In this thesis we introduce a half-wavelength loop antenna for operation as an internal antenna for mobile phones. First, we introduce a single loop antenna for single-band operation (eg., UMTS band), and experimental and simulated results are presented. Next, we introduce a dual-band loop structure which covers the operating bandwidths of the GSM/DCS dual-band mobile phone. The proposed dual-loop antenna is studied, especially for the effects between the two loops of the antenna. Both of the single-loop and dual-loop antennas have the characteristics of generating similar surface currents on the ground plane with that of the conventional monopole and planar inverted-F mobile phone antennas.

By employing a low-cost loop antenna of simple structure, a novel antenna design to efficiently make use of the system ground plane of a PDA (personal digital assistant) is proposed. Owing to a small distance of 3 mm between the antenna and the ground plane, the propose antenna has a very low profile. By selecting a proper loop¡¦s length-to-width ratio, two resonant modes close to each other can be excited, which lead to an impedance bandwidth of 17%. In addition, because of the same direction of the surface currents on the radiating metal plate, the antenna peak gain reaches about 4.5 dBi, which is attractive for application in PDAs.

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.

In this dissertation, different from the conventional PIFA structure, the novel internal loop and slot antennas suitable for multiband mobile phone application are proposed. The loop antennas here use the technique of meandering the loop pattern to control the frequency ratio of the three resonant loop modes, and then the multiband operation can be obtained. For the slot antenna, different from the conventional slot antenna operating in a half-wavelength, the monopole slots antenna operating in it¡¦s quarter-wavelength mode are proposed. By properly adjusting the position of the monopole slot and the tuning stub of the microstrip feedline, the monopole slot antenna can achieve the multiband operation with a small occupied area in the mobile phone. In addition, the user¡¦s hand and head effects on the loop antenna are also studied. The obtained results indicate that, when the user¡¦s hand and head is close to or cover a certain portion of the antenna, large decrease in the antenna¡¦s radiation efficiency and great distortion in the antenna¡¦s radiation pattern will occur for all the three excited resonant modes of the loop antenna, no matter the unbalanced or balanced modes. Further, the efficiency drops caused by the user¡¦s hand and head over the GSM900 band are much larger than that over the GSM1800/1900 bands.

Novel compact antenna designs for WiMAX (Worldwide interoperability for microwave access) operation in the mobile phone are presented in this thesis. In the first design, the antenna is integrated at one corner of system circuit board of the mobile phone and consists of two radiating portions; the monopole slot is formed by integrating the two portions. In the second design, two different antenna structures are used to achieve all WiMAX operating bands. Finally, in the third design, the chip antenna comprises a resonant monopole patch, a resonant shorter slot and a matching longer slot. The latter two slots are embedded within the monopole patch to achieve a compact integration. Detailed antenna designs and experimental results are presented and discussed.

Two novel internal WWAN antennas having multi-band operation capability and suitable to be embedded in the laptop computers are proposed. The first antenna is a penta-band printed monopole slot antenna, which can cover GSM850/900/1800/1900/UMTS operation. The second antenna is a penta-band printed dual-loop antenna. The antenna can cover GSM850/900/1800/1900/UMTS operation and occupies a small size. The effects of the environment and the user¡¦s hand on the internal laptop computer antenna are also studied. Take the first antenna as an example; the obtained results show that the effects of the internal environment of the laptop computer are mostly on the antenna¡¦s impedance matching, which however can be improved by adjusting the parameters of the antenna. On the other hand, since the user¡¦s hands are lossy materials, a decrease in the antenna¡¦s radiation efficiency is observed when the user¡¦s hand is in the vicinity of the internal antenna.

In this thesis, two types of handset antenna design respectively for dual-band GSM850/1900 operation and seven¡Vband LTE/WWAN operation are presented. The proposed antennas can achieve decreased antenna size and enhanced operating bandwidth by shaping the system ground plane of the handset. The seven-band LTE/WWAN antenna is printed on the system circuit board with good radiation characteristics and occupies a small size of 24.5 x 10 mm2. At first, we propose a half-loop antenna structure which integrates its facing edge of the system ground plane as the resonant path of the antenna. In this case, the required length of the half-loop antenna structure is only about a half compared with the traditional loop antenna. Next, to enhance the operating bandwidth of the antenna, a parasitic shorted monopole strip is added and a shaped system circuit board is used. The shaped system circuit board can integrate the battery with the circuit board to help reduce the thickness of handset. Also, much enhanced operating bandwidth for the lower band can be obtained, owing to the enhanced surface current excitation in the system ground plane resulting from properly shaping the system circuit board. Effects of the user¡¦s head and hand on the proposed antenna are studied, and the simulated SAR and HAC results are also analyzed for bio-compatibility issue.

