Zig-Zag Monofilar Spiral Shaped CRLH TL Based Compact Lowpass mono-/duo-/tri-/quad-bandpass Filter

ABSTRACT

Planar compact lowpass mono-/duo-/tri-/quad-bandpass filters design based on CRLH TL are presented. Filters are designed by cascading two unit-cells composed of Zig-Zag monofilar spiral lines (ZZMSL) and Zig-Zag open ring (ZZOR) loaded on the main transmission line. Only the length of ZZMSL which is housed within the fixed length of ZZOR is utilized to generate the multiple passbands, so all of the filters are of the same size. At the lowpass (LP) band of the filter’s −3 dB cut-off frequency of 0.71 GHz, the filter’s footprint area (excluding the feed line), is 0.083 λ_g  × 0.034 ${\lambda }_g$. The LP band's measured −3 dB cut-off frequency is 0.71 GHz, with a minimal in-band insertion loss of 0.22 dB and a return loss better than 20 dB from DC to 0.46 GHz. The measured center frequencies for four bandpass passbands are 1.3, 2.08, 3.37, and 4.6 GHz, with a −3 dB FBW of 76.15%, 10.57%, 8.6%, and 7.8%, respectively. The minimal insertion losses within the BPs are 0.26, 0.26, 0.39, and 0.4 dB, respectively, whereas the return losses are 33, 36, 19, and 37 dB. Lower in-band insertion loss, good band-to-band isolation, the controllable center frequency with good out-of-band skirts, higher compactness, and lower circuit complexity are all advantages of the proposed lowpass quad-bandpass filter. The Lowpass quad-bandpass filter is finally manufactured. A good agreement between electromagnetic simulation, circuit model simulation, and experimental measurement results validates the design process and filter performance.

KEYWORDS:

• CRLH TL
• Filter
• Lowpass quad-bandpass
• Monofilar spiral

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Abhishek Kumar

Abhishek Kumar is currently pursuing his PhD as a research fellow in Department of ECE from the Birla Institute of Technology, Mesra, Ranchi, India. He completed his ME degree in wireless communication from Department of ECE, Birla Institute of Technology, Mesra, Ranchi, in 2015. His research interests include design and development of microwave circuits using left-handed metamaterials for wireless communication systems.

Dileep Kumar Upadhyay

Dileep Kumar Upadhyay is currently working as an assistant professor in Department of ECE, Birla Institute of Technology, Mesra, Ranchi since August 2007. He received his BTech degree in electronics and communication engineering in 2005 from Uttar Pradesh Technical University, Lucknow and completed his ME degree in wireless communication from Department of ECE, Birla Institute of Technology, Mesra, Ranchi, in 2007. He received his PhD degree in March, 2014 from Department of ECE, Birla Institute of Technology, Mesra, Ranchi. His current research interests include RF circuit design, metamaterial, DRA, defected ground plane and fractal geometry-based microwave circuits. E-mail: [email protected]