Two novel antenna designs for mobile handsets are proposed in this thesis. With a helix loading, an inverted-L monopole antenna capable of generating two resonances at about 900 and 1850 MHz is first presented. The operating bandwidths obtained cover the required bandwidths of the GSM/DCS/PCS bands. Besides, an internal mobile handset antenna comprising a PIFA and a PILA, which are, respectively, designed for covering the GSM and DCS/PCS bands is also presented. The PIFA and PILA together occupy a compact volume of 7.2 ¡Ñ 20 ¡Ñ 40 mm3, and are suitable to be built-in within the housing of a mobile handset.

Σκοπός της συγκεκριμένης εργασίας είναι η μελέτη και η σχεδίαση τυπωμένων κεραιών ανεστραμμένου – F για φορητές τερματικές συσκευές. Οι κεραίες αυτές χρησιμοποιούνται σε κινητά τερματικά, όπως κινητά τηλέφωνα, φορητοί υπολογιστές, PDA κ.τ.λ. και παρουσιάζουν πολλά πλεονεκτήματα, με κυριότερα το χαμηλό κόστος, την ευκολία κατασκευής, το μικρό τους μέγεθος και τη δυνατότητα μαζικής παραγωγής. Αρχικά στο πρώτο κεφάλαιο παρουσιάζονται ορισμένες γενικές βασικές αρχές των κεραιών και εισάγεται η έννοια της ηλεκτρικά μικρής κεραίας. Επίσης παρουσιάζεται η κεραία ανεστραμμένου – F και διατυπώνεται η θεωρία των ειδώλων στην οποία βασίζεται η αρχή λειτουργίας της συγκεκριμένης κεραίας. Στο κεφάλαιο 2 αναφέρονται οι προτάσεις και οι υλοποιήσεις που έχουν γίνει μέχρι στιγμής για την κεραία ανεστραμμένου – F στην βιβλιογραφία ενώ στη συνέχεια (κεφάλαια 3 μέχρι 7) παρουσιάζονται αναλυτικά ορισμένες κεραίες που έχουν κάποια επιπλέον πλεονεκτήματα ως προς τις υπόλοιπες ομοειδείς. Ιδιαίτερη βάση δόθηκε στις κεραίες που καλύπτουν τις ISM ζώνες στα 2.4 GHz και 5.2/5.8 GHz εξαιτίας της ευρύτατης χρήσης των ζωνών αυτών.Τέλος στο κεφάλαιο 9 επιχειρείται μια μικρή εισαγωγή στα συστήματα απόκλισης χώρου με την παρουσίαση και αξιολόγηση ενός συστήματος με τέσσερις κεραίες. / This diploma thesis includes the analysis, design and simulation of printed inverted - F antennas for dual band operating portable terminal devices. These antennas are widely used in mobile phones,laptops, PDAs,etc and have many advantages over other printed antennas such as extremely low cost, fabrication flexibility and compact size.

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.

Abstract In this thesis, bandwidth (BW) enhanced antennas for mobile terminals and multilayer ceramic packages are presented. The thesis is divided into two parts. In the first part, electrically frequency-tunable mobile terminal antennas have been studied. The first three antennas presented were of a dual-band planar inverted-F type (PIFA) and were tuned to operate in frequency bands appropriate to the GSM850 (824–894 MHz), GSM900 (880–960 MHz), GSM1800 (1710–1880 MHz), GSM1900 (1850–1990 MHz) and UMTS (1920–2170 MHz) cellular telecommunication standards with RF PIN diode switches. The first antenna utilized a frequency-tuning method developed in this thesis. The method was based on an integration of the tuning circuitry into the antenna. The tuning of the second antenna was based on a switchable parasitic antenna element. By combining the two frequency-tuning approaches, a third PIFA could be switched to operate in eight frequency bands. The planar monopole antennas researched were varactor-tunable for digital television signal reception (470–702 MHz) and RF PIN diode switchable dual-band antenna for operation at four cellular bands. The key advantage of the former antenna was a compact size (0.7 cm3), while for the latter one, a tuning circuit was implemented without using separate DC wiring for controlling the switch component. The second part of the thesis is devoted to multilayer ceramic package integrated microwave antennas. In the beginning, the use of a laser micro-machined embedded air cavity was proposed to enable antenna size to impedance bandwidth (BW) trade-off for a microwave microstrip in a multilayer monolithic ceramic media. It was shown that the BW of a 10 GHz antenna fabricated on a low temperature co-fired ceramic (LTCC) substrate could be doubled with this technique. Next, the implementation of a compact surface mountable LTCC antenna package operating near 10 GHz was described. The package was composed of a BW optimized stacked patch microstrip antenna and a wide-band vertical ball grid array (BGA)-via interconnection. Along with the electrical performance optimization, an accurate circuit model describing the antenna structure was presented. Finally, the use of low-sintering temperature non-linear dielectric Barium Strontium Titanate (BST) thick films was demonstrated in a folded slot antenna operating at 3 GHz and frequency-tuned with an integrated BST varactor.