Jose Alfredo Tirado-Mendez

IMPROVING FREQUENCY RESPONSE OF MICROSTRIP FILTERS USING DEFECTED GROUND AND DEFECTED MICROSTRIP STRUCTURES

In this work, the introduction of Defected Microstrip Structures and Defected Ground Structures is presented to improve the performance of a traditional stepped-impedance microstrip lowpass fllter. The attenuation in the stop-band is enhanced by more than 15dB and selectivity is increased, without modifying the insertion loss in the pass band. A comparison of characteristics in fllters is made when the combination of Defected Ground and Defected Microstrip Structures, as well as when only the flrst one are used. A model of the Defected Microstrip Structure and the corresponding equations to obtain the equivalent lumped and distributed element values are also given.

Ultra-Wideband Planar Inverted-F Antenna (PIFA) for Mobile Phone Frequencies and Ultra-Wideband Applications

A new planar inverted-F antenna with a very large bandwidth starting from 817MHz to 11.5GHz (VSWR < 3) is proposed as an alternative for high performance mobile phones intended to cover the major part of the mobile phone frequencies worldwide as well as the ultra-wideband (UWB) frequency range. A prototype of the antenna was constructed and the re∞ection coe-cient and radiation patterns were measured to demonstrate an adequate radiation performance. The antenna dimensions of 4 £ 2:5 £ 0:5cm 3 are compatible with the requirements imposed by the most recent commercially available smartphones. Besides, the easy construction without a matching network or a complicated geometry is an additional feature that can be re∞ected in low fabrication cost.

Ultra-Wideband Slotted Disc Antenna Compatible with Cognitive Radio Applications

In this paper, a new ultra-wideband (UWB) disc antenna compatible with cognitive radio is presented. The proposed antenna is developed to operate from 0.77 to 11.23GHz. It consists of a circular disc radiator with a rectangular slot on the patch and the implementation of the bevel technique on the ground plane. A prototype of the antenna has been constructed and shows adequate impedance matching, radiation pattern and gain for cognitive radio applications.

Comparison of defected ground structure (DGS) and defected microstrip structure (DGS) behavior at high frequencies

A novel Defected Microstrip Structure is proposed, which behaves in a similar way than a conventional unit cell Defected Ground Structure (DGS) concerning band-stop response and selectivity. As a difference from the DGS, the DMS structure frequency response is almost the same when the microstrip length varies. To show this fact, a λ2 and a λ4 50 Ohms microstrips were used for different DGS and DMS cell sizes.

Omnidirectional UWB antenna for monitoring applications at UHF and microwave bands

A highly omnidirectional UWB antenna is presented. The device is suitable for monitoring purposes. The measured bandwidth goes from 0.27 GHz to 17.7 GHz, with S11 of ≤ -10 dB. The H-Field radiation pattern has an out-of-roundness less than ±3 dB in the entire band. The antenna has a structure of a π/4 bi-orthogonal rectangular monopole with bevel angle.

Novel Dual Band Resonant Cylindrical Hat-Covered Monopole for Personal Communications

A cylindrical hat-loaded method is employed to make monopoles behave as dual band resonators. The two frequency bands are obtained by perturbing higher propagation modes by modifying the hat length. The longer the cylindrical hat is, the lower the resonant frequencies are obtained. The hat length behaves as an inductive load, also increasing the electric length of the monopole. As a result, a compact resonant structure is got, working at two different frequencies without modifying the omnidirectional radiation pattern at both bands.

Application of defected microstrip structure in tuning a square patch antenna

The present work establishes the use of the effect of a defected microstrip structure (DMS), to tune the resonant frequency of a square patch antenna, providing a novel method to match the element to the desired operating frequency, showing good results concerning VSWR, without degrading the radiation pattern and the gain.

Non-linear performance in power amplifiers and LNA at 900 MHz and 1900 MHz by using low-level voltage supply

This paper is related to different high-linear low noise amplifiers (LNA) and high-efficiency power amplifiers (PA) performance at 1900 MHz and 900 MHz, respectively, concerning electromagnetic compatibility for being used in personal communication systems. A class A and E PAs and a common-emitter degenerated by inductance (CEDI) and an active feedback common-emitter (AFCE) LNAs were designed, simulated and compared in relation to their intermodulation product performance. The nonlinear and efficiency characteristics of a low-voltage supplied high-efficient class E PA for ISM band systems are reported. Concerning low-level voltage supplied LNAs, a very low nonlinear behavior was obtained, considering the 1 dB compression point, the intermodulation products and the third-order interception point in a wide frequency range. Such structures were polarized with 2.4 V and by using SiGe HBT as active elements