Composite Right/left-handed Research Articles

A novel miniaturized microstrip filtering power divider with high selectivity based on composite right/left-handed (CRLH) concept

Abstract This paper proposes a compact microstrip filtering power divider (FPD) with high selectivity and equal power division ratios based on the composite right/left-handed (CRLH) concept. The proposed equal microstrip FPD is designed by cascading two CRLH unit cells and a grounded via hole. The proposed CRLH unit cell is realized by an interdigital capacitor loaded between two transmission lines (TL) on the upper metal layer and the fractal/meander complementary split-ring resonator (FMCSRR) on the ground plane. The grounded via hole has been used to improve frequency selectivity and out-of-band rejection of the proposed microstrip FPD. The equivalent circuit model compared with full-wave simulation results of the proposed microstrip FPD has been provided. The proposed microstrip FPD has been fabricated and measured, and a good agreement has been found between the simulation and measurement results. The proposed microstrip FPD has a passband covering 2.38–2.45 GHz, and its measured 3 dB fractional bandwidth is about 2.9 %. The total size of the proposed microstrip FPD is 0.17 λ g × 0.07 λ g. Compared with other reported FPDs, the presented microstrip FPD has many advantages like compact size, low loss, easy fabrication, extremely sharp rejection skirts around the desired passband and high selectivity.

A novel compact directional coupler with high directivity based on CRLH transmission lines

Designing and fabricating a directional coupler with composite right/left-hand (CRLH) transmission lines with a coupling level of 15 dB is presented in this paper. Compared to conventional couplers, this asymmetric structure has achieved this coupling level compared to the simple transmission line. This structure is comprised of interdigital capacitors and short connection stubs. The distance between two coupled lines is equal to 0.4 mm, and the stubs are spirally designed to compress the structure. The subs’ length is approximately equal to λ/4, and the impedance of the ports is equal to 50 Ω. After designing and simulating, the coupler was fabricated and measured. The directional coupler at the frequency of 1.9 GHz has an isolation level of 44 dB and a directivity of 67.1 dB. Overall, construction and simulation results are in good agreement.

A wide angle beam scanning CRLH leaky-wave antenna with non-identical elements per unit-cells

In this research article, a wide-angle scanning leaky-wave antenna (LWA) based on the composite right/left-handed (CRLH) metamaterial (MTM) operating over the C-band spectrum for mobile applications is proposed, investigated, and realized. The proposed LWA includes nine CRLH-MTM-based unit-cells. The properties of CRLH-MTM have been applied using series slots and shunt metallic via-holes. Each unit cell consists of three patches, two external patches, and one smaller middle patch implemented between them. One slot has been etched on each external patch; the width of these two slots is unequal. Moreover, the distance of the middle patch with each side patch is different. The results show that using this method of realizing non-identical elements caused the achievement of proper return-loss at the transition frequency and provided the balanced CRLH metamaterial condition. Additionally, using CRLH-MTM properties by realizing series capacitance (slot) and shunt inductance (via-holes) made the wide-angle scant from backward to forward radiation pattern. The results demonstrate that the LW antenna with small dimensions of 251.5 × 30 × 1.575 mm3 operates over a frequency range of 4.8–6.13 GHz covering a wide beam scanning range from −63° to +65° with broadside radiation at the center frequency of 5.46 GHz. The radiation gain of the proposed antenna varies from 6.2–13.1 dB. The achievements confirm the effectiveness of the proposed methods to realize a high-performance LW-antenna with the advantages of simple design, low profile, low cost, and easy of manufacture for mobile applications.

