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Han, C. C.

Publications and source records attributed to Han, C. C..

6 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Linear analysis of an axially grooved rectangular gyrotron for harmonic operation

In an axially grooved rectangular waveguide the linearized Vlasov equation is solved to find the perturbed distribution function resulting from the electromagnetic forces on the electrons. The resulting beam current and the propagating electromagnetic waves of the cold tube are used in the inhomogeneous Maxwell's equation to derive the general dispersion equation. This equation is then transformed into the electron beam frame and the resulting linear growth rate of amplification is calculated. By maximizing the linear growth rate, the operational parameters of the gyrotron are then optimized.

Ferendeci, A. M.↗
NASA NTRS1984

Theory of high-harmonic rectangular gyrotron for TE(mn) modes

In this paper, the linearized relativistic Vlasov equation is solved and a dispersion relation is calculated for the interaction between a relativistic electron beam and the electromagnetic fields of a rectangular waveguide supporting TE(mn) modes. The dispersion relation is simplified to the special case of a frame of reference moving with the electrons and the resulting coupling coefficient epsilon(mn)super l is calculated for various TE(mn) modes. The dependence of epsilon(mn)super l on the parity of the harmonic number l and various mn modes of the waveguide are discussed.

Ferendeci, A. M.↗
NASA NTRS1984

A new multiple beam satellite antenna for 30/20 GHz communications coverage of CONUS-experimental evaluation

Additional frequency bands are needed to satisfy requirements related to the rapid growth of satellite communications, and the utilization of the 30/20 GHz frequencies is being considered. The present investigation is concerned with the experimental verification phase of an antenna technology study sponsored by NASA. The feasibility of narrow (0.3 degree) directive beam scanning over the entire continental U.S. (CONUS) from a single antenna at 30/20 GHz is demonstrated. The POC (Proof-of-Concept) model is based on an employment of an offset shaped dual reflector optics. The main reflector and the subreflector are both fabricated from aluminum. Attention is given to feed array and beam-forming network, multiple beam antenna range tests, an analysis, and test results.

Smoll, A. E.↗
NASA NTRS1972

Optimization in the design of a 12 gigahertz low cost ground receiving system for broadcast satellites. Volume 1: System design, performance, and cost analysis

The technical and economical feasibility of using the 12 GHz band for broadcasting from satellites were examined. Among the assigned frequency bands for broadcast satellites, the 12 GHz band system offers the most channels. It also has the least interference on and from the terrestrial communication links. The system design and analysis are carried out on the basis of a decision analysis model. Technical difficulties in achieving low-cost 12 GHz ground receivers are solved by making use of a die cast aluminum packaging, a hybrid integrated circuit mixer, a cavity stabilized Gunn oscillator and other state-of-the-art microwave technologies for the receiver front-end. A working model was designed and tested, which used frequency modulation. A final design for the 2.6 GHz system ground receiver is also presented. The cost of the ground-terminal was analyzed and minimized for a given figure-of-merit (a ratio of receiving antenna gain to receiver system noise temperature). The results were used to analyze the performance and cost of the whole satellite system.

Ohkubo, K.↗
NASA NTRS1972

Optimization in the design of a 12 gigahertz low cost ground receiving system for broadcast satellites. Volume 2: Antenna system and interference

The antenna characteristics are analyzed of a low cost mass-producible ground station to be used in broadcast satellite systems. It is found that a prime focus antenna is sufficient for a low-cost but not a low noise system. For the antenna feed waveguide systems are the best choice for the 12 GHz band, while printed-element systems are recommended for the 2.6 GHz band. Zoned reflectors are analyzed and appear to be attractive from the standpoint of cost. However, these reflectors suffer a gain reduction of about one db and a possible increase in sidelobe levels. The off-axis gain of a non-auto-tracking station can be optimized by establishing a special illumination function at the reflector aperture. A step-feed tracking system is proposed to provide automatic procedures for searching for peak signal from a geostationary satellite. This system uses integrated circuitry and therefore results in cost saving under mass production. It is estimated that a complete step-track system would cost only $512 for a production quantity of 1000 units per year.

Ohkubo, K.↗