With the current scenario of development of antennas in the wireless communication field, the need of compact multiband, multifunctional and cost effective antenna is on the rise. The objective of this thesis is to present fixed and reconfigurable techniques and methods for small and slim multiband antennas, which are applicable to serve modern small and slime wireless, mobile and cognitive radio applications. In the fixed designs, independent control of the operating frequencies is investigated to enhance the antennas capabilities and to give the designer an additional level of freedom to design the antenna for other bands easily without altering the shape or the size of the antenna. In addition, for mobile phone antenna, the effect of user’s hand and mobile phone housing are studied to be with minimum effect. Although fixed multiband antennas can widely be used in many different systems or devices, they lack flexibility to accommodate new services compared with reconfigurable antennas. A reconfigurable antenna can be considered as one of the key advances for future wireless communication transceivers. The advantage of using a reconfigurable antenna is to operate in multiband where the total antenna volume can be reused and therefore the overall size can be reduced. Moreover, the future of cell phones and other personal mobile devices require compact multiband antennas and smart antennas with reconfigurable features. Two different types of frequency reconfigurability are investigated in this thesis: switchable and tunable. In the switchable reconfigurability, PIN diodes have been used so the antenna’s operating frequencies can hop between different services whereas varactor diode with variable capacitance allow the antenna’s operating frequencies to be fine-tuned over the operating bands. With this in mind, firstly, a switchable compact and slim antenna with two patch elements is presented for cognitive radio applications where the antenna is capable of operating in wideband and narrow bands depending on the states of the switches. In addition to this, a switchable design is proposed to switch between single, dual and tri bands applications (using a single varactor diode to act as a switch at lower capacitance values) with some fine tuning capabilities for the first and third bands when the capacitance of the diode is further increased. Secondly, the earlier designed fixed antennas are modified to be reconfigurable with fine-tuning so that they can be used for more applications in both wireless and mobile applications with the ability to control the bands simultaneously or independently over a wide range. Both analytical and numerical methods are used to implement a realistic and functional design. Parametric analyses using simulation tools are performed to study critical parameters that may affect the designs. Finally, the simulated designs are fabricated, and measured results are presented that validate the design approaches.

In this thesis, we propose a new bandwidth-enhancement method of using a parasitic open slot to achieve a wide lower band for the internal laptop computer antenna with a small size to cover the GSM850/900 operation and a wide upper band to cover the GSM1800/1900/UMTS operation as well. The occupied antenna volume is only 48 ¡Ñ 10 ¡Ñ 3.5 mm^3 above the top edge of the display ground. For practical application, we analyze the effects of the antenna position, nearby metal plate, shielding metal plate, keyboard ground, FR4 substrate, and the size of display ground on the performance of the WWAN antenna. In addition, effects of the user¡¦s whole-body on the proposed antenna are also analyzed. Owing to the user¡¦s whole-body being mainly lossy materials, a decrease in the antenna¡¦s radiation efficiency is observed when the user¡¦s whole-body is in close proximity to the WWAN laptop computer antenna.

When the conventional mobile communication antennas embedded in the laptop computers, it is difficult to achieve enough bandwidths or a larger antenna size is required for covering the GSM/DCS operation. To overcome this problem, three new mobile communication internal antennas, having multi-band operation capability and suitable to be embedded in the laptop computers are proposed. At first, we introduce a monopole antenna with a shorted parasitic element. This antenna can provide wide bandwidths to cover GSM900, DCS, PCS, and UMTS operations. Then, in order to additionally achieve the GSM850 operation to form the penta-band operation, we present a wideband monopole antenna with a shorted structure. Finally, we propose an open-loop antenna with a shorted parasitic element. The antenna occupies a smaller volume and is capable of providing wide bandwidths to cover GSM850, GSM900, DCS, PCS, and UMTS operations. Detailed antenna designs and experimental results are presented and discussed.

