Experimental results on bistatic rain scattering at 14.3 GHz

A bistatic rain scatter experiment at 14.3 GHz was conducted on two scattering paths. The experiment was made for more than two years on the Kashima-Inubo path and for more than one year on the Kashima-Hiraiso path. Statistical analyses of the data were made to obtain, e.g., cumulative distributions of the received power, worst month statistics of the received power, and cumulative duration time distributions of the received power. It is found that the effect of rain attenuation reduces statistical variations of the received power. A brief discussion on the prediction of the received power is presented. Also presented are the experimental results showing that the effect of antenna polarization on the received power is well described by the Mie theory.     

Forward scattering due to rain at 11 GHz

Forward scattering from rain was measured at 11 GHz over a 9-km line-of-sight path. For rain rates of 100-150 mm/h, the scattered signal was observed to be about 40 dB below the direct signal. Good overall agreement was obtained between theory and experiment.     

Earth cover back scattering characteristics at the frequencies 94 GHz and 136 GHz

There are presented experimental investigations of interrelationships of wide-spread terrain-surface types with their biogeophysical parameters over the short millimeter wave range. Found angular, polarization and frequency dependencies, as well as the considered regularities may be useful when choosing apparatus parameters of remote-sensing systems, and also when working out and evaluating algorithms of their operation.     

Millimeter wave scattering and propagation in rain: a computationalstudy at 94 and 140 GHz for oblate spheroidal and spherical raindrops

Electromagnetic scattering from raindrops at 94- and 140-GHz frequencies is investigated. The differences in the scattering properties of spherical and oblate spheroidal model raindrops are illustrated for side and vertical incidence cases. Various backscattering and propagation parameters are evaluated using the Marshall-Palmer, Joss thunderstorm, and Joss drizzle drop size distributions. The Doppler spectrum at vertical incidence is substantially affected by the model raindrop shape. The radar reflectivity and the specific attenuation are not significantly affected     

94 GHz low-noise HEMT

A high-performance 0.1 mu m gate-length, AlGaAs/GaInAs/GaAs pseudomorphic high electron mobility transistor has been successfully developed. The device exhibits a minimum noise figure as low as 3.0 dB with an associated gain of 5.1 dB at 94 GHz. This is the first low-noise operation of transistors at 94 GHz.<>     

94 GHz phase-shift-keying modulator

This paper describes a kind of low insertion loss phase-shift-keying modulators used in 94GHz digital communications systems. A BPSK modulator with a insertion loss lower than 3.8dB has been achieved by connecting a circulator and a fin-line PIN diode phase shifter in series. The bandwidth is 2.5GHz given a phase error of ±5⁰. The circuits and experimental results are also given out.     

非球形冰晶在94/220 GHz毫米波的散射特性模拟计算

针对94/220 GHz双频雷达的数据处理,分析了不同形状冰晶对这两个波段的单散射特性及衰减特性,探讨了单形状冰云及具体冰云模型的回波特性,结果表明:1)当冰晶较大时,冰晶的后向散射及衰减对冰晶形状较敏感,相同最大尺度下,六角形冰晶后向散射及衰减最大、子弹花次之、雪花最小;2)单形状冰晶云的雷达反射率因子对冰晶形状、冰水含量、滴谱的中值尺度较敏感,同样滴谱条件下,220 GHz的衰减系数约是94 GHz的5~25倍;3)具体冰云模型的雷达反射率因子随粒子浓度、冰水含量、中值尺度增加而增加,对粒子谱的形状参数敏感性较低.     

Some experimental results on bistatic scatter from rain

A bistatic scatter experiment was conducted on a 55.2-km scatter path in Japan, at a frequency of 6.72 GHz, continuously from August 1975 to September 1977. In this bistatic scatter experiment the forward scatter experiment and a direct path measurement were made simultaneously, and a scanning-beam experiment was performed during two rainfalls. Investigations were made on the relationship between the equivalent radar reflectivity factorZ_{e}for a 2.3-km common volume height above sea level and the surface rain rateR(mm/h) directly under the common volume, and the distribution ofZ_{e}. TheZ_{e}-Rrelationship was found to beZ_{e} = 151.4 R^{1.45}on an average for total data including all rain types. The distribution ofZ_{e}can be approximated by the lognormal distribution for a rainy period. The directivity of scattering from an ensemble of raindrops was measured by scanning the beam from a horn antenna in the vertical plane. For practical purposes the directivity was found to be similar to that of an electric dipole.     

94 GHz integrated horn monopulse antennas

A monolithic azimuthal monopulse antenna for 94-GHz applications has been developed. The structure consists of a single dipole suspended in one plane of an integrated horn cavity to obtain the sum pattern, and an antiparallel pair of dipoles suspended in a different plane of the same horn cavity to achieve the difference pattern. Pattern measurements of microwave models and on the millimeter-wave antennas show good agreement with theory and exhibit symmetry with a sharp -30-dB null at broadside for the difference antenna. Microwave model measurements show input impedances close to 50 Ω, with greater than -25-dB isolation between sum and difference antennas across a 10% bandwidth     

94 GHz microstrip monolithic GaAs mixer

A microstrip monolithic GaAs mixer has been designed and fabricated for operation in the millimetre-wave band. A 6.5 dB minimum conversion loss has be achieved in narrowband operation (fLO = 93.7GHz and fIF= 130MHz); this figure includes the effect of losses and mismatch in the circuit and test fixture.     

