Yang Ruike

The Study of MMW and MW Attenuation Considering Multiple Scattering Effect in Sand and Dust Storms at Slant Paths

The influence of sand and dust storms on modern MMW and satellite communication systems reliability have been paid more attention to. The attenuations induced by sand and dust storms are estimated by means of Mie-theory and Rayleigh approximation, in the case of the tenuous distribution of particles. With the particle density increasing, however, these method become inadequate, the multiple scattering effects then become dominant for attenuation estimation. The attenuations considering multiple scattering effects are estimated by Monte-Carlo and four fluxes method at horizontal paths. At slant paths, based on multi-layer media model, the attenuations considering multiple scattering effects are calculated by layered Monte-Carlo method at 100, 37, 24, and 14GHz. It is shown that the multiple scattering effects should be considered at the attenuation prediction in the sand and dust storm, which the visibility is about 0.5km and smaller than 0.5km and frequency is about 20GHz. Above 30GHz, the multiple scattering effects due to sand and dust particles should be considered, as visibility is about 1km and smaller than 1km at slant paths.

Influence of rain Doppler frequency on MMW Doppler fuze

Guided weapon systems require a proximity fuze device to trigger the explosive warhead. Various proximity fuze types are currently employed. The millimeter wave (MMW) radio Doppler fuze is a potential advantage system, and it is required for a wide range of military application. In this paper, the MMW fuze Doppler Effect is discussed in the encounter course of fuze and target. The target Doppler frequencies (DF) caused by the target moving relative to fuze are calculated at 35 and 95GHz. The relationship of the target DF with the distance between fuze and target is obtained. The rain Doppler frequencies induced by the volumetric rain medium for the interested rain area around target moving relative to fuze are calculated at 35 and 95GHz. The relation of the rain DF with the distance between fuze and the interested rain area are given. The influences of rain DF on target DF are analyzed. It is shown that when the distance between fuze and target is less than about 30m, the difference between the rain DF and the target DF decrease gradually with the distance decreasing. The influences of rain DF clutter on target DF information become gradually bigger with the distance approach, especially, for heavier rainfall, a smaller target and a wider fuze radar beam. Therefore, when the encounter distance between fuze and target is less than about 30m, the influence of the rain Doppler clutter on the target Doppler signal is severe, and need be considered for the MMW Doppler fuze application.

Two-Frequency Mutual Coherence Function of Millimeter Wave in Rain

In this paper, the general formulations of two-frequency mutual coherence function, Γ, for a pulse wave propagating in random discrete media are summarized. The relations of the amplitudes and phases of the Γ to ωd are given by Ishimaru et al, based on average particle in cloud and rain. In practice, since the particles sizes in random discrete media are in a size distribution spectrum, the Γ ought to be derived from a particles size distribution. Based on an approximately solution, we describe these examples of millimeter waves (94, 220GHz) pulse propagating in rain and show that the Γ s amplitudes and phases obvious varies as rainfall and frequency. For a kind of rain, considering raindrops size distribution and average raindrop size, respectively, the Γ s amplitudes and phases are calculated. The numerical results show that the differences between the results calculated by raindrops size spectrum and by average size are remarkable, especially for heavy rainfall. Therefore, It is shown that the Γ calculated by a particles size distribution is more reasonable than by average size. For the Γ numerical analyses, particles size distribution ought to be adopted. This study is important for us to provide adequate bandwidths to achieve high-rate pulse communications and improve MMW radar system performances and atmospheric remote-sensing techniques.

Distortion and Delay of Laser Pulse Propagation in Sand and Dust Storm

The pulse distortion and time delay of laser nanosecond pulse propagating through the atmosphere including sand and dust storm layer are investigated mainly at 0.69 and 3.8 mum, respectively. It is shown that the delay of 10ns laser pulse propagating through 5km sand and dust storm with No = 1.630 x 105 / m3 are about Ins and 10 ns, at 0.69 and 3.8 mum, respectively. The pulse spread of a 10 ns laser pulse is over 40 ns at 3.8 mum. The pulse delay and spread increase rapidly with the sand particle density increasing in atmosphere. The narrower the pulse width is, the more the pulse distortion is. Hence, for a laser pulse propagating in sand and dust atmosphere, the pulse delay and distortion are quite severe and need be taken into account for a narrower pulse laser system.

Study of the influence of rain backscattering enhancement on MMW radar performance

In this paper, the multiple scattering and backscattering enhancement theory is discussed. The multiple scattering and backscattering enhancement caused by rain is analyzed for 35 and 95GHz millimeter wave (MMW). The higher frequency, the more backscattering enhancement by rain is. The influence of the rain backscattering enhancement on MMW radar detection performance is studied. The results show that the signal to clutter ratio for MMW radar is evidently decreased and the clutter to noise ratio is increased considering the rain backscattering enhancement. The MMW radar detection performance can be degenerated severely due to the backscattering enhancement of rain.