Total Antenna Efficiency Research Articles

Multiband Printed Meandered Loop Antennas With MIMO Implementations for Wireless Routers

Low-profile meandered loop antennas with multiple-input-multiple-output (MIMO) implementations that cover multiple communication bands for wireless routers and access points are presented. The antennas operate in the 4G LTE (699-798 MHz) band, UMTS (DCS/PCS) bands (1.7-2.0 GHz), WiMAX bands (2.3 and 3.5 GHz), and Wireless LAN bands (2.4 and 5 GHz) with <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> = - 6 dB matching criterion (VSWR 3:1). The two antenna designs are in 1 × 2 MIMO configuration. The antennas exhibit an omnidirectional pattern in these bands with reasonable gain and total antenna efficiency. The antennas also have low envelope correlation well below 0.5 dB. A prototype antenna was fabricated and tested for experimental verification. Both simulated and measured data are provided.

Investigation of a high power electromagnetic pulse source

A high power electromagnetic pulse source with a resonant antenna driven by a compact power supply was investigated in this paper. To match the impedance of the resonant antenna and initial power source, a compact power conditioning circuit based on electro exploding opening switch (EEOS) and pulsed transformer was adopted. In the preliminary experiments, an impulse capacitor was used to drive the system. With the opening of the EEOS at the current of 15 kA flowing trough the primary of the transformer, the resonant antenna was rapidly charged to about -370 kV within a time of about 100 ns. When the switch in the resonant antenna closed at the charging voltage of about -202 kV, the peak intensity of the detected electric field at a distance of about 10 m from the center of the source was 7.2 kV∕m. The corresponding peak power of the radiated electromagnetic field reached 76 MW, while the total radiated electromagnetic energy was about 0.65 J. The total energy efficiency of the resonant antenna was about 22% which can be improved by increasing the closing rapidity of the switch in the antenna.

Adaptive penta-band handset antenna with hand effect compensation

The increase in the number of cellular operating bands and the ever-increasing criteria antenna size reduction has pushed the need to use switchable antenna structures. Further, the presence of a hand in the close vicinity of the antenna causes deterioration in performance. The authors present a switchable antenna technique, evaluate the effect of the human hand on it and discuss a novel method to compensate for the mismatch. A penta-band switchable planar inverted-F antenna covering 824-960 and 1710-2170-MHz has been used in this study. The presence of the hand was observed to cause 2.0-6.0-dB loss in efficiency for the low band. Using the proposed extra-ground antenna switching method and the dynamic antenna matching, technique the total efficiency of the antenna can be improved by 0.5-2.5-dB compared to the mismatched case.

Flat-Shaped Dielectric Lens Antenna for 60-GHz Applications

We describe the performance of a flat shaped dielectric lens antenna designed to produce a flat-top beam in H-plane and a nearly omni-directional pattern in E-plane in the 60-GHz band. Such radiation characteristics may be useful for access points or user terminals in high data rate wireless local area networks. For the antenna design, a specific two-stage methodology combining 2-D and 3-D modeling has been implemented. First, the lens shape is optimized in 2-D using a 2-D FDTD kernel coupled to a genetic algorithm. Second, all building blocks of the final antenna (3-D lens with a finite thickness, antenna feed) are optimized using the solution of the 2-D problem as an initial guess. This strategy has been validated experimentally: a 2.5-mm-thick flat lens in Rexolite with a shaped profile in H-plane has been fabricated and measured. It is shielded by two 1-mm-thick half metallic disks. The radiation patterns are very stable from 57 to 63 GHz, and the total antenna efficiency is better than 50%.