Enhanced 2-port MIMO antenna with composite two-step metasurface for 77 GHz Vehicle-to-Everything applications

The article presents a 2-port multiple-input multiple-output (MIMO) antenna array designed for millimeter-wave band operation, specifically optimized for Vehicle-to-Everything (V2X) applications. To enhance performance, a novel approach employing two types of metasurfaces on a single plate is utilized. The first metasurface, based on a loop structure, aims to improve the frequency bandwidth, while the second metasurface, utilizing a composite right/left-handed (CRLH) design, focuses on reducing mutual coupling. These two steps result in an improved frequency bandwidth exceeding 45% and a decreased structure width of about 50% compared to other designs. Notably, the compact nature of these metasurfaces, measuring approximately 32 × 3 mm2, is a significant feature that reduces manufacturing costs. The arrayed antenna, with 20 series elements, is suitable for medium-range radar in V2X applications, although our method is generally applicable to other ranges. Additionally, the radiation pattern exhibits a 40-degree beam rotation within the frequency bandwidth, making it well-suited for V2X applications. The results demonstrate impressive diversity performance, with a consistent maximum gain of 16 dB across the entire frequency bandwidth of approximately 68 GHz to 82 GHz, representing an 18.2% coverage.

A new technique for improving performance of conventional CRLH resonators using IDC/UISs with enhanced harmonic suppression in balanced dual-band BPFs

Abstract The design of balanced filters based on composite right/left hand (CRLH) structure is well developed. Among those, few designs exist which although they provide some good responses, suffer from narrow stopbands and interdependent passbands. This paper proposes a new technique for improving the characteristics of dual-band balanced bandpass filters (B-BPFs) based on planar CRLH. Using unequal inductive stubs (UISs) attached to the interdigital capacitor (IDC) unit cell, we were able to achieve outstanding harmonic suppression and passband controllability. This structure offers higher degrees of freedom compared to conventional designs and provides better control over the filter specifications. Mathematical modeling, analysis, simulation, fabrication, and performance measurement of the proposed technique in a dual-band B-BPF are also provided. Our work resulted in an independent and controllable dual-band B-BPF with ultra-wide upper differential-mode (DM) stopband of 5.9f 1 and common-mode (CM) suppression of 40.4 and 32.6 dB for the first and second bands, respectively.

An impedance matching section based on composite right/left‐handed transmission line model in viewpoint of phase shift and noise figure

AbstractIn this paper, a genetic‐based synthesis approach for an impedance matching section based on a composite right‐/left‐handed (CRLH) transmission line model called CRLH transmission line impedance matching section (CRLHTLIMS) in viewpoint of transmission phase shift and noise figure is newly presented. To find the unknown values of right‐/left‐handed inductances and capacitances of a CRLHTLIMS, a type of global optimization algorithm called continuous parameter genetic algorithm is used. The length, transmission phase shift, and noise figure of the CRLHTLIMS are computed by using simple equations. Different examples for a uniform CRLHTLIMS are given. According to the results, this approach is an easy and effective way for the synthesis of transmission line impedance matching sections in viewpoint of transmission phase shift and noise figure.

CRLH Leaky-Wave Antenna with High Gain and Wide Beam-Scanning Angle for 5G mmWave Applications

In this paper, a novel composite right-/left-handed (CRLH) leaky-wave antenna with a simple structure, low cost, high gain, and wide beam-scanning range performance for the millimeter wave (mmWave) band. The proposed antenna comprises a series-fed array of asymmetrically slotted elliptical CRLH unit cells loaded with a short-circuit stub. By optimizing the length of the stub, the condition of the CRLH structure is balanced to enable beam scanning from the backward to the forward direction within the mmWave band. The proposed antenna exhibits a wide beam-scanning angle of 112° (-60° to 52°), coupled with high gain and radiation efficiency at the designated band. Furthermore, it is fabricated on a traditional microwave substrate, Rogers RT/duroid 5880, thus offering a cost-effective approach to streamlining the manufacturing process. The measurement results confirmed a peak realized gain of 16.8 dBi. The excellent performance achieved using a low-cost design makes the proposed antenna attractive for 5G mmWave applications.

