Electronic Steering Research Articles

Use of the Clinac-35 for tissue activation in noninvasive measurement of capillary blood flow.

Through adjustment of operating parameters responsible for the acceleration, steering, and focusing of electrons en route to the target, we have extracted a 30-MV x-ray beam from the Clinac-35 linear accelerator that is suitable for use in photon activation -15O decay studies of tissue perfusion. This beam is significantly more efficient than the "standard" 25-MV beam in producing 15O in situ through activation of tissue oxygen, thereby substantially reducing the dose to tissue required to yield a desired initial 15O activity. Production and characteristics of the higher energy beam are discussed, and data obtained from its application to measurement of capillary blood flow in animal tumors are presented and analyzed.

Electronic steering of antenna nulls for interference reduction

The paper reports on theory, tests and design of a low-cost broadband radio-frequency device that combines signals from two antennas to selectively null interfering signals. The theory and analysis of limitations pertain to both manual and adaptive null control devices. Tests illustrate cases in which nulling works well and those where propagation features limit null effectiveness. An important result of the tests is recognition that much work remains to be done to determine optimum antenna pairs for particular types of interference. An analysis section provides equations of general use for designing alternative implementations.

Compound Scanning with an Electrically Steered Beam

Compound scanning using electronic steering of an array of transducers makes it possible to widen the area being explored and to increase the amount of information contained in an ultrasonic image. The principle and the operating characteristics of the method are described and its effectiveness demonstrated by in vitro and in vivo experiments. Possible improvements and applications are discussed.

Compound scanning with an electrically steered beam

Compound scanning using electronic steering of an array of transducers makes it possible to widen the area being explored and to increase the amount of information contained in an ultrasonic image. The principle and the operating characteristics of the method are described and its effectiveness demonstrated by in vitro and in vivo experiments. Possible improvements and applications are discussed.

Electromagnetic generation of electronically steered ultrasonic bulk waves

The frequency dependence of the propagation direction of ultrasonic shear and longitudinal waves generated by a meander-line electromagnetic transducer (EMAT) at MHz frequencies has been determined. The results are found to agree well with theory and demonstrate that electronic beam steering is possible using EMAT’s. The relative efficiency of generation in aluminum was also studied and, for a specific meander-line geometry with a permanent magnet providing the necessary static magnetic field, it was found to be relatively flat versus frequency. Efficiency for shear-wave generation (frequency range, 5–9 MHz) was about 4 dB per conversion less than the Rayleigh-wave generation efficiency at 4.6 MHz, and for longitudinal waves (frequency range, 10–24 MHz) about 10 dB less.

A limited-scan phased-array antenna for use with a clutter-mapping radar system

The design and construction of an electronic-scan phased-array antenna system for use with a clutter-mapping radar system is described. The phased array is capable of \pm-20\deg of electronic beam steerng and full hemispheric mechanical steerability. It is composed of 780 short-backfire radiators with a total gain of 36 dB. It is vertically polarized and has phase-monopulse-tracking ability. The electronic beamforming and steering is controlled by a digital system using a PDP-11/20 general-purpose computer system. The same computer is used to control the digital clutter-mapping system, which is composed of an A/D converter, multiplexer, digital tape recorder, high-speed disk storage, and an intensity-modulated graphic recorder.

Arrays of parametric receiving arrays

Theory is presented to describe the response of arrays whose elements consist of parametric end-fire receivers. The results of measurements on arrays containing up to four elements are presented in support of the theory. Electronic steering of this type of array is also addressed. The use of very small transducers in the formation of narrow receiver beams at low frequencies is demonstrated.

Array of Parametric Receiving Arrays

Theory is developed to describe the performance of arrays whose elements consist of parametric receiving arrays. The directivity of the resulting array of parametric receivers is shown to depend upon the separation of elements as well as the separation between pumps and receivers. The theory evolved is validated by comparison to experimental data obtained with a two-element array in a fresh water lake. Electronic steering of this type of array is also discussed. [Work supported by Office of Naval Research.]

Electrooptical processing for radio astronomy

A recent report of the first computer-generated radio-derived photographs of the Whirlpool Galaxy will no doubt provide impetus for additional radio photography of astronomical events. Electro-optical techniques, developed in the past decade for obtaining high resolution range, range-rate, and angular target data with array radars, may be highly suitable for generating visible images of astronomical events. The electrooptical processor can furnish continuously and unambiguously, in the form of an optical image, the distribution of radio emission present in the entire effective scan sector of an array without the necessity of electronic steering.

Experimental designs in investigations of mechanical properties in biological tissues.

A combination of materials testing machine with electronic steering and recording system that satisfies requirements from a rheological and biological point of view is presented. The aim of improving equipment in this field is to control testing conditions, both with regard to testing milieu and the behavior of time-dependent materials, and also to facilitate mathematical and statistical interpretation.

Development of integrated microwave components for ground-based phased arrays (Electronic steering module) : J. Austin and L. R. Pfieffer, January (1968), 44 pp. AF-19-628-5167 FR. UDC. 539.23/621.396.677/621.396.765/621.375.8

Development of integrated microwave components for ground-based phased arrays (Electronic steering module) : J. Austin and L. R. Pfieffer, January (1968), 44 pp. AF-19-628-5167 FR. UDC. 539.23/621.396.677/621.396.765/621.375.8

Coaxial Ferrite Phase Shifter for High Power Applications

The low- and high-power behavior of a coaxial ferrite-loaded transmission line has been studied experimentally at microwave frequencies. Longitudinal magnetic biasing fields both above and below the cutoff range (ω/γ−4πMs≤Hdc≤ω/γ) were explored, the two regions yielding devices with markedly different characteristics. The mechanical structure consisted of a rigid ⅞-in. coaxial line fully loaded with Trans-Tech 1–103 ferrite together with appropriate quarter-wave dielectric transformers. (1) Operation below cutoff (0≤Hdc<ω/γ−4πMs), f=3080 Mc: These parameters permit construction of a compact, light-weight phase shifter producing 360° of phase shift in 10 in. of active length upon application of only 100 oe. Approximate values for hcrit are determined from the measured threshold powers and plotted versus applied field. (2) Operation above resonance (Hdc>ω/γ), f=1350 Mc: With these parameters, a device can be built that is capable of handling at least several hundred kilowatts of rf peak power while maintaining a figure of merit of 1000 or more. The loaded coaxial line provides 360° of phase shift in 24 in. of active length when biased from 950 to 1350 oe. The high-power and loss characteristics of the latter device permit application to electronic steering of the transmitter beam in a linear array antenna where relatively few phase shifters suffice. The low-field device is suited for beam control in a planar array where large numbers of relatively small phase shifters of medium peak-power capability are needed.