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New generation of satellite system communication is moving toward frequencies above 20 GHz and non-geostationary satellites. In order to guaranty the quality of service, specific Fade Mitigation Techniques have to be applied, like Advanced Coding and Modulation (ACM). In order to accurately design ACM, time series of attenuation should be used. As there are no measurements available, the simulation of attenuation times series for non-geostationary earth-space links becomes critical. This paper presents a model consisting in a combination of a Numerical Weather Prediction model (Weather Research and Forecasting), a synthetic rain cell model MultiEXCELL and Optical Flow techniques. It gives an efficient method to generate more realistic rain attenuation time series. Long-term CCDF statistics of simulated attenuation data are validated by comparison with the Alphasat measurement data over 2 years at Louvain-la-Neuve ground station. [ABSTRACT FROM AUTHOR]

The radio frequency (RF) noise performance of graded-channel metal-oxide-semiconductor (MOS) transistors (GCMOS) has displayed impressive reduction in minimum noise figure (N [F.sub.min]) as compared to classical MOSFET transistors. The studies have shown that the use of gate-length GCMOS has given a competitive RF noise performance when compared to gate-length classical nMOS transistors.

This paper reviews and analyzes a fully integrated electrostatic discharge (ESD)-protected low-noise amplifier (LNA) for low-power and narrowband applications using a cascode inductive source degeneration topology, designed and fabricated in 130-nm CMOS silicon-on-insulator technology. The designed LNA shows 13-dB power gain at 2.4 GHz with a noise figure of 3.6 dB and input return loss of -13 dB for power consumption of 6.5 mW. An on-chip 'plug-and-play' ESD protection strategy based on diodes and a power clamp is used at the input and output of the LNA, and has an ESD protection level up to 0.8-, 0.9-, and 1.4-A transmission line pulse current. This corresponds to 1.2-, 1.4-, and 2-kV human body model stress applied at, respectively, the RF input, RF output, and [V.sub.DD] bus. Measurement shows a minor RF performance degradation by adding the protection diodes. Index Terms--CMOS, electrostatic discharges (ESDs), low-noise amplifier (LNA), narrowband, partially depleted (PD) silicon-oninsulator (SOI), RF, transmission line pulse (TLP).

The impact of mutual coupling induced by two closely spaced minimum scattering antennas at the subscriber unit on 2 x 2 multiple-input multiple-output channels and communications is investigated. Both (de)correlation effects and variations of antenna gain resulting from coupling mechanisms are considered. Relationships between coupling and correlations/channel Frobenius norm are discussed, pointing out the role of the interelement spacing, the array orientation, and the richness of scattering. The analysis also yields useful insight into the influence of mutual coupling on capacity and system performance. Index Terms--Antenna array, multiple-input multiple-output (MIMO) systems, mutual coupling.

Space-time code (STC) designs classically rely on the assumption of independent and identically distributed (i.i.d.) Rayleigh channels. However, poor scattering conditions may have detrimental effects on the performance of STCs. In this letter, we derive code-design criteria leading to robust STCs in a large variety of slow-fading propagation conditions. No channel knowledge is assumed at the transmitter. Codes satisfying these criteria are shown to perform much better on real-world channels than codes designed only for i.i.d, channels. As examples, the robustness of various spatial multiplexing schemes, linear dispersion codes, and space--time trellis codes is discussed based on those criteria. Index Terms--Correlated channels, multiple-input multipleoutput (MIMO), space-time coding, spatial multiplexing (SM).

The wireless channel for nomadic diversity-based wireless networks operating at 1.9 GHz is characterized. Using a 1 x 2 wideband measurement chain, four typical indoor office and industrial environments have been investigated: a corridor, an office room, a laboratory room and a large industrial hall. The measurement equipment is constituted by an 80-MHz transmitter. At the receiver, two omnidirectional antennas are connected to a wideband channel sounder through a switch, in order to measure an estimate of the instantaneous vector channel. Special attention is given to the experimental procedure itself, so as to take into account the specificity of nomadic systems (as opposed to usual mobile systems). The measurement analysis reveals that the shadowing, Rician K-factor and delay-spread are lognormally distributed. A path-loss model is derived, and cross-correlations between K-factor, delay-spread and shadowing are analyzed. The channel correlations at the user terminal or at the access point are also derived, and related to the individual channel characteristics. Index Terms--Diversity, indoor radio communications, radio propagation, Rician channels, wireless LAN.

