Propagation Of Evanescent Modes Research Articles

Compact HMSIW diplexer loaded with modified circular complementary split ring resonators for WiMAX /WLAN applications

The paper presents a miniaturized diplexer based on a half mode substrate integrated waveguide (HMSIW) loaded with a novel metamaterial unit cell. The proposed diplexer is implemented by cascading two HMSIW bandpass filters loaded with modified circular complementary split-ring resonators (MC-CSRRs) operating at distinct frequencies. The working principle behind the operation of diplexer is the theory of evanescent mode propagation that aids in the miniaturization of the diplexer in addition to the 50 % size reduction contributed by the HMSIW. The performance of the diplexer is investigated by varying the substrate thickness and substrate material. To authenticate the proposed idea, the diplexer operating at 3.5/5.8 GHz is designed using the full-wave simulator, fabricated and experimentally measured. The proposed diplexer yields the advantages of low insertion loss, smaller footprint, reasonable isolation and individual control of operating frequencies. A second-order diplexer is designed and simulated that results in improved isolation and selectivity.

Design and implementation of compact tri- and quad-band SIW power divider using modified circular complementary split-ring resonators

AbstractThis paper presents a miniaturized tri- and quad-band power divider (PD)based on substrate integrated waveguide (SIW). By adopting different types of modified circular complementary split-ring resonators on the top surface of SIW, multiple passbands are generated propagating below the SIW cut-off frequency. The working principle is based on evanescent mode propagation that decreases the operating frequency of the PD and helps in the miniaturization of the proposed structure. The operating frequency of the proposed PD can be individually controlled by changing the dimensions of the resonator. To verify the proposed concept, a tri-band and a quad-band PD exhibiting 3 dB equal power division at 2.41/3.46/4.65 GHz and 2.42/3.78/4.74/5.8 GHz are designed using the full-wave simulator, validated through circuit model, fabricated and experimentally verified. The measured results agree well with the simulations. The proposed PDs have good performance in terms of reasonable insertion loss, isolation, minimum amplitude and phase imbalance, smaller footprint, easy fabrication and integration. The size of the fabricated prototype is 18.3 mm × 8.4 mm, which corresponds to 0.205λg × 0.094λg, λg being the guided wavelength at the first operating frequency.

Highly Miniaturized Dual-band Power Divider based on HMSIW for 5G/ WLAN Applications

A highly compact dual-band power divider (PD) based on the HMSIW structure is investigated in this paper. The dual-band operation is achieved by incorporating an inner modified circular complementary split-ring resonator (MC-CSRR) and outer circular CSRR on the top metal layer of HMSIW. The operating frequency of the PD decreases due to evanescent mode propagation. This assists in miniaturizing the structure apart from the 50% size reduction offered by the HMSIW. By asymmetric placement of two output ports of a PD, it is possible to achieve an unequal PD with an arbitrary power division ratio. To exhibit the proposed idea, two dual-band PD prototypes, one with equal power division and the other with unequal power division are designed, fabricated and experimentally verified. The PD occupies a compact size of 0.128 λg× 0.122 λg, where λg being the guided wavelength at the first operating frequency. The proposed PD with advantages of lower insertion loss, better return loss, minimum amplitude and phase imbalance between the output ports is beneficial for 5G FR1 n78 (3.3- 3.8 GHz) and WLAN (5.17 GHz) communications.

Compact dual-band SIW filters loaded with double ring D-shaped resonators for sub-6 GHz applications

In this paper, a compact substrate integrated waveguide (SIW) based dual-band filter which utilizes the dual resonance provided by asymmetric double-ring D-shaped resonators that are incorporated on the upper metallic layer of SIW is communicated. The two passbands are generated well below the cut-off frequency of the SIW due to evanescent mode propagation. Such propagation is responsible for the substantial miniaturization of the filter as well. Two types of two-pole dual-band filters are designed that exhibit low insertion loss, wide out-of-band-rejection, compact size, easy fabrication and integration with other microwave components. To validate the proposed idea, three filter prototypes working around 2.66 and 3.54 GHz are designed, fabricated for demonstration and experimentally tested. Parametric analysis is performed to verify the dependence of filter parameters on the proposed filter prototype. Expected agreements are achieved between the experimental and simulated results. The proposed filter finds applications in the upcoming 5G sub-6 GHz communication.