Composite Right/Left-Handed Leaky-Wave Antenna with Electrical Beam Scanning Using Thin-Film Ferroelectric Capacitors

This article presents a wide-angle-scanning leaky-wave antenna (LWA) based on a composite right/left-handed (CRLH) transmission line. In contrast to traditional semiconductor elements, thin-film ferroelectric capacitors were implemented in the CRLH unit cells to enable electric beam scanning. The proposed CRLH LWA has a single-layer design without metalized vias and is compatible with PCB and thin-film technologies. To fabricate the CRLH LWA prototype, dielectric material substrates and thin-film ferroelectric capacitors were manufactured, and their characteristics were investigated. Double-sided metalized fluoroplast-4 reinforced with fiberglass with a permittivity of 2.5 was used as a substrate for CRLH LWA prototyping. A solid solution of barium strontium titanate (BaxSr1−xTiO3) with a composition of x=0.3 was used as a ferroelectric material in electrically tunable capacitors. The characteristics of the manufactured ferroelectric thin-film capacitors were measured at a frequency of 1 GHz using the resonance method. The capacitors have a tunability of about two and a quality factor of about 50. The antenna prototype consists of ten units with a total length of 1.25 wavelengths at the operating frequency of close to 2.4 GHz. The experimental results demonstrate that the main beam can be shifted within the range of −40 to 16 degrees and has a gain of up to 3.2 dB. The simple design, low cost, and excellent wide-angle scanning make the proposed CRLH LWA viable in wireless communication systems.

A PITD algorithm for analyzing composite right‐/left‐handed transmission line

AbstractIn this letter, a novel numerical algorithm is proposed for analyzing the composite right‐/left‐handed (CRLH) transmission line (TL). The proposed algorithm adopts the precise‐integration time‐domain technique to construct the update equation, overcomes the Courant–Friedrich–Levy (CFL) stability condition, and solves the CRLH TL equations in an explicit way. The implementation of the proposed algorithm is simple and straightforward. Numerical results validate that the proposed algorithm can solve CRLH TL equations correctly when large time steps are used, and improves computational efficiency compared with the conventional FDTD method.

A Singly Curved Conformal Phased Array with Integrated Particles-Based CRLH Phase Shifters

In this paper, a four unit cell micron-sized magnetic particles embedded composite right/left-handed (CRLH) transmission line metamaterial phase shifter is proposed. The variable phases are achieved by activating the micron-sized magnetic particles along the length of stub transmission lines of the CRLH transmission line structure. This causes to effectively change the inductance of stub transmission lines, which changes the phase of the RF signal. These structures can be activated in a symmetric or asymmetrical manner to obtain wide range of phase shifts. A prototype of cascaded four unit cell CRLH transmission line phase shifter with embedded silver-coated ferrites (magnetic particles) is designed, fabricated and tested for phase shifters applications. The measured phase response of the proposed phase shifter is in close agreement with the simulated phase response. Next, for the performance analysis of proposed phase shifter, a 1 × 4 conformal curved-shaped phased array operating at 5.8 GHz is fed with the four unit cell cascaded phase shifter in CST full-wave simulator. The conformal phased array with proposed integrated phase shifters was simulated for broadside pattern correction and main beam scanning at 20 degree on curved-shaped surface with different bend angles. The radiation pattern results obtained with the proposed integrated phase shifters are in close agreement with those obtained with direct excitation of the array.