Absorption Loss Reduction in a Mobile Terminal With Switchable Monopole Antennas

A method for compensating part of the user effect on a mobile terminal antenna was experimentally evaluated. A dynamic selection between two separately located antennas was used to reduce absorption caused by the user's index finger. The method was examined in the 900 MHz and 1900 MHz bands with dual-band monopole antennas. The performance of the method was evaluated in terms of antenna total efficiency, body loss, mismatch loss, and absorption loss. It was found that a 3.1 dB reduction in average body loss is achieved in the low band if feed is switched to the unloaded antenna instead of the loaded one. The corresponding reduction in the higher band is 1.0 dB.

The Mutual Coupling Reduction between Two J-Shaped Folded Monopole Antennas for Handset

In this study, we propose a method to reduce the mutual coupling between two J-shaped folded monopole antennas (JFMAs), which cover the IEEE 802.11 b/g (2400-2484MHz) band. First, the change in mutual coupling with the spacing between the two antenna elements is investigated by considering two feeding models, and the effects of changes in the coupling on the antenna efficiency are studied. Subsequently, we try the method to reduce mutual coupling, the method involves the use of a bridge line that links the two antennas. The mutual coupling can be significantly reduced and the total antenna efficiency can be improved by linking two shorting strips with the bridge line. In a past study, we had found that in the case of L-shaped folded monopole antennas (LFMAs), the mutual coupling and antenna efficiency vary with the linking location on the bridge line. Moreover, we compare the characteristics of the LFMA and JFMA and show that the JFMA is effective when miniaturized.

A Frequency-Agile Compact Array With a Reconfigurable Decoupling and Matching Network

A novel frequency reconfigurable compact array incorporating a reconfigurable decoupling and matching network (DMN) is proposed. The array radiating part consists of two printed monopole antennas. An inductive biasing line is devised to control the PIN diode states so that the array operating frequency is switchable between 2.5 and 3.5 GHz bands. The element spacing is chosen to be as small as 0.05λ 0 at 2.5GHz, which leads to a strong mutual coupling between antenna ports. A reconfigurable DMN is proposed to mitigate the mutual coupling effect for both 2.5 and 3.5GHz bands. Simulation results show that the use of the DMN realizes a well matched (S 11 &#60;= −10dB) and decoupled (S 21 &#60;= −20dB) bandwidth of 70MHz and 120MHz in the lower and higher bands, respectively. The antenna total efficiency can be substantially affected by the internal resistor when the PIN diodes are in the ‘ON’ state. The compact size and frequency reconfigurability feature greatly save the antenna real estate. The decoupled array can be useful for a multi-input multi-output (MIMO) diversity system.

Effects of Chassis Currents on Hearing Aids Compatibility in the Handset

In this paper, we investigate the effects of the chassis wavemodes on the near-field electromagnetic intensities that contribute to hearing aid compatibility (HAC) tests at two different frequencies, 900 and 1880 MHz. For a comprehensive view, we also examine the far-field properties of the antenna total efficiency and bandwidth. Additionally, we examine the specific absorption rate in relation to the chassis wavemodes. The examined parameters are then related to the HAC. It was found that the chassis wavemodes have a significant effect on the antenna near-field performance, especially at the 900-MHz frequency range. We show that the optimum near-field antenna performance is achieved when the antenna resonant frequency is aligned with the chassis resonant frequency. With this, a decrease of about 50% can be achieved in the peak magnetic field intensity and a 30% decrease in the peak electric field intensity; hence, a better possibility in passing the HAC compliance tests. Moreover, controlling the chassis wavemodes has a similar effect to that of increasing the distance from the HAC scan plane—a rapid decrease in the field intensities can be achieved. Our analyses are done through simulations and these are validated against measurements.

Inkjet-Printed RF Structures on BST-Polymer Composites: An Application of a Monopole Antenna for 2.4 GHz Wireless Local Area Network Operation

In this study, 0–3 ceramic–polymer composite substrates are utilized in RF applications in combination with inkjet printing technology. The substrates were fabricated from barium–strontium–titanate and polyphenylene sulfide. The relative permittivity and loss tangent were measured by inkjet-printed silver transmission lines and resonant techniques. They increased from 3.2 to 14.2 and from 0.003 to 0.0055, respectively, at 5 GHz with increasing ceramic loading up to 36.4 vol%. An antenna for 2.4 GHz wireless local area network band was proposed. A return loss of >−15 dB and a total antenna efficiency of >60% were measured across the band.