Abstract In this thesis, new methods for mobile terminal antenna frequency control and user effect compensation are presented. The thesis is divided into two parts. The first part includes frequency reconfigurable and tuneable antennas for mobile terminals. At first, the efficient frequency reconfiguration methods for a slot-, planar inverted-F (PIFA) and inverted-F (IFA) antennas are presented. Methods are based either on the use of RF switches, or on variable capacitor loading. One of the frequency tuneable antennas is used for the antenna frequency bandwidth enhancement in an internal digital television reception antenna, offering a continuous tunability range from 470 MHz to 702 MHz with 8 MHz instantaneous bandwidth. The second part of this thesis is concentrated on the user effect on the mobile terminal antennas, and especially, on the active compensation of the user-induced losses. At first, an experimental user effect study is conducted for triple-band PIFA and the body loss, comprising both the reflection loss and absorption loss, is characterized and formulated. It was observed that with the highly loaded mobile terminal antenna the majority of the losses are absorption losses and the user-induced reflection losses play a minor role. An active method of compensating the body loss, and especially the absorptive part of it, is designed and developed in this thesis. The switchable two-antenna arrangement is applied to a dual-band top-bottom PIFA that yielded up to 9 dB compensation of the body loss with a specific phantom hand grips in the lower band (GSM 850). In the higher band (GSM 1900 and WCDMA) 2 dB compensation is obtained. The same method is verified with two side by side-located PIFA and monopole configurations in order to compensate the effect of the user’s index finger. The losses from switching circuitry proved to be smaller than the benefit achieved by the compensation method. / Tiivistelmä Tässä työssä esitään uudenlaisia menetelmiä matkaviestinantennin taajuussäätöön ja käyttäjän vaikutuksen kompensointiin. Työ jakautuu kahteen osaan, joista ensimmäisessä käsitellään taajuussädettäviä matkaviestinantenneja. Aluksi esitetään tehokkaita taajuussäätömenetelmiä rako-, tasomainen käännetty-F- ja käännetty-F -tyyppisille antennirakenteille. Menetelmät perustuvat joko RF kytkimen tai säädettävän kapasitanssin käyttöön. Yhtä säätömenetelmää sovelletaan päätelaitteen sisäisen vastaanottoantennin taajuuskaistanleveyden kasvattamiseen. Säätömenetelmällä saavutettu jatkuva säätöalue on 470–702 MHz ja hetkellinen kaistanleveys on 8 MHz. Työn toisessa osassa keskitytään käyttäjän matkaviestimen antennille aiheuttamaan vaikutukseen ja erityisesti käyttäjän aiheuttamien häviöiden kompensointiin. Aluksi esitetään kokeellinen tutkimus käyttäjän vaikutuksesta kolmikaistaiseen PIFA-antenniin. Tutkimuksessa arvioidaan kehohäviöiden määrää, antennin impedanssimuutoksesta aiheutuvaa heijastushäviötä ja absorptiohäviötä. Tutkimuksen perusteella absorptiolla on suurempi vaikutus kokonaishäviöön kuin heijastushäviöllä. Työssä esitetään aktiivinen kehohäviön ja erityisesti absorptiohäviön kompensointimenetelmä. Menetelmässä antennikytkentää sovelletaan päätelaitteen ylä- ja alapäähän sijoitettuihin kaksitaajuus antenniin. Tutkimuksen perusteella todetaan, että tietyn käsiotteen aiheuttamia häviöitä voidaan kompensoida 9 dB matalammalla taajuuskaistalla (GSM 850) ja 2 dB korkeammalla taajuuskaistalla (GSM 900 ja WCDMA). Kompensointimenetelmän toimivuus todennetaan myös kahdella monopoli- ja PIFA-antennirakenteella käyttäen erilaista antennijärjestelyä, jossa pääpaino on käyttäjän etusormesta johtuvien häviöiden kompensoinnissa. Antennikytkennän aiheuttamat häviöt ovat pienemmät kuin kompensointimenetelmällä saavutettu etu.

No / A procedure to reduce the effect of the mobile antenna on the handset by using balanced antennas has been investigated. Use of this type of antenna may degrade the antenna performance, such as bandwidth and gain, although it can cause less effect on the body to which they are adjacent. If the antennas are well designed, the maximum specific absorption rate (SAR) values are likely to be reduced when placed next to the head, since the coupling of such antennas to the body of the handset is very weak. A study on balanced and unbalanced antennas for mobile handsets next to the human head is presented, using a hybrid electromagnetics method for the analysis. The method uses the hybridisation technique between the frequency-domain method of moments (MoM) and the finite-difference time-domain method (FDTD). The antenna was modelled using MoM whereas the head tissues were modelled using FDTD. Two antennas were designed and investigated with respect to the SAR and radiation performance for two different antenna positions on the top edge of a mobile handset. Radiation patterns are presented and compared, with and without the head, and the maximum SAR values and field distributions inside the head are discussed. The balanced antenna shows good improvements with respect to the unbalanced antenna in terms of the SAR values and variations of the input impedances.