A compact high gain filtering patch antenna for multiband wireless system

A novel compact multilayer patch antenna is designed for triple-band operation with filtering characteristics. The multiband antenna with filtering characteristics is necessary to suppress adjacent band interference. Further, it brings higher out-of-band suppression without deteriorating the in-band gain. This filtering antenna offers size compactness, high gain, and high selectivity with reduced interference. On exciting the antenna, the electromagnetic (EM) coupling takes place from feed to patch through the slotted ground. Then the magnetic field reaches its maximum at the middle of the rectangle patch while the electric field reaches its maximum at the edges. These fields couple with the ‘U’ shaped metallic loops and bring field distribution in it and thus contribute to dual-band resonance at 2.45GHz and 4.15GHz. For better impedance matching, the two ‘U’ shaped metallic loops are employed. The additional middle band at 3.25GHz is attained through the employment of a split rectangular ring around the center patch. The bottom ground is etched with a bent horizontal slot to achieve proper positioning of the lower resonance. The modified CRLH feeding structure is adopted in this antenna to realize radiation null between operating bands. The dimension of the CRLH branches decides the positioning of radiation nulls in the spectrum of interest. This null reduces the interband interference and it is an important feature for any multiband communication system. The usage of via between patch and feed increases the electrical length of an antenna and thus provides size miniaturization. Whereas the position of the via in the patch decides the impedance matching. thus multiple iterations of simulation were done to optimize the via position for better impedance matching. The designed antenna has a compact dimension of 0.21λo × 0.21λo. The realized triple bands have −10dB impedance bandwidth of 180MHz (2.31 to 2.49GHz), 350MHz (3.1 to 3.45GHz), and 850MHz (3.6 to 4.45GHz) with a maximum gain of 5.2dB. Thus the multi-layer antenna not only has proven to be multiband but also incorporated filtering characteristics to lessen interband interferences. The proposed antenna would be beneficial in a multiband wireless system that supports services such as Wifi, WiMAX, and 5G. The antenna is the perfect candidate for the unmanned ariel vehicle (UAV) to be used in emergency and military applications.

Slotted Substrate-Integrated Waveguide Leaky-Wave Antenna with Improved Backward Scanning Bandwidth and Constant Gain in X-band

An H-shaped slotted leaky-wave antenna (LWA) is proposed based on balanced composite right/left-handed (CRLH) transmission lines (TLs) to improve the backward scanning bandwidth and achieve constant gain. The proposed antenna consists of a substrate-integrated waveguide (SIW) unit cell array configured by an H-shaped slot cut in the top layer of the SIW and a patch embedded beneath the H-shaped slot. The proposed design improves the backward scanning bandwidth compared to planar SIW LWAs. The measured beam radiation is in the range from −79° to 80° over the frequency range of 7.6–12.5 GHz. Moreover, a constant gain of greater than 10 dB is achieved over the entire X-band frequency range.

MmWave Zero Order Resonant Antenna with Patch-Like Radiation Fed by a Butler Matrix for Passive Beamforming.

A small zero-order resonant antenna based on the composite right-left-handed (CRLH) principle is designed and fabricated without metallic vias at 30 GHz to have patch-like radiation. The mirror images of two CRLH structures are connected to design the antenna without via holes. The equivalent circuit, parameter extraction, and dispersion diagram are studied to analyze the characteristics of the CRLH antenna. The antenna was fabricated and experimentally verified. The measured realized gain of the antenna is 5.35 dBi at 30 GHz. The designed antenna is free of spurious resonance over a band width of 10 GHz. A passive beamforming array is designed using the proposed CRLH antenna and the Butler matrix. A substrate integrated waveguide is used to implement the Butler matrix. The CRLH antennas are connected to four outputs of a 4×4 Butler matrix. The scanning angles are 12∘, -68∘, 64∘, and -11∘ for excitations from port 1 to port 4 of the 4×4 Butler matrix feeding the CRLH antenna.

Compact dual-band balanced bandpass filter using CRLH resonator with intrinsic common-mode suppression and multiple transmission zeros

In this paper, a newly composite right-/left-handed (CRLH) resonator is presented and applied to constitute a compact dual-band balanced bandpass filter (BPF). The proposed CRLH resonator contains two spiral coupled line segments. By imposing the differential-mode (DM) and common-mode (CM) excitation, the DM and CM equivalent circuits of the presented resonator and their lumped-element circuit models are built for investigating the resonant property. The CRLH resonator has two DM resonances and are adopted to design two DM passbands. Also, the CM resonances are all far away from DM resonances, achieved intrinsic desirable CM rejection within DM frequency range without any auxiliary elements. Attributing to the mixed electric and magnetic coupling between two coupled resonators and the introduced source-loaded coupling, multiple transmission zeros are obtained and therefore enhance the selectivity and attenuation in stopband. Finally, a well-designed dual-band balanced BPF is fabricated. Verification of the presented structure and design method’s validity is evidenced by the measured results, which are in agreement with the simulations.

