Design and fabrication of a miniaturized lowpass-bandpass diplexer with wide tuning range and high isolation

ABSTRACT

In this article, a compact lowpass-bandpass (LP-BP) diplexer with high isolation for wireless telecommunication applications is presented. The −3 dB cut-off frequency of the lowpass filter (LPF) is equal to 1 GHz. The roll-off-rate (ROF or ζ) parameter is sharp and equal to 108.8 dB/GHz, and the rejection level in the stopband is 20 dB. The center frequency of bandpass filter (BPF) is 2.4 GHz. The tuning range of −3 dB cut-off frequency of the LPF is wide and ranges from 0.3 to 0.89 GHz. The tuning range of center frequency of the BPF is wide and ranges from 2.65 to 3.1 GHz. The obtained isolation between the two output ports is better than 30 dB. The proposed tunable LP-BP diplexer is designed, simulated, fabricated and measured. The results of measurement and simulation are in good agreement with each other. The proposed diplexer has a compact size of 64 × 38 mm².

KEYWORDS:

• Lowpass filter (LPF)
• bandpass filter (BPF)
• diplexer
• tunable
• isolation

ORCID

Gholamhosein Moloudian http://orcid.org/0000-0001-7825-9408

Additional information

Notes on contributors

Sadegh Rayatzadeh

Sadegh Rayatzadeh was born in Aghajari, Iran in 1987. He received the associate’s degree in Electrical from Technical and Vocational University of Noorabad, the BSc degree in Electrical Engineering from Islamic Azad University of Behbahan and the M.Sc. degree in Electronics from Islamic Azad University of Behbahan, all in Electrical Engineering in 2008, 2014 and 2019, respectively. In 2013, he joined to department of Electronics Engineering at Aghajari Oil and Gas Production Company (AOGPC) and now he is an Electronics Engineer. His research interests include design and analysis of RF and microwave circuits.

Gholamhosein Moloudian

Gholamhosein Moloudian was born in Kazerun, IRAN in 1988. He received his associate’s degree in Electronics from Technical and Vocational University of Yasouj, the BSc degree in Electronics from Higher Education Center of Shiraz, the MSc degree in Electronics from Islamic Azad University of Bushehr, and the PhD degree in Electronics from Islamic Azad University of Arak, all in Electrical Engineering with highest honors, in 2008, 2010, 2012, and 2018, respectively. He is currently working with the Department of Electrical Engineering at Salman Farsi University of Kazerun as a lecturer and researcher. His research interests include design and analysis of RF/microwave circuits and MEMS sensors.