Novel planar balanced bandpass filter with wideband common‐mode suppression and in‐band common‐mode noise absorption

Abstract

This paper presents a novel planar balanced bandpass filter (BPF) with wideband common mode (CM) noise suppression and in-band CM noise absorption using coupled lines (CLs) with short-circuited stubs to realize high selectivity and wideband differential mode (DM) filtering performance. Two one-quarter wavelength stubs loaded with grounded resistors are introduced to realize wideband CM noise suppression. Thus, CM noise can be suppressed under a certain level at all frequencies. Four resistors are used to achieve CM noise absorption by dissipating the CM noise into heat, which can avoid the noise being reflected to the communication system and realize a wide absorption bandwidth with 90% absorption efficiency. For demonstration, an absorptive balanced BPF operating at 3.5 GHz with wide 3-dB fractional bandwidth (FBW) of 79.43% is fabricated and experimentally validated. It is worth noted that the absorptive balanced BPF can realize broadband CM noise suppression from 0 to 8 GHz, and the CM noise is well absorbed more than 10 dB from 2.41 to 4.63 GHz. Besides, wideband CM noise absorption with 90% efficiency from 2.51 to 4.60 GHz is realized, which indicates potential applications in improving the performance of the balanced radio frequency (RF) circuits. Good agreements between the simulated and measured results are observed.

Balanced Microwave Transmission Lines, Circuits, and Sensors

“…To end this section devoted to balanced filters, let us mention that a significant effort has been dedicated recently to the implementation of reflection-less structures, where either the common-mode (in the differential mode passband) or the differential mode (outside the differential-mode passband), or both modes simultaneously, are absorbed [92], [130], [172], [188], [189], [190], [191], [192], [193], [194], [195], [196]. Many different strategies for absorbing the common and/or the differential mode in the required frequency bands have been reported.…”

A novel balanced‐to‐unbalanced negative group delay power divider with good common‐mode suppression

“…The impact of additive noise on the system, including environmental noise and interference between the transmission signals, will also be increased. The interference signal and environmental noise can be effectively removed by the balanced device, such as balanced filters, [1][2][3] balanced power dividers, [4][5][6] and balanced couplers. 7 The balanced-to-unbalanced (BTU) components can realize the conversion from the balanced port to the unbalanced port.…”

A Novel Balanced-to-balanced Differential-mode Negative Group Delay Microwave Circuit with Excellent Common-mode Suppression

“…When developing today's increasingly complex microwave circuits and systems, engineers must contend with two issues: common-mode noise and signal crosstalk [1]. Balanced circuits can offer considerable immunity to environmental noise and broadband common-mode suppression (CMS) capability in comparison to conventional single-ended circuits [2]. Therefore, balanced microwave devices, such as the balanced power divider [3], balanced duplexer [4], and balanced coupler [5], have been widely adopted.…”