Nikolina Jankovic

Compact Tri-Band Bandpass and Bandstop Filters Based on Hilbert-Fork Resonators

In this work, a multi-mode Hilbert-fork resonator consisting of two dual-mode resonators is presented. The behavior of the proposed configuration is analyzed in detail. To demonstrate the potential of the proposed resonator, tri-band bandpass and bandstop filters operating at 2.4/3.5/5.2 GHz have been designed, fabricated and measured. Both filters are characterized by good performances and very compact size of only 0.21λ<i>g</i> × 0.11λ<i>g</i> and 0.22λ<i>g</i> × 0.1λ<i>g</i> , respectively.

A Microwave Microfluidic Sensor Based on a Dual-Mode Resonator for Dual-Sensing Applications

In this paper, we propose a novel microwave microfluidic sensor with dual-sensing capability. The sensor is based on a dual-mode resonator that consists of a folded microstrip line loaded with interdigital lines and a stub at the plane of symmetry. Due to the specific configuration, the resonator exhibits two entirely independent resonant modes, which allows simultaneous sensing of two fluids using a resonance shift method. The sensor is designed in a multilayer configuration with the proposed resonator and two separated microfluidic channels—one intertwined with the interdigital lines and the other positioned below the stub. The circuit has been fabricated using low-temperature co-fired ceramics technology and its performance was verified through the measurement of its responses for different fluids in the microfluidic channels. The results confirm the dual-sensing capability with zero mutual influence as well as good overall performance. Besides an excellent potential for dual-sensing applications, the proposed sensor is a good candidate for application in mixing fluids and cell counting.

Compact tri-band bandpass filter based on quarter-wavelength resonators

In this work, a planar microstrip tri-band filter based on quarter-wavelength resonators is presented, which allows independent control of the positions of all three passbands. Furthermore, the topology of the filter provides five transmission zeros and thus results in a highly selective response in all passbands. A synthesis procedure of the filter is presented and used to design a tri-band filter which operates at WLAN frequencies of 2.4/3.5/5.2 GHz. The designed filter outperforms all other state-of-the-art tri-band filters in terms of compact size, high selectivity and transmission, and return-loss characteristics.

Multiple Fano-Like MIM Plasmonic Structure Based on Triangular Resonator for Refractive Index Sensing

In this paper, we present a Fano metal-insulator-metal (MIM) structure based on an isosceles triangular cavity resonator for refractive index sensing applications. Due to the specific feeding scheme and asymmetry introduced in the triangular cavity, the resonator exhibits four sharp Fano-like resonances. The behavior of the structure is analyzed in detail and its sensing capabilities demonstrated through the responses for various refractive indices. The results show that the sensor has very good sensitivity and maximal figure of merit (FOM) value of 3.2 × 105. In comparison to other similar sensors, the proposed one has comparable sensitivity and significantly higher FOM, which clearly demonstrates its high sensing potential.

Balanced bandpass filter based on square patch resonators

This paper proposes a novel balanced bandpass filter that consists of square patch resonators with rectangular slots. The behaviour of the square patch resonator is analysed in detail and its ability for application in balanced filters is discussed. A bandpass balanced filter operating at 1.8 GHz has been designed. The filter is characterized by a simple design procedure, excellent passband performance, and common-mode rejection below 30 dB in the passband.

A compact wideband filter based on a grounded transversal resonator

In this work, a grounded transversal resonator is presented which exhibits tri-mode behaviour and provides two transmission zeros. The proposed resonator is analyzed and used to design a very compact low-loss wideband bandpass filter with a central frequency of 4 GHz. The fabricated filter exhibits 3-dB fractional bandwidth of 83.5%, good in-band and out-of-band performances and a compact size of only 0.29λ_g × 0.19λ_g, where λ_g denotes the guided wavelength on the given substrate at the central frequency.

Mu-near-zero propagation in quasi-TEM microstrip circuits

This paper presents the theoretical analysis and experimental demonstration of mu-near-zero (MNZ) propagation in quasi-TEM microstrip circuits achieved by using metamaterials of the resonant type. We show that two frequencies exist which may support MNZ propagation and how the actual operating of MNZ frequency depends on the properties of the host. The phenomena of MNZ propagation is then used to propose an entirely new class of MNZ bandpass filters characterized by significantly reduced variation of group delay in comparison to conventional solutions.

Novel Dual-band Band-Pass Filters Based on Surface Plasmon Polariton-like Propagation Induced by Structural Dispersion of Substrate Integrated Waveguide

In this paper, we present two novel dual-band bandpass filters based on surface plasmon polariton-like (SPP-like) propagation induced by structural dispersion of substrate integrated waveguide (SIW). Both filters are realized as a three-layer SIW where each layer represents a sub-SIW structure with intrinsic effective permittivity that depends on its width and filling dielectric material. The layers are designed to have effective permittivities of opposite signs in certain frequency ranges, which enables SPP-like propagation to occur at their interfaces. Since three layers can provide two distinct SPP-like propagations, the filters exhibit dual-band behaviour. A detailed theoretical and numerical analysis and numerical optimization have been used to design the filters, which were afterwards fabricated using standard printed circuit board technology. The independent choice of geometrical parameters of sub-SIWs and/or the corresponding dielectric materials provide a great freedom to arbitrarily position the passbands in the spectrum, which is a significant advantage of the proposed filters. At the same time, they meet the requirements for low-cost low-profile configuration since they are realized as SIW structures, as well as for excellent in-band characteristics and selectivity which is confirmed by the measurement results.

High-Resolution Plasmonic Filter and Refractive Index Sensor Based on Perturbed Square Cavity with Slits and Orthogonal Feeding Scheme

We present a plasmonic bandpass filter and refractive index sensor based on perturbed square cavity resonator with slits, which is fed by orthogonally oriented feeding waveguides. The slits provide size reduction in comparison to conventional square cavities and better coupling to the waveguides, while the perturbation and orthogonal feeding scheme provide a pair of transmission zeros in the response of the structure. In that manner, a bandpass filter with high transmission, narrow bandwidth, and excellent selectivity can be readily designed. Moreover, with a slight modification of the structure, a very sharp Fano-like response can be obtained and employed for refractive index sensing with high sensitivity and figure of merit.

Microstrip-Ridge Gap Waveguide Filter Based on Cavity Resonators With Mushroom Inclusions

In this paper, we propose a novel microstrip-ridge gap waveguide (MS-RGW) filter configuration, which is based on cavity resonators with mushroom inclusions. The resonators are realized as defects in surrounding mushroom-based perfect magnetic conductor (PMC), and thus, the filter configuration does not require additional conductive layers nor rearrangement of the PMC elements. The hosting MS-RGW is fed through transition from SMA to microstrip ridge, enabling simple fabrication and excellent impedance matching in a wide frequency range. To demonstrate the potential of the proposed structure, four narrowband filters have been designed, fabricated, and measured. The filters exhibit excellent in-band characteristics and small dimensions.