Multimode CRLH SIW Transmission Lines for Wideband Multiport Directional Couplers and Miniaturized Beamforming Networks

In this article, a multimode composite right/ left-handed (CRLH) substrate-integrated waveguide (SIW) transmission line technology is proposed, which aims to broaden the operating bandwidth of the multiport directional couplers (DCs) and solve the oversize of the beamforming network (BFN). Its core is to etch multiple interdigital slots (IDSs) on the conductor surface of the multimode SIW transmission line, which can control the electromagnetic fields of different modes in the transmission line under the condition of less electromagnetic energy leakage. By adjusting the position and size of the IDSs, the desired phase constants and electromagnetic field distributions of different modes can be obtained simultaneously. Based on the proposed multimode CRLH SIW transmission line, the six-port, the eight-port, and the ten-port DCs are designed, respectively. Compared with the traditional multiport DCs based on the SIW, the bandwidth of the proposed six-port and eight-port DCs is broadened by about 87.3%. Based on the proposed multiport DCs, the miniaturized BFNs and the miniaturized multibeam array antennas (MBAs) can be realized by adding appropriate fixed phase shift. Finally, to verify the feasibility of applying multiport DCs based on the multimode CRLH SIW transmission lines to the miniaturized BFNs and the miniaturized MBAs, a 3 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 3 BFN, a 4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 4 BFN, and a three-port MBA are fabricated, measured, and discussed. Their sizes are reduced by 58%, 49%, and 60%, respectively, compared with their SIW butler matrix (BM) counterparts.

Millimeter-wave low-loss on-chip metamaterial for 5G communication based on non-periodic composite right-/left-handed transmission line

This Letter reports a millimeter-wave low-loss on-chip metamaterial based on a concept of a non-periodic composite right-/left-handed (CRLH) transmission line (TL). Compared with a classic periodic unit cell, a non-periodic CRLH TL is proposed to obtain higher transmittance and better reflectivity. First, based on the CRLH TL theory, the LC values of the periodic transmission line were calculated. Second, Ti factors were derived using Chebyshev low-pass filter prototypes and the bandpass transformation theory. Third, these values were then used to calculate the factors of the non-periodic structure, which was eventually implemented using lumped elements. By analyzing the dispersion property, the proposed non-periodic CRLH metamaterial features both right-handed (forward wave) and left-handed (backward wave) propagating modes, which accounts for its wide bandwidth. For demonstration, a gallium arsenide-based integrated passive device process is adopted. As its main advantages, the fabricated metamaterial shows a high and flat transmission with minimum insertion loss of 0.68 dB at 30.2 GHz, and a low reflectivity better than −10 dB from 14 to 51 GHz of which the fraction bandwidth is over 120%.

Reconfigurable CRLH‐inspired antenna based on Hilbert curve EBG structure for modern wireless systems

AbstractThis paper presents a novel antenna design with an enhanced gain‐bandwidth product for modern communication networks, including 5G systems. The design is consistent with 17 unit cells of a composite right/left‐hand (CRLH) structure with an electromagnetic band gap of Hilbert inclusions. Therefore, the resulting design occupies an area of 40 × 200 mm2 of a Taconic RF‐43 substrate. The maximum antenna gain is 16 dBi at 5.5 GHz, which is very applicable for long‐range communication systems. Nevertheless, the antenna performance is controlled with optical switches of light‐dependent resistors (LDR) technology. Therefore, the antenna performance is tested with different switching seniors to investigate the possibility of reconfiguration scenarios at various frequency bands. However, the antenna gain is highly affected by changing LDR switching status; for example, at 5.5 GHz, the antenna gain is varied between 7 and 16 dBi. Thus, the proposed antenna is an excellent candidate for direct amplitude modulation. Finally, the antenna simulation results and measurements agree very well with each other.

