Jari Holopainen

Antenna for Handheld DVB Terminal

For the reception of terrestrial television, traditionally Yagi or whip antennas are used. Due to their large size they cannot be used in the reception of digital television on handheld devices (DVB-H), which operate at the frequency band 470 – 702 MHz. The DVB-H system is under development and small internal antenna solutions for handheld devices are not yet available. Due to the long wavelengths, any antenna placed inside a portable terminal will be electrically small. The antenna volume is the fundamental factor determining its performance. With traditional microstrip antennas such as PIFAs the required bandwidth could not be obtained inside a pocket-size terminal. Therefore, a broadband planar antenna structure for a DVB-H receiver is presented in this paper. The antenna structure is based on the compact coupling element antenna structure [1] that was earlier applied for GSM systems [2].

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.

Internal Broadband Antennas for Digital Television Receiver in Mobile Terminals

The Implementation of internal broadband antennas for digital television receiver (DTV) in mobile terminals operating at the lower UHF band is studied comprehensively. Certain challenges such as inherently narrow impedance bandwidth of electrically small antennas and limited volume available for the antennas inside mobile terminals are identified and handled. The proposed design principle for DTV antennas is to decrease the total efficiency of the antenna to a level which is just good enough to ensure a sufficient signal-to-noise ratio and that way make the size of the antenna sufficiently small. The limits for the size of broadband capacitive coupling element-based DTV antenna structures inside handsets of different sizes are studied. In the end, a manufactured prototype and simulated design are presented and compared with the limits studied earlier in the paper. The results show that the studied antenna concept is a promising candidate for broadband DTV antennas in mobile terminals. The work also increases general understanding on the implementation of antennas based on the radiation of the finite ground plane.

Mobile terminal antennnas implemented by using direct coupling

The current trend in mobile terminals is an increasing number of systems. The volume occupied by the antennas of the radio systems is becoming more and more problematic and new low-volume antenna solutions are needed. Since the EMC shielding and the ground plane operate as the main radiating structure especially below 1 GHz, a very small antenna structure can be achieved by using a direct feed, i.e. galvanically inducing currents on the surface of the chassis. The feed can be placed over an impedance discontinuity, e.g. formed by a slot. Using this approach, an antenna structure for a small handheld digital television (DVB-H) receiver is presented. The antenna gain exceeds the specification by a 4-dB margin. The introduced antenna structure can also be used for multi-system terminals.

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.

Near-Field Control of Handset Antennas Based on Inverted-Top Wavetraps: Focus on Hearing-Aid Compatibility

In this letter, it is shown that inverted-top wavetraps, which are quarter-wavelength-long resonators, can be used to control the near-fields of a mobile terminal antenna. The local reduction of the near-fields is especially important for the operation of the hearing aid of the user. The reshaping of the near-fields may also enable reduced specific absorption rate (SAR) values.

Five-element inverted-F antenna array for MIMO communications and radio direction finding on mobile terminal

A five-element inverted-F antenna array on mobile terminal for both multiple input multiple output (MIMO) communications and radio direction finding (RDF) applications is presented. The multi-element antenna (MEA) system has been designed to be used in the frequency band of the future Long Term Evolution (LTE) system at 3400–3600 MHz and integrated along the edges of the upper ground plane of a clamshell type mobile terminal. Without using any specific multi-antenna isolation techniques, the antennas have been optimized to have acceptable mutual coupling and small envelope correlation in order to provide enhanced capacity with multiple input multiple output (MIMO) techniques. The ambiguities of the proposed design in RDF applications have also been investigated. A prototype has been fabricated and tested. Good agreement between numerical simulations and experimental results has validated the antenna concept.

User Effect of Antennas for Handheld DVB Terminal

The user effect study for handheld DVB antennas was performed by simulating the radiation and total efficiencies of the antennas as a function of frequency. Because of the losses caused by the user, a 4-dB margin to the realized gain specification in the antenna prototypes located in free space is needed to fulfil the DVB-H specification also when the effect of the users hands are taken into account. Also, the detuning of the matching due to the hands was examined.

Mobile terminal antennas implemented using optimized direct feed

A novel antenna structure based on optimized direct feed is presented in this paper. The antenna structure consists of the chassis of a mobile terminal, a feed structure and a matching circuitry. The chassis is cut in two pieces, which are connected with an inductor. The value of the inductor is tuned so that the lowest resonant frequency of the chassis equals the center frequency of the operating band. The feed structure excites very strongly the resonant wavemode of the chassis and thus very large bandwidth is available. The feed structure can be integrated e.g. on the PCB of a mobile terminal and thus the antenna is very low-profile. The antenna structure has been demonstrated with a simulated and measured prototype that covers the GSM850/900 systems.

Equivalent circuit model-based approach on the user body effect of a mobile terminal antenna

The user body effect on the operation of mobile terminal antennas is investigated based on equivalent circuit modelling. The purpose is to increase the understanding of the phenomenon, which is important, for example, when designing mobile terminal antennas with minimised user effect.