Farzin Shama

This paper presents the design and fabrication of a novel suppressing cell (SC) implemented on a RO4003 substrate for microwave circuit applications. Experimental results indicate that the SC functions as a low-pass filter (LPF) with a 3 dB cutoff frequency at 5.7 GHz and a transition band of 0.6 GHz from −3 dB to −20 dB. The design achieves an ultra-wide stopband from 6.3 GHz to 50 GHz, with significant attenuation noted in the S22 parameter around 38 GHz, effectively covering five harmonics of the cutoff frequency. The return loss in the passband is measured at 10 dB, with an insertion loss of just 0.5 dB at 1.3 GHz. Additionally, the size of the SC is compact at 15.3 mm × 10.5 mm (15.3 λg × 10.5 λg), and the group delay in the passband exhibits minimal variation, recorded at only 0.53 ns.

This study presents an innovative approach to the design of an optical analog‐to‐digital converter (OADC) that employs square nonlinear ring resonators. The configuration consists of dielectric silicon rods alongside nonlinear rods fabricated from doped glass, utilizing the Kerr optical effect to realize the intended operational capabilities. The proposed architecture incorporates a nonlinear three‐channel demultiplexer along with an optical encoder. The nonlinear demultiplexer transforms the continuous input signal into three distinct quantized levels, while the optical encoder produces two‐bit binary codes corresponding to the demultiplexer's output channel. The performance of this optical analog‐to‐digital converter (OADC) has been evaluated through plane wave expansion (PWE) and finite difference time domain (FDTD) methodologies. Results demonstrate that the OADC exhibits a compact footprint of 324 µm² and achieves a sampling rate of 125 GS/s, significantly exceeding the capabilities of traditional analog‐to‐digital converter designs.

This study presents the design and implementation of a miniaturized suppressing cell (MSC) functioning as a low‐pass filter (LPF) utilizing an interdigital shaped resonator. The MSC is engineered to effectively control harmonics in power amplifiers (PAs), particularly in applications for next‐generation 5G systems. The LPF achieves a cut‐off frequency of 2.21 GHz, demonstrating a sharp transition region spanning 0.6 GHz, where the attenuation transitions from −3 to −40 dB. Notably, the filter exhibits an ultra‐extended rejection bandwidth, maintaining at least −20 dB from 2.8 to 29.17 GHz. The measured flat group delay further confirms the excellent passband performance of this LPF, indicating minimal signal distortion. Given the critical role of harmonic control circuits (HCCs) in enhancing the efficiency and linearity of various PA classes, including class‐F and class‐F ⁻¹ configuration, the proposed MSC serves as a vital component in HCC designs. This advancement not only contributes to improved performance in PAs but also supports the demands of modern wireless communication systems, reinforcing the MSC's significance in high‐frequency applications.

Ultra-wideband (UWB) applications require low-power and low-noise amplifiers (LNAs) that can operate over a wide frequency range. However, conventional LNAs often suffer from poor linearity and high-power consumption. This research work proposes a novel LNA design that uses the adjusted derivative superposition (DS) technique and feedback to improve the linearity and reduce the power consumption of UWB LNAs. The DS technique enhances the third-order intermodulation (IM3) cancellation by adjusting the bias currents of the transistors, whereas the feedback improves the stability and input matching of the LNA. The LNA is implemented using a degenerated common source topology in a 180 nm standard CMOS technology. The simulation results show that the LNA achieves a power gain of 10–12.2 dB, an input third-order intercept point (IIP3) of about 12 dBm, and a noise figure of less than 2.5 dB over the UWB frequency band of 3.1–10.6 GHz. The input reflection coefficient is less than -10 dB, and the power consumption is 11.6 mW with a 1.5 V power supply. The designed LNA offers a novel and innovative solution for UWB applications that significantly improve the performance and efficiency of UWB LNAs whereas reducing the cost and complexity of implementation.

