Hildeberto Jardon-Aguilar

State of the art in ultra-wideband antennas

Ultra wide-band (UWB) technology is one of the most promising solutions for future communication systems due to its high-speed data rate and excellent immunity to multipath interference. In this context, the UWB antenna design plays a unique role because it behaves like a band pass filter and reshapes the spectra of the pulses, so it should be designed to avoid undesired distortions; some of the critical requirements in UWB antenna design are: ultra wide bandwidth, directional or omni-directional radiation patterns, constant gain and group delay over the entire band, high radiation efficiency and low profile. This work reviews the state of the art in UWB antennas, where planar monopole antennas show a special interest because they exhibit excellent performance in matching impedance bandwidth as well as pattern. Some experimental and simulation results on a proposed UWB antenna are also given.

Design and simulation of a 1 to 14 GHz broadband electromagnetic compatibility DRGH antenna

This work presents the design and simulation of a 1-14 GHz double ridged guide horn antenna (DRGH) with coaxial input feed section. This antenna, due to the large frequency bands required by standards, is suitable to be used in electromagnetic compatibility (EMC) testing. The horn-antenna model analyzed dates back to the early 1970s when J. L. Kerr suggested the use of a feed horn launcher whose dimensions where found experimentally. Although this type of horn has become the preferred test antenna of EMC testing for the 1-18 GHz range, which has been widely used for over four decades, no explanation of the effect of the launcher dimensions and the ridges shape into the flared section on the antenna parameters was found in the open literature. To investigate this phenomenon in detail, the entire horn has been modeled, including the coaxial feed using a time domain method. The simulations indicate that deficiencies in the radiation pattern start to appear at frequencies above 6 GHz and it starts to split at frequencies above 12 GHz. In spite those problems, the designed antenna can work well up to 14 GHz.

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 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.

Orthogonal Ultra-Wideband Planar Monopole Antenna for EMC Studies

A novel orthogonal ultra-wideband antenna with a more stable radiation pattern at high frequencies is presented. Here it is showed that using an orthogonal planar monopole antenna the stability of the radiation pattern at high frequencies of the operational bandwidth is enhanced without affecting the radiation patterns at lower frequencies. Using the obtained results an orthogonal UWB planar monopole antenna was designed with an operational bandwidth of 19.4 GHz. The measured antenna bandwidth goes from 530 MHz to 20 GHz for a VSWR les 2. The radiation pattern remains is enhanced with respect to a conventional planar monopole antenna with similar characteristics. The radiator used on the single and an orthogonal UWB planar monopole antenna is rectangular with a bevel and height-width ratio techniques that optimized the impedance bandwidth.

Directional UWB planar antenna for operation in the 5-20 GHz band

A novel directional ultra-wideband (UWB) planar antenna is presented in this paper. The obtained antenna bandwidth is in order of 10:1. The directional behaviour is taken by slating a planar monopole antenna with respect to the ground plane. The UWB and directional characteristics of this antenna are obtained by optimizing simultaneously four parameters: bevelling and slating angles, the size of the matching impedance hole and the ratio between the height and width of the radiating element. The construction simplicity of the antenna is one of its main features

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.

An UWB microstrip feeding quasi circular antenna

We present the analysis of a quasi circular planar antenna for UWB applications. Analysis includes comparison of coplanar and microstrip feeding. Evolution from the circular antenna requires modifications in the structure and ground plane to soften the edges obtaining improvements in the antenna parameters agreeing with the theory proposed by John Kraus. Evolution is performed for a circular antenna with a design frequency of 4.5 GHz with a bandwidth of approximately 20 GHz. The antenna feeding impedance is proposed as 50 ohms, built over a substrate of RF35-A 0.762 mm × 35 mm × 50 mm. The improvements obtained are reflected in the number of resonances of the antenna throughout the operating bandwidth.