 10^{-9} Hz/s; the drift can be interpreted as a constant sunward acceleration of each particular spacecraft of a_P = (8.74 \pm 1.33) x 10^{-10} m/s^2. This signal is known as the Pioneer anomaly; the nature of this anomaly remains unexplained. We discuss the efforts to retrieve the entire data sets of the Pioneer 10/11 radiometric Doppler data. We also report on the recently recovered telemetry files that may be used to reconstruct the engineering history of both spacecraft using original project documentation and newly developed software tools. We discuss possible ways to further investigate the discovered effect using these telemetry files in conjunction with the analysis of the much extended Doppler data. We present the main objectives of new upcoming study of the Pioneer anomaly, namely i) analysis of the early data that could yield the direction of the anomaly, ii) analysis of planetary encounters, that should tell more about the onset of the anomaly, iii) analysis of the entire dataset, to better determine the anomaly's temporal behavior, iv) comparative analysis of individual anomalous accelerations for the two Pioneers, v) the detailed study of on-board systematics, and vi) development of a thermal-electric-dynamical model using on-board telemetry. The outlined strategy may allow for a higher accuracy solution for a_P and, possibly, will lead to an unambiguous determination of the origin of the Pioneer anomaly.Comment: 43 pages, 40 figures, 3 tables, minor changes before publicatio