An ultra-compact triple-band bandpass filter based on dual-mode quarter-wave resonator for GSM, GPS, and WiFi applications is presented in this study. The filter consists of three quarter-wave resonators assisting in controlling each passband independently. The first operating frequency band is obtained by the direct-feed resonator which acts as a source to load coupling for the inner two resonators which are operating at higher frequency bands. The outermost resonator is coupled to the inner loaded resonators, thus a pair of transmission zeros between each passband can be excited and hence high-frequency selectivity can be obtained. To miniaturize the overall size of the filter, all resonators are folded and are jointly connected through a common metallic via with the ground. The design has a symmetric structure therefore, even-odd mode analysis method is applied to obtain the three controllable operating frequency bands. The first operating band is centered at 850 MHz which caters for GSM applications, while the second and third frequency bands centered at 1.57 GHz and 2.4 GHz fall in the GPS and WiFi wireless applications. The filter with an ultra-compact size of 0.10 λ g × 0.09 λ g (0.009λ 2 g) despite feed lines (λ g is the waveguide length centered at 850 MHz) is designed, fabricated and measured for the purpose of validation. Both the simulated and measured results are in good agreement and endorse the design concept. INDEX TERMS Tri-band filter, quarter-wavelength resonator, microstrip BPF filter, transmission zeros, wireless applications.

This manuscript presents a UWB filter with three notch bands for WiMAX, WLAN, and X-Band Satellite Communication by introducing inverted E-and T-shape resonators shorted at the center, designed and fabricated for the use of UWB applications authorized by the US Federal Communications Commission. First, a UWB filter ranges from 2.8 GHz to 10.6 GHz is designed by employing four λ/4 wavelength short-circuited stubs and then couples E-and T-shape resonators on either side of the main transmission line of the proposed UWB filter to achieve notch bands response centered at the resonance frequency of 3.3 GHz for WiMAX applications, 5.1 GHz for WLAN wireless applications, and 8.3 GHz for X-band satellite communication systems, respectively. The proposed filter is able to produce three individually control stopband frequencies centered at 3.3 GHz, 5.1 GHz, and 8.3 GHz with minimum attenuation levels of −28 dB, −19 dB, and −15 dB, respectively. This indicates that the presented filter can efficiently reject superfluous bands at 3.3 GHz in WiMAX system, 5.1 GHz in WLAN system, and 8.3 GHz in satellite communication systems to improve the performance of the UWB communication systems. Finally, the proposed filter with circuit area 34 mm × 12 mm × 0.762 mm is designed and fabricated. A reasonable agreement can be seen between the simulated and fabricated measurements.

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This paper presents a modern compact quad-band bandpass filter (BPF) using dual-mode stub loaded half wave (λ/2) resonators, where a couple of directly fed resonators are loaded with two identical inner resonators such that the direct fed resonators will act as feeding structure for the loaded resonators. Based on the proposed stub loaded resonators, a modern filter with seven transmission zeros (TZs) is designed by folding the two identical inner resonators. The proposed design has a symmetrical geometry, therefore even-odd mode analysis is used to predict the resonant frequencies of the passbands. The first and second passbands are obtained through fundamental odd and even modes respectively while the third one is achieved by placing loaded inner resonators in the proposed design. The second even harmonic of the direct fed resonators is utilized to achieve the fourth passband and is controlled by the stubs loaded at the middle of the resonators. The filter is simulated and fabricated for the purpose of validation, wherein a good agreement can be seen in both simulated and experimental results.

The objective of this study is to explore the capability of the Regional Climate Model (RegCM3), to predict the extreme weather events in south-Asian region with particular reference to precipitation during monsoon season (July, August and September) over northern mountainous and southern plain regions of Pakistan. Different cumulus parameterization schemes in RegCM3 for prediction of convective precipitation are tested for monsoon period during the years 1998 and 2001. The model results are compared with the Climate Research Unit (CRU) observational data and the surface synoptic data of the Pakistan Meteorological Department (PMD). The year 1998 was a dry year and proved to be the beginning of a severe drought lasted up to the year 2000. While in year 2001 the precipitation over some parts of the country exceeded the normal, especially the northern parts of the country observed exceptionally high rainfall rate. The results indicate that some convective parameterization schemes of RegCM3 well captured the summer monsoon precipitation over Pakistan. However, the schemes need to be selected carefully depending upon the region of interest. It was found that the Grell scheme with both closures: Arakawa-Schubert (AS) and Fritsch-Chappell (FC) satisfactorily captured the monsoon phenomenon in Pakistan specially for the northern mountainous regions.