Decoupling method between two L-shaped folded monopole antennas for handsets using a bridge line

This study analyses the reduction of mutual coupling between two L-shaped folded monopole antennas (LFMAs) operating at 2 GHz on the finite ground plane. Firstly, the change in mutual coupling with respect to the spacing between the two elements in two array models is investigated and the effects on the antenna efficiency are studied. Subsequently, the authors proposed an effective method to reduce mutual coupling by using a bridge line that links two antennas. From the viewpoint of mutual coupling and total antenna efficiency, it is desirable to place shorting strips of both LFMA elements in such a manner that they face each other. Moreover, drastically reduced mutual coupling and improved total antenna efficiency can be obtained by linking two feeding strips with a bridge line.

Analysis of decoupling method between J-shaped folded monopole antennas for IEEE 802.11b/g on handset

This letter presents a mutual coupling reduction method between two J-shaped folded monopole antennas (JFMA), which cover Wireless Local Area Network (WLAN), especially for IEEE 802.11b/g band on handset. IEEE 802.11b/g is used to 2.4GHz (2400-2484MHz) band. We proposed an effective method to reduce mutual coupling by using a bridge line that links two antennas. As the analytical results, by linking the shorting strips of two JFMA elements with a bridge line, we obtained a sufficiently reduced mutual coupling and improved total antenna efficiency.

A Novel High-Gain Dual-Band Antenna for RFID Reader Applications

A novel high-gain dual-band antenna for radio frequency identification (RFID) reader applications covering free ISM bands of 2.45 and 5.8 GHz is presented in this letter. The antenna is composed of a U-shaped copper strip with unequal arm, a printed rectangular ring, and the ground plane. A good impedance bandwidth of 120 MHz has been achieved from 2.37 to 2.49 GHz for the lower band, while the upper band covers 420 MHz (from 5.55 to 5.97 GHz). The U-shaped feeding strip excites the rectangular ring effectively by providing a good impedance matching with over 85% of total antenna efficiency in both the frequency bands and also 9.56 and 10.17 dBi gain in the lower and higher frequency band, respectively.

A Compact Dual-Band Feed for Reflector Antennas Based on Choke Horn and Circular Eleven Antenna

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A novel dual-band feed for reflector antennas is presented. This feed is a combination of a novel circular Eleven feed for C band and a compact choke horn for Ku band. The combined feed has been characterized in terms of total feed efficiency of reflector antenna and coupling coefficient of C and Ku bands (<formula formulatype="inline"><tex Notation="TeX">$≪ -18~$</tex> </formula>dB) over all operating frequencies. An experimental model has been manufactured and measured. The measured results agree well with the simulated ones. The dual-band feed is compact in size and can be a good candidate for satellite terminals and other applications. </para>

In-Band Frequency-Tunable Ceramic Planar Inverted-F Antenna (PIFA) Utilizing an Integrated BST-Based Variable Capacitor

The dielectric properties of low-sintering-temperature (LTCC) Barium Strontium Titanate (BST) thick film paste at high frequencies (0.8–5 GHz) are briefly presented. The utility of the BST paste was demonstrated by tuning the resonance frequency of a ceramic PIFA for mobile terminals operating at 2 GHz. The frequency tuning achieved can be used to compensate frequency detuning caused by the proximity of the user to the antenna. The impact of tuning on the antenna's total efficiency and radiation pattern was experimentally studied through a comparison with the performance of a reference antenna not incorporating the varactor.

