Composite Right/left-handed Leaky-wave Antenna Research Articles

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 miniaturized CRLH based SIW leaky‐wave antenna for continuous backward‐to‐forward fast beam scanning with low side lobe levels

AbstractIn this study, a substrate‐integrated waveguide (SIW)‐based miniaturized leaky‐wave antenna (LWA) with fast beam scanning is proposed. The proposed LWA exhibits composite right/left‐handed (CRLH) property and its unit cell consist of an inverted Z‐shaped slot etched on the top layer of SIW. By sweeping frequency from 9.4 to 11.4 GHz, the proposed CRLH LWA can steer the frequency beam continuously from −40° to 51°, which shows fast beam scanning within the impedance bandwidth (2 GHz) of LWA. The good leakage constant contributes to the miniaturization of the LWA with electrical dimensions of 3.38λ0 × 0.34λ0 mm2. The antenna attains a peak gain of 12.5 dBi with maximum radiation efficiency of 92%. The antenna attains low sidelobe levels below 12 dB; the low sidelobe levels in the LWA are obtained by creating symmetricity in the unit cell around the centerline. The designed LWA is a viable contender for X‐band beam scanning applications.

A Multilayered SIW-Based Circularly Polarized CRLH Leaky Wave Antenna

In this article, a multilayered circularly polarized (CP) leaky-wave antenna (LWA) is proposed, based on the composite right/left-handed (CRLH) transmission line concept. The proposed design is composed of a substrate integrated waveguide (SIW) structure and its multilayered unit cell consists of H-shaped interdigital (ID) slots on the top with a truncated patch, sandwiched between the two substrates. Circular slots are introduced periodically on the ground plane to achieve wideband circular polarization. Proposed CRLH SIW-based LWA shows the capability of continuous beam scanning from −38° to +71° within the frequency range of 7.6–10.6 GHz while maintaining good circular polarization in the frequency range of 8.3–10.6 GHz. The peak gain of the proposed LWA is 10 dB and the average radiation efficiency is 86.1% over the complete impedance bandwidth. The measured results of the fabricated prototype are in good agreement with the simulated ones. The proposed antenna can be used for <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 radar and satellite applications.

Broadband scanning leaky‐wave antenna based on interdigital coupled‐type composite right/ left‐handed transmission line structure

Owing to its unique nonlinear dispersion characteristics, the composite right/left-handed (CRLH) transmission line (TL) have been widely implemented in the design of leaky-wave antennas. A novel CRLH-TL unit is proposed in this article using the metal patch and pillars to connect the interdigitated line. Not only the parasitic resonance in the conventional interdigital CRLH TL is eliminated by etching the annular gap on the ground, but the miniaturization is also achieved. Then, a broadband high-performance full-plane scanning leaky-wave antenna is designed based on the unit in balanced state. The measured bandwidth with return loss <−10 dB is 3.97 to 5.86 GHz and the peak gain over the operating bandwidth is higher than 9.17 dB. There is no parasitic resonance in the operating bandwidth and the antenna has a lower operating frequency than the classic Interdigital Coupled-Type (ICT) CRLH leaky-wave antenna of the same length.

Continuous Beam Scanning at a Fixed Frequency With a Composite Right-/Left-Handed Leaky-Wave Antenna Operating Over a Wide Frequency Band

Fixed-frequency beam scanning leaky-wave antennas (LWAs) that can scan their main beam over a specific frequency band are highly desired for future wireless communication systems. A composite right-/left-handed (CRLH) LWA is developed in this article that facilitates fixed-frequency continuous beam scanning over a wide operational frequency band. A variation of a simple single-layer nonreconfigurable frequency-based continuous beam scanning CRLH LWA is considered first. Its dispersion properties are approximately investigated using an equivalent circuit model. It is reported how two groups of varactor diodes can be incorporated into its basic circuit model to electronically control its dispersion behavior. An optimized reconfigurable CRLH LWA with practical dc biasing lines is then realized from this nonreconfigurable design. Fixed-frequency continuous beam scanning, from backward to forward directions through broadside, is reported over a wide operational frequency band. Simulations predict that the antenna can operate from 4.75 to 5.25 GHz with the main beam being continuously scannable at each frequency point. A prototype was fabricated, assembled, and tested. The measured results confirm its simulated performance characteristics.

