Juan I. Sancho

Design of UWB folded-plate monopole antennas based on TLM

From the current distribution on planar monopoles, transmission line modeling is applied to study this kind of antennas. Some reported techniques for broadband monopoles are approached by using this model from a qualitatively point of view. Conclusions are derived that help to match the monopoles over an ultrawide bandwidth regardless of whether they are folded or not. Folded configurations are obtained in order to provide solutions to specific designs and improve radiation pattern maintaining the planar monopole broadband behavior. Three compact folded prototypes with greater than 1:38 bandwidth are implemented and tested. Pulse distortion is also discussed for this type of applications.

UWB Staircase-Profile Printed Monopole Design

In printed monopoles, the current distribution along the lower monopole sheet and upper groundplane edges can be made analogous to a transmission line distribution by an appropriate antenna feed design. Accordingly, the VSWR < 2 impedance bandwidth upper frequency limit can be estimated for staircase-profile printed 2D ultrawideband (UWB) monopoles. Following this guideline, three tailored-bandwidth prototypes are designed, implemented and measured. They retain their length and width while multiplying their upper frequency (4.87, 8.7, and 15.15 GHz) by the number of monopole profile steps (1, 2, and 3). The deviation is found mainly below 13% in relation to the reference formula. The concept of angular range based on pattern stability factor (PSF) is introduced to compare the solid angle of UWB pattern stability operation when increasing the bandwidth. The angular range degradation versus impedance bandwidth improvement shows all the possible performance levels of the antennas. Thus, the design of UWB printed monopoles is approached from both points of view, i.e., impedance bandwidth and pattern stability.

Synthesis of TLM-Based UWB Planar Monopole Impedance Bandwidth

A simple formula based on transmission line modeling (TLM) is proposed to determine the impedance bandwidth upper frequency limit for a staircase-profile planar monopole antenna. After a brief description of TLM analogy for planar monopoles, the formula is derived from a theoretical exposition. Accordingly, four prototypes are designed, implemented and measured in such a way that they are required to cover direct sequence ultrawideband (DS-UWB) first band (up to 4.85 GHz), UWB (up to 10.6 GHz) and possible future broadband systems (e.g., up to 15 and 21.4 GHz). The formula predicts this limit with a maximum error of 7.4% in the prototypes studied. The height of the antennas is chosen so that they help to filter WLAN 5 GHz band on the H-plane. This condition determines the lower impedance bandwidth limit (1.3 GHz for all of them). The resulting improvement on antenna system transfer functions (ASTF) is also discussed.

Reconfigurable Matching Network for 2.45 GHz printed IFA on metallic environments

A Reconfigurable Matching Network based on microstrip technology and PIN Diodes has been designed and measured to retune a 2.45 GHz IFA antenna on a metallic environment. The aim is to guarantee a matching bandwidth of 100 MHz (2.4-2.5 GHz) for separation distances from 15 to 25 mm between the antenna and a metal plate. As a consequence, the use of this Reconfigurable Matching Network allows the antenna to be placed 40% closer to the metal plate.

FPGA-Based Cognitive Radio Platform with Reconfigurable Front-End and Antenna

This chapter presents an FPGA-based SDR platform which serves as a proof-of-concept for cognitive radio techniques. The platform is based on a fully reconfigurable hardware and operates as a 12.8 Mbps RF-to-Ethernet bridge in the Industrial, Scientific, and Medical (ISM) bands of 868 MHz and 2.45 GHz. The data-processing algorithms of the platform are implemented in an FPGA using Xilinx’s System Generator rapid prototyping tool. A MicroBlaze processor is also included to control the dynamic partial reconfiguration of the FPGA for small in-band frequency changes. In order to achieve full-band reconfiguration, a commercial RF front-end and a custom reconfigurable antenna are integrated. Design and implementation details are presented, along with measurement results.