A 2 by 2 array of fan dipoles was designed as a feed for an existing 9.14 meter diameter reflector. Baffles (conducting fences) were utilized to reduce mutual coupling between dipoles and to improve the feed radiation pattern in the H plane. Significant strut scattering effects are noted in the secondary patterns of the reflector antenna.
Topics: NASA Technical Reports Server (NTRS), ACOUSTIC SCATTERING, ANTENNA ARRAYS, DIPOLE ANTENNAS,...
This research in computational electromagnetics developed a new method for predicting the near-field mutual coupling effects in phased array antennas, using the finite element method (FEM) in combination with integral equations. Accurate feed modeling is accomplished by enforcing continuity between the FEM solution and an arbitrary number of wave guide models across a ground plane aperture. A periodic integral equation is imposed above the antenna's physical structure in order to enforce the...
Topics: DTIC Archive, McGrath, Daniel T, AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF...
Topics: DTIC Archive, *RADIO LINKS, *MODEMS, LINE OF SIGHT, DEPLOYMENT, LESSONS LEARNED, HIGH RATE,...
The limitations of different E-field antenna coupler or preamplifier circuits are presented. All circuits were evaluated using actual Loran or Omega signals. Electric field whip or wire antennas are the simplest types which can be used for reception of VLF signals in the 10 to 100 kHz range. JFET or MOSFET transistors provide impedance transformation and some voltage gain in simple circuits where the power for operating the preamplifier uses the same coaxial cable that feeds the signal back to...
Topics: NASA Technical Reports Server (NTRS), ANTENNA COUPLERS, COUPLING CIRCUITS, LORAN C, PREAMPLIFIERS,...
High-performance mixers at terahertz frequencies require good matching between the coupling circuits such as antennas and local oscillators and the diode embedding impedance. With the availability of amplifiers at submillimeter wavelengths and the need to have multi-pixel imagers and cameras, planar mixer architecture is required to have an integrated system. An integrated mixer with planar antenna provides a compact and optimized design at terahertz frequencies. Moreover, it leads to a planar...
Topics: NASA Technical Reports Server (NTRS), ASTROPHYSICS, SUBMILLIMETER WAVES, ANTENNA COUPLERS, BEAM...
The paper demonstrates suspended rectangular and circular patch antennas with electromagnetically coupled inverted microstrip feed for linear as well as dual linear polarization/frequency applications. The measured results include the return loss and the impedance bandwidth of the antennas.
Topics: NASA Technical Reports Server (NTRS), PATCH ANTENNAS, LINEAR POLARIZATION, MICROSTRIP ANTENNAS,...
A new dual-frequency feed system at Goldstone is designed to receive the Phobos spacecraft signal at L-band (1668 + or - 40 MHz) and transmit to the spacecraft at C-band (5008.75 + or - 5.00 MHz) simultaneously. Hence, calculations of the time delay from the C-band range calibration coupler to the phase center of the L-C dual feed and back to the L-band range calibration coupler are required to correct the range measurements. Time delays of the elements in the dual-frequency feed system are...
Topics: NASA Technical Reports Server (NTRS), ANTENNA COUPLERS, ANTENNA FEEDS, C BAND, DOWNLINKING, HORN...
This report details results on two antenna-coupled millimeter-wave electro-optic modulators, the slot-vee antenna-coupled modulator and a 94 GHz directional coupler modulator. The slot-vee-coupled modulator gave 0.17 m-squared per Watt semitivity, but known defects in the chip imply much better performance is possible. The 94 GHz directional coupler improvements anticipated were not realized due to fabrication problems. A detailed theoretical study of the effects of velocity mismatch on...
Topics: DTIC Archive, Bridges, William H, CALIFORNIA INST OF TECH PASADENA OFFICE OF SPONSORED RESEARCH,...
Basic antenna theory which states that the field radiated from an antenna array is equal to the sum of the currents flowing in each element of the array is discussed. The feedline distribution system guarantees the proper amplitude and phase of the current for each element of an array. The difference in electrical lengths of the feedlines to the elements has to equal the desired phase angle. The current for voltage delay in a transmission line is equal to the transmission line electrical length...
Topics: NASA Technical Reports Server (NTRS), ANTENNA ARRAYS, ANTENNA COUPLERS, ANTENNA RADIATION PATTERNS,...
