Design of a miniature dual-band bandpass filter with interlocked stepped-impedance resonators for 5G new radio access technology

Abstract

AbstractA miniature dual-band bandpass filter with interlocked stepped-impedance resonators (SIRs) is presented in this paper, which was designed for the student design competition held in European Microwave Week 2019. This bandpass filter is required to have two concurrent passbands, namely, the first passband at 900–1000 MHz and the second passband at 1427–1518 MHz bands, which cover six designated bands in sub-6 GHz range of fifth generation (5G) New Radio Access Technology. Three stopbands are required at 500–850, 1050–1350, and 1600–2000 MHz, respectively. To achieve the best figure of merit, an interlocked configuration of two SIRs is proposed. One advantage is that the impedance ratio of the inter-locked SIR can be controlled to have two passbands at the required frequencies. Second, the coupling section of the interlocked SIR gives three transmission zeros distributed to every stopbands such that the stopband suppression are dramatically enhanced. The measured results show that the passband insertion losses are 2.16 dB at the first passband and 1.33 dB at the second passband, and the return losses are greater than 10 dB. The stopband suppression at the transmission zeros are greater than 38 dB. The circuit is very compact as 41.40 × 19.96 mm2, equivalent to $0.25 \times 0.12\,\lambda _g^2$.