A miniaturized microstrip low‐pass filter (LPF) has been designed and fabricated using semicircular‐shaped resonators. The designing procedures as well as the LC equivalent circuit of each step have been reported. Due to the small size of the presented filter, flat group delay in the pass‐band, low insertion loss (IL), and high return loss (RL) in operational frequency. By producing adjusted transmission zeros (T_Zs), the second to fourth unwanted harmonics were attenuated using the proposed LPF. The machine learning approach has been utilized to adjustment of the filter parameters. The 3 dB cut‐off frequency (F_c), T_Zs, IL, and RL were predicted using the group method of data handling neural network (GMDHNN). Ninety simulations were performed with different inductor and capacitor values. The collected data were used for neural network training. The GMDHNN can diagnose the efficient inputs, so this feature was applied to determine the efficient L and C elements on T_Zs, F_c, IL, and RL. Finally, the fabricated filter results are well‐matched with the simulation ones. IL and RL of the suggested filter in operational frequency are −0.09 and −17.26 dB, respectively. The total filter size is only 14.65 mm × 3.5 mm.

A new structure of microstrip-based low-pass filter with wide stopband and sharp roll-off is introduced, in this paper. In the proposed topology, resonators with T and modified L Shapes have been used. To improve the suppression factor and relative stopband bandwidth, the second resonator has been added to the first resonator. The designed filter has been fabricated on a 20 mm thickness RO4003 substrate, which has a loss tangent of 0.0021 and a relative dielectric constant equal to 3.38. All parameters including roll of rate, stopband, bandwidth, return loss, insertion loss, and figure of merit have significant coefficients. Simulation has been ran using advanced design system software. The 3dB cutoff frequency is appropriate. The value of the insertion loss parameter is <0.1 dB and the S11 parameter is −22 dB at this point. The stopband is extended from 2.42 up to 24 GHz, which shows an ultra-stopband. The results of the simulation and experiment are almost similar, which indicates a proper performance of the designed structure.

In the present study, a new miniaturizing method has been applied to design a very compact Gysel power divider with n^th harmonics elimination. The designed power divider has perfect harmonics suppression with excellent isolation, high return loss, and low insertion loss. Moreover, a lowpass filter has high proficiency. It has been located in place of the original transmission lines a λ/4. The observed outcomes of the lowpass filter show that the use of this filter suppressed the extra harmonics and has decreased the size of the circuit power divider. Moreover, LC equivalent circuits of all steps are illustrated. The circuit of the power divider can be studied via the odd and even mode method. This proposed Gysel power divider worked at the center frequency of 1 GHz. The proposed Gysel power divider is manufactured and measured for verification. The measured outcomes display excellent settlement by the simulated results. The maximum insertion loss, |S11|, |S22|, and |S23|, are 3.11, 24.6, 17, and 14.5 dB, respectively.

This paper aims to design and fabricate a class-F⁻¹ power amplifier (PA) to act at 2.4 GHz frequency with high power-added efficiency (PAE). For this purpose, a harmonic control network is introduced, which consists of three parts: a harmonic control circuit, a transistor bias circuit, and a suppression circuit. Each part of the harmonic control network is individually designed and finally, they were optimized together in the final amplifier circuit. The fabricated PA results mimic the simulation one. The presented PA has functional specifications like high PAE, the ability to control the second and third harmonics, and a low drain voltage supply of 2.2 V. Due to these excellent features, this PA is suitable for wireless applications.

In this paper, a bandpass filter (BPF) has been designed using bent and coupled-line structure. The design process of the filter to achieve a BPF with good characteristics is completely explained. Therefore the LC equivalent circuit of The BPF is presented as the analytical description. The proposed filter can pass frequencies between 2.2 and 3.6 GHz with an insertion loss <0.4 dB, which is suitable for wireless applications. The fractional bandwidths (FBW) of the filter is about 48%. Some characteristics such as small size, low insertion loss, high return loss wide upper stopband bandwidth, and good suppression level in stopband are among the advantages of this study to be mentioned. Finally, the presented filter was fabricated, and the measured results have a proper agreement with the simulation results.