This report considers the impact of antenna mutual coupling on adaptive phased array radar signal processing. First, the impedance matrix is developed via the method of moments and utilized in an airborne phased array radar data generation code. Next, the effect of mutual coupling on the true and estimated covariance matrices is considered. Finally, performance results are considered for a space-time adaptive processing algorithm in terms of probability of detection as well as plots of the test...
Topics: DTIC Archive, Himed, Braham, RESEARCH ASSOCIATES FOR DEFENSE CONVERSION MARCY NY,...
Army Research Laboratory has been researching methods to maintain fielded -legacy systems built with technology that is no longer available in the commercial market. One method under examination is using the VHSIC Hardware Description Language (VHDL) to document circuits for future redesign and reengineering for efficient reprocurement of spare electronic components. This report describes a case where structural VHDL modeling methods were studied while documenting the structure of three...
Topics: DTIC Archive, Brodsky, Jared M, ARMY RESEARCH LAB FORT MONMOUTH NJ ELECTRONICS AND POWER SOURCES...
Long-range transport aircraft such as the C-130/Hercules require reliable HF communication systems for their global missions. In some cases dual HF systems are installed using two separate antennas, in a SIMOP mode: one antenna for transmitting and the other for receiving, at arbitrary frequencies over the 2-30 MHz HF frequency range. Candidate antennas for such HF systems are probes on the vertical stabilizer or the wingtips and dorsal or wing-root notch antennas. Previous work has modeled the...
Topics: DTIC Archive, Kubina, Stanley J, CONCORDIA UNIV MONTREAL (QUEBEC) CA ELECTROMAGNETIC COMPATIBILITY...
The physical layout of the array elements and the proximity of the microstrip feed network makes the input impedance and radiation pattern values dependent upon the effects of mutual coupling, feedline discontinuities and feed point location. The extent of these dependences was assessed and a number of single patch and module structures were constructed and measured at an operating frequency of approximately 4.0 GHz. The empirical results were compared with the ones which were theoretically...
Topics: NASA Technical Reports Server (NTRS), ANTENNA ARRAYS, ELECTRONIC MODULES, JUNCTION TRANSISTORS,...
Theoretical and numerical analyses were performed to develop a computer algorithm for computing antenna mutal gain for arbitrary arrangements and orientations of antennas located in the near-field of each other and operating in the presence of near-field scattering obstacles. The mathematical expressions and algorithm were developed based on the use of the complex far- field electric field data for each antenna. The algorithm, designated as GTSAF, has been implemented and employed to generate...
Topics: DTIC Archive, Cown, Barry J, GEORGIA TECH RESEARCH INST ATLANTA ELECTRONICS AND COMPUTER SYSTEMS...
The Mariner Mars 1971 S-band antenna subsystem is used to transmit and receive S-band signals to and from the Deep Space Instrumentation Facility ground stations. The antenna subsystem consists of a low-gain antenna, a medium-gain antenna, a directional coupler, a high-gain antenna, and all transmission lines required to interconnect the antennas to the spacecraft radio frequency subsystem. The low-gain antenna is used to transmit signals during cruise and receive signals throughout the...
Topics: NASA Technical Reports Server (NTRS), ANTENNA DESIGN, MARINER SPACECRAFT, MARS PROBES, PERFORMANCE...
Space environment benefits of body-centric wireless communications are numerous, particularly in the context of long duration Lunar and Martian outposts that are in planning stages at several space agencies around the world. Since crew time for such missions is a scarce commodity, seamless integration of body-centric wireless from various sources is paramount. Sources include traditional data, such as audio, video, tracking, and biotelemetry. Newer data sources include positioning, orientation,...
Topics: NASA Technical Reports Server (NTRS), BIOTELEMETRY, WIRELESS COMMUNICATION, SLOT ANTENNAS,...
Mutual coupling between rectangular apertures in a finite antenna array, in an infinite ground plane, is analyzed using the vector potential approach. The method of moments is used to solve the equations that result from setting the tangential magnetic fields across each aperture equal. The approximation uses a set of vector potential model functions to solve for equivalent magnetic currents. A computer program was written to carry out this analysis and the resulting currents were used to...
Topics: NASA Technical Reports Server (NTRS), ANTENNA ARRAYS, COMPUTER PROGRAMS, MATHEMATICAL MODELS,...
A simple technique was developed to account for the higher order mode coupling between adjacent coupling slots in the feed waveguide of a planar slot array. The method uses an equation relating the slot impedance to the slot voltage and a reaction integral involving the equivalent magnetic current of the slot aperture and the magnetic field coupled from an adjacent slot. In the proposed method, one uses the Elliott s design technique to determine tilt angles and lengths of the coupling slots....