Miniaturized half-mode substrate integrated waveguide diplexer based on SIR–CSRR unit-cell

A miniaturized diplexer based on half-mode substrate integrated waveguide (HMSIW) technology by loading a novel metamaterial unit-cell is proposed. The stepped-impedance resonator (SIR) technique has been used in order to miniaturize the physical size of the conventional complementary split ring resonators (CSRRs). The proposed metamaterial unit-cell, which is called SIR–CSRR, consists of two modified rings which the stepped-impedance slot lines are utilized instead of the conventional slot lines in the CSRRs. The proposed diplexer has been designed by cascading two bandpass filters with different center frequencies. The HMSIW bandpass filters are implemented by etching two SIR–CSRR unit-cells with different sizes. The design procedure is based on the theory of evanescent mode propagation which the SIR–CSRR unit-cells behave as an electric dipoles. A forward-wave passband below the intrinsic cutoff frequency of the HMSIW structure has been achieved by loading the SIR–CSRR unit-cells on the metal surface of the HMSIW structure. This proposed diplexer represent high selectivity and compact size by using of the sub-wavelength resonators. The designed diplexer has been fabricated and experimental verification have been provided. The measured results are in a good agreement with the simulated ones. The total size of the proposed diplexer is about 0.27λg × 0.11λg. The proposed diplexer show significant advantages in terms of size reduction, low loss, high selectivity, high Q-factor, easy bandpass frequency shifting, easy fabrication and, easy integration with other planar microwave circuits.

Ultracompact two‐way and four‐way SIW/HMSIW power dividers loaded by complementary split‐ring resonators

In this paper, two ultracompact power dividers based on the substrate integrated waveguide (SIW) and half-mode SIW (HMSIW) technologies loaded by complementary split-ring resonators (CSRRs) are presented. The presented structures are designed based on the theory of evanescent mode propagation. To obtain a size reduction, the CSRR unit cells are etched on the metallic surface of the SIW and HMSIW structures. First, a two-way HMSIW power divider is reported. In this circuit, the concept of HMSIW is utilized aiming at a further size reduction in addition to the size reduction by the CSRR unit cells. Then, a four-way SIW power divider is designed so that the direct coaxial feed is used for the input port and microstrip transmission lines are used for the output ports. Both two-way and four-way SIW/HMSIW power dividers at 5.8 GHz covering WLAN are designed, fabricated, and measured. They respectively have 0.18 × 0.21 λg2 and 0.38 × 0.21 λg2 total size. A fair agreement between simulated and measured results is achieved. The measured insertion losses are 0.5 ± 0.5 and 0.6 ± 0.5 dB for the two-way and four-way SIW/HMSIW power dividers, respectively, in the operating band of interest.

A novel wideband half-mode SIW bandpass filter based on evanescent-mode technique using complementary Z-shaped resonator

In this paper, a novel wideband bandpass filter using half-mode substrate integrated waveguide (HMSIW) structure loaded by complementary Z-shaped resonator (CZR) is proposed. The working principle of the proposed filter is based on the evanescent-mode propagation. The CZR unit-cell behave as a magnetic dipole, which is able to generate a backward-wave passband region below the cut-off frequency of the SIW–CZR structure. Since, the electrical size of the proposed CZR unit-cell is larger than the conventional complementary electric-LC unit-cell with the same size, therefore this unit-cell is a good candidate to miniaturize the SIW structure. As well as, the SIW filter loaded by the proposed CZR unit-cell presents a wider bandpass compared to the SIW filter loaded by the conventional resonant metamaterial unit-cells. In order to validate the ability of the proposed CZR unit-cell in size reduction and increasing bandwidth, the proposed one- and two-stage HMSIW–CZR filters have been fabricated and tested. The measured S-parameters of the fabricated filters are in a good agreement with the simulated ones. It is the first time that the CZR unit-cells were combined with the SIW structure to miniaturize the SIW structure and increase the bandwidth. The total size of the proposed two-stage filter is 0.62 λg × 0.26 λg.

