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A compact two‐element multiple‐input‐multiple‐output (MIMO) antenna system with improved impedance matching and isolation is presented for future sub‐6 GHz 5G applications. The two identical tapered microstrip line fed modified rhombus‐shaped radiating elements are placed in the same orientation at a compact substrate area of 0.24λ0 × 0.42λ0 (where, λ0 at 3.6 GHz) on a shared rectangular ground. A remodeled T‐shaped ground stub is placed between a pair of radiating element to achieve improved impedance bandwidth and isolation. Further, a split U‐shaped stub connected to center of each radiating element to achieve the desired resonant frequency of 3.6 GHz. The proposed antenna covers a −10 dB operating band of 3.34 to 3.87 GHz (530 MHz) with more than 20 dB isolation between a pair of elements. MIMO performances are also analyzed and experimentally validated. The measured performances of a prototype are found in good agreement with simulated performances. Further, the simulation study is carried out to see the effect of housing and extended ground plane on two‐element MIMO antenna for practical application. An idea of realization of 12‐element MIMO is also studied using the proposed two‐element MIMO antenna. [ABSTRACT FROM AUTHOR]

Abstract: A compact lowpass filter (LPF) with wide stopband which uses four non‐uniform cascaded defected ground structure (DGS) units along with a 50 Ω microstrip line is reported in this article. Each DGS unit, which consists of a combination of three isosceles U‐shaped DGSs is analyzed in terms of an equivalent RLC circuit model. Every DGS of the DGS unit along with microstrip line provides one attenuation pole. It is found through performance comparison of the proposed U‐shaped DGS with dumbbell‐ and fork‐shaped DGSs that the proposed U‐shaped DGS is compact and provides higher quality factor. Further, the modeling of the proposed LPF is carried out using equivalent RLC circuit model. The results obtained through numerical and circuit simulations are compared. The proposed LPF has size of 14.44 mm × 3.4 mm, 3‐dB cut‐off frequency of 14.2 GHz, and greater than 40 dB and 22 dB stopband rejection up to 21.8 GHz and 30 GHz respectively. The proposed LPF is fabricated and experimentally tested. The experimental results are nearly in agreement with corresponding numerical/circuit simulation results. [ABSTRACT FROM AUTHOR]

A super-compact ultra-wideband (UWB) microstrip band-pass filter (BPF) with good selectivity and wide stopband is proposed in this paper. The super-compactness along with wide stopband of the proposed filter is achieved by integrating modified multimode resonator-based UWB BPF and defected ground structure (DGS)-based compact low-pass filter (LPF). The LPF structure is designed using four non-uniform configurations of DGS units along with a 50 Ω microstrip line. Each DGS unit is formed by cascading three isosceles U-shaped DGSs. Further, an equivalent RLC circuit model of the LPF is proposed to validate the numerical simulation and experimental results of LPF. The proposed filter has simulated passband frequency range 3-11 GHz with wide stopband: attenuation better than 40 dB and 25 dB over the frequency ranges 11.7-20.5 GHz and 11.2-30 GHz respectively. The experimental results for the proposed filter are nearly in agreement with corresponding numerical simulation results. [ABSTRACT FROM AUTHOR]