Janne Ilvonen

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).

Broadband Equivalent Circuit Model for Capacitive Coupling Element–Based Mobile Terminal Antenna

In this letter, it is shown how the behavior of a capacitive coupling element (CCE)-based mobile terminal antenna can be modeled at the UHF band as a combination of the separate wavemodes of the structure. The proposed equivalent circuit model improves the general understanding of the operation of the antenna structure. It can be used for analyzing the combined performance of the capacitive coupling element and terminal chassis, but it also helps in analyzing how different parts of the antenna structure contribute to the impedance and radiation.

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.

Effect of the User's Hands on the Operation of Lower UHF-Band Mobile Terminal Antennas: Focus on Digital Television Receiver

This paper deals with the effect of the users hands on the performance of lower UHF-band antennas in handheld terminals. It is studied that how the input impedance, efficiency, and far-field directional pattern of the internal broadband digital television antenna are affected by the presence of the users hands. The main part of the study has been carried out by applying finite-difference time-domain simulations. Measurements have been performed to support the results obtained by simulations. In the worst case, as much as 7-11 dB decrease of the antenna efficiency compared to free space case is shown. The results also indicate that the power absorption to the hand(s) is generally a more severe problem for the total efficiency than the change of the matching. On the other hand, it is also shown that in certain cases, the total efficiency of the antenna can even be improved due to the hands of the user. The results of this paper increase the understanding of the effect of the users hands on the operation of the lower UHF-band antennas, whose operation is based on the radiation of a finite ground plane.

On Design and Evaluation of Harmonic Transponders

Performance and characterization of harmonic transponders is investigated both theoretically and experimentally. The harmonic response of a transponder based on a Schottky diode is analytically derived in the case when the excitation power is low. Theoretical calculations prove that at high frequencies, capacitive nonlinearity contributes more to frequency multiplication than resistive nonlinearity. This means that the feasibility of a particular diode for harmonic transponder applications largely depends on its varactor properties. Figures-of-merit (FOM) are derived both for the mixing diode and the transponder antenna. The validity of the proposed theoretical model is investigated experimentally using a harmonic transponder operating at 1 GHz fundamental frequency.

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.

Antenna Matching at Harmonic Frequencies to Complex Load Impedance

Analysis of a self-resonant, dual-frequency-matched antenna is presented. The operating frequencies of the antenna are harmonically separated, and 1-GHz fundamental and 2-GHz second harmonic frequencies are used. This type of antenna can be used, e.g., in harmonic transponder applications, where the antenna is loaded with a nonlinear element, which is typically a Schottky diode. In this letter, the impedance properties of the studied antenna are investigated using an example Schottky diode. Compared to conventional 50- Ω environments, the frequency-dependent impedance of the Schottky diode provides additional challenges for antenna matching, which are also addressed. Rather than providing a design for an application-specific antenna, the current study presents certain “building blocks” that may be useful for particular antenna designs.

Harmonic Transponders: Performance and Challenges

Performance of a harmonic transponder strongly depends on the properties of the antenna and diode used, which makes finding a good combination of them very important. For a transponder with a fixed antenna geometry, the effect of different diodes is analyzed through electromagnetic simulations and theoretical calculations. The antenna used in the transponder is directly matched to the impedance properties of a particular diode. Effects of both detector and varactor diodes on the return loss characteristics of the antenna and the obtainable transponder response are observed. Criteria for selecting a suitable diode are given. Benefits and drawbacks of using different antenna matching techniques are discussed, and principal design steps are given both for transponders matched directly to the antenna and for transponders with external matching circuits.