A very compact planar fully integrated circulator operating at millimeter wavelength has been designed using a magnetic substrate combining a polymer membrane with an array of ferromagnetic nanowires. The original feature of this substrate, called magnetic nanowired substrate (MNWS), relies on the fact that the circulation effect is obtained without requiring any biasing dc magnetic field. This leads to a significant reduction of device dimensions since no magnetic field source is needed, and a realistic ability for integration with monolithic microwave integrated circuits. The circulator design is performed by an efficient analytical model including a self design of the impedance matching network. This model also allows a physical understanding of the circulation mechanism through the access to the electromagnetic field patterns inside the circulator substrate. Based on the excellent agreement between the theoretical and experimental results, the model is used to predict the improvement of circulator performances resulting from a reduction of dielectric and conductor losses. Insertion losses lower than 2 dB with an isolation higher than 45 dB are expected for MNWS circulators with a low-loss substrate and thick metallic layers. Index Terms--Circulator, ferromagnetic nanowires, integrated, microstrip, nonreciprocal.

Based on symbol-related array factor, a new interpretation of the impact of transmit correlation on the performance of spatial multiplexing (SM) is presented. With the focus on the data rate advantage of SM, several communication techniques proposed to exploit the potential of multiple-input multiple-output (MIMO) systems are discussed.

This paper presents a new efficient multiline model for monolithic inductors. A preliminary model was developed by Huynen, which divided the spiral in sections of coupled transmission lines whose parameters are calculated by a variational principle. This model has been improved for inductors with high trace width-to-gap ratios and it has been demonstrated to be adequate for predicting S-parameters characterizing the inductor over a wide frequency band, even above its self-resonant frequency. This new design tool is shown to be useful for analyzing and optimizing inductor topologies built on both insulating and semiconducting substrates. Index Terms--Inductor model, integrated circuit (IC) modeling, substrate loss.

To evaluate the performance of future microcellular IMT-2000 modems, simple physical models are required, so that a number of system characteristics, such as the signal bandwidth, the antenna beamwidth, or the base station height can be accounted for at a limited computational cost. This paper describes a deterministic three-dimensional electromagnetic model, which allows simulation of the radiowave propagation for microcellular wide-band communication systems in urban areas. The model is based on a UTD ray-tracing tool and makes use of an improved mirror method. Simulated power-delay profiles are plotted against measured power-delay profiles recorded at 1.87 GHz in a street of Louvain-la-Neuve, Belgium, by means of an 80-MHz channel sounder. Despite several discrepancies, a satisfying matching is found considering three orders of reflection and single diffraction. Predictions of rms delay-spread accounting for the sounder limited bandwidth are presented. Finally, simulated and measured channels are also compared through the resulting performance of a typical IMT-2000 service in the presence of multiple access interference. Index Terms--Communication system performances, ray tracing, wide-band radio channel measurements.

Summary: Due to the congestion of the spectrum and the need for wider bandwidths, ultrahigh throughput satellites (UHTSs) are moving towards the use of higher frequency bands (Q/V and W bands). These frequencies are however severely impaired by atmospheric phenomena causing attenuation, scintillation and depolarization and compromising the quality of service (QoS). In order to study the Earth‐space link, several experimental campaigns have been performed up to the Q band with geostationary (GEO) satellites. This paper introduces a new propagation experiment that will extend the characterization of the Earth‐space channel up to the W band and low Earth orbits (LEOs). [ABSTRACT FROM AUTHOR]

A scheme which combines probing and calibration structure design for the use of silicon-on-insulator metal oxide semiconductor field effect transistors (MOSFET) in microwave measurement is discussed. The scheme permits an accurate identification of non-quasi-static small-signal model parameters for MOSFET equipment. The intrinsic and extrinsic parameters are drawn from S-parameters measurements at a single bias point in saturation.

A new spectral domain formulation of the propagation characteristics for planar and coplanar lines is presented. It is based on a newly established variational principle, valid for a spatial as well as for a spectral formulation. In combination with conformal mapping, it drastically reduces the complexity of the numerical computation and leads to rapidly convergent results even when higher order modes are considered. Mathieu functions are shown to be very efficient expressions for trial fields of the dominant and the higher order modes in slots. Calculation is fast: it is made on-line on a regular PC. Results obtained on open and shielded lines have been successfully checked with new experimental data and with previously published data. The method is general enough to accommodate gyrotropic substrates. The paper however is limited to isotropic media.