94 GHz dielectric slab-line leaky-wave antenna

A leaky-wave planar antenna for millimetre-wave frequencies is described using a dielectric slab line, fed by a slotted waveguide array. The radiation of the planar antenna is induced by line discontinuities such as metallic discs on the guide surface.     

Millimeter-wave bistatic scattering from ground and vegetationtargets

A 35-GHz bistatic radar system was used to measure the attenuation through trees and the bistatic scattering pattern of tree foilage. The data were found to be in good agreement with a first-order multiple scattering model. Measurements were also made to study the angular vibration of the bistatic scattering coefficient of a smooth sand surface, a rough sand surface, and a gravel surface. The measurements, which were made for HH, HV (horizontal transmit, verticle receive), and VV polarization configurations over a wide range of the azimuth angle and the scattering angle, provide a quantitative reference for the design and use of millimeter-wave bistatic radar systems     

94 GHz transistor amplification using an HEMT

Transistor amplification at 94 GHz has been demonstrated for the first time. A single-stage amplifier employing a high-electron-mobility transistor (HEMT) exhibits a small-signal gain of 3.6 dB and an output power of 3.4 mW with 2 dB gain.     

94 GHz InP MMIC five-section distributed amplifier

A single-stage 94 GHz InP MMIC amplifier with 6.4 dB gain at 94 GHz has been developed, which is the highest-frequency MMIC amplifier reported to date. Lattice-matched GaInAs/AlInAs HEMTs with 0.1 mu m mushroom gates were the active devices. The CPW MMIC chip dimensions are 500 mu m*670 mu m.<>     

Optimum polarizations in the bistatic scattering from layeredrandom media

Investigates the polarimetric bistatic scattering characteristics of layered random media. On applying the Born approximation, the authors have calculated the bistatic Mueller matrix of a half-space random medium. The power received by a receiving antenna is the quantity chosen to optimize. The variables of the problem are the polarizations of the transmitting and receiving antennas. For the case when the polarizations of the transmitting and receiving antennas are identical, the authors have calculated the optimum polarizations and they have found that the optimum polarizations include both linear and elliptical polarizations. The conditions for maximum and minimum received power are also obtained. In the backscattering case, they have considered the situation when the transmitting and receiving antennas have independent polarizations. For a two-layer problem, they have observed the influence of the thickness of the layer in the classification of the optimum polarizations     

A 94 GHz planar monopulse tracking receiver

This paper describes the design, fabrication and measurements of a 94 GHz integrated monopulse receiver with IF beam control. The receiver is integrated on a single chip, and is based on a 23 GHz local oscillator driving four separate phase-coherent 94 GHz subharmonic mixers. The resulting IF signals are takeoff-chip to a IF monopulse processor, which produces sum and difference monopulse patterns for the elevation and azimuth coordinates. Voltage-controlled phase-shifters in each of the IF channels allow the monopulse patterns to be electronically steered. All of the receiver circuits are realized using uniplanar coplanar-waveguide (CPW), slot lines and coplanar striplines (CPS). These features result in a compact, low-cost system suitable for tracking systems operating in poor visibility conditions, as well as in collision avoidance receivers for automotive applications. To our knowledge, this work represents the first demonstration of a fully integrated millimeter-wave subsystem to date     

Reflectivity of some materials at 94 GHz

In order to better understand the characteristics of discrete natural land clutter at millimeter wavelengths, an experimental investigation of the relative reflectivity of various materials at 94 GHz was performed using a substitution technique. The data show that nonconducting materials have a relative reflectivity on the order of 2–3%, and that absorbed water can increase the relative reflectivity significantly.     

Analytical calculation of bistatic radar cross-sections for rain scatter problems

A formula is derived for the effective bistatic radar cross-section of a rain cell with Gaussian reflectivity profile assuming antennas with Gaussian radiation patterns. The size and location of the rain cell are arbitrary, as is the bistatic scattering geometry. The expression is analytical, avoiding the need for numerical integration, and general, allowing treatment of cases with only partial beam intersection. Using a recently proposed model, sidelobe contributions and multiple cells embedded within widespread rain debris can be incorporated.     

60 GHz and 94 GHz antenna-coupled LiNbO3 electroopticmodulators

Antenna-coupled LiBbO₃ electrooptic modulators can overcome the material dispersion which would otherwise prevent sensitive high-frequency operation. The authors previously demonstrated the concept with a phase modulator at X-band. They have extended this demonstration to a narrowband 60-GHz phase modulator and broadband amplitude modulator designs at 60 and 94 GHz, respectively