No / Noise amplitude distribution measurements relevant to%satellite-mobile radio systems are reported. The rationale for the%measurements is outlined and the choice of measurement parameters%justified. The measurement equipment and measurement methodology are%described in detail. Results characterizing the elevation angle%distribution of impulsive noise are presented for rural, suburban and%urban environments and also for an arterial road (U.K. motorway)%carrying high density, fast moving traffic. Measurements of the levels%of impulsive noise to be expected in each environment for high- and%low-elevation satellite scenarios using appropriate antenna%configurations are also presented

A mobile phone antenna with a radiating coupling feed is presented. By using the radiating coupling feed, the conventional coupled-fed loop antenna and coupled-fed shorted monopole antenna can be efficiently incorporated into the antenna structure and respectively excite a wide band resonant mode to cover GSM850/900 and GSM1800/1900/UMTS/LTE2300/2500 for the seven-band operation. Besides, the antenna can be in compact integration with the extended ground plane such that more electronic components in the mobile phone can be accommodated in the practical applications. In order to study the near-field radiation characteristics of the antenna, SAR and HAC are also simulated and analyzed.

In this dissertation, a variety of multiband communication device antennas using the coupling-feed mechanism are presented. The coupling feed contributes additional capacitance to the antenna¡¦s input impedance which shows a high inductive component for the traditional case of using a direct feed. In the first and second antenna designs, with the coupling feed, the high input inductance of the antenna is effectively compensated. This behavior leads to a dual-resonance excitation for the lower band of the antenna. Two wide operating bands are achieved, allowing the antenna¡¦s lower and upper bands to easily cover GSM850/900 and GSM1800/1900/UMTS operation. For the last two antenna designs, owing to the coupling feed, the very large input impedance seen at antenna¡¦s lower band is greatly decreased and results in successful excitation of the one-eighth wavelength (£f/8) mode of the antenna. The specific absorption rate and hearing aid compatibility results for these mobile phone antennas are also analyzed. The effects of presence of the user¡¦s hand on the laptop computer antenna performance are also studied in this dissertation.

This thesis presents solutions and studies related to the design of wideband antennas for wireless handheld terminal applications. A method of electrically shortening the terminal chassis length to obtain resonance at high frequencies has been proposed and evaluated, thereby increasing the antennas impedance bandwidth. No significant effect on the lower frequency band in a dual-band antenna prototype has been observed, making the method suitable for multi-band applications. The chassis has further been utilized as a zero-thickness 0.9 - 2.7 GHz high efficiency antenna by inserting a notch in the chassis center, and a feasibility study for typical phones has been performed. Additionally, the effect of talk position on the chassis wave-mode has been investigated, where the standard equivalent circuit model for terminal antennas has been modified to include the presence of the users head. The model has been used to explain measured and simulated effects concerning frequency detuning, efficiency reduction and bandwidth enhancements when the terminal is placed in talk position. The use of a hands-free earpiece cord is currently mandatory for FM radio reception as the cord is utilized as antenna. However, there is currently a market driven demand for removing the cord requirement since many modern phones are equipped with speakers and Bluetooth headsets. In this thesis, an active ferrite loop antenna is proposed as an internal replacement/complement with a performance of -23 dB (G/T degradation) compared to a full-size lossless dipole in urban environments. Also, a modification to the cord is suggested for DVB H reception. Complex matching networks have been investigated to increase the bandwidth of dual band PIFA antennas, and a printed dual band dipole has been integrated with a modified Marchand balun for dual resonance at two separate frequency bands, thus covering the commercial cellular bands 824-960 and 1710-2170 MHz with a single antenna.

<p>This thesis presents solutions and studies related to the design of wideband antennas for wireless handheld terminal applications. A method of electrically shortening the terminal chassis length to obtain resonance at high frequencies has been proposed and evaluated, thereby increasing the antennas impedance bandwidth. No significant effect on the lower frequency band in a dual-band antenna prototype has been observed, making the method suitable for multi-band applications. The chassis has further been utilized as a zero-thickness 0.9 - 2.7 GHz high efficiency antenna by inserting a notch in the chassis center, and a feasibility study for typical phones has been performed. Additionally, the effect of talk position on the chassis wave-mode has been investigated, where the standard equivalent circuit model for terminal antennas has been modified to include the presence of the users head. The model has been used to explain measured and simulated effects concerning frequency detuning, efficiency reduction and bandwidth enhancements when the terminal is placed in talk position.</p><p>The use of a hands-free earpiece cord is currently mandatory for FM radio reception as the cord is utilized as antenna. However, there is currently a market driven demand for removing the cord requirement since many modern phones are equipped with speakers and Bluetooth headsets. In this thesis, an active ferrite loop antenna is proposed as an internal replacement/complement with a performance of -23 dB (G/T degradation) compared to a full-size lossless dipole in urban environments. Also, a modification to the cord is suggested for DVB H reception.</p><p>Complex matching networks have been investigated to increase the bandwidth of dual band PIFA antennas, and a printed dual band dipole has been integrated with a modified Marchand balun for dual resonance at two separate frequency bands, thus covering the commercial cellular bands 824-960 and 1710-2170 MHz with a single antenna.</p>