Wang Maoyan

A Ka-band T/R front-end for phased array radar

In this paper, a Ka-band transmitter/receiver (T/R) front-end for a phased-array radar is proposed. The transceiver includes a receiver channel and a transmitter channel. A function link shared with the receiver channel and the transmitter channel is comprised of a 5-bit phase shifter and a variable gain amplifying circuit including an attenuator and a low noise amplifier. Connection to either the final power amplifier on transmitter or the LNA on receiver is accomplished by using two single-pole double-throw switches (SPDTs). Experimental results of the front-end verify the validity of the design. A noise figure of 4.9 to 5.6dB, a receiver gain of 24.4 to 29.4dB and a output power from 0.74W to 1W are obtained within a frequency range from 34.5GHz to 35.5GHz. The digital phase shift provides 10.2° root-mean square(RMS) phase shift error at 35GHz.

FDTD Simulation on Terahertz Waves Propagation Through a Dusty Plasma

The frequency dependent permittivity for dusty plasmas is provided by introducing the charging response factor and charge relaxation rate of airborne particles. The field equations that describe the characteristics of Terahertz (THz) waves propagation in a dusty plasma sheath are derived and discretized on the basis of the auxiliary differential equation (ADE) in the finite difference time domain (FDTD) method. Compared with numerical solutions in reference, the accuracy for the ADE FDTD method is validated. The reflection property of the metal Aluminum interlayer of the sheath at THz frequencies is discussed. The effects of the thickness, effective collision frequency, airborne particle density, and charge relaxation rate of airborne particles on the electromagnetic properties of Terahertz waves through a dusty plasma slab are investigated. Finally, some potential applications for Terahertz waves in information and communication are analyzed.

Reflection Characteristics of Layered Media in Polar Mesopause Related to Polar Mesosphere Summer Echoes

Polar mesosphere summer echoes (PMSE) are very strong radar echoes from altitudes close to the polar summer mesopause. The data from sounding rocket campaigns indicate that the radar signal to noise ratio (SNR), electron density and dust charge density of polar mesosphere in summer show obvious layered structure. In this paper the theory of wave propagation in layered media is used to study the reflectance and SNR at each layer in polar mesosphere. The calculated SNR using theory of dusty plasma is found in good agreement with the experimental result, which may imply that the intensity of the radar echoes reflected by the layered structure in polar mesosphere where polar mesosphere summer echoes used to occur can interpret partially the phenomenon of PMSE. In other words, reflection may play an important role in the occurrence of PMSE.

Study on the Relation Between the Reflectivity and Frequency in Dusty Plasma of the Polar Summer Mesopause

Relation between the volume reflectivity and frequency in view of the polar mesosphere summer echoes (PMSE) is studied using the small-scale structure of electron density caused by charged dust particles. A theoretical expression for the radar volume reflectivity is derived, which agrees with the statistical result. Both the theoretical and statistical results are confirmed with the data obtained from simultaneous observations at three frequencies. Hence the small-scale structure caused by charged dust particles may be a useful tool for the study on the generation mechanism of PMSE.

Mie Series Study on Electromagnetic Scattering of Metallic Sphere Covered by Double-negative Metamaterials

How to overcome the instability of the two-layer dispersive media mie series formula is firstly discussed when the electric size of sphere is large. Then, the radar cross section of an impedanced-matched, ideal, homogeneous double-negative (DNG) metamaterials sphere is computed. The backward radar cross section of the DNG media sphere adds up to zero. The radar cross section of metallic sphere covered by DNG media or ferrite are compared. Numerical results show that DNG media can make the radar cross section of metallic sphere decrease just like ferrite.