Limitations in the 2D description of the electromagnetic waves propagation in thin dielectric and magnetic layers

The propagation of electromagnetic waves trapped within dielectric and magnetic layers is considered. The description within the three-dimensional theory is compared to the simplified analysis in two dimensions. Two distinct media configurations of different topology are dealt with: a plane slab and a hollow cylinder. Choosing the appropriate values for the geometrical parameters (layer thickness, radius of the cylinder) and for the electromagnetic properties of the media one can trap exactly one mode corresponding to that obtained within the two-dimensional electromagnetism. However, the symmetry between electric and magnetic fields suggests, that the two versions of the simplified electromagnetism ought to be equally considered. Its usual form is incomplete to describe all modes. It is also found that there exists a domain of optimal values of parameters for which the 2D model works relatively correctly. However, in the case of a cylindrical surface we observe several differences which may be attributed to the curvature of the layer, and which exclude the propagation of evanescent modes. The two-dimensional electrodynamics, whichever form is used, turns out still too poor to describe the so-called ‘hybrid modes’ excited in a real layer. The obtained results can be essential for proper description of the propagating waves within thin layers for which 3D approach is not available due to mathematical complexity and reducing the layer to a lower dimensional structure seems the only possible option.

Miniaturized substrate integrated waveguide filter using fractal open complementary split-ring resonators

A miniaturized substrate integrated waveguide (SIW) bandpass filter using fractal open complementary split-ring resonators (FOCSRRs) unit-cell is proposed. The proposed structure is realized by etching the proposed FOCSRR unit-cells on the top metal surface of the SIW structure. The working principle of the proposed filter is based on the evanescent-mode propagation. The proposed FOCSRRs behave as an electric dipoles in condition of the appropriate stimulation, which are able to generate a forward-wave passband region below the cutoff frequency of the waveguide structure. Since, the electrical size of the proposed FOCSRRs unit-cell is larger than the conventional OCSRRs unit-cell; therefore, the FOCSRR unit-cell is a good candidate to miniaturize the SIW structure. The proposed filter represents high selectivity and compact size because of the utilization of the sub-wavelength resonators. The introduced filter is simulated by a 3D electromagnetic simulator. In order to validate the ability of the proposed topology in size reduction, 1- and 2-stage of the proposed filters have been fabricated based on the standard printed circuit board process. The measured S-parameters of the fabricated filters are in a good agreement with the simulated ones. The proposed SIW filters have many advantages in term of compact size, low insertion loss, high return loss, easy fabrication and integration with other circuits. It is the first time that the FOCSRR unit-cells were combined with the SIW structure for miniaturization of this structure. Furthermore, a wide upper-stopband with the attenuation >20 dB in the range of 3–8 GHz is achieved. The results show that, a miniaturization factor about 75.5% has been obtained.

Miniaturised equal/unequal SIW power divider with bandpass response loaded by CSRRs

A miniaturised equal/unequal substrate integrated waveguide power divider with bandpass filtering response loaded by complementary split-ring resonators (CSRRs) is proposed. The proposed structure is based on the theory of evanescent mode propagation. The use of the CSRRs enables the filtering function of the power divider and is able to reduce its size. By changing the orientations of the CSRRs, the equal/unequal power dividers are achieved. In the unequal power divider, the power ratio can be arbitrarily controlled by carefully tuning the parameters of the CSRRs and locations of the output ports. Three miniaturised filtering power divider samples with power division ratios of 1:1, 1:4 and 1:8 are fabricated and tested. These designs resonate at the frequency of 5.8 GHz covering WLAN. The sizes of the proposed power dividers (1:1, 1:4 and 1:8) are only 0.37 × 0.21λ g 2, 0.3 × 0.16λ g 2 and 0.3 × 0.15λ g 2, respectively.

Dynamics of structural interfaces: Filtering and focussing effects for elastic waves

Dynamics of thick interfaces separating different regions of elastic materials is investigated. The interfaces are made up of elastic layers or inertial truss structures. The study of evanescent mode propagation and transmission properties reveals that the discrete nature of structural interfaces introduces unusual filtering characteristics in the system, which cannot be obtained with multilayered interfaces. An example of metamaterial is presented, namely, a planar structural interface, which acts as a flat lens, therefore evidencing the negative refraction and focussing of elastic waves.

