Hehong Fan

Noise performance analyses for TWT electron gun

A noise performance analytical model considering shot noise and velocity noise was proposed for TWT electron gun. Simulations show that electron beam conformations and velocity distributions can be influenced apparently by the noises. And current & velocity fluctuations were simulated, with equivalent distributed noise impedances calculated from it. Starting from structure and operation parameters of electron gun, the model shows to be an effective tool for electron gun noise performance analysis and design.

Rayleigh scattering measurement of residual gas inside microwave vacuum electronic devices

We propose a method to measure the residual gas in microwave vacuum electronic devices (VED) in long-term storage based on Rayleigh scattering, and establish the relation between the gas state and the intensity of scattered light. This method can be used to monitor the status of VED in long-term storage.

Electromagnetic band gap substrate for planar microstrip meander line travelling wave tube

Novel dual-square electromagnetic band gap (EBG) substrate is investigated to improve the performance of planar microstrip meander line travelling-wave tube (MML-TWT). According to the simulation results, this EBG structure can improve coupling impedance double and extend bandwidth from 9.5GHz to 10.5GHz. This structure also can be fabricated in one-dimensional for the MML-TWT. In other words, it has same transverse dimension of MML-TWT, which is important to fabricate the planar travelling wave tube.

Integrated Microstrip Meander Line Traveling Wave Tube Based on Metamaterial Absorber

An integrated microstrip meander line (MML) slow-wave structure (SWS) comprised of an MML SWS and compact wideband metamaterial absorber (MMA) is proposed and demonstrated theoretically and experimentally in this paper. The MMA consists of metallic rectangular resonators with a metallic ground plane and a separating dielectric layer. Simulation results show that the MMA has multidistinctive absorption peaks; the bandwidth at 56-GHz peak frequency is reach up to 30 GHz. The integrated MML SWS can provide flatter gain response of output power than that made by the MML SWS with a traditional resistive coating attenuator. Experimental results are in close agreement with simulation results. A traveling wave tube (TWT) is simulated based on this integrated MML SWS. The output power of this TWT is 48.21 W at 33 GHz corresponding to a maximum gain of 30.3 dB; the output power gain is greater than 25 dB across the entire working frequency range.

Impacts of cubic Boron Nitride (CBN) support rods on TWT performance

We propose new support rod material in helix TWTs to improve the heat dissipation performance of the tubes, which is the cubic Boron Nitride (CBN) crystal with the second highest thermal conductivity and relatively low dielectric constant. The high frequency characteristics and the beam-wave interaction of helix slow wave structure with CBN and BeO support rods are simulated and analyzed, respectively. The results show that the difference between saturated output powers is less than 10%, and backward wave oscillation power hole still exists. Temperature distribution on a TWT with CBN support rod is also obtained with lower temperature than one with BeO rods. CBN can be made as support rods of TWT with high heat dissipation capability.

Measurement experiment of residual gas inside vacuum electronic devices based on Rayleigh scattering

We performed an experiment demonstration for verifying the measurement method based on Rayleigh scattering to test the residual gas in a storing vacuum electronic devices (VED), using high pulse power ultraviolet laser and CCD detector. The normalized intensities of scattered light are obtained before and after degassing the test tube. The experimental results validate the measurement method we proposed before.

Study for noise performance parameter estimation of TWT electron gun

Noise performance parameters are important parameters for TWTs used in many scenarios. We proposed in the paper an electron gun noise parameter estimation method for electron guns with non-ideal electron-beams. And noise parameters for several electron guns were simulated and analyzed. The results can be used for reference of low-noise electron gun design.

Performance degradation simulation for M-type cathode based on ion bombardment

Simulation of M-type cathode performance degradation is studied based on ion bombardment with interdiffusion effect considered. Sputtered volume, sputter distribution and ion spot occurrence time can be estimated, with estimated sputtered volume close to former researches. For M-type Re-coated cathode with 300nm-thick film, ion spots were estimated to appear after 2.06×105 hs working.

P4-18: Cold testing platform for Electromagnetic Band Gap waveguide

A high space resolution platform has been built to measure the cold test parameters of Electromagnetic Band Gap (EBG) waveguide. The space resolution of this platform can be reached to 4µm and controlled by FPGA and computer through LABVIEW. An EBG waveguide is fabricated for measurement. The mode field of cross section and propagate constants have been simulated by our coding and tested by this platform‥

Band gap analyses for high impedance electromagnetic surfaces using adaptive finite element method in frequency domain

An adaptive finite element method in frequency domain (A-FEM-FD) is presented, which is suitable for the band gap analyses of high impedance electromagnetic surfaces. Three new types of EBG structures are simulated and the regions of their in-plane band gaps for both TE and TM modes are given, which are consistent with the test results by Agilent E8363B VNA.