Jari Holopainen

Mobile Terminal Antenna Performance With the User's Hand: Effect of Antenna Dimensioning and Location

This letter reports a systematic simulation study of the performance of mobile terminal antennas in the vicinity of the users hand. The effects of antenna dimensioning and antenna location on the ground plane of the device are demonstrated. The studied performance parameters are quality factor, radiation efficiency, and frequency detuning. Based on the results, beneficial approaches and general guidelines for antenna designs with a reduced effect of the users hand can be given. For instance, it is shown that the radiation efficiency with the users hand stays nearly constant (variation <;0.2 dB) despite the changes in the antenna element height (2-6.6 mm at 900 and 2000 MHz).

Design Strategy for 4G Handset Antennas and a Multiband Hybrid Antenna

A novel design strategy for multi-standard mobile handset antennas is presented and verified with experimental results. The results show that the presented antenna operates with better than -3 dB (50%) efficiency across the frequencies of 698-2900 MHz and 3250-3600 MHz, thus having state-of-the-art performance. The antenna is shown to have a robust performance with a user, and it can fulfill the specific absortion rate (SAR) and hearing aid compatibility (HAC) requirements. In addition, it is demonstrated how the multi-antenna functionality can be included within the antenna structure, simultaneously achieving a small antenna volume of 750 mm3. The diversity gain and isolation are better than 10 dB at the frequency band 2110-3600 MHz. Hence, the proposed antenna is well suited for future LTE-A mobile handsets.

Optimal Dual-Antenna Design in a Small Terminal Multiantenna System

This letter introduces a novel 2.6-GHz multiple-input-multiple-output (MIMO) antenna system for mobile terminals. The antenna structures consist of a broadband main antenna covering most of the LTE-A bands and a narrowband second antenna operating at the 2.6-GHz band. The main antenna is a traditional monopole-type capacitive coupling element (CCE) placed on the short edge of the terminal. The second antenna consists of two out-of-phase fed inductive coupling elements (ICEs) placed on the long edges of the chassis. The main purpose of the letter is to demonstrate that this kind of antenna system offers good performance in terms of electromagnetic (EM) isolation and envelope correlation between the antennas. This has been experimentally verified and is originated on the fact that both antennas excite effectively different orthogonal wavemodes, which is studied with the help of the theory of characteristic wavemodes.

Multiband Frequency Reconfigurable 4G Handset Antenna with MIMO Capability

A novel frequency reconfigurable 4G Multiple-Input Multiple-Output (MIMO) handset antenna is presented and verified with experimental results. Frequency tuning is used to minimize the antenna volume and to compensate for the losses related to user-originated impedance detuning. Both antenna elements are independently frequency reconfigurable and can cover most of the LTE-A bands. The study compares the losses of CMOS- and MEMS-based digitally tunable capacitors (DTC). In addition, two prototypes with total antenna volumes of 1170 and 3900 mm 3 have been studied. The results show that the larger antenna structure operates with an efficiency better than 49% across the frequencies of 698-960 MHz and better than 56% across the frequencies of 1430-2690 MHz, when a MEMS-based DTC is used. In addition, a new method is introduced to estimate the suitability of the antenna geometry for frequency tunable antennas.

Compensation of finger effect on a mobile terminal antenna by antenna selection

In this paper, compensation of the effect of the users finger on the operation of a mobile terminal antenna is studied, using antenna selection as the compensation method. A dual-element antenna is compared with a single-element antenna occupying the same total antenna volume. The results show that antenna selection can provide an improvement of at least 2 dB in total efficiency at GSM1800 frequency band when the antenna is under influence of the index finger of the user.