<p>This thesis considers integration of antennas and active electronics manufactured on the same substrate. The main topic is on-chip antennas for commercial silicon processes, but hybrid integration using printed circuit board technology is also addressed.</p><p>The possible use of micromachining techniques as a means of reducing substrate losses of antennas manufactured on low resistivity silicon wafers is investigated. Compact dipole, loop, and inverted-F antennas for the 20-40 GHz frequency range are designed, implemented, and characterized. The results show significantly improved antenna efficiency when micromachining is used as a post-processing step for on-chip antennas manufactured in silicon technology.</p><p>High resistivity wafers are used in a commercial silicon germanium technology to improve the efficiency of dipole antennas realized using the available circuit metal layers in the process. Monolithically integrated 24 GHz receivers with on-chip antennas are designed and evaluated with regard to antenna and system performance. No noticeable degradation of the receiver performance caused by cross talk between the antenna and the integrated circuit is observed.</p><p>For low frequency antenna arrays, such as base station antennas, hybrid integration of active devices within the antenna aperture is treated. A compact varactor based phase shifter for traveling wave antenna applications is proposed and evaluated. Electrically steerable traveling wave patch antenna arrays, with the phase shifters implemented in the same conductor layer as the radiating elements, are designed and manufactured in microstrip technology. It is experimentally verified that the radiation from the feed network and phase shifters in the proposed antenna configuration is small.</p>

This thesis considers integration of antennas and active electronics manufactured on the same substrate. The main topic is on-chip antennas for commercial silicon processes, but hybrid integration using printed circuit board technology is also addressed. The possible use of micromachining techniques as a means of reducing substrate losses of antennas manufactured on low resistivity silicon wafers is investigated. Compact dipole, loop, and inverted-F antennas for the 20-40 GHz frequency range are designed, implemented, and characterized. The results show significantly improved antenna efficiency when micromachining is used as a post-processing step for on-chip antennas manufactured in silicon technology. High resistivity wafers are used in a commercial silicon germanium technology to improve the efficiency of dipole antennas realized using the available circuit metal layers in the process. Monolithically integrated 24 GHz receivers with on-chip antennas are designed and evaluated with regard to antenna and system performance. No noticeable degradation of the receiver performance caused by cross talk between the antenna and the integrated circuit is observed. For low frequency antenna arrays, such as base station antennas, hybrid integration of active devices within the antenna aperture is treated. A compact varactor based phase shifter for traveling wave antenna applications is proposed and evaluated. Electrically steerable traveling wave patch antenna arrays, with the phase shifters implemented in the same conductor layer as the radiating elements, are designed and manufactured in microstrip technology. It is experimentally verified that the radiation from the feed network and phase shifters in the proposed antenna configuration is small.

There are large groundplane variations for the folder-type mobile phone in the talk and idle conditions, which makes its embedded antennas not easy to maintain good radiation characteristics in the two states. The radiation efficiencies in the idle condition are often less than 15%. To solve this problem, two novel antennas for the folder-type mobile phone are proposed. The first antenna is the coplanar coupled-fed planar inverted-F antenna. The antenna can cover GSM850/900/DCS/PCS operation in the talk condition, and the radiation efficiencies over the desired operating bands in the idle condition is larger than 32%, which is acceptable for practical applications for the folder-type mobile phone. The second antenna is the ultra-wideband coupled-fed loop antenna. The antenna can cover GSM850/900/DCS/PCS/UMTS penta-band operation in the talk condition. In the idle condition, good performances over the five operating bands can still be obtained, and the radiation efficiencies are better than 53%. The effects of the housing and the user's hand and head on the antenna are also studied. From the obtained results, it is seen that the effects of the housing on the radiation efficiencies are small. However, since the user's hand and head are high-loss materials, large decrease in the radiation efficiencies is usually observed.