Yuliang Dong

Propagation Matrix Method Study on THz Waves Propagation in a Dusty Plasma Sheath

Terahertz (THz) waves propagation in a stratified media slab containing dusty plasmas are investigated using the propagation matrix method. The dispersive permittivity of conductors and dusty plasmas at THz frequencies are given. After the validation of the method is performed, the propagation properties of aluminum coated by dusty plasmas with and without vacuum interlayer are compared. The THz reflection and transmission coefficients for a dusty plasma slab with different medium parameters are discussed.

Wave propagation and Lorentz force density in gain chiral structures

The electromagnetic coupling and mechanical interaction between a plane wave and dispersive gain chiral structures are investigated using the Auxiliary Differential Equation Finite Difference Time Domain (ADE-FDTD) method. Utilizing the constitutive relations containing frequency-dependent Lorentzian models and a Condon model, the wave equations and time-averaged Lorentz force density for the magneto-electric coupling chiral media are presented. Numerical results show that the cross-polarized transmission coefficient is larger than the co-polarized transmission coefficient for a gain chiral slab with certain thickness. The gradient force engendered by bound currents of the cross-polarized waves in chiral media is larger than the scattering force to pull the slab towards the incident source. The complicated optical pulling or pushing force density among slabs, which is illuminated by a normally incident plane wave, containing chiral materials with different medium parameters is achieved.

Microstrip Wide Band-pass Filter Based on Substrate Integrated Waveguide (SIW)

A novel microstrip wide band-pass filter using the substrate integrated waveguide (SIW) technique (K. Wu et al., 2003) is described in this paper. The SIW is one of alternatives for packaging the microwave components on the same substrate. The filter exhibits 52.7% bandwidth (6.67 GHz-11.45 GHz in the center frequency 9.06 GHz) for -10.2 dB return loss and 2.3 dB insertion loss in the pass-band. The proposed filter has a compact size and it is suitable for designing microwave and millimeter-wave circuits.

A Low-Profile Wideband LTCC Integrated Circularly Polarized Helical Antenna Array for Millimeter-Wave Applications

A low-profile wideband low-temperature cofired ceramic integrated circularly polarized helical antenna array for millimeter-wave applications is presented. The major consideration of the antenna element design is to achieve good circular polarization and wide bandwidth when the helix has just about one turn which is beneficial for low profile. The turn is composed of 6  1/5-turn horizontal segments with straight-edge connections implemented by via holes. A 2  2 helical antenna array with a dimension of 25  15  1.316 (0.15λ0, is the wavelength at 35 GHz) mm is also designed. The simulated results show that the proposed helical antenna array has a wide impedance bandwidth from 26.5 to 40 GHz for |S11| < –13 dB and AR < 3 dB. The proposed antenna array was also measured and good agreement is achieved between the simulated and measured results.

35-GHz Wideband Vertical Off-Center-Fed Dipole and Its Array in LTCC Technology

A 35-GHz wideband low-temperature co-fired ceramic (LTCC) vertical off-center-fed dipole antenna is presented. The widened bandwidth of the dipole antenna is achieved by paralleling a ring-shaped stub placed above the ground with a vertical off-center-fed dipole. The fabricated dipole antenna with a dimension of 7.5  19  0.94 mm exhibits a measured –10-dB S11 bandwidth of 25.4% covering the frequency range of 31.2 to 40 GHz and a measured maximum gain of 4.4 dBi at 32 GHz with a fluctuation of 1.7 dB over 31 to 39 GHz frequency range. Then, a 2  2 array was designed. The array with a dimension of 15  25  0.94 mm exhibits a measured –10-dBS11 bandwidth of 28.6% covering the frequency range of 30 to 40 GHz and a maximum gain of 10.37 dBi at 31 GHz with a fluctuation of 1.8 dB over 31 to 39 GHz frequency range. The radiation performances of the dipole antenna and its array were also measured. Good agreement is obtained between the simulations and measurements.

Numerical simulation on electromagnetic properties of the solid rocket plume affected by the environmental pressure

The effect of environmental pressure of reflection and transmission coefficients of the solid rocket plume at 2000K region is studied by using the propagation matrix method. The complex relative permittivity of dusty plasma, the concept of charging response factor and the propagation matrix method are introduced in this paper. The change of environment pressure will induce variation in the electron concentration, collision frequency between electrons and molecules, as well as charging frequency of electrons in rocket plume. As a result, the changes will influence the complex relative permittivity of the rocket plume which in fact is the weakly ionized dust plasma. Numerical results show that the pressure decreases, the reflection coefficient and the transmission coefficient decrease with the increase of flight height. The transmission signal is reduced, the theoretical results and experimental observations are consistent.