Meandered-slot antennas for sensor-RFID tags

This letter introduces a planar antenna layout suited to Sensor-RFID fabrication. The geometry is based on a meandered-slot profile on a suspended patch and permits to host sensors and electronics in a small space. The available geometrical parameters are optimized by means of a Genetic Algorithm (GA) procedure aimed to maximize the antenna realized gain. The antenna performances are discussed through examples and prototypes

Design of a broadband HF antenna for multimode naval communications

This paper describes a multifunction HF-loaded antenna for broadband naval communications based on both groundwave and near vertical incidence skywaves. The antenna, denoted as bifolded monopole, is designed according to a new loading strategy which avoids the use of complicated external networks. Numerical simulations and measurements on a scaled prototype have shown that interesting capabilities are obtained by using just four or five loading circuits

Time domain synthesis of pulsed arrays

Pulsed arrays are becoming popular in new ultrawideband applications to enhance the robustness of transmitted and received signals in complex environments and to identify the angle of arrival of multiple echoes. A global synthesis technique is here proposed to shape the array field in accordance to given angle-time constraints. The synthesis problem is cast as the inverse Radon transform of a desired array mask, applying the alternate projections method to include constraints over the input signals' waveform and to improve the synthesis robustness. The unknown array currents are generated as linear combinations of Hermite-Rodriguez functions in order to achieve a simple and realizable beamforming network. The effectiveness of the method is demonstrated by many examples

Miniaturised wearable UHF-RFID tag with tuning capability

By carving a 'square-smile'slot profile over a folded patch, a miniaturised UHF-RFID tag is obtained, having a convenient two-step tuning mechanism (coarse and fine). This is useful to adapt the same tag to European and US frequencies and to make on-site corrections. The antenna is half the size of a credit card and can be read up to 5m when attached onto the body. The flexible and lightweight EPDM foam substrate makes the tag suited to be integrated in badges, wallets, pockets, plasters, wristbands and various garments

Multiport sensor RFIDs for wireless passive sensing of objects - Basic theory and early results

A new family of passive sensor radio-frequency identification devices is here proposed for applications in the context of wireless sensor networks. The new tags, working in the ultra-high frequency band, are able to detect the value or the change of some features of the tagged body without using any specific sensor. Such tags are provided with multiple chips embedded either within a cluster of cooperating antennas or in a single multiport antenna, and exploit the natural mismatch of the antenna input impedance caused by the change of the tagged object. A basic theory of multiport sensor tags is formulated with the purpose to describe the possible classification and detection performances in a unitary context. Some numerical examples and a first experiment corroborate the feasibility of the idea