Study and development of a reconfigurable receiver carrier system (Doctoral thesis)

Ράπτης, Βασίλειος Π.


Recent technological developments provide the fact that wireless communication devices could be smaller in size. Specifically, the size of the antenna is obviously an important factor which limits the overall size of the devices. Over the past few years, new low profile antenna designs have been developed for portable wireless devices. The basic feature of low-profile antennas is their limited bandwidth. The problems that need to be solved when using these devices with regard to the antenna system are reported below: The proximity of the user towards the device or other external environmental factors (such as metal objects, walls, trees) alter the antenna frequency resonance. This fact deteriorates the received signal quality from the antenna during reception and additional transmitted power is needed in order to maintain the communication link during broadcast. The use of wide bandwidth antennas during broadcasting, as opposed to narrowband antennas, creates interference problems from neighboring stations. Consequently, the use of filters at the input of the receiving signal is necessary to eliminate noise from neighboring frequencies. This translates into a further reduction in the power of the received signal from these antennas and in the demand of additional material costs. These problems are confronted in this thesis. An antenna is suggested with narrow bandwidth and with continuous re-tuning of its operating frequency. The methodology that is followed by priority order is modeling, simulation, constructing and measurement of the PIFA antennas and finally the construction of a system which has the capability of changing the resonant frequency using a variable capacitor. The results - conclusions of this dissertation are oriented towards using a variable capacity of a varactor embedded into a PIFA antenna, which this fact gives the capability of changing the resonant frequency for avoiding the unwanted phenomenon at GSM frequencies.
Institution and School/Department of submitter: Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Φυσικής
Subject classification: Κεραίες
Keywords: Κεραίες,GSM,Επαναπροσδιοριζόμενη,Varactor,PIFA,Antenna,Reconfigurable
URI: http://olympias.lib.uoi.gr/jspui/handle/123456789/29371
Appears in Collections:Διδακτορικές Διατριβές

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