Ruben Flores-Leal

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.

Inductively-Loaded Yagi-Uda Antenna With Cylindrical Cover for Size Reduction at VHF-UHF Bands

A new technique is employed to reduce the size of Yagi-Uda antennas. The technique consists of adding short circuited cylindrical covers to the structure, making the elements be inductively loaded, and as a result, increase the electric length. A prototype resonating at 660 MHz is developed, and compared to a conventional Yagi-Uda antenna. An effective area reduction of 35% is achieved without decreasing, considerably, the gain, preserving the bandwidth, and front to back lobe ratio.

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.

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.

Multiband–multislot planar antenna based on small loop-radiator

In this article, a novel multiband–multislot planar antenna is presented. The proposed antenna is based on the small loop- and slot radiators, showing multiple resonances. The antenna is built on a substrate with a permittivity of 2.2 and a thickness of 1.27 mm. The antenna resonates at 0.84, 1.55, 2.5 and 4.8 GHz behaving with quasi-omnidirectional radiation patterns, which can be employed in the state of the art automotive technology, laptops and tablets among other terminal devices. The resonances can be shifted to lower or higher frequencies depending on the slots’ length and width, as well as the magnetic coupling among them. Moreover, additional resonances can be introduced by etching new slots on the substrate metallization.

IFA and PIFA Size Reduction by Using a Stub Loading

A proposed technique for size reduction of a conventional inverted-F antenna (IFA) and a planar inverted-F antenna (PIFA) by employing a reactive load generated by a short-circuited stub is presented. The reduction factor of both antennas is around 30%, and the main parameters of the devices are preserved, including a fractional bandwidth of 4% and a gain of −2 dB. Both antennas operate around 1.5 GHz.

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 complementary split ring resonators for size reduction in patch antenna arrays

Abstract In this paper, a novel technique for reducing the dimensions of patch antennas and their arrays is presented. The procedure uses complementary split ring resonators (CSRRs) for increasing the slow-wave effect on the radiator, and therefore augmenting its electrical length, which implicates the modified antenna gets a lower physical dimension than a conventional one for a given frequency. Led by the use of CSRRs, the patches may be closer to each other, without affecting the side lobes magnitude either the directivity of the array compared to a conventional one. As an example, a 4 × 1 patch array was designed and its total area was 40% smaller compared to a conventional one, considering the same design conditions with and without CSRRs. The gain, directivity, and coupling of the prototype were not affected.

On the importance of the vertical radiation pattern on simulations of WSNs

Applications of wireless sensor networks have nowadays expanded their technical requirements. One of them is the form how nodes are distributed, from random positions to a predetermined location of nodes. In this concern, those applications that require a specific planning of position of nodes usually consider simple characteristics of the antenna radiation pattern (an isotropic pattern, for instance). Depending on the particular application, nodes can be located not only at different distances from each other, but also at different heights, which could introduce less gain due to the vertical pattern of the antenna. Thus, this paper addresses the importance of considering the vertical radiation pattern of antennas on simulations of wireless sensor networks, when nodes have a fixed position. By taking a commercial antenna and its measured radiation pattern, an evaluation of the achieved gain and its impact on a link budget is presented.

Ultra-wideband PIFA with a convex-shaped feeding line

In this work, an ultra-wideband planar inverted-F antenna is presented, fed by a convex-shaped structure. The antenna shows a measured ultra-wide bandwidth starting at 2.7 GHz and ending at 13 GHz, for a VSWR less than 2. The antenna shows an omnidirectional pattern at the X–Y plane with a very low out-of-roundness all over the bandwidth. The group delay of the antenna is very stable, obtaining a variation less than 1 ns. As a result, very low dispersion over the entire bandwidth is presented, as well as low cross-polarization level.