An inkjet‐printed inverted‐F antenna for 2.4‐GHz wrist applications

AbstractIn this article, an inkjet‐printed inverted‐F antenna suitable for a watch‐type wireless communication device is presented. The antenna and covering the 2.4 WLAN band (2.4–2.484 GHz) has thickness (2 mm3) and size (40 × 25 mm2). The performance of the printed antenna is experimentally studied and compared with a reference antenna made of Rogers copper laminate. The effect of inkjet‐printed layer thickness on the antenna performance is presented. In addition, the impact of the user's hand proximity on the antenna performance is studied experimentally. The results showed that the total antenna efficiency increases by 13% and 27% with an increase of 1.5 μm in printed layer thickness and a user's hand to antenna distance of 12.5 mm, respectively. The shape of the radiation pattern of the antenna is distorted due to the proximity of the user's hand. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2936–2938, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24777

Low-Sintering-Temperature Ferroelectric-Thick Films: RF Properties and an Application in a Frequency-Tunable Folded Slot Antenna

This investigation is one of the first steps toward the realization of low-cost, mass-producible, tunable antenna applications utilizing an integrated ferroelectric-thick film made of bariumstrontiumtitanate material. The dielectric properties of the electric-field-adjustable fired BST thick film are presented in the frequency range of 16 GHz. The key advantages of the material are high tunability (25% with 2.5 V/mum), compatibility with silver electrodes, and the ability to produce film thicknesses down to 25 mum. The utilization of the material is demonstrated by tuning the operating frequency of a folded slot antenna with an integrated variable capacitor. In addition, the impact of tuning on the antenna's total efficiency and radiation pattern is experimentally studied through a comparison with the performance of a reference antenna not incorporating the varactor.

Optimization of PIFA-IFA combination in handset antenna designs

As commercial needs have expanded the functions of the wireless cellular handsets, multiantenna development in one handset has become more and more common. This paper addresses a multiantenna solution for the wireless handset application. A planar inverted "F" antenna (PIFA) was designed as the main antenna of the handset to cover the 800 MHz band (824 MHz-894 MHz) and the 1900 MHz band (1850 MHz-1990 MHz). A side-mounted inverted "F" antenna (IFA) was designed as the 1575.42 MHz global positioning system (GPS) antenna. The location of the feed/ground pins of both antennas affected not only the total antenna efficiency, but also the polarization of the GPS IFA. The length of the GPS IFA affected the isolation between the two antennas and the specific absorption rate (SAR) of the PIFA at the 1900 MHz band. A three-dimensional efficiency measurement of the prototypes in both free space and against-head position will be presented. Measurement of SAR and its distribution will also be presented to demonstrate the impact of the IFA on the near field of the PIFA.

Two-port model of an antenna for use in characterizing wireless communications systems, obtained using efficiency measurements

The agreement in these efficiency measurements validates the accuracy of the Satimo range, while highlighting the simplicity of the Wheeler cap. When one needs pattern data or the efficiency of an antenna in the presence of a surrogate hand and head, then a spherical near-field range, such as the Satimo system, is necessary. However, it is seen that a network analyzer and a Wheeler cap are sufficient for accurately measuring total antenna efficiency versus frequency for a small, solitary antenna. This total efficiency is the transfer function of the antenna, and may be used by system designers to evaluate the antenna's bandpass and band-reject properties.

Comparisons between a shaped and nonshaped small Cassegrain antenna

An X-band 8.5-ft brassboard antenna system was designed and developed which required a 70% total antenna efficiency and a 25 dB isolation between the circularly polarized transmit and receive ports. To maximize the aperture efficiency, a shaping technique was used to generate a specially contoured subreflector and main reflector. To reduce cost, a configuration was chosen such that the shaped main reflector could be matched with negligible phase error using a commercially available paraboloid. The antenna gain of this shaped system with an electrically small subreflector (10.7 lambda ) is 0.75 dB higher than that of a conventional system using the same paraboloid and a matching hyperbolic subreflector. Measured results demonstrated that even for a small system the antenna performance can be appreciably improved at low cost by using a shaped subreflector.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>