Composite Right/Left-Handed Leaky-Wave Antennas for Wide-Angle Beam Scanning With Flexibly Chosen Frequency Range

A composite right/left-handed (CRLH) leaky-wave antenna (LWA) can effectively scan the radiation beam from backward-to-forward direction. However, in most cases, a large range of frequency sweep is required to achieve a wide-angle beam scan, which could limit their applications. An in-depth study is conducted on an equivalent circuit model for a CRLH LWA unit cell to find the controlling parameters on the frequency sweeping range. A systematic design guideline is given for a CRLH LWA for a wide-angle beam scan in a flexibly chosen frequency range. It is shown that beam scanning by sweeping frequency in a target range can be achieved by systematically designing the unit cell parameters. To verify our approach, a novel CRLH unit cell is developed and used to design an LWA for a wide-angle beam scan in a narrow frequency range. Finally, the concept is validated through realization of the antenna and its measurement. The measured results show that the antenna prototype can scan its beam from −56° to +51° when frequency sweeps from 5.1 to 6.11 GHz (i.e., 18.02% of fractional bandwidth).

Design of CRLH Leaky-Wave Antenna With Low Sidelobe Level

Composite right/left-handed (CRLH) waveguide leaky-wave antenna (LWA) with low sidelobe level (SLL) and high radiation efficiency is investigated and designed in this paper. Due to the characteristic of negative and positive dominant mode propagation constant of the CRLH transmission line, a backward to forward beam-steering LWA can be realized through frequency scanning. The leaky-wave radiation is analyzed first based on a Ka-band CRLH waveguide with straight slots differently offset on the broadwall. The propagation constant maintains almost invariable as the slot offset varies, meanwhile the attenuation constant has a considerable dynamic range. Thus meandering long slot, whose offset varies along the CRLH waveguide, can be cut on the broadwall to generate a tapered excitation distribution. A prototype of the proposed CRLH waveguide LWA with meandering long slot is designed and fabricated to validate the design. Measurement results show that continuous beam-steering capability from −29° to +31° is achieved, meanwhile the optimized SLLs for the designed antenna patterns are kept below −18.5 dB in the major operating band with the minimum SLL of −22.4 dB at 33 GHz, and the average radiation efficiency is 65.4%. The realized SLLs and radiation efficiency performances of our CRLH LWA surpass others reported in open literatures.

Composite right/left‐handed based compact and high gain leaky‐wave antenna using complementary spiral resonator on HMSIW for Ku band applications

In this communication, a novel compact high gain composite right/left-handed (CRLH) based leaky-wave antenna (LWA) is presented at Ku band. A half-mode substrate-integrated waveguide incorporated with a suitably oriented complementary quad spiral resonator (CQSR) is used to achieve a CRLH LWA. The unit cell is realised by a CQSR in such a way that the orientation of spirals exhibits higher leakage loss having a minimum cross coupling between them. The antenna is capable of scanning backward to forward along with a broadside direction in visible space. The proposed configuration has a length of 4.85 λ 0 which can scan within the frequency range of 13.5-17.8 GHz having a beam scanning range of 86° (-66° to 20°) and a maximum gain of 16 dBi. The simulated reflection coefficient of the proposed antenna is below -10 dB throughout the working frequency range with a side-lobe level of below -10 dB. The designed prototype is more compact in nature having high gain, fair scanning range, and good cross-polarisation level along with simpler design methodology and tuning capability to enhance the gain as well as radiation efficiency maintaining a fixed size. The proposed antenna could be a promising candidate in Ku-band applications like fixed satellite services, and broadcast satellite services etc.

A Miniaturized Reconfigurable CRLH Leaky-Wave Antenna Using Complementary Split-Ring Resonators

Composite Right-/Left-Handed (CRLH) Leaky-Wave Antennas (LWAs) are a class of radiating elements characterized by an electronically steerable radiation pattern. The design is comprised of a cascade of CRLH unit cells populated with varactor diodes. By varying the voltage across the varactor diodes, the antenna can steer its directional beam from broadside to backward and forward end-fire directions. In this paper, we discuss the design and experimental analysis of a miniaturized CRLH Leaky-Wave Antenna for the 2.4 GHz WiFi band. The miniaturization is achieved by etching Complementary Split-Ring Resonator (CSRR) underneath each CRLH unit cell. As opposed to the conventional LWA designs, we take advantage of a LWA layout that does not require thin interdigital capacitors; thus we significantly reduce the PCB manufacturing constraints required to achieve size reduction. The experimental results were compared with a nonminiaturized prototype in order to evaluate the differences in impedance and radiation characteristics. The proposed antenna is a significant achievement because it will enable CRLH LWAs to be a viable technology not only for wireless access points, but also potentially for mobile devices.

