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ISSN: 1937-8718

Vol. 112

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2021-04-19 PIER C Vol. 112, 45-54, 2021. doi:10.2528/PIERC21032102

An Analysis of High Selectivity and Harmonic Suppression Based on Stepped-Impedance Resonator Structure for Dual-Mode Diplexer

Jessada Konpang and Natchayathorn Wattikornsirikul

A high selectivity microstrip dual-mode diplexer with a stepped-impedance opened-end structure is implemented to reduce the size of a dual-mode resonator and suppress the harmonics. The proposed dual-mode resonator structure consists of a microstrip half-wavelength resonator and an open-circuited stepped-impedance stub. The stepped-impedance opened-end structure can control an even mode in the upper and lower desired bands to improve the cutoff responses. The sharp cutoff selectivity of the filter is created to improve the diplexer performance and wide suppress harmonics. The dual-mode diplexer prototype is analyzed, fabricated, and measured. The measured result agrees well with the analyzed result. The simulated and measured dual-mode diplexers are designed at the operational frequency of Tx/Rx at 1.95 GHz and 2.14 GHz, respectively. It is shown that the dual-mode filter has a wide stopband, including the first spurious resonance frequency due to the stepped-impedance stub.

2021-04-16 PIER C Vol. 112, 35-44, 2021. doi:10.2528/PIERC21031404

A New Reflectionless Filter Composed of Discharging Circuit

Aixia Yuan, Shao-Jun Fang, Ying Wang, Yu Lin Feng, and Tielin Zhang

A new reflectionless filter with discharging circuit is presented. Under the premise of keeping the original filter unchanged, a discharging circuit is added. The relationship between the passband and stopband of the discharging circuit and the original filter is similar to the duality of the circuit. Without affecting the performance of the original filter, the reflected energy of the original filter is discharged to the ground through discharging circuit, so as to achieve no reflection of the filter, avoiding the interference to the input. Analytical design equations are provided so that the reflectionless filter can be designed. According to this design method, the reflectionless dual-band bandpass filter is designed and fabricated. Simulation and measurement results are in agreement. It has good reflectionless performance. The feasibility of the design method is verified.

2021-04-13 PIER C Vol. 112, 21-34, 2021. doi:10.2528/PIERC21021002

Simultaneous Measurement of Temperature and Strain Using Multi-Core Fiber Within-Line Cascaded Symmetrical Ellipsoidal Fiber Balls-Based Mach-Zehnder Interferometer Structure

Farhan Mumtaz, Hongfeng Lin, Yutang Dai, Wenbin Hu, Muhammad Aqueel Ashraf, Lashari Ghulam Abbas, Shu Cheng, and Pu Cheng

Simultaneous measurement of temperature and strain using multi-core fiber (MCF) with an in-line cascaded symmetrical ellipsoidal fiber balls structure of Mach-Zehnder interferometer (MZI) is presented. The sensor is fabricated by using an ordinary fusion apparatus. The thermo-coupling effect is realized through Germanium (Ge)-doped central and hexagonal distributed outer cores of MCF. A high-quality transmission spectrum is obtained with a fringe visibility of 12-15 dB and higher extinction ratio. The sensor exhibits superior mechanical strength compared with the fragile structures, such as tapered, etched, misaligned and offset fibers. The temperature sensitivity of 137.6 pm/°C and 68.1 pm/°C in the range of 20-90°C, and the strain sensitivity of -0.42 pm/με and -1.19 pm/με in the range of 0-801 με are obtained, when probe ``L'' is 40 mm and 20 mm, respectively. Simultaneous measurement of temperature and strain can be achieved by solving the coefficient matrix and tracing the wavelength shifts in the interference spectrum. Besides, the sensor has many advantages, such as high sensitivity, easy fabrication, simple structure, being stable and inexpensive, which may find potential applications in the field of optical sensing.

2021-04-11 PIER C Vol. 112, 11-20, 2021. doi:10.2528/PIERC21030408

Dual-Band Subharmonic Mixer for WiFi Application with Improved Conversion Loss and RF-to-IF Isolation

Kumari Pushpa and Jayanta Ghosh

A dual-band subharmonic mixer that employs both the second and fourth harmonics of a local oscillator signal in the mixing process is demonstrated for WIFI application. The design results in a simple and cost-effective mixer as it requires only one local oscillator (LO). A quarter-wave stepped impedance stub has been used to suppress both bands of radio frequency (RF) signal. The proposed dual-band subharmonic mixer is designed for two RF bands with the center frequencies at 2.45 GHz and 5 GHz using a single LO frequency at 1.3 GHz. For mixing purpose, the second and fourth harmonics of LO are utilized. Experimental measurements show high port-to-port isolation and achieve minimum conversion losses of 6.87 dB and 10.0 dB at 2.59 GHz and 5 GHz, respectively. The 3-dB RF bandwidth is 2.3 to 2.95 GHz for the second harmonic and 4.8 to 5.5 GHz for the fourth harmonic of LO signal. The input P1-dB compression points for two modes of the mixer are -9 dBm and -5 dBm, respectively. The RF-to-IF isolations are more than 18 dB (maximum 36 dB) and 20 dB (maximum 33 dB), over both the RF bands.