A number of efficient and diverse mathematical methods have been used to model electromagnetic wave propagation. Each of these methods possesses a set of key elements which eases its understanding. However, the modelling of the propagation in concrete becomes impossible without modelling its electrical properties. In addition to experimental measurements; material theoretical and empirical models can be useful to investigate the behaviour of concrete's electrical properties with respect to frequency, moisture content (MC) or other factors. These models can be used in different fields of civil engineering such as (1) electromagnetic compatibility which predicts the shielding effectiveness (SE) of a concrete structure against external electromagnetic waves and (2) in non-destructive testing to predict the radar wave reflected on a concrete slab. This paper presents a comparison between the Jonscher model and the Debye models which is suitable to represent the dielectric properties of concrete, although dielectric and conduction losses are taken into consideration in these models. The Jonscher model gives values of permittivity, SE and radar wave reflected in a very good agreement with those given by experimental measurements and this for different MCs. Compared with other models, the Jonscher model is very effective and is the most appropriate to represent the electric properties of concrete.

The study of electromagnetic waves propagating in concrete is a complex problem. Understanding the phenomenon of interaction between the wave and the matter is related to the knowledge of the variation process of concrete's electromagnetic properties in terms of its physical characteristics. In particular, dielectric permittivity of concrete is affected by moisture content and change in the frequency of the electromagnetic field applied. In this study, we apply the three-parameter Jonscher model (n, χ r , ε ∞) to show the dispersive aspect of the concrete. The validation of this model is carried out through tests on mortar and concrete at the laboratory, on the one hand, and by comparison of the results with data obtained previously by other researchers, on the other hand. The Jonscher model matches very well the experimental measurements of the concrete. At different moisture levels, heterogeneities and porosities, the results obtained are very good. This shows that this model is very effective and very suitable to represent the dielectric properties of concrete.

A CMOS transceiver fully compliant with IEEE 802.11a in the unlicensed national information infrastructure (UNII) band (5.15-5.35 GHz) achieves a receiver sensitivity of 5 dBm for 64-QAM (quadrature amplitude modulation) with an error vector magnitude (EVM) of 29.3 dB. A single-sideband mixing technique for local-oscillator signal generation avoids frequency pulling. Realized in 0.18m CMOS and operating from 1.8-V power supply, the design consumes 171 mW in receive mode and 135 mW in transmit mode while occupying less than 13 mm 2 .

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Fractional-N frequency synthesis has been introduced to alleviate integer-N Phase Locked Loop (FLL) frequency resolution problems as the requirement for fast switching time and low phase noise become increasingly stringent. Since its introduction, many Fractional-N PLL architectures have been implemented [ 1] [2]. However, these architectures, although they solve the frequency resolution issue, they also generate other unwanted problems. It is the aim of this paper to outline those problems as well as provide a new fractional-N architecture that significantly alleviates the problems. The new architecture has been implemented in sub-micron RFCMOS technology. Measured phase noise results satisfy several cellular system requirements.