A Wilkinson Power Divider with Harmonic Suppression and Size Reduction using High-low Impedance Resonator Cells

A miniaturized Wilkinson power divider using high-low impedance resonator cells are designed and fabricated. The proposed power divider occupies 23.7% of the conventional structure circuit area at the operating frequency of 0.9 GHz and it is also able to suppress harmonics. According to the measured results at 0.9 GHz, the insertion-losses of output ports are 3.087 dB, the return-losses at all ports are more than 30 dB, and the isolation between output ports is better than 35 dB. Also, 2nd to 10th spurious frequencies are suppressed. According to the measured S11, when it is less than -15 dB (from 0.65 GHz to 1.1 GHz) the fractional bandwidth of the proposed structure is 50%. Good agreement between simulation and measured results is achieved

A Compact Microstrip Lowpass Filter with Ultra-Wide Rejection Band and Sharp Transition Band Utilizing Combined Resonators with Triangular Patches

In this paper, a microstrip lowpass filter with -3 dB cut-off frequency of 1.8 GHz consisting of two resonators with different triangular patches and four high-low impedance resonators as suppressing cells has been designed. To design this filter, the influence of each transmission line on the frequency response of the utilized resonators has been clarified by calculating the equations of S21 and S11 based on the lumped circuit of them separately. The designed filter has been constructed and tested, and an good agreement between the simulation and measurement results has been achieved. The stopband covers an ultra-wide frequency range from 1.94 to 34.556 GHz with a suppression level of -21.2 dB. Furthermore, the insertion loss in the passband region is close to zero from DC to 1.68 GHz and an acceptable return loss (17.44 dB) in this band can prove desired in-band character. Moreover, the proposed filter provides a sharp transition band equal to 228 (dB/GHz). The designed lowpass filter has a high figure of merit equal to 26583.4

A Design of Branch-Line Coupler with Harmonic Suppression and Size Reduction Using Closed-Loop and Open-Loop Resonators

In this paper, a branch-line coupler using closed-loop and open-loop resonators with the operating frequency of 2.69 GHz is proposed. The designed microstrip circuit not only is able to suppress the second and the third unwanted harmonics but also reduces the occupied area to 59% of the traditional branch-line coupler. To explain how the employed resonators can suppress spurious frequencies, transmission zeros of both resonators based on their equivalent LC has been calculated, separately. To prove the abilities of the proposed branch-line coupler, the designed circuit has been fabricated and tested resulting in a good agreement between the measurement and simulation results. According to the S11 when it is less than -15 dB the bandwidth of the designed branch-line coupler is about 500 MHz, from 2.42 to 2.92 GHz .The comparison between the results of simulation and measurement are in good agreement

Simulation of three mutually coupled oscillators

In a practical multipurpose high frequency circuit, different oscillators are not completely isolated from each other. Instead, they interact with the environment, or with other oscillator. The interference between different oscillators may lead to generation of undesired signals. Therefore, the effect of oscillators on each other must be considered in the circuit design. As oscillators have nonlinear behavior, simulation of some of them which are coupled to each other needs more attention. In this report we present a mathematical model for three mutually coupled voltage controlled oscillators and solve it by a numerical method. The approach is illustrated by numerical experiments on realistic designs

Compact active duplexer based on CSRR and interdigital loaded microstrip coupled lines for LTE application

In this paper, a four-port compact active duplexer based on a complimentary split ring resonator (CSRR) and interdigital loaded microstrip coupled lines (CSRR-IL MCL) is presented. Interdigital capacitor is used on the top layer of the proposed structure and CSRR transmission lines are used on the bottom layer of the coupled lines in order to increase the coupling of the proposed circuit and create triple band resonances, respectively. The proposed active duplexer has one input port and three output ports operating in three distinct operation frequencies which are 1.4 GHz, 1.8 GHz, and 3.2 GHz. The active duplexer is designed to target LTE applications which are prevalent among the new technologies and devices. The input signal is split in terms of frequency into the three designed frequencies and is amplified by 13 dB gain of the amplifiers placed at the output ports. The fractional bandwidths of the proposed structure at 1.4 GHz, 1.8 GHz, and 3.2 GHz are 5.2%, 2.8%, and 9.4%, respectively. It is worth mentioning that the size of the proposed active duplexer is 0.29λ0 × 0.38λ0. The design guide of the proposed structure is presented, and it will be shown that the simulation as well as the measurement results of the proposed active duplexer have an acceptable agreement with each other. It should be noted that the VSWR of the proposed structure is less than 1.5 which means that the active duplexer has low return loss, and it is the plus point of it

The impact of social media in business growth and performance: A scientometrics analysis

The purpose of this research is to investigate the status and the evolution of the scientific studies on the applications of social media in the business. The present research is an applied scientific method based on quantitative approach by using library method and scientometrics indicators. With the use of bibliometric library of R software, scientific products in the field of social media applications in business from 2005 to the end of January 2019, the study overviews trends and achievements of this field. The results show that from the beginning of 2005 through January 2019, 2682 articles have been indexed in Web of Science in the field of social media and business; however, since 2009, scientific productions in this topic have grown rapidly and in 2017, there was a substantial increase in the number of studies. The findings also show that the United States with 1269 published articles and the Business Horizons Magazine with the publication of 73 articles, pioneered in the publications of this topic. Analyzing the content of the works produced in the applications of the social media and businesses can help us better understand the growth trend in this area

Signal and noise properties of TWFETs (model, concept, and potential)

We report mm-wave signal and noise performance of a TWFET (Traveling-Wave FET). For the first time a CAD model (with possibility of including temperature dependence) for simultaneous signal and noise performance determination, based on coupled modes theory and full semidistributed modeling [4], is here proposed

Linearity improvement of a dual-band Doherty power amplifier using E-CRLH transmission line

A dual-band Doherty power amplifier (DB-DPA) using the extended composite right and left handed transmission lines (E-CRLH TL) is proposed. In this structure the λ/4 transmission lines are replaced with open-ended E-CRLH TL. The power amplifier exhibits dual-band property at f1=2.5GHz, f2=3.4GHz input frequencies and suppresses the second harmonics (2f1, 2f2) at the amplifier output. The simulation studies show that the second harmonic and second order intermodulation (IM2) of the proposed DB-DPA are improved compare to the conventional DPA. This improvement is obtained because of the quad band property of E-CRLH transmission lines. Then, the proposed DB-DPA is examined using various multi tones signals. The better ACPR and efficiency are achieved compare to the conventional Doherty power amplifiers. The measurement results confirm the accuracy of the simulation results

A linearity improved quad-band amplifier based on E-CRLH

This paper outlines a new class of quad-band amplifier (QBA) realized using extended composite right- and left-handed coupled lines. The design procedure to reach the QB CLs with predefined frequency operations and characteristic impedance of their ports is clearly presented. Designed and fabricated QBA operation frequencies are fb1 = 2.9 GHz and fb2 = 4.3 GHz (output port B) ff1 = 3.8 GHz and ff2 = 5 GHz (output port C) and the proposed structure exhibits a matching (-10 dB) bandwidth of over 300 MHz in each operation frequency bands. In addition, the insertion loss is smaller than 1 dB. The length and the width of the proposed QBA are approximately 7.7 and 2.4 cm, respectively. To further demonstrate the idea, a QBA is successfully designed and fabricated. The simulated and measured results of the proposed QBA are presented to verify the proposed idea