SIW Triplets Including Meander-Line and CRLH Resonators and Their Applications to Quasi-Elliptic Filters

This article presents a design technique of quasi-elliptic filters by applying two novel planar triplets, which eliminates the need for negative couplings. A composite right-/left-handed (CRLH) resonator, together with a meander-line resonator, is investigated first in this article. These two resonators demonstrate a significant difference with respect to their phase shift characteristics that are completely opposite below and above their resonant frequencies. With such a feature, two meander-line and CRLH-loaded substrate integrated waveguide (SIW) triplets are proposed, which can produce a transmission zero (TZ) above and below the passbands if an inductive cross coupling is applied. Therefore, all couplings would be positive regardless of the location of TZs. The applications of the two triplets to quasi-elliptic filters, which are realized by parallel and cascaded triplet topologies, are then illustrated. Two filter prototypes operating at the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$X$</tex-math> </inline-formula> -band are designed and fabricated for validation. They show outstanding electrical performance in terms of high selectivity, low loss, and compactness. It indicates that a joint application of conventional shunt <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> resonant nodes and a CRLH node is a viable option in filter design.

Steerable composite right–left‐hand‐based printed antenna circuitry for 5G applications

AbstractIn this article, the proposed antenna structure is designed for modern wireless communication systems. The antenna structure is consistent with 11‐unit cells of composite right–left‐hand (CRLH) inclusions mounted on an FR4 substrate. Therefore, the antenna size is miniaturized effectively to 30 × 20 mm2 to cover the frequency bands around 2.45 GHz, for Wi‐Fi, and 4.2–6 GHz, for sub‐6 5G, networks. The design process is conducted on a circuit model and numerical simulations by evaluating the unit cell transmission phase spectra. For this, a comparison between the circuit model and the numerical simulations is invoked for validation. Such an antenna is found to provide a maximum gain of 6.2 dBi at 4.6 GHz. Next, 11 PIN diodes control the current motion between the antenna patch and the CRLH array. Therefore, PIN arrays are connected to the patch and the ground plane to maintain the surface current motion that realizes main lobe beam steering. The proposed antenna performance is simulated numerically using the CSTMWS software package. Then, it is fabricated and tested experimentally for validation. An excellent agreement is achieved between the simulated and measured results. Finally, it is found this antenna provides excellent beam steering −92° to 92° to suit many modern networks.

Electronic Beam Steering Metamaterial Antenna with Dual-Tuned Mode of Liquid Crystal Material

In this study, a dual-tuned mode of liquid crystal (LC) material was proposed and adopted on reconfigurable metamaterial antennas to expand the fixed-frequency beam-steering range. The novel dual-tuned mode of the LC is composed of double LC layers combined with composite right/left-handed (CRLH) transmission line theory. Through a multi-separated metal layer, the double LC layers can be loaded with controllable bias voltage independently. Therefore, the LC material exhibits four extreme states, among which the permittivity of LC can be varied linearly. On the strength of the dual-tuned mode of LC, a CRLH unit cell is elaborately designed on three-layer substrates with balanced dispersion values under arbitrary LC state. Then five CRLH unit cells are cascaded to form an electronically controlled beam-steering CRLH metamaterial antenna on a downlink Ku satellite communication band with dual-tuned characteristics. The simulated results demonstrate that the metamaterial antenna features' continuous electronic beam-steering capacity from broadside to -35° at 14.4 GHz. Furthermore, the beam-steering properties are implemented in a broad frequency band from 13.8 GHz to 17 GHz, with good impedance matching. The proposed dual-tuned mode can make the regulation of LC material more flexible and enlarge the beam-steering range simultaneously.