Topics: NASA Technical Reports Server (NTRS), COUPLED MODES, SLOT ANTENNAS, WAVEGUIDES, ANTENNA ARRAYS,...
The possible transmission of high power laser beams over long distances and their conversion to thrust, electricity, or other useful forms of energy is considered. Specific topics discussed include: laser induced chemistry; developments in photovoltaics, including modification of the Schottky barrier devices and generation of high voltage emf'sby laser radiation of piezoelectric ceramics; the thermo electronic laser energy converter and the laser plasmadynamics converters; harmonic conversion...
Topics: NASA Technical Reports Server (NTRS), CONFERENCES, ENERGY CONVERSION, LASER APPLICATIONS, LASER...
Scanning mode for a microwave radiometer having large aperture antenna is determined from scientific needs by engineering tradeoffs. Two configurations of the scan drive mechanism with an integral momentum compensation are formulated for 1.OM and 1.4M diameter antennas. As the formulation is based on currently available components, it is possible to design and fabricate the formulated mechanism without new hardware development. A preliminary specification for major components of formulated...
Topics: NASA Technical Reports Server (NTRS), ANTENNA COMPONENTS, MECHANICAL DRIVES, MICROWAVE RADIOMETERS,...
Research on metal-barrier-metal structures is reviewed. Topics discussed include: demonstration of antenna coupling and rectification characteristics with high resistance evaporated structures at a wavelength of 10 microns; application of these devices to coherent conversion of laser radiation and infrared and optical circuit elements; and comparison of the point-contact type of diode structure and the newly developed photolithographic structures.
Topics: NASA Technical Reports Server (NTRS), ELECTRON TUNNELING, JUNCTION DIODES, TUNNEL DIODES, ANTENNA...
In this paper, it has been clearly shown that induced parasitic rf currents can seriously degrade the performance of a radiating system; yet the significance of these undesired spurious currents has been largely ignored by antenna designers, and field users alike. It has been shown that parasitic currents can be effectively suppressed in both narrowband and wideband antenna systems by means of quarter-wavelength stubs (resonance method) and broadband cable chokes. Although effective current...
Topics: DTIC Archive, Campbell,Donn V, ARMY COMMUNICATIONS-ELECTRONICS COMMAND FORT MONMOUTH NJ, *Antenna...
A full-scale study was conducted by the Naval Air Development Center, Warminster, PA (NADC), for the C3 Division of the U.S. Army Avionics Research and Development Activity (AVRADA), Fort Monmouth, NJ, to test and evaluate production prototype antenna systems that essentially met the requirement for SINCGARS operation when installed on an Army UH-1 helicopter. The results of these tests determined a suitable tail whip antenna to be used on the UH-1 to satisfy the SINCGARS requirement between 30...
Topics: DTIC Archive, Caralyus,Joseph, ARMY AVIATION SYSTEMS COMMAND ST LOUIS MO, *TAIL ASSEMBLIES,...
A new type of phase calibration generator (PCG) coupler was developed for the Deep Space Network (DSN) X-band antennas that can be located directly behind the feedhorn. The advantage of this is that the calibration includes more of the system. The disadvantage is that the overmoded waveguide at this location must be coupled in a mode-selective manner. Low-power and high-power PCG couplers have been successfully produced, and the RF test results from a PCG coupler are given.
Topics: NASA Technical Reports Server (NTRS), ANTENNA COUPLERS, CALIBRATING, DEEP SPACE NETWORK, RADIO...
A corrugated horn antenna, adapted to be coupled to a waveguide at its apex for X-band excitation is further adapted to be connected to waveguides through a circumferential slot for S-band excitation at four distinct phases selected for the desired S-band polarization. The circumferential slot is positioned along the axial length of the horn for good impedance matching and is provided with an X-band choke in the form of two concentric choke slots. For further improvement in impedance matching,...
Topics: NASA Technical Reports Server (NTRS), ANTENNA COUPLERS, BANDWIDTH, HORN ANTENNAS, SUPERHIGH...
A coupled cavity traveling wave tube with a velocity taper, which affords beam wave resynchronization and thereby enhances is described. The wave velocity reduction is achieved by reducing the resonant frequencies of the individual resonant cavities as a function of the distance from the electron gun, through changes in internal cavity dimensions. The required changes in cavity dimensions can be accomplished by gradually increasing the cavity radius decreasing the gap length from cavity to...