A CRLH leaky wave antenna on SIW with continuous scan using novel S-slots

ABSTRACTThis article realises a leaky wave antenna based on composite right left-handed (CRLH) transmission line (TL) with novel S-shaped slots on substrate integrated waveguide (SIW). For realising CRLH TL and for providing series capacitance, the slots are etched in the top layer of SIW. The proposed unit cell is repeated in one dimension to get an array, showing continuous beam scanning in a wide range of 74° for fractional bandwidth of 43%, beam scanning starts from −49° to 25° for the frequency scan of 30–42.8 GHz. Simulated results shows almost constant and high gain values of ~15 dBi (max) in the specified scan range, with more than 75% radiation efficiency. The proposed antenna is very small, compact and is having dimensions of 48.7 × 7.6 mm2. A prototype of the proposed antenna is fabricated and tested for verification, a good agreement between simulated and measured S parameters has been observed.

On Increasing the Slow-Fading Channel Diversity Using Block-Coded MIMO-OFDM With Reconfigurable Antennas

In this paper, we propose a new block coding scheme to increase the diversity gain of multiple-input–multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems over slow-fading wireless channels. We assume that the antenna elements at the transmitter are reconfigurable and capable of independently changing the physical characteristics of their radiation patterns. The composite right-left handed leaky-wave antenna is an example of reconfigurable antennas with such characteristics. We use this feature of the antennas and develop a block coding scheme that exploits, in addition to the spatial and frequency diversity, a new additional degree of diversity, which is called state diversity. We determine the maximum achievable diversity order of the proposed coding scheme in spatially correlated frequency-selective channels. To demonstrate the performance of the proposed block coding technique, we provide numerical results and compare them with those of the previously developed coding schemes for MIMO-OFDM systems. The results indicate that the proposed code achieves significantly higher diversity and coding gain, even in spatially correlated channels, compared with the existing counterparts.

Feasibility of graphene CRLH metamaterial waveguides and leaky wave antennas

The feasibility of composite right/left-handed (CRLH) metamaterial waveguides based upon graphene plasmons is demonstrated via numerical simulation. Designs are presented that operate in the terahertz frequency range along with their various dimensions. Dispersion relations, radiative and free-carrier losses, and free-carrier based tunability are characterized. Finally, the radiative characteristics are evaluated, along with its feasibility for use as a leaky-wave antenna. While CRLH waveguides are feasible in the terahertz range, their ultimate utility will require precise nanofabrication, and excellent quality graphene to mitigate free-carrier losses.

Composite Right/Left-Handed Ridge Substrate Integrated Waveguide Slot Array Antennas

A composite right/left-handed (CRLH) ridge substrate integrated waveguide (RSIW) is proposed and applied to slot array antennas, where the longitudinal slots are etched on the surface of CRLH RSIW, behaving as the radiating elements. Two slot array antennas are designed, fabricated, and measured, one with fixed slot offset, and the other one with varied slot offsets used for achieving low side-lobe level (SLL) of radiation patterns. Compared with the slot array antennas using CRLH rectangular waveguides, the investigated CRLH RSIW ones have the advantages of miniaturized size in transverse direction, relative low cost, low profile, and easy to integrate with other planar circuits. Besides, unlike other proposed planar CRLH leaky wave antennas (LWAs), slots of varied offsets can be adopted on the CRLH RSIW surface to achieve a tapered excitation. Thus the radiation patterns can be optimized for low SLL. In summary, this CRLH RSIW enables a tapered excitation in the beam-steering antenna design while keeps a relative simple structure.

CRLH Leaky Wave Antenna Based on ACPS Technology With 180$^{\circ}$ Horizontal Plane Scanning Capability

This study presents a novel composite right/left-handed (CRLH) leaky wave antenna (LWA) with horizontal plane scanning capability. This LWA consists of 10 CRLH unit cells and coplanar waveguide to coplanar stripline transitions. The proposed balanced CRLH unit cell is based on an asymmetric coplanar stripline structure (ACPS). The parameters of the CRLH unit cell can be determined analytically, enabling easy modification for any other frequency band. Because of its planar and horizontal plane scanning property, the proposed design can also be extended to a sector-shaped multisection LWA, achieving a scanning range of more than 180° in the horizontal plane. By varying the operating frequency, the CRLH leaky wave antenna shows the continuously beam-scanning property from backward to forward in the horizontal plane. A 10-cell prototype exhibits the beam-scanning capability in the horizontal plane, and a 20-cell multisection sector-shaped LWA confirms the approach of designing the wide-range beam-scanning LWA. Experimental results show that the proposed design is in good agreement with the simulation. The planar and low-profile characteristics of the novel CRLH LWA make it suitable for integration with other microwave circuits, and can be applied to applications that require a wider beam-scanning range.

