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A new method is presented to estimate the loss resistance of antennas located slightly above a lossy medium. This technique is more specifically developed for the context of body area networks. This method is based on the estimation of the antenna resistance above the medium and above a perfect electric conductor.

International audience; A circular patch antenna fed by a coplanar waveguide (CPW) line is proposed to obtain circular polarisation (CP). The CP results from the combined excitation of the patch by an inclined slot (integrated in the CPW feedline) and the CPW feedline termination. The asymmetrical characteristics of the excitation involve the excitation of both the odd and the even modes in the CPW line.

The authors propose an efficient amelioration of the concept of large bandwidth aperture-coupled microstrip antennas by coupling a CPW line-fed slot to a microstrip antenna. The CPW fed aperture-coupled microstrip antenna investigated has a large bandwidth with high gain and low crosspolarisation levels, is compact with only one substrate, and may be easily connected to both passive and active components. A numerical model has been developed and the theoretical results are in good agreement with the experiments.

A metallic electromagnetic bandgap material (EBG) is realised by combining 4/spl times/4 unit cells in a square geometry and excited by a microstrip line through a slot-aperture. It is shown that this structure is a radiating one, called an EBG patch, resonating at a lower frequency than the plain patch showing the same dimensions. An analytical model for the wavenumber of the EBG material facilitates the design of the EBG patch.

A CPW-fed slot antenna including pin diodes for multifrequency operation within a frequency octave and more is presented. The use of GaAs beam-lead pin diodes limits the influence of the parasitic resistance and reactance presented by surface mount diodes. The simplicity of the structure results in a simplified and compact biasing circuit.

International audience; pin diode control is used to obtain a dual-band operation of a capacitively coupled patch antenna fed by a coplanar waveguide (CPW). The beam-lead pin diodes are inserted in the excitation slot and reduce the coupling length of the slot in their ON state. The frequency ratio of the two operating frequencies is 1.22 at 4.0 GHz. Details of the antenna design and experimental results are presented and discussed.

International audience; The influence of capacitors periodically soldered along the radiating edges of a leaky wave antenna (LWA) is described. As the propagation characteristics are modified, the main beam is tilted from the angle observed for the unloaded LWA. This property allows beam steering applications at a fixed frequency if bias-controlled reactances are used.

Injection locked oscillator arrays based on CPW-fed antennas have been realised which operate at 4 GHz. Their main characteristics are the simplicity and compactness of the design. One side of the substrate is devoted to oscillator circuitry while the other side includes the radiating elements and the injection circuit. Results concerning the beam scanning control and power performance are presented.

The authors present a small series-fed array of microstrip leaky wave antennas (LWAs) operating at 6.85 GHz and showing a narrow dual-beam pattern (17/spl deg//spl times/22/spl deg/). The excitation is provided by a slotted coplanar waveguide. This type of antenna could be used as a radar sensor in Janus systems for contactless measurements of velocity and distance.

International audience; The authors describe twin Vivaldi antennas directly fed by a coplanar waveguide. They have been designed and measured for various angles between the radiating slots. All the designs show a centred zero in the E plane with a low cross-polarisation. In the H plane they provide zeros for /spl phi/=90/spl deg/ and 270/spl deg/ and are omnidirectional for other values.

International audience; A circularly polarised patch antenna, fed by a coplanar waveguide, is investigated experimentally. The antenna is excited by a couple of 100 Ω slotlines which are combined to obtain a 50 Ω coplanar waveguide. The axial ratio and the bandwidth of the antenna are similar to those obtained with other types of feeding.

The paper presents the first rigorous modelling of a coplanar-fed aperture-coupled microstrip antenna (CPWFA). The model is used in an extensive comparison with microstrip line-fed aperture-coupled microstrip antennas (MLFA). Very similar properties are observed and a simple rule for the design of CPWFA from knowledge of the corresponding MLFA is given.