Topics: NASA Technical Reports Server (NTRS), ANTENNAS, COUPLING, VELOCITY COUPLING, WAVE INTERACTION,...
The design, development, and testing of a transformer to convert an unbalanced to a balanced transmission line are described. Application of known principles has resulted in a transformer of broad frequency range. There is, also, a brief mathematical explanation of the theory involved in the procedure. An impedance match with a voltage standing wave ratio of 2:1 or less was obtained. Although two 5%ohm dummy loads were used in the design, application of the transformer with loads which have a...
Topics: DTIC Archive, REGNIER, LUCIEN A., AERONAUTICAL SYSTEMS DIV WRIGHT-PATTERSON AFB OH, *AIRCRAFT...
A multiplexing antenna assembly can efficiently couple AC signal/energy into, or out of, rotating equipment. The unit only passes AC energy while blocking DC energy. Concentric tubes that are sliced into multiple pieces are assembled together so that, when a piece from an outer tube aligns well with an inner tube piece, efficient energy coupling is achieved through a capacitive scheme. With N outer pieces and M inner pieces, an effective N x M combination can be achieved in a multiplexed...
Topics: NASA Technical Reports Server (NTRS), MULTIPLEXING, ROTATION, ANTENNA DESIGN, ANTENNA COUPLERS,...
Prototype equipment was developed for flight evaluation which provides enroute navigation in both latitude-longitude and rho-theta coordinates. The nonprecision approach capabilities of this equipment was evaluated. The antenna/preamplifier coupler, the RF processor, tracking loop hardware, tracking loop software, and the video output are discussed. Laboratory and flight test results are evaluated.
Topics: NASA Technical Reports Server (NTRS), AIRCRAFT EQUIPMENT, GENERAL AVIATION AIRCRAFT, LORAN C,...
This report summarizes a generalized formulation for three-dimensional antenna coupling and isolation problems. The formulation is developed for a generic transmit/receive configuration. The formulation is based on representing the boundary conditions arising in the problem by using integro-differential representations of Maxwell's equations. To streamline the derivations, integral operators are introduced. The resulting system of coupled equations for the electric and magnetic fields is solved...
Topics: DTIC Archive, Medgyesi-Mitschang, L N, NAVAL RESEARCH LAB WASHINGTON DC, *ANTENNA ARRAYS, *ANTENNA...
Circuit separates out, from multiplied signals, antenna element signals which have desirable phase angles and feeds them to appropriate antenna elements of phased array. System may be used in either transmitting or receiving mode.
Topics: NASA Technical Reports Server (NTRS), ANTENNA COUPLERS, CIRCUITS, FREQUENCY MULTIPLIERS, PHASE...
During the last three years of research we have contributed to the technology development for multilayer microwave/millimeter wave integrated circuits (multilayer MMICs) of the future. Such multilevel integration would allow implementation of smaller sized, higher density, and multi-functional microwave/millimeter wave circuits and systems, that are more reliable and cost effective. Specifically, we have (1) investigated new transmission media that are better suited for multilayer integration,...
Topics: DTIC Archive, Das, N. K., POLYTECHNIC UNIV BROOKLYN NY DEPT OF ELECTRICAL ENGINEERING, *INTEGRATED...
In a proposed scheme for coupling light into a quantum-well infrared photodetector (QWIP), an antenna or an array of antennas made of a suitable metal would be fabricated on the face of what would otherwise be a standard QWIP. This or any such coupling scheme is required to effect polarization conversion: Light incident perpendicularly to the face is necessarily polarized in the plane of the face, whereas, as a matter of fundamental electrodynamics and related quantum selection rules, light...
Topics: NASA Technical Reports Server (NTRS), ANTENNA ARRAYS, ANTENNA COUPLERS, QUANTUM WELL INFRARED...
An array antenna is an assembly of radiating elements in one of many possible geometrical configurations with outputs of the individual elements in the array combined to produce radiation of desired pattern shape and gain. The advantages of array antennas over a single antenna include the following: 1) high gain and high resolution without increasing the physical size of each element, 2) electronic control of radiation patterns, such as scanning of main beam and shaping of radiation pattern,...
Topics: DTIC Archive, Takamizawa, Koichiro, MASSACHUSETTS UNIV AMHERST, *INTERACTIONS, *ISOLATION, *ANTENNA...
