A Study Of Ultra Wideband Slot Loop And Tapered Slot Antennas

Nowadays, the ultra-wideband technology has found practical use in wirelesscommunication, modern radar and radio astronomy. As one of the most criticalcomponents in such systems, ultra-wideband antennas attract great study interestsrecently. On the other hand, the planar slot antenna is a frequently-used antenna type forits simple configuration and low profile. The dissertation is mainly concerned with twotypes of slot-based antennas: the slot loop antenna and the tapered slot antenna. Themajor works and contributions of the dissertation are outlined as follows:1. The ultra-wideband microstrip-to-slotline transition baluns are studied. In thisdissertation, a coupled line microstrip-to-slotline transition is firstly presented. Byemploying tapered structures, the proposed design is with low frequency cut off whilemaintains compact size and more than10:1bandwidth. Secondly, a cross junctionmicrostrip-to-slotline transition is proposed. The mutual coupling between theoverlapped microstrip open stub and slotline short stub is taken into consideration whilethe unequal-section-length multi-section matching transformer is also used to achievethe desired22:1broadband performance. Finally, a transition based on dual branch lineconfiguration is demonstrated. The proposed transition is capable of realizing thetransition between low impedance microstrip to high impedance wide slotline in a broadfrequency band without employing area-consuming multi-section matching transformer.2. The wideband slot loop antennas are studied. A wideband slot loop antenna isdesigned to cover the commonly used commercial frequency bands. The capacitive andinductive loadings are implemented to widen the bandwidth of the antenna. Two slotloop elements are back-to-back arranged to form a dual-element array. A distanceadjustable back-reflector is placed behind the array. By proper selecting the distancebetween the reflector and the array, continuous working bands with stable directionalradiation properties can be achieved, making the antenna a good candidate for multiplenarrowband antennas replacement.3. The tapered slot antennas are studied. A CPW-fed tapered slot antenna isdesigned. The corrugated edge structure is implemented as the outer profile while acurve composed of elliptical line and straight line is applied as the inner tapered profile.The proposed design is with single-planar configuration and compact size. A modifiedantipodal Vivaldi antenna is proposed. The tapered slot edge structure is applied tominiaturize the size of the antenna. The modification is proved capable of improving the antenna’s low end radiation characteristics. Finally, a resistance-loading Vivaldi antennais designed. Four chip resistors are symmetrically loaded in the antenna arms. Theantenna achieves17.5:1bandwidth while its aperture width maintains about1/5maximum working wavelength.4. The ultra-wideband dual-polarization tapered slot antenna arrays are studied. Adual-polarization four-element Vivaldi array for anechoic chambers applications isproposed. The array is arranged in a novel “#”-shaped form, which is capable ofavoiding grating lobe and realizing high port-isolation in the desired working band. Anultra-wideband dual polarization8×8-element array is proposed. Tapered slot elementswith±45°scan ability are used in the design. Mutual coupling between elements areanalyzed and metal edges are employed to suspend truncation effects in finite array.Power dividers integrated with the dual-polarization elements are also investigated.Finally, a prototype of the array is fabricated. The measured results validate that thearray is able to work in the desired wide frequency band.