Superluminal propagation of evanescent modes as a quantum effect

AbstractContrary to mechanical waves, the two‐slit interference experiment of single photons shows that the behavior of classical electromagnetic waves corresponds to the quantum mechanical one of single photons, which is also different from the quantum‐field‐theory behavior such as the creations and annihilations of photons, the vacuum fluctuations, etc. Owing to a purely quantum effect, quantum tunneling particles including tunneling photons (evanescent modes) can propagate over a spacelike interval. With this picture we conclude that the superluminality of evanescent modes is a quantum mechanical rather than a classical phenomenon.

Superluminal propagation of evanescent modes as a quantum effect

Contrary to mechanical waves, the two-slit interference experiment of single photons shows that the behavior of classical electromagnetic waves corresponds to the quantum mechanical one of single photons, which is also different from the quantum-field-theory behavior such as the creations and annihilations of photons, the vacuum fluctuations, etc. Owing to a purely quantum effect, quantum tunneling particles including tunneling photons (evanescent modes) can propagate over a spacelike interval. With this picture we conclude that the superluminality of evanescent modes is a quantum mechanical rather than a classical phenomenon.

Experimental observation of evanescent-wave amplification and propagation in microwave regime

Surface plasmon can lead to wave propagation not only along the surface as a dielectric waveguide but also in the normal direction to the surface because of the evanescent-wave amplification by metamaterial. In this letter, the authors design a surface plasmon structure to implement the electric and magnetic plasma resonances in microwave regime. Near the plasma resonant frequency, they directly observe the strong surface plasmon by experiments. The evanescent waves can be transmitted in an exponentially increasing and decreasing distribution, which is the evanescent-mode propagation by the tunneling effect.

Higher order mode impedances and cut-off frequencies of overmoded coaxial waveguides

Using both theoretical and experimental methods the critical geometrical ratios for effective higher order mode superposition in coaxial waveguides are identified for SDMA beam forming antenna applications. Higher order mode impedances are also important in the design of such antennas and a closed form expression for the power-voltage definition of impedance is derived together with estimates for the voltage-current and power-current forms. An industry standard finite element solver is used to confirm the accuracy of these formulations for a 60 mm radius overmoded coaxial waveguide. In the second part of the paper, the mode chart is used to design a coaxially fed, overmoded air-spaced coaxial waveguide “T” junction supporting the TEM, TE 11 and TE 21 modes. A Green's function based model of the input impedance of this junction establishes that the power-voltage characteristic impedance occurs naturally in calculations requiring absolute impedance values. Finally, this input impedance model, which includes higher order and evanescent mode propagation, is demonstrated to agree well with experimental data for this junction.

Optical modeling of waveguide photonic nanostructures using the radiation spectrum method (RSM) with evanescent modes

In this work, we study the effects of the evanescent modes in the simulation and modeling of optical integrated circuits based on photonic bandgap structures. We show that the contribution of these modes in the energy transfer in structures like the MOEM structures, can not be neglected. The radiation spectrum method, recently developed by the authors for the guided wave devices, is thus extended to account for the evanescent mode propagation. Applying this technique on an air-gap in a suspended waveguide a model of this gap is developed in terms of its parameters. This model is then integrated in an all optical simulator to predict the performance of photonic structures. Such technique enables to design and to optimize the photonic integrated circuits taking the evanescent modes effects into account.

Observable tachyons in the tunneling regime?

AbstractSome aspects are discussed of experiments reporting superluminal velocities of electromagnetic waves propagating across a photonic barrier. Emphasis is put on optical tunneling in frustrated total internal reflection while using the propagation of evanescent modes as guiding idea. This allows to distinguish between obvious and hidden time scales in tunneling by monitoring nonspecular deformations of the incoming beam. The possibility of using specially designed systems for a detailed study of these deformations is addressed.

Observable tachyons in the tunneling regime?

Some aspects are discussed of experiments reporting superluminal velocities of electromagnetic waves propagating across a photonic barrier. Emphasis is put on optical tunneling in frustrated total internal reflection while using the propagation of evanescent modes as guiding idea. This allows to distinguish between obvious and hidden time scales in tunneling by monitoring nonspecular deformations of the incoming beam. The possibility of using specially designed systems for a detailed study of these deformations is addressed.