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Generalized analysis and solution techniques were developed to evaluate the shunt power losses in electrochemical systems designed with a common or circulating electrolyte supply. Sample data are presented for a hypothetical bulk energy storage redox system, and the general applicability of the analysis technique is discussed.
Topics: ELECTRON TUNNELING, JUNCTION DIODES, TUNNEL DIODES, ANTENNA COUPLERS, ANTENNA DESIGN, CONDUCTION...
For high resolution imaging and spectroscopy in the FIR and submillimeter, space observatories will demand sensitive, fast, compact, low-power detector arrays with 104 pixels and sensitivity less than 10(exp -20) W/Hz(sup 0.5). Antenna-coupled superconducting tunnel junctions with integrated rf single-electron transistor readout amplifiers have the potential for achieving this high level of sensitivity, and can take advantage of an rf multiplexing technique. The device consists of an antenna to...
Topics: NASA Technical Reports Server (NTRS), ANTENNA COUPLERS, HIGH RESOLUTION, IMAGING TECHNIQUES,...
The Finite Difference Time Domain (FDTD) technique has been applied to a wide variety of electromagnetic analysis problems, including shielding and scattering. However, the method has not been extensively applied to antennas. In this short paper calculations of self and mutual admittances between wire antennas are made using FDTD and compared with results obtained using the Method of Moments. The agreement is quite good, indicating the possibilities for FDTD application to antenna impedance and...
Topics: NASA Technical Reports Server (NTRS), ANTENNA COUPLERS, ANTENNA DESIGN, ELECTRICAL IMPEDANCE,...
Measurement of land surface snow remains a significant challenge in the remote sensing arena. Developing the tools needed to remotely measure Snow Water Equivalent (SWE) is an important priority. The Wideband Instrument for Snow Measurements (WISM) is being developed to address this need. WISM is an airborne instrument comprised of a dual-frequency (X- and Ku-bands) Synthetic Aperture Radar (SAR) and dual-frequency (K- and Ka-bands) radiometer. A unique feature of this instrument is that all...
Topics: NASA Technical Reports Server (NTRS), ANTENNA DESIGN, ANTENNA FEEDS, REFLECTOR ANTENNAS, BROADBAND,...
A systematic analysis of mutual coupling compensation using microstrip techniques is presented. A method for behind-the-array coupling of a phased antenna array is investigated as to its feasibility. The matching scheme is tried on a rectangular array of one half lambda 2 dipoles, but it is not limited to this array element or geometry. In the example cited the values of discrete components necessary were so small an L-C network is needed for realization. Such L-C tanks might limit an otherwise...
Topics: NASA Technical Reports Server (NTRS), ANTENNA COUPLERS, DIPOLE ANTENNAS, ELECTRONIC EQUIPMENT,...
The effects of the use of an X-band carrier frequency on the transmission link margins and on the affected ground station equipment are investigated. The specific effects of the X-band carrier frequency allocation on the link margin are detailed. This includes an examination of a Local User Terminal's (LUT) coverage circle radius requirements, detailed elements of the link calculation, and specific spacecraft and ground configurations that would satisfy the link requirements. The requirements...
Topics: NASA Technical Reports Server (NTRS), GROUND STATIONS, LANDSAT SATELLITES, RADAR TRANSMISSION,...
The design and design data for broadband loop antenna systems are presented. An investigation of some simple systems for possible Loran C receivers which require a bandwidth of greater than 20 KHz is discussed. Designs are presented for a 60 KHz WWVB antenna, several Loran C variations, and some 1750 meter band antennas. Signals received on all these, including one airborne experiment where a Loran C receiver gave the correct time difference reading within 1 microsecond while flying on a...
Topics: NASA Technical Reports Server (NTRS), ANTENNA DESIGN, LOOP ANTENNAS, LORAN C, ANTENNA COUPLERS,...
This effort was directed toward demonstration of the efficacy of a concept for mitigation of the rotor blade modulation problem in helicopter communications. An antenna is envisioned with radiating elements mounted on the rotor and rotating with it. The rf signals are coupled to the radio stationary with respect to the airframe via a coupler of unique design. The coupler has an rf cavity within which a mode is established and the field distribution of this mode is sampled by probes rotating...
Topics: DTIC Archive, Pogorzelski, Ronald J, JET PROPULSION LAB PASADENA CA, *HELICOPTER ROTORS, *AIRCRAFT...