NOVEL COMPOSITE RIGHT/LEFT-HANDED LEAKY-WAVE ANTENNAS BASED ON THE FOLDED SUBSTRATE-INTEGRATED-WAVEGUIDE STRUCTURES

In this paper, novel composite right/left-handed (CRLH) leaky-wave antennas based on folded substrate-integrated-waveguide (FSIW) structures are proposed. The proposed leaky-wave antennas were realized by periodically loading the radiating slots on the top metallization of the FSIW-based CRLH transmission lines. The structural advantages of the FSIW combined with the unique dispersion characteristics of the CRLH transmission line enable the proposed leaky-wave antennas to present continuous beam-scanning capability from backflre to endflre directions, occupy smaller footprint size, and provide more design ∞exibility than the conventional CRLH leaky-wave antennas. Two of such CRLH leaky-wave antennas were developed. In addition to the continuous beam scanning, it is found that the radiation e-ciency and polarization of the FSIW-based leaky- wave antennas can be easily tuned by means of the slot size and slot orientation, respectively, indicating their potential for versatile applications. Calculated and experimental results are presented and compared. A good agreement is obtained. To the best of our knowledge, it is the flrst time that the leaky-wave antenna exploits both of the dispersion behavior of the CRLH transmission lines and the structural beneflts of the FSIW conflguration.

A Tapered CRLH Interdigital/Stub Leaky-Wave Antenna With Minimized Sidelobe Levels

A nonuniform (NU) tapered composite right/left-handed (CRLH) leaky-wave antenna (LWA) with minimized sidelobe level (SLL) is proposed. The design of this antenna is performed using an automated cosimulation approach based on a genetic algorithm optimization. Fair agreement is found between the full-wave and the experimental results. The experimental results show an 8-dB SLL reduction compared to a uniform CRLH LWA with the same gain in a 12-unit-cell structure.

Evolution of Composite Right/Left-Handed Leaky-Wave Antennas

In this paper, the evolution of the composite right/left-handed (CRLH) leaky-wave antennas (LWAs) yielding several novel CRLH LWA is reviewed. Starting with the concept of CRLH LWAs, the concave and convex passive CRLH LWAs are discussed along with the conformation effects in each case and a dispersion engineering method is introduced to compensate for the conformation effect to refocus the main radiation beam. Next, planar and conformal varactor-based electronically controlled CRLH LWAs are reviewed. In the planar case electronic beam steering and beamwidth controlling are discussed while in the case of conformal version electronic radiation aperture selectivity as well as electronic beam focusing is discussed. Finally, a dual polarized CRLH LWA is presented which is a balanced four-port coupled CRLH LW-TL that conserves its CRLH nature under both common-mode and differential-mode excitations but with two orthogonal E-planes resulting in two orthogonal polarizations for the radiated fields.

DOUBLE-SIDE RADIATING LEAKY-WAVE ANTENNA BASED ON COMPOSITE RIGHT/LEFT-HANDED COPLANAR-WAVEGUIDE

A double-side radiating leaky-wave antenna based on composite right/left-handed (CRLH) coplanar-waveguide (CPW) is proposed. Dispersion diagram of the unit cell is investigated, and balanced property is conflrmed. Thus, the CRLH leaky-wave antenna can have backflre radiation due to the left-handed property of the CRLH structure and broadside radiation at the balancing frequency point. The measured results show that the proposed antenna can ofier a scanning angle covering almost backflre-to-endflre directions.

Microwave Analog Real-Time Spectrum Analyzer (RTSA) Based on the Spectral–Spatial Decomposition Property of Leaky-Wave Structures

A novel analog real-time spectrum analyzer (RTSA) for the analysis of complex nonstationary signals (such as radar, security and instrumentation, and electromagnetic interference/compatibility signals) is presented, demonstrated, and characterized. This RTSA exploits the space-frequency mapping (spectral-spatial decomposition) property of the composite right/left-handed (CRLH) leaky-wave antenna (LWA) to generate the real-time spectrograms of arbitrary testing signals. Compared to digital RTSAs, it exhibits the advantages of instantaneous acquisition, low computational cost, frequency scalability, and broadband or ultra-wideband operation. The system is demonstrated both theoretically by a commercial full-wave simulator and an efficient Green's function approach and experimentally by a parallel-waveguide prototype including a metal-insulator-metal CRLH LWA, 16 patch antenna probe detectors circularly arranged around the LWA, and a digital oscilloscope performing analog/digital conversion and time-domain acquisition before the postprocessing and displaying of the spectrogram. The system is tested for a large diversity of nonstationary signals and generates, in all cases, spectrograms that are in excellent agreement with theoretical predictions. The fundamental tradeoff between time and frequency resolutions inherent to all RTSA systems is also discussed, and an interchangeable multi-CRLH LWA solution is proposed to handle signals with different time durations.