Antennas for Digital Television Receivers in Mobile Terminals

The incorporation of new services in handheld devices, such as the Digital Video Broadcast-Handheld (DVB-H) operating at the lower ultrahigh-frequency (UHF) band poses a challenge for antenna designers. Wideband small antennas or electrically tunable narrowband small antennas are needed to fulfil the performance requirement. It is well known that below 900 MHz the operation of embedded mobile terminal antennas is based on utilizing the whole structure of the terminal as a radiator. However, even this way reaching the whole required impedance bandwidth of about 46% at about 0.61-GHz center frequency is possible only either with clamshell-type terminals used as thick dipoles by feeding them from the hinge or with “large tablet”-sized terminals. With the popular smartphone-sized terminals with a monoblock structure the available bandwidth with good total efficiency is clearly smaller. We study the options to implement antennas for smartphone-type mobiles for receiving digital TV broadcasts at about 0.47-0.75-GHz frequencies. The mainly studied technology is the nonresonant capacitive coupling element (CCE)-type antennas having one of the smallest achieved volume-to-bandwidth ratios. We show that for a fixed-frequency antenna with a volume of less than a few cubic centimeters the total efficiency will become rather low due to moderate matching level, but the requirement of the DVB-H standard for the realized gain can easily be met. Additionally, we show that by having switching between two bands, one can implement a dual-antenna configuration with small total volume and significant multiple-input-multiple-output (MIMO) gain. Furthermore, we study the very important effect of the users hands on the antenna performance and find that the effect can range from some increase of the total efficiency due to improved matching to significant losses caused by the hands. Finally, we propose some possible ways ahead in solving this very challenging antenna design problem.

Concept for Frequency-Reconfigurable Antenna Based on Distributed Transceivers

This letter presents a new concept for frequency-reconfigurable antennas. The concept involves a multiport antenna, whose elements are mutually coupled. By properly weighting the excitation signals in each port, the total reflected power can be minimized, and radiation efficiency maximized. Different frequency components of the transmitter can be weighted differently to obtain broad instantaneous band. The concept is studied by simulations.

Performance analysis of broadband coupling - element - based multiantenna structure for mobile terminal with hand effects

This paper presents a comprehensive simulation study on the performance of broadband coupling-element-based multiantenna structures on a mobile terminal at the 2000 MHz Universal Mobile Telecommunications System (UMTS) frequency band with varying two significant hand effects; vertical position of hand along terminal chassis, and distance between hand palm and terminal chassis. The results reveal that there exists an MEG imbalance between antenna elements due to hand effects and it is shown that an MEG imbalance of 3.7 dB lead to a reduction of 1.9 dB in diversity gain at 99% reliability level using maximal ratio combining (MRC) technique. For a two-element antenna configuration, the impact of MEG imbalance on diversity gain is more significant when only one antenna element is in close proximity to the hand, compared to when both antenna elements are in the presence of the hand. It is also shown that a broadband multiantenna structure with elements vertically oriented along the edges of a small 100 mm x 40 mm mobile terminal chassis achieves better performance in port-to-port isolation, MEG imbalance and diversity gain compared to other studied multiantenna configurations when the users hand is present.

RFID-Based Book Finder [Education Corner]

Locating items rapidly and accurately has become a crucial part of our modern society and industry. Accurate locating not only saves time and money but also reduces waste, as products do not get lost along supply chains. One promising indoor tracking method is provided by radio-frequency identification (RFID) technology. The main benefit of RFID technology is the ability to inventory items simultaneously and rapidly without the requirement of line of sight to the target. Because RFID tags are attached to various objects and are used in different environments, RFID engineers are required to design RFID tags that operate reliably within varying environments and medium materials. In this article, an RFID system is introduced to locate library books at the Aalto University School of Electrical Engineering. In the suggested approach, the books placed outside the main library are equipped with an ultrahigh frequency (UHF) RFID tag and can be located using a hand-held RFID reader device (Figure 1). In addition to locating the books, the system keeps the book inventory up to date.

Extension to Characterization Model for GPS Antenna Performance in Mobile Terminals

A new, extended model to evaluate the performance of Global Positioning System (GPS) antennas in mobile terminals is introduced. The new model is demonstrated using three different antennas with two orientations, and it is shown to give a more reliable prediction of the GPS antenna performance compared to the earlier model. Also, a new parameter for characterizing the ability of the GPS antenna to reject the reflected waves from the ground is introduced.