Hongxia Yi

NUMERICAL OPTIMIZATION OF PITCH PROFILE FOR OVERALL EFFICIENCY ENHANCEMENT OF A SPACE TWT

Obtaining higher e-ciency during the development of space Traveling Wave Tubes (TWTs) is always one of the most important goals for scientists. In this paper, a scheme of obtaining the maximum theoretical overall e-ciency is explored by optimizing the helix pitch proflle of a TWT based on the collectability of spent beam. The collectability of the spent beam was evaluated by the maximum collector e-ciency, and this maximum collector e-ciency was employed to calculate the maximum theoretical overall e-ciency. The energy distribution of the spent beam and the output power of TWTs were calculated by the 3-D large signal Beam-Wave Interaction Simulator (BWIS) of MTSS. The detailed design of a Ku-band helix TWT is described according to three optimization goals (theoretical overall e-ciency, theoretical collector e-ciency and electronic e-ciency). The simulation results indicate that the optimization for high interaction circuit e-ciency or collector e-ciency by itself is not adequate to obtain maximum overall e-ciency. The maximum theoretical overall e-ciency of 77% was achieved via the optimization of slow wave structure for theoretical overall e-ciency.

Influence of interface status on heat dissipation capability of collector for travelling wave tube

In the paper, Influence of interface status (ratio of brazing area and fit clearance) of brazed collector parts on contact heat resistance was theoretically analysised. And by ANSYS simulation, influence of ratio of brazing area and fit clearance on heat dissipation capability of collector for travelling wave tube was studied.

Photonic crystal-structure for corrugated rectangular waveguide slow-wave structure

A slow-wave structure(SWS) based on corrugated rectangular waveguide(CRWG) assisted by photonic crystals(PhCs) lateral walls for traveling wave tubes(TWT) is demonstated. Compared with traditional structure, it overcomes mode-competition problems and improves the stability of TWT. In this paper, The PhC-rectangular corrugated waveguide is designed for high output power.

The small signal theory assistant analysis of negative-positive phase velocity tapering

The fundamental method of the design of an ultra-broadband helix traveling wave tube (TWT) with two-section output circuit was analyzed using Pierce small signal theory, and shaped a special helix pitch profile with reduced phase-velocity followed by a positive phase-velocity taper. The slow wave structure with semi-metallic rods, which has good thermal dissipation capability and gives negative dispersion characteristics, was used to reduce the second harmonic content of a wide-band TWT in this paper.

Optimization design of slow wave structure using genetic algorithm

In this paper, a scheme of obtaining the maximum theoretical overall efficiency is explored by optimizing the helix pitch profile of a TWT based on the collectability of spent beam. The detailed design of a Ku-band helix TWT is described according to three optimization goals (theoretical overall efficiency, theoretical collector efficiency and electronic efficiency). The simulation results indicate that the optimization for high interaction circuit efficiency or collector efficiency by itself is not adequate to obtain maximum overall efficiency. The maximum theoretical overall efficiency of 77% was achieved via the optimization of slow wave structure for theoretical overall efficiency.

The small signal theory analysis and optimization design of high efficiency broadband TWTs

Broadband helix traveling wave tube (TWT), because of its wide bandwidth and high gain, has potential applications in electronic countermeasure (ECM) systems and space exploration. Its a challenge to obtain high efficiency TWT over a multi-octave band, since its fundamental efficiency is degraded and harmonic power content is enhanced at lower band frequencies and the efficiency at high frequencies deteriorates because of insufficient interaction impedance and large distributing loss. The fundamental method of the design of an ultra-broadband TWT usually uses two-section output circuit: the first output section using unloaded circuit is to make the growing wave gain occur only at lower end of the band; the second output section using a loaded helix circuit is designed to be in synchronism with the RF wave at all frequency. In this paper, this fundamental method was analyzed using Pierce small signal theory, and then the special helix pitch profile using only negative dispersion slow wave structure (SWS) was shaped to satisfy the design request. The helix pitch profile was optimized to obtain a higher electronic efficiency using genetic algorithm at high frequency (18GHz).