f. setoudeh

This paper presents a compact topology for implementing multiband bandpass filters. The design uses interconnected multimode resonators (MMRs) and multi-level impedance structures to achieve a specific frequency response. This approach simplifies the design of quadruple bandpass filters for 4G and 5G applications. Since line widths cannot be adjusted post-construction, resonance positions require tuning. To evaluate the filter design process, a prototype incorporating MMRs was designed, manufactured, and analyzed, demonstrating close alignment between analytical predictions and experimental measurements, despite no simulation or optimization being performed during the design phase, except for result verification.Additionally, a design criterion is established to facilitate the rapid and reliable synthesis of multiband responses by varying only a few geometrical parameters of the MMRs. A simulation of this structure was conducted using CST software to confirm the proposed theory's accuracy. A reverse-biased varactor diode, which functions as a capacitor with specific admittance, is utilized to provide the necessary tuning capability. The paper also highlights the impact of the varactor diode's admittance on resonance location adjustments. To validate the design, the authors present a fabricated prototype of the proposed filter, which features quarter bands at 1.8, 2.1, 2.7, and 3.4 GHz, achieving an attenuations greater than -15 dB. The quarter band filter is primarily used in wireless telecommunications networks. Due to their specialized design, these filters can process multiple frequency bands simultaneously, enhancing communication quality and increasing network capacity in crowded and interference-prone environments.

The Differential transform method (DTM) is used in the analysis of ordinary, partial, and high-order differential equations. Recently, the DTM is used in the nonlinear analysis of physical nonlinear dynamic systems.

The DTM method is used to analyze and analytically solve the nonlinear mathematical model of bias current-controlled Colpitts oscillator with variable coefficients.  Intervals of the validity of the proposed method are evaluated by using the fourth order Runge-Kutta method (RK4M).  In this note, the Lyapunov exponent (LE) can be used to analyze the Colpitts oscillator. By using DTM, the LEs are calculated analytically with unknown parameters in a short interval of time t[0, 3 Sec].

In this paper, intervals of the validity of the proposed method are evaluated using RK4M. In addition, LEs are calculated using analytical and numerical methods based on DTM technique and Wolf method, respectively.  LEs of the proposed system are presented as a function of the control parameter to confirm the applied technique’s usefulness.  

By comparing these two methods, the proposed DTM analytical technique is relatively more precise. Simulation results confirmed the impact of different parameters on LEs with two different initial conditions. The results show good accuracy of the DTM in short time intervals t[0, 3 Sec].

The Differential transform method (DTM) is used in the analysis of ordinary, partial, and high-order differential equations. Recently, the DTM is used in the nonlinear analysis of physical nonlinear dynamic systems.

The DTM method is used to analyze and analytically solve the nonlinear mathematical model of bias current-controlled Colpitts oscillator with variable coefficients.  Intervals of the validity of the proposed method are evaluated by using the fourth order Runge-Kutta method (RK4M).  In this note, the Lyapunov exponent (LE) can be used to analyze the Colpitts oscillator. By using DTM, the LEs are calculated analytically with unknown parameters in a short interval of time t[0, 3 Sec].

In this paper, intervals of the validity of the proposed method are evaluated using RK4M. In addition, LEs are calculated using analytical and numerical methods based on DTM technique and Wolf method, respectively.  LEs of the proposed system are presented as a function of the control parameter to confirm the applied technique’s usefulness.

By comparing these two methods, the proposed DTM analytical technique is relatively more precise. Simulation results confirmed the impact of different parameters on LEs with two different initial conditions. The results show good accuracy of the DTM in short time intervals t[0, 3 Sec].   

The objective of this research is to improve the 3-D imaging system using near-infrared light emission in breast tissue to achieve a more accurate diagnosis of the tumor. Experimental results in this research on this imaging system indicate that a more accurate diagnosis of abnormal areas depends on the location of the sources and detectors. Therefore, an improved location model has been proposed to determine a more suitable placement of sources and detectors. In this article, no human breast cancer samples were examined due to inaccessibility to a 3-D imaging system using near-infrared lights. Since such experiments should be conducted several times to obtain more accurate reconstructed images, the proposed method was evaluated using the optical images reconstruction toolbox of NIRFAST 7.2 in the MATLAB programming environment. The results were then compared with the results of similar articles. The obtained results showed that the proposed placement of sources and detectors can detect abnormal areas with a much lower error rate. Furthermore, the proposed placement of sources and detectors achieved a good result in simultaneously diagnosing two abnormal areas.