International Journal of Microwave and Wireless Technologies, 2014
ABSTRACT In this paper, a switchable antenna with capability to operate in ultrawideband (UWB) fr... more ABSTRACT In this paper, a switchable antenna with capability to operate in ultrawideband (UWB) frequency from 3 to 10.7 GHz with two switchable notch bands of 3.3–3.7 and 3.7–4.2 GHz, is presented for cognitive radio (CR) and multiband orthogonal frequency-division multiplexing (MB-OFDM) applications. The proposed antenna has a simple structure and compact size of 17 × 24 mm2. The antenna in the UWB characteristics is obtained using a circular radiator patch with an embedded T-slot on the patch and a rectangular parasitic element that is attached to the patch. The reconfigurability is also achieved by two L-shaped parasitic elements placed in the left and right of the patch that two ideal switches is inserted over the these elements and the circular patch. The function of the antenna can be changed by tuning status of the switches that make the notch bands in application frequencies. The measurement and simulation results show that the antenna has good characteristics for CR application and MB-OFDM, where the UWB antenna is required for spectrum sensing and the switchable band rejection antenna is used for reconfigurable operation.
ABSTRACT In this study, a compact ultra-wideband (UWB) bandpass filter (BPF) with sharp roll-off,... more ABSTRACT In this study, a compact ultra-wideband (UWB) bandpass filter (BPF) with sharp roll-off, improved out-of-band performance and dual-band-notch operation is presented and its design procedure is discussed. In the proposed structure, in order to reject the unwanted harmonic pass bands, a pair of modified cross-shaped coupled lines (CCLs) is implemented along the ports of the filter. Moreover, a pair of half-circle-shaped stubs and a stepped-impedance stub are loaded on the main resonator in order to obtain additional transmission zeros (TZs) which are controllable separately. Implementation of the CCLs and the stub loaded resonator (SLR) reduce the total size of the presented microstrip BPF. Besides, by extending and folding the upper coupled line of each CCLs and also through an open stub which is protruded inside a slot on the main resonator, dual-band-notch operation is added to the performance of the presented filter. The fabricated prototype has a small size and is capable to cover frequency band of 2.8–10.69 GHz with two band-notch functions at 4.9–5.4 and 7.83–8.25 GHz which suppresses the interference between UWB spectrum with wireless local area network (WLAN) and satellite communication frequency bands, respectively. The proposed filter has a compact size while showing good return loss and insertion loss characteristic in the frequency band of interest.
Abstract: the problematic reduction of civic engagement in local communities of Khuzistan provinc... more Abstract: the problematic reduction of civic engagement in local communities of Khuzistan province in the southwest of Iran has became a serious issue for research in social planning and policy making. It has occasioned an attempt to search for risk factors as deterrents to ...
International Journal of Microwave and Wireless Technologies, 2014
ABSTRACT In this paper, a switchable antenna with capability to operate in ultrawideband (UWB) fr... more ABSTRACT In this paper, a switchable antenna with capability to operate in ultrawideband (UWB) frequency from 3 to 10.7 GHz with two switchable notch bands of 3.3–3.7 and 3.7–4.2 GHz, is presented for cognitive radio (CR) and multiband orthogonal frequency-division multiplexing (MB-OFDM) applications. The proposed antenna has a simple structure and compact size of 17 × 24 mm2. The antenna in the UWB characteristics is obtained using a circular radiator patch with an embedded T-slot on the patch and a rectangular parasitic element that is attached to the patch. The reconfigurability is also achieved by two L-shaped parasitic elements placed in the left and right of the patch that two ideal switches is inserted over the these elements and the circular patch. The function of the antenna can be changed by tuning status of the switches that make the notch bands in application frequencies. The measurement and simulation results show that the antenna has good characteristics for CR application and MB-OFDM, where the UWB antenna is required for spectrum sensing and the switchable band rejection antenna is used for reconfigurable operation.
ABSTRACT In this study, a compact ultra-wideband (UWB) bandpass filter (BPF) with sharp roll-off,... more ABSTRACT In this study, a compact ultra-wideband (UWB) bandpass filter (BPF) with sharp roll-off, improved out-of-band performance and dual-band-notch operation is presented and its design procedure is discussed. In the proposed structure, in order to reject the unwanted harmonic pass bands, a pair of modified cross-shaped coupled lines (CCLs) is implemented along the ports of the filter. Moreover, a pair of half-circle-shaped stubs and a stepped-impedance stub are loaded on the main resonator in order to obtain additional transmission zeros (TZs) which are controllable separately. Implementation of the CCLs and the stub loaded resonator (SLR) reduce the total size of the presented microstrip BPF. Besides, by extending and folding the upper coupled line of each CCLs and also through an open stub which is protruded inside a slot on the main resonator, dual-band-notch operation is added to the performance of the presented filter. The fabricated prototype has a small size and is capable to cover frequency band of 2.8–10.69 GHz with two band-notch functions at 4.9–5.4 and 7.83–8.25 GHz which suppresses the interference between UWB spectrum with wireless local area network (WLAN) and satellite communication frequency bands, respectively. The proposed filter has a compact size while showing good return loss and insertion loss characteristic in the frequency band of interest.
Abstract: the problematic reduction of civic engagement in local communities of Khuzistan provinc... more Abstract: the problematic reduction of civic engagement in local communities of Khuzistan province in the southwest of Iran has became a serious issue for research in social planning and policy making. It has occasioned an attempt to search for risk factors as deterrents to ...
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Papers by P. Rezaei