Nuno Pires

Ultra Wideband ring monopole miniaturization using dielectric loading sandwich

A simple miniaturization technique using dielectric loading was applied to the design of Ultra Wideband (UWB) microstrip fed ring monopoles. The method consists of gluing a commercially available substrate layer to each metallization side. Two antenna prototypes were built and tested to validate the concept. The larger prototype covers the whole UWB bandwidth with |S11| ≪ −10dB. The smaller has considerable reduced size, making it suitable for use in a Universal Serial Bus (USB) dongle. The larger structure was further investigated by testing the influence of a close metallic box on antenna matching.

Radiation efficiency of a coplanar-fed ultra-wideband antenna

This paper presents a study on the radiation efficiency of Ultra-Wideband (UWB) antennas. Measurement were made using a cavity-based method with source stirring. A novel post-processing filtering technique of the measured data is introduced. The approach was tested on a coplanar-line-fed UWB monopole. The efficiency of this antenna was also computed with two commercial electromagnetic packages. Simulations and measurement agree to predict a radiation efficiency of over 95% through the 3.1-10.6 GHz operating bandwidth.

Design of an Ultra Wideband Universal Serial Bus device mounted antenna

The present paper reports on the simulation, construction and measurement of a planar Ultra Wideband (UWB) monopole antenna designed to operate inside a Universal Serial Bus (USB) dongle, aiming at usage in industrial applications. Inexpensive FR4 substrate with εr = 4.4 and 0.8 mm thickness was used and the antenna shape and dimensions fit in a common case. The built antenna prototype was tested inside a USB device case in free space and in a realistic antenna deployment scenario, with the dongle connected to a laptop computer. It was found that the designed antenna exhibits acceptable |S11| matching in the frequency range [2.5; 12] GHz, allowing its usage in UWB and other wireless services such as Bluetooth, LTE and IEEE 802.11.

Novel Approach to the Measurement of Ultrawideband Antenna Efficiency

This letter presents a new cavity-based approach for measuring the radiation efficiency of ultrawideband (UWB) antennas. The procedure is based on a generalized Wheeler cap method that is only practical for narrowband measurements, and so this letter introduces an extension to UWB using source-stirring. The number of required measurements needed is relatively low and independent of the frequency span, therefore making the technique convenient for UWB. A complete post-processing procedure to automatically identify and remove erroneous radiation efficiency predictions is presented. The new method was tested with a coplanar-fed UWB monopole and compared to existing UWB efficiency cavity-based measurement methods. The results show good agreement with simulations and compare favorably to other UWB-centric methods, confirming the proposed approach as a good alternative to measure UWB antenna radiation efficiency.

Influence of dielectric loading on the fidelity factor of an Ultra Wideband monopole antenna

This paper reports a study of the influence on the fidelity factor due to loading an Ultra Wideband monopole with a pair of dielectric substrate pads. The fidelity factor was calculated, with and without loading, using the simulated transmitted and received pulses in three points in the azimuth plane. Results show that this dielectric loading technique does not cause significant pulse distortion. The fidelity factor is affected only by an average of 2.8% relative to the unloaded antennas in all situations considered. Two versions of the same antenna design were studied: coplanar- and microstrip-fed. It was found that the influence of feeding on the fidelity factor is also minimal.

Design and Measurement of a Differential Printed Antenna for a Wireless Sensor Network Node

This letter presents the design and measurement of an antenna integrated into an agricultural sensor network node operating on the 2.4-GHz ISM band using the ZigBee protocol stack. The novel structure, coined bowtie-shaped folded dipole (BSFD), has a differential 100-

Novel approach to the measurement of ultra wideband antenna efficiency

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Performance Study of a UWB Antenna in Proximity to a Human Arm

input impedance matching a particular controller widely used in wireless sensor network (WSN) applications. This letter also presents a survey of existing WSN antennas to which the proposed design compares favorably. The challenges of testing a differential antenna using conventional single-ended equipment are addressed regarding antenna impedance and radiation pattern measurements. The differential antenna input impedance was confirmed with four different test setups using a conventional vector network analyzer. The radiation pattern of the proposed antenna was measured in-prototype resorting to a spectrum analyzer. The measured patterns show that the proposed antenna has a maximum received power over 4 dB compared to two early versions of the WSN node that used commercial off-the-shelf antenna solutions. The performance was also confirmed in a field test where a BSFD-equipped prototype achieved close to a 300-m range, tripling that typical for ZigBee applications.

Influence of the human body on a new coplanar-fed Ultra-Wideband antenna

This letter presents a new cavity-based approach for measuring the radiation efficiency of ultrawideband (UWB) antennas. The procedure is based on a generalized Wheeler cap method that is only practical for narrowband measurements, and so this letter introduces an extension to UWB using source-stirring. The number of required measurements needed is relatively low and independent of the frequency span, therefore making the technique convenient for UWB. A complete post-processing procedure to automatically identify and remove erroneous radiation efficiency predictions is presented. The new method was tested with a coplanar-fed UWB monopole and compared to existing UWB efficiency cavity-based measurement methods. The results show good agreement with simulations and compare favorably to other UWB-centric methods, confirming the proposed approach as a good alternative to